Non-Conventional Features of Plant Oil-Based Acrylic Monomers in Emulsion Polymerization

Review Non-Conventional Features of Plant Oil-Based Acrylic Monomers in Emulsion Polymerization

Ananiy Kohut 1, Stanislav Voronov 1, Zoriana Demchuk 2 , Vasylyna Kirianchuk 1, Kyle Kingsley 2, Oleg Shevchuk 1, Sylvain Caillol 3 and Andriy Voronov 2,*

1 Department of Organic Chemistry, Institute of Chemistry and Chemical Technologies, Lviv Polytechnic National University, 79000 Lviv, Ukraine; [email protected] (A.K.); [email protected] (S.V.); [email protected] (V.K.); [email protected] (O.S.) 2 Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND 58108-6050, USA; [email protected] (Z.D.); [email protected] (K.K.) 3 ICGM, Univ Montpellier, CNRS, ENSCM, 34095 Montpellier, France; [email protected] * Correspondence: [email protected]

Academic Editor: Dimitrios Bikiaris Received: 8 June 2020; Accepted: 29 June 2020; Published: 30 June 2020

Abstract: In recent years, polymer chemistry has experienced an intensive development of a new field regarding the synthesis of aliphatic and aromatic biobased monomers obtained from renewable plant sources. A one-step process for the synthesis of new vinyl monomers by the reaction of direct transesterification of plant oil triglycerides with N-(hydroxyethyl)acrylamide has been recently invented to yield plant oil-based monomers (POBMs). The features of the POBM chemical structure, containing both a polar (hydrophilic) fragment capable of electrostatic interactions, and hydrophobic acyl fatty acid moieties (C15-C17) capable of van der Waals interactions, ensures the participation of the POBMs fragments of polymers in intermolecular interactions before and during polymerization. The use of the POBMs with different unsaturations in copolymerization reactions with conventional vinyl monomers allows for obtaining copolymers with enhanced hydrophobicity, provides a mechanism of internal plasticization and control of crosslinking degree. Synthesized latexes and latex polymers are promising candidates for the formation of hydrophobic polymer coatings with controlled physical and mechanical properties through the targeted control of the content of different POBM units with different degrees of unsaturation in the latex polymers.

Keywords: biobased polymers; plant oil-based monomers; mixed micelles; methyl-β-cyclodextrin inclusion complex; emulsion polymerization

1. Introduction The problem of depletion of fossil raw materials has become of global importance and is complicated not only by economic but also environmental and political factors [1]. However, synthetic polymers are still one of the most widely used materials in everyday use. Environmental analysis shows that huge amounts of plastic waste are found in the environment, and their contribution to the ever-increasing amount of solid waste is a signiﬁcant environmental threat [2]. Plant oils are low-cost raw materials for the manufacture of monomers and polymers [3–5], which have several advantages over conventional polymeric materials, namely biodegradability, non-toxicity, biocompatibility, and hydrophobicity. Therefore, an important task for synthetic chemists is to consider renewable raw materials as an alternative to raw counterparts of fossil origin. Due to the wide range of plant oils, the variety of their chemical compositions, and, in many cases, abandon of resources, they became an interesting object to be used in polymers synthesis as a renewable raw material.

Molecules 2020, 25, 2990; doi:10.3390/molecules25132990 www.mdpi.com/journal/molecules Molecules 2020, 25, x FOR PEER REVIEW 2 of 19

Molecules 2020, 25, 2990 2 of 19 abandon of resources, they became an interesting object to be used in polymers synthesis as a renewable raw material. The total production of plant oils in in the world in in 2019 amounted amounted to to more more than than 200 200 million million tons, tons, of which about 15% are used as raw materials for the synthesis of new chemical compounds and materials [6]. [6]. The The presence presence of of plan plantt oils oils or their derivatives (fatty ac acids)ids) in various compositions of polymeric materials improves their optical (gloss), ph physicalysical (flexibility, (flexibility, adhesion) [7,8], [7,8], and chemical (resistance toto water water and and chemicals) chemicals) properties properties [9]. The [9]. synthesis The synthesis of biobased of biobased monomers monomers from renewable from renewableresources isresources a promising is a platform promising for theplatform synthesis for andthe implementationsynthesis and implementation of new environmentally of new environmentallyfriendly industrial friendly polymer industrial materials polymer [10]. However, materials biomass[10]. However, molecules biomass rarely molecules possess suitable rarely possessreactive suitable functions reactive for radical functions polymerization. for radical polymerization. Indeed, the Indeed, double the bonds double of bonds vegetable of vegetable oils are oilspoorly are reactivepoorly reactive in radical in polymerization. radical polymerization. Therefore, Therefore, synthesizing synthesizing radically radically polymerizable polymerizable biobased biobasedmonomers monomers is a real challengeis a real challenge [11]. It should[11]. It sh beould noted be thatnoted methods that methods for the for synthesis the synthesis of vinyl of vinylmonomers monomers based based on soybean, on soybean, olive, olive, and linseed and linseed oils through oils through plant plant oil direct oil direct transesterification transesterification with withN-(hydroxyethyl)acrylamide N-(hydroxyethyl)acrylamide [10,12 ,[10,12,13]13] has been has recentlybeen recently developed developed along along with methodswith methods of their of theircopolymerization copolymerization [14]. [14]. The The ability ability of of these these plant plant oil-based oil-based monomers monomers (POBMs) (POBMs) toto undergoundergo free radical (co)polymerization(co)polymerization reactions reactions has beenhas confirmedbeen confirmed and demonstrated and demonstrated [12,14,15]. [12,14,15]. The conversion, The conversion,polymerization polymerization rate, and molecular rate, and weight molecular of the polymersweight ofhave the polymers been shown have to dependbeen shown on unsaturation to depend onof theunsaturation plant oil chosen of the forplant POBMs oil chosen synthesis for POBMs [12,14]. synthesis [12,14].

2. Features Features of of Synthesis Synthesis of of Vinyl Vinyl Monomers from Plant Oils Tang etet al. al. [16 ][16] reported report oned the on synthesis the synthesis of N-hydroxyalkylamides of N-hydroxyalkylamides and methacrylate and methacrylate hydrophobic hydrophobicmonomers through monomers the through interaction the ofinteraction plant oil of triglycerides plant oil triglycerides with amino with alcohols amino (Figure alcohols1). (FigureThey developed 1). They developed a new interesting a new interesting approach approach that involves that theinvolves use of the a two-step use of a two-step process. process. In the ﬁrst In thestage, first the interactionstage, the ofinteraction triglycerides of with triglyceride amino alcoholss with with amino the formationalcohols ofwithN-hydroxyalkylamides the formation of Nby-hydroxyalkylamides the amidation reaction: by the amidation reaction:

Figure 1. TransformationTransformation of of triglycerides in in N-hydroxyalkylamides and and methacrylate methacrylate monomers. monomers. Reprinted with permission from [[16].16]. Copy Copyrightright (2015) American Chemical Society.

Aminoalcohols, namely namely ethanolamine ethanolamine (R (R = =H,H, n n= 1),= 1),3-amino-1-propanol 3-amino-1-propanol (R = (R H,= nH, = 2), n =and2), N-methylethanolamineand N-methylethanolamine (R = (R CH= 3CH, n 3=, n1),= were1), were used used as aschemicals chemicals which which enables enables the the synthesis synthesis of of a wide range of new monomers. In the second stage,stage, the corresponding monomers were synthesized by the interactioninteraction betweenbetween N-hydroxyethylamidesN-hydroxyethylamides R’–C(O)–N(R)–(CHR’–C(O)–N(R)–(CH22))nn–CH2OHOH and methacrylic anhydride. In such aa way,way, methacrylate methacrylate monomer monomer CH CH2=2=C(CHC(CH33)–C(O)–O–CH)–C(O)–O–CH22–(CH–(CH22)n–N(R)–C(O)––N(R)–C(O)– (CH2))77–CH=CH–(CH–CH=CH–(CH2)27)–CH7–CH3 based3 based on on high high oleic oleic soybean soybean oil oil was was synthesized. synthesized. A study of free radical polymerization of these monomers revealed that the double bonds in the fatty acidacid chainschains remain remain una unaffectedﬀected during during the the reaction. reaction. The The synthesized synthesized methacrylate methacrylate monomers monomers based basedon high on oleic high soybean oleic soybean oil, depending oil, depending on the nature on the of na theture branches of the inbranches the side in chain, the side have chain, a wide have range a wideof glass range transition of glass temperatures transition temperatures [16]. In further [16]. studies, In further Tang studies, and co-authors Tang and used co-authors more than used twenty more thanamino twenty alcohols amino to establish alcohols the to mechanism establish the of amidation mechanism of plantof amidation oils, in particular of plant high-oleicoils, in particular soybean high-oleicoil [8]. Depending soybean onoil the [8]. nature Depending of the acylon the fatty nature acid of and the amide acyl structures,fatty acid and the polymersamide structures, have a wide the

Molecules 2020, 25, 2990 3 of 19 Molecules 2020, 25, x FOR PEER REVIEW 3 of 19 polymersrange of glass have transition a wide range temperatures of glass – transition from viscoelastic temperatures to thermoplastic – from viscoelastic materials. Theto thermoplastic possibility of materials.controlled The hydrogenation possibility of of cont unsaturatedrolled hydrogenation double bonds of was unsaturated also shown, double which bonds provides was controlalso shown, over whichthermal provides and mechanical control over properties thermal of and polymers mechanical [8]. properties of polymers [8]. On thethe other other hand, hand, Harrison Harrison and Wheelerand Wheeler have shown have forshown the first for time the [17 first] that time the polymerization[17] that the polymerizationrate decreases with rate increasing decreases unsaturation with increasing degree un ofsaturation acrylates containing degree of acyl acrylates moieties containing of unsaturated acyl moietiesfatty acids. of unsaturated They explained fatty that acid thes. They retarding explained of the that polymerization the retarding rate of the and polymerization the low conversion rate and are thedue low to the conversion interaction are ofdue radicals to the withinteraction the mobile of radi hydrogencals with atomsthe mobile in the hydrogen acyl moieties. atoms in This the leads acyl moieties.to the formation This leads of new to allylic the formation radicals of lowof new activity allylic which radicals retards of propagation low activity of polymerwhich retards chains (chainpropagation transfer of reaction,polymer retardationchains (chain of transfer the process) reaction, [17]. retardation of the process) [17]. Through the esterificationesterification reaction of fatty alcoholsalcohols with acryloyl chloride, Chen and Bufkin synthesized a a range range of of acrylates, acrylates, including including linoleyl linoleyl acrylate, acrylate, oleyl oleyl acrylate, acrylate, and andlauryl lauryl acrylate, acrylate, and studiedand studied their their copolymerizability. copolymerizability. They They showed showed that that the the presence presence of of fatty fatty fragments fragments in in acrylate molecules determines their polarity, which leads to alternatingalternating copolymerization with methyl methacrylate [[18].18]. In theirtheir nextnext study study [19 [19],], Chen Chen and and Bufkin Bufkin confirmed confirmed Harrison’s Harrison’s research research results results [17] and [17] showed and showedthat the presencethat the ofpresence fatty acid of moietiesfatty acid in themoieties structure in the of the structure new acrylates of the leadsnew toacrylates a decrease leads in bothto a decreasethe polymerization in both the rate polymerization and polymer molecularrate and polymer weights becausemolecular of chainweights transfer because reactions. of chain Increasing transfer reactions.the content Increasing of unsaturated the content acyl groups of unsaturated in the copolymer acyl groups also reducesin the copolymer its glass transition also reduces temperature. its glass Thetransition authors temperature. suggested the The mechanisms authors suggested for crosslinking the mechanisms acrylate copolymers for crosslinking and studied acrylate their copolymers physical and studied mechanical their properties physical and [19]. mechanical properties [19]. Through amidation amidation of of triglycerides triglycerides with with amino amino alcohols, alcohols, natural natural derivatives derivatives of surfactants of surfactants and lubricantsand lubricants werewere obtained obtained [20]. It [20 was]. It demonstrated was demonstrated that the that high the reactivity high reactivity of the ofvinyl the group vinyl groupof the acrylateof the acrylate monomers monomers based basedon plant on plant oils oilsdeterm determinesines the the course course of of their their polymerization polymerization and copolymerization by a free radical mechanism [[21].21]. Caillol Caillol et et al. [22,23] [22,23] proposed methods for the synthesis ofof a a new new monomer monomer from from cardanol cardanol (Figure (Fig2),ure which 2), iswhich isolated is fromisolated cashew from nuts. cashew Reactivity nuts. Reactivityof the cardanol-based of the cardanol-based monomer in monomer the copolymerization in the copolymerization reactions with reactions the POBMs with wasthe studiedPOBMs [was24]. studied [24].

Figure 2. Structure of cardanol and a cardanol-based monomer.monomer. Adapted from [22]22] with permission from The Royal Society of Chemistry.

Cardanol-based polymerspolymers have have a controlleda controlled ﬂexibility flexibility due due to “internal to “internal plasticization”, plasticization”, which occurswhich occursdue to thedue presence to the presence of a long of side a long chain. side The chain. presence The ofpresence these fragments of these fragments also provides also polymeric provides polymericmaterials basedmaterials on cardanol based withon cardanol hydrophobic with properties.hydrophobic It shouldproperties. be noted It should that cardanol be noted exhibits that cardanolantimicrobial exhibits and antimicrobial anti-thermite and properties anti-thermite and, under properties certain and, conditions, under certain can provide conditions, them can to providecopolymers them based to copolymers on it. It is compatiblebased on it. with It is a compatible wide range with of polymers, a wide range such asof alkyds,polymers, melamines, such as polyesters,alkyds, melamines, etc. [22]. polyesters, etc. [22]. In the study [[23],23], synthetic pathways to molecularmolecular blocks from cardanol by one- or two-stage methods were reported. In particular: 1) 1) dimerization/oligomerization dimerization/oligomerization of of cardanol, cardanol, to increase its functionality; 2)2) synthesis synthesis of reactive of reactive amines byamines thiolene by coupling; thiolene 3) coupling; epoxidation 3) and epoxidation (meth)acrylation and (meth)acrylationof cardanol for the of synthesis cardanol of polymersfor the synthesi and materialss of withpolymers oxirane and or (meth)acrylatematerials with groups. oxirane or (meth)acrylateA feature ofgroups. cardanol-based monomers and polymers is the presence of aromatic fragments and fattyA moieties feature inof theircardanol-based structure at monomers the same time. and polymers The authors is the showed presence that of cardanol-based aromatic fragments polymeric and fatty moieties in their structure at the same time. The authors showed that cardanol-based polymeric

MoleculesMolecules 20202020,, 2525,, 2990x FOR PEER REVIEW 44 ofof 1919 Molecules 2020, 25, x FOR PEER REVIEW 4 of 19 materials have prospective properties for manufacturing coatings, in particular, with enhanced materialsmaterialsmechanical have have and prospective prospectivethermal properties proper properties ties[23]. for for manufacturing manufacturing coatings, coatings, in in particular, particular, with with enhanced enhanced mechanicalmechanicalRecently, and and thermalmethacrylated thermal properties properties ricinoleic [23]. [23]. acid monomer (Figure 3) was synthesized by the esterificationRecently,Recently, reaction methacrylatedmethacrylated of ricinoleic ricinoleic ricinoleic acid acidwith acid monomer 2-hydroxyethyl monomer (Figure (Figure methacrylate3) was synthesized3) was [25]: synthesized by the esteriﬁcation by the esterificationreaction of ricinoleic reaction acidof ricinoleic with 2-hydroxyethyl acid with 2-hydroxyethyl methacrylate methacrylate [25]: [25]: O OOH O OOH OH + O OH HO O + HO

OOH OOH O O O O O

Figure 3. Schematic of synthesis of methacrylated ricinoleic acid monomer. FigureFigure 3. 3. SchematicSchematic of of synthesis synthesis of of methacry methacrylatedlated ricinoleic ricinoleic acid acid monomer. monomer. Other plant oil-based methacrylates have been widely studied in atom transfer radical Other plant oil-based methacrylates have been widely studied in atom transfer radical polymerizationOther plant (ATRP). oil-based A method methacrylates for the ATRP have ofbeen lauryl widely methacrylate studied was in developedatom transfer by Mandal radical et polymerization (ATRP). A method for the ATRP of lauryl methacrylate was developed by Mandal et al. polymerizational. to obtain narrowly (ATRP). distributed A method forpolymers the ATRP with of laurylpredefined methacrylate molecular was weights developed [26]. by Fatty Mandal alcohol et to obtain narrowly distributed polymers with predefined molecular weights [26]. Fatty alcohol al.derived to obtain methacrylates narrowly distributed were used topolymers prepare withwell predefineddefined main molecular chain substituted weights [26].polymethacrylates Fatty alcohol derived methacrylates were used to prepare well defined main chain substituted polymethacrylates by derivedby copper-mediated methacrylates ATRP were [27].used to prepare well defined main chain substituted polymethacrylates copper-mediated ATRP [27]. by copper-mediatedIt should be noted ATRP that [27]. all known methods for the synthesis of monomers from plant oil triglyceridesItIt should should arebe be notedmulti-stage noted that that all alland known known involve methods methods several fo forsteps,r the the synthesis synthesiswhich makes of of monomers monomers their implementation from from plant plant oil oilin triglyceridestriglyceridesindustry more areare challenging. multi-stagemulti-stage and and involve involve several several steps, steps, which which makes makes their implementation their implementation in industry in industrymoreRecently, challenging. more challenging.we developed a one-step process for the synthesis of new vinyl monomers by the directRecently,Recently, transesterification we developeddeveloped reaction aa one-step one-step of plant process process oil triglycerides for for the the synthesis synthesis with N of-(hydroxyethyl)acrylamide newof new vinyl vinyl monomers monomers by the by(Figure direct the N directtransesterification4) [13,28]. transesterification reaction reaction of plant of oil plant triglycerides oil triglycerides with -(hydroxyethyl)acrylamide with N-(hydroxyethyl)acrylamide (Figure4 )[(Figure13,28]. 4) [13,28]. O O H2C OC R1 H2C OH O O O O H2C OC R1 H2C OH O O H C CHO C NH CH CH O O R HC O C R2 + 3 H2C CH C NH CH2 CH2 OH HC OH + 3 2 2 2 C O H C CH C NH CH CH O R HC O C R2 + 3 H2C CH C NH CH2 CH2 OH HC OH + 3 2 2 2 C O H C OH H2C O CR3 2 H C OH H2C O CR3 2 FigureFigure 4. Schematic of of synthesis synthesis of of acrylic acrylic monomers monomers based based on on plant plant oil oil triglycerides triglycerides where where R1 R, R1,R2, R23, Figure 4. Schematic of synthesis of acrylic monomers based on plant oil triglycerides where R1, R2, R3 Rare3 are saturated saturated and and unsaturated unsaturated fatty fatty acid acid chains chains wi withth one one or or several several double bonds. Reprinted withwith arepermissionpermission saturated fromfrom and [ [10].10unsaturated]. Copyright fatty (2015)(2015) acid AmericanAmerican chains wi ChemicalChemicalth one or Society.Society. several double bonds. Reprinted with permission from [10]. Copyright (2015) American Chemical Society. UsingUsing thisthis process, process, a range a ofrange POBMs of wasPOBMs synthesized was synthesized [10,12]. In the [10,12]. reaction, InN -(hydroxyethyl)the reaction, acrylamideN-(hydroxyethyl)acrylamideUsing canthis beprocess, considered a ascanrange an be alcohol ofconsidered POBMs ROH – whereaswas an thesynthesizedalcohol unsaturated ROH [10,12].– fragment where In theCHthe 2unsaturated= CH–C(O)–reaction, NNH–CHfragment-(hydroxyethyl)acrylamide2 –CHCH22=CH–C(O)–NH–CH– is a residue can –R. be2 Upon–CH considered2– theis a alcoholysisresidue as an–R. alcohol Upon (transesterification), the ROH alcoholysis – where a(transesterification), residuethe unsaturated exchange fragmentbetweena residue CH theexchange2=CH–C(O)–NH–CH triglyceride between and theN2 -(hydroxyethyl)acrylamide–CHtriglyceride2– is a residue and N –R.-(hydroxyethyl)acrylamide Upon occurs the alcoholysis leading to(transesterification), occurs formation leading of the to acorrespondingformation residue exchange of the monomers. corresponding between the monomers. triglyceride and N-(hydroxyethyl)acrylamide occurs leading to formationTheThe POBMsPOBMsof the corresponding synthesissynthesis waswas monomers. conductedconducted inin THFTHF withwith anan excessexcess ofof NN-(hydroxyethyl)acrylamide-(hydroxyethyl)acrylamide (molar(molarThe ratioratio POBMs ofof NN synthesis-(hydroxyethyl)acrylamide-(hydroxyethyl)acrylamide was conducted in totoTHF triglyceridetriglyceride with an excess asas 5.9:5.9: of1) N in-(hydroxyethyl)acrylamide orderorder toto achieveachieve completecomplete (molartransesterificationtransesterification ratio of N-(hydroxyethyl)acrylamide of of the the triglycerides. triglycerides. The The yieldto yield triglyceride of the of thedesired desiredas 5.9: monomers 1) monomers in order was to was aboutachieve about 94–96%. complete 94–96%. The transesterificationThereaction reaction by-product by-product of (glycerol)the (glycerol)triglycerides. and and the The theexcessive excessiveyield Nof-(hydroxyethyl)acrylamide theN-(hydroxyethyl)acrylamide desired monomers was are about areeasily easily 94–96%. removed removed The by reactionbywashing washing by-product with with brine brine (glycerol) after after diluting diluting and the the excessivereaction reaction mixtures mixturesN-(hydroxyethyl)acrylamide with with CH CH2ClCl22. .The The POBMs POBMs are easily sparingly sparingly removed soluble by washinginin waterwater with remainremain brine inin thetheafter organicorganic diluting phase.phase. the reaction To avoidavoid mixtures freefree radicalradical with polymerization,polymerization, CH2Cl2. The POBMs 2,6-di-2,6-di- tertsparinglytert-butyl-p-cresol-butyl-p-cresol soluble in(0.05(0.05 water toto 0.1%0.1%remain byby in weight)weight) the organic waswas addedadded phase. asas To anan avoid inhibitorinhibitor free totoradical thethe reactionreaction polymerization, mixturesmixtures prior2,6-di-prior thethetert synthesis.synthesis.-butyl-p-cresol (0.05 toUponUpon 0.1% thethe by alcoholysis weight)alcoholysis was of of oliveadded olive oil as withoil an withinhibitorN-(hydroxyethyl)acrylamide, N-(hydroxyethyl)acrylamide, to the reaction mixtures 2-N -acryloylaminoethylprior 2-N -acryloylaminoethylthe synthesis. oleate CHoleate2Upon=CH–C(O)–NH–CH CH the2=CH–C(O)–NH–CH alcoholysis2CH of 2olive–O–C(O)–(CH2CH oil2–O–C(O)–(CH with 2N)7-(hydroxyethyl)acrylamide,–CH=2)CH–(CH7–CH=CH–(CH2)7–CH23)7is–CH predominantly 2-3 N -acryloylaminoethylis predominantly formed. oleateformed. CH 2=CH–C(O)–NH–CH2CH2–O–C(O)–(CH2)7–CH=CH–(CH2)7–CH3 is predominantly formed.

Molecules 2020, 25, 2990 5 of 19 Molecules 2020, 25, x FOR PEER REVIEW 5 of 19

ThisThis monomer monomer contains contains one one double double bond bond in in the the acryloylamide acryloylamide moiety moiety and and one one double double bond bond in thein thefatty fatty acid acid chain. chain. Such Such a structure, a structure, in incomparison comparison with with the the so soybeanybean oil-based oil-based monomer 2-2-NN-acryloylaminoethyl-acryloylaminoethyl linoleatelinoleate (CH(CH2=CH–C(O)–NH–CH2=CH–C(O)–NH–CH2CH2CH2–O–C(O)–(CH2–O–C(O)–(CH22))77–CH–CH=CH–CH=CH–CH22–– CH=CH–CHCH=CH–CH22–(CH–(CH2)23)–CH3–CH3)3 reduces) reduces the the extent extent of of th thee chain chain transfer transfer reaction. reaction. Accordingly, Accordingly, fewer fewer less less activeactive radicals radicals are are formed formed and and the the polymerization polymerization re reactionaction proceeds to higher conversion with a a less less pronounced retardation retardation effect. effect. This This leads leads to to the the fo formationrmation of of polymers (cop (copolymers)olymers) with with a a higher molecularmolecular weight and a lower polydispersity index. TheThe composition composition of of plant plant oils oils is is known known to to depend depend on on the the type type of of crop raw material. Therefore, Therefore, anan importantimportant stepstep was was to determineto determine the contentthe content of di ffoferent different fatty acid fatty chains acid in chains the mixture in the of mixture monomers of monomersobtained upon obtained the transesterification upon the transesterification of olive oil of with oliveN-(hydroxyethyl)acrylamide. oil with N-(hydroxyethyl)acrylamide. The content The of contentfatty acid of chains fatty inacid the chains oil was in determined the oil was from determined the integral from intensities the integral of the characteristic intensities protonof the characteristicsignals of each proton fatty acid signals chain andof each glycerol fatty fragments acid chain using and1H-NMR glycerol spectroscopy fragments of using the plant 1H-NMR oil [29] spectroscopy(Figure5). of the plant oil [29] (Figure 5).

triglyceride В D fragm ents of saturated fatty acids O CH2 CH2 CH2 CH3 R n O 1 В D С С oleic R2 O CH2 CH2 CH2 CH2 CH CH CH2 CH2 CH3 O R 4 6 linoleic O В D С А С F CH2 CH2 CH2 CH2 CH CH CH2 CH CH CH2 CH2 CH3 4 3 R3 O В D С АА С Е CH2 CH2 CH2 CH CH CH CH CH CH CH CH CH CH CH 4 2 2 2 2 3 linolenic

В С α α D β А E

654321 δ, ppm FigureFigure 5. 11H-NMRH-NMR spectrum spectrum of of olive oil. Adapted Adapted with with permission permission from [12]. [12]. Copyright Copyright (2016) (2016) American Chemical Society.

TheThe content of the linolenic acid units (linolenate) in olive oil was calculated by measuring the integralintegral valuevalue ofof the the signal signal at at 1 ppm, 1 ppm, which which corresponds corresponds to the to protons the protons of the methylof the methyl group in group a linolenic in a linolenicacid chain acid (signal chain E (signal in Figure E in5). Figure Taking 5). into Taking account into only account one ofonly the one signals of the of signalsα-protons of α-protons of glycerol, of glycerol,i.e., the signal i.e., the at 4.27 signal ppm at (Figure 4.27 ppm5), the (Figure ratio of5), the the integral ratio of values the integral is two α values-glycerol is protonstwo α-glycerol to three protons ofto thethree linolenic protons acid of methyl the linolenic group. acid It should methyl be keptgroup. in mind It should that three be kept linolenic in mind acid that chains three can linolenicundergo acid transesterification chains can undergo in the transesterification same glycerol molecule. in the same A field glycerol correction molecule. factor A is field the ratio correction of two factorprotons is ofthe glycerol ratio of to two nine protons protons of of glycerol the linolenic to nine acid protons methyl of groups. the linolenic By converting acid methyl the ratio groups. of these By convertingareas to percentages, the ratio of a these ratio ofareas 22.2% to percentages, glycerol to 100% a ratio linolenic of 22.2% acid glycerol was obtained to 100% [linolenic29]. Calibration acid was of obtainedthe integral [29]. value Calibration of one of of the the glycerol integralα value-proton of signalsone of the to theglycerol value α in-proton the 1H-NMR signals spectrum to the value in the in thesignal 1H-NMR region spectrum at 0.98 ppm in the directly signal gives region the at percentage 0.98 ppm directly of linolenic gives acid the in percentage the sample of linolenic0.73%. acid − in theThe sample percentage −0.73%. of linoleic acid chains (linoleates) in olive oil was determined from the ratio of the integralThe percentage value of of the linoleic signal acid at ~2.74 chains ppm, (linoleates) which corresponds in olive oil towas the determined methylene protonsfrom the between ratio of thetwo integral double value bonds of (signal the signal A in Figureat ~2.745), ppm, to the wh integralich corresponds value of one to the of glycerol methyleneα-protons. protons Thebetween field twocorrection double factor bonds (33.3) (signal is the A ratioin Figure of two 5), glycerol to the integral protons value to six of possible one of methylene glycerol α protons-protons. in The linoleate. field correctionThe amount factor of linoleic (33.3) acid is the is calculated ratio of two by subtracting glycerol protons the twiced to contentsix possible of linolenic methylene acid, determinedprotons in linoleate.from the peakThe amount at 2.74 ppmof linoleic [26]. acid is calculated by subtracting the twiced content of linolenic acid, determinedThe percentage from the ofpeak oleic at acid2.74 chainsppm [26]. (oleates) was determined from the ratio of the integral value of theThe signal percentage at ~2.02 of ppm, oleic which acid chains corresponds (oleates) to was the protonsdetermined in the fromα-position the ratio to of the the double integral bond value of ofall the unsaturated signal at ~2.02 fatty ppm, acids which (signal corresponds C in Figure 5to), the to theprotons integral in the value α-position of one ofto glycerolthe doubleα-protons. bond of all unsaturated fatty acids (signal C in Figure 5), to the integral value of one of glycerol α-protons. Accordingly, the ratio of two glycerol protons to twelve possible protons in the α-position to the

Molecules 2020, 25, 2990 6 of 19

Accordingly, the ratio of two glycerol protons to twelve possible protons in the α-position to the double bond of all unsaturated fatty acids is the ﬁeld correction factor equal to 16.7. The percentage of oleic acid was calculated by subtracting the content of unsaturated linolenic and linoleic acid chains from the determined value [29]. The content of saturated fatty acid chains was determined from the fact that the total content of fatty acids is 100%, and the amount of unsaturated fatty acid chains was subtracted from 100%. The determined content of fatty acid chains is given in Table1. These data are in a good agreement with the literature data obtained by gas chromatography of olive oil [30].

Table 1. Content of fatty acid chains in olive oil.

Field Correction Factor Content of Fatty Acids in the Oil, % Fatty Acid Signal (Protons) Chains % Calculated Literature data Linolenate 0.95–1.05 ppm 2H/9H 22.2 0.73 <1% (E) (-CH3) Linoleate 2.75–2.85 ppm 2H/6H 33.3 8.06 2 0.73 = 6.6 3.5–21 (A) (-CH=CH-CH2-CH=CH-) − · Oleate 1.97-2.11 ppm 2H/12H 16.7 87.56 (0.73 + 6.6) = 80.23 55–83% (C) (-CH2-CH=CH-CH2-) − Content of saturated fatty acid chains: 100 (0.73 + 6.6 + 80.23) = 12.44 1–20% −

Thus, according to 1H-NMR spectroscopy, the olive oil triglycerides include: saturated fatty acid chains (C18:0) 12.44%; oleic acid chains (C18:1) 80.23%; linoleic acid chains (C18:2) 6.60%; − − − and linolenic acid chains (C18:3) 0.73%. − These results are consistent with the literature data obtained by gas chromatography of olive oil, where the saturated chains make up 1–20%, oleic acid chains 55–83%, linoleic acid chains 3.5–21%, and linolenic acid chains less than 1% [31]. Using this approach, monomers based on various plant oils were successfully synthesized and characterized (Table2).

Table 2. Physico-chemical characteristics of POBMs.

Content of Unsaturated Fatty Acids, % Iodine Value Molar Mass, Monomer from Oil (Same for Oil), g/g g/mol C18:1 C18:2 C18:3 High Oleic Sunﬂower 86–89 3–6 0.5–1 105 (82) 379.0 1 Oil (HOSFM) Olive Oil (OVM) 65–85 3.5–20 0–1.5 110 (90) 379.3 2 High Oleic Soybean Oil 70–73 13–16 0–1 124(105) 379.3 2 (HOSBM) Canola Oil (CLM) 60–63 18–20 8–10 137 (96) 379.0 2 Corn Oil (COBM) 23–31 49–62 0–2 139 (120) 377.0 1 Sunﬂower Oil (SFM) 14–35 44–75 0–1 146 (128) 377.5 2 Soybean Oil (SBM) 22–34 43–56 7–10 149 (139) 377.3 2 Linseed Oil (LSM) 12–34 17–24 35–60 194 (177) 375.6 1 1 Calculated. 2 Experimental.

The monomer structure was conﬁrmed by FTIR and 1H-NMR spectroscopy [12]. A 1H-NMR spectrum of the olive oil-based monomer is shown in Figure6. Similar spectra are recorded for other POBMs, which conﬁrms the presence of the acryloylamide moiety in their molecules. This allows for predicting similar reactivity of the vinyl group in the monomers acryloylamide moiety in the radical polymerization [12]. Molecules 2020, 25, 2990 7 of 19 MoleculesMolecules 2020 2020, ,25 25, ,x x FOR FOR PEER PEER REVIEW REVIEW 77 of of 19 19

(D)(D) LL HH (C)(C) OO (B)(B) (F)(F) (K)(K) (L)(L) HH CC NHNH CC CHCH33 CC CC OO (G)(G) (I)(I) (J)(J) (J)(J) (L)(L) (M)(M) (A)(A)HH OO (E)(E) MM

II FF GG EE JJ AABB DD KK CC HH

654321654321 δ,δ, ppmppm FigureFigure 6.6. 11H-NMRH-NMR spectrum spectrum of of the thethe olive olive oil-based oil-based mono monomer.monomer.mer. Adapted Adapted with with permission permission from from [12]. [[12].12]. CopyrightCopyright (2016)(2016) AmericanAmerican ChemicalChemical Society.Society.

TheThe FTIRFTIR spectroscopyspectroscopy data data indicate indicate the the additionaddition of of fattyfatty acidacid acylacyl moietiesmoieties toto thethe acrylamideacrylamide fragmentfragment (e.g.,((e.g.e.g.,, for forfor the thethe olive olive monomer—Figuremonomer—Figure 7 7).7).). FTIRFTIRFTIR spectraspectraspectra of ofof monomers monomersmonomers based basedbased on onon other otherother plant plantplant oilsoils areare prettypretty similar.similar.similar. Hence, Hence, the the synthesized synthesized PO POBMsPOBMsBMs can can be be attributedattributed to to thethe conventionalconventional vinylvinyl monomersmonomers becausebecausebecause the thethe acryloylamide acryloylamideacryloylamide moiety moietymoiety provides providesprovides the thethe participation participationparticipation of these ofof thesethese monomers monomersmonomers in the inin free thethe radicalfreefree radicalradical polymerization. polymerization.polymerization.

νν(NH)(NH) n(C-CO-O)n(C-CO-O) n(=CH,CHn(=CH,CH)) 22 esterester alkenealkene n(O=C-O-C)n(O=C-O-C)

esterester n(C=O)n(C=O) n(C=C)n(C=C) esterester δδ(N-H)(N-H) n(CHn(CH)) 22 n(C=O)n(C=O) amideamide IIII alkanealkane amideamide II

40004000 3500 3500 3000 3000 2500 2500 2000 2000 1500 1500 1000 1000 500 500 -1-1 WavenumberWavenumber (cm(cm )) FigureFigure 7.7.7.FTIR FTIRFTIR spectrum spectrumspectrum of theofof olivethethe oliveolive oil-based oil-basedoil-based monomer. monomono Adaptedmer.mer. AdaptedAdapted with permission withwith permissionpermission from [12]. from Copyrightfrom [12].[12]. (2016)CopyrightCopyright American (2016)(2016) Chemical AmericanAmerican Society. ChemicalChemical Society.Society.

TheThe contentcontent ofof fattyfatty acidacid chainschains inin thethe monomermonomer mixturemixture producedproduced byby thethe transesterificationtransesterificationtransesterification ofof plantplant oilsoils withwith NN-(hydroxyethyl)acrylamide-(hydroxyethyl)acrylamide was was determined determined on onon the the example example of of thethe oliveolive monomermonomer 1 byby calculatingcalculating the the ratioratio ofof thethe integralintegral valuesvalues inin thethe 11H-NMRH-NMR spectra spectra of of the the commercialcommercial oiloil andand thethe resultingresulting monomermonomer mixturemimixturexture (Figure(Figure(Figure8 8).).8). 1 AccordingAccording toto thethe 11H-NMRH-NMR spectroscopy spectroscopy data,data, thethe monomermonomer mixturemixture consistsconsists of:of: saturatedsaturated fattyfatty acid chains (C18:0) 11.47% (stearic and palmitic); oleic acid chains (C18:1) 81.9%; linoleic acid chains acidacid chainschains (C18:0)(C18:0)− −−11.47%11.47% (stearic(stearic andand palmitic);palmitic); oleicoleic acidacid chainschains (C18:1)(C18:1)− −−81.9%;81.9%; linoleiclinoleic acidacid (C18:2) 5.9%; and linolenic acid chains (C18:3) 0.73% after the olive oil transesterification. chainschains (C18:2)(C18:2)− −−5.9%;5.9%; andand linoleniclinolenic acidacid chainschains (C18:3)(C18:3)− −−0.73%0.73% afterafter thethe oliveolive oiloil transesteritransesterifification.cation. Thus,Thus, thethe majormajor componentcomponent ofof thethe oliveolive monomermonomer isis aa monomer monomer with with oleic oleic acid acid chains chains (81.9%) (81.9%)(81.9%) – – 2-2-NN-acryloylaminoethyl-acryloylaminoethyl oleate. oleate.oleate. The TheThe soybean soybeansoybean monomer monomemonome isrr mainly isis mainlymainly a monomer aa monomermonomer with linoleicwithwith linoleiclinoleic acid chains acidacid chainschains (57.5%)(57.5%) –– 2-2-NN-acryloylaminoethyl-acryloylaminoethyl linoleatelinoleate whereaswhereas thethe linseedlinseed monomermonomer predominantlypredominantly consistsconsists ofof aa monomermonomer withwith linoleniclinolenic acidacid chainschains (58%)(58%) –– 2-2-NN-acryloylaminoethyl-acryloylaminoethyl linolenate.linolenate.

Molecules 2020, 25, 2990 8 of 19

(57.5%) – 2-N-acryloylaminoethyl linoleate whereas the linseed monomer predominantly consists of a monomer with linolenic acid chains (58%) – 2-N-acryloylaminoethyl linolenate. Molecules 2020,, 25,, xx FORFOR PEERPEER REVIEWREVIEW 8 of 19

Monomer Monomer 3.00

4.00 0.16 0.04

Olive oil 3.00

3.92 0.04 0.18 0.04

321 δ, ppmppm

11 Figure 8. 1HH NMR NMR spectra spectra of of the the olive olive oil oil and and the the olive olive oil-based oil-based monomer. monomer.

One of the most important characteristics of mono monomersmers is the degree of unsaturation, which for POBMs is determined by the number of the double bonds in the fattyfatty acidacid chains.chains. To To compare the monomers in terms of the unsaturation degree, th theireir iodine values were determineddetermined and compared with thosethose for for the the corresponding corresponding plant plant oils oils used used for the forfor synthesis thethe synthesissynthesis of the POBMsofof thethe POBMsPOBMs (Table2 ). (Table(Table The obtained 2).2). TheThe obtainedresults show results that show the iodine that the value iodine for the value monomers for the monomers is higher than is higher those for than the those oils, duefor the to the oils, presence due to theofthe an presencepresence unsaturated ofof anan acryloylamide unsaturatedunsaturated moiety.acryloylamideacryloylamide Depending moiemoie onty.ty. the DependingDepending type of oil, onon the thethe iodine typetype valuesofof oil,oil, forthethevarious iodineiodine valuesmonomers for various differ. monomers For instance, differ. the iodineFor instance, value forthe 2-iodineN-acryloylaminoethyl value for 2-N-acryloylaminoethyl-acryloylaminoethyl oleate (110 g/100 oleateoleate g) is (110significantly(110 g/100g/100 g)g) is loweris significantlysignificantly than that lowerlower for 2- thanthanN-acryloylaminoethyl thatthat forfor 2-2-N-acryloylaminoethyl-acryloylaminoethyl linoleate (149 linoleatelinoleate g/100 g) due(149(149 tog/100g/100 the g)g) di ffduedueerent toto theunsaturationthe differentdifferent unsaturationunsaturation degree of the degreedegree molecules. ofof thethe Besides molecules.molecules. the acryloylamide BesidesBesides thethe acryloylamideacryloylamide moiety, there aremoiety,moiety, two doubletherethere areare bonds twotwo doublein the fatty bonds acid in chain the fatty of the acid soybean chain monomer of the soybean molecule monomer [10]. The molecule low solubility [10]. The of these low monomerssolubility of in waterthesethese monomersmonomers implies their inin highlywaterwater impliesimplies hydrophobic theitheir highly nature hydropho [12]. bic nature [12]. Analysis of the data obtained from the synthesissynthesis and characterizationcharacterization of plant oil-based acrylic monomers allows for drawingdrawing thethe POBMPOBM generalgeneral formulaformula (Figure(Figure9 9)) as: as:

Figure 9. General formula of the plant oil-based monomers. Reprinted from [32]. Copyright (2018), Figure 9. General formula of the plant oil-based monomers. Reprinted from [32]. Copyright (2018), with permission from Elsevier. with permission from Elsevier. 3. Features of Homo- and Copolymerization of Plant Oil-Based Acrylic Monomers The reactivity of the POBMs in the free radical polymerization reactions (chain growth reaction) isis determineddetermined byby thethe presencepresence ofof anan acryloylamideacryloylamide moietymoiety containingcontaining aa vinylvinyl groupgroup whichwhich isis common for all monomers. However, the POBMs contain a certain amount of unsaturated fatty acid chains of various structures (the different numbers of both double bonds and hydrogen atoms in the α-position-position toto thethe doubledouble bonds).bonds). ThisThis causescauses thethe monomersmonomers toto participateparticipate inin chainchain transfertransfer reactionsreactions

Molecules 2020, 25, 2990 9 of 19

3. Features of Homo- and Copolymerization of Plant Oil-Based Acrylic Monomers The reactivity of the POBMs in the free radical polymerization reactions (chain growth reaction) is determined by the presence of an acryloylamide moiety containing a vinyl group which is common for all monomers. However, the POBMs contain a certain amount of unsaturated fatty acid chains of various structures (the different numbers of both double bonds and hydrogen atoms in the α-position to the double bonds). This causes the monomers to participate in chain transfer reactions due to the abstraction of the allylic hydrogen atoms and the formation of less active radicals. Hence, the monomer chain transfer constants CM clearly depend on monomer structure as follows: 0.033 (most unsaturated LSM) > 0.026 (SBM) > 0.023 (SFM) > 0.015 (least unsaturated OVM) with respect to decreasing number of C H groups in the α-position of the fatty acid double bonds) [12]. This impacts the polymerization − conversion and molecular weights of the resulting polymers (copolymers) from the POBMs. The features of homopolymerization kinetics for 2-N-acryloylaminoethyl oleate revealed that the orders of reaction with respect to monomer and initiator are 1.06 and 1.2, respectively. The unsaturation degree of fatty acid chains in the POBM molecules was used as a criterion for comparing the kinetic data of homopolymerization of 2-N-acryloylaminoethyl oleate and 2-N-acryloylaminoethyl linoleate. The observed deviations of the orders of reaction are due to the specific mechanism of the homopolymerization reaction of 2-N-acryloylaminoethyl oleate which includes two simultaneous reactions (chain propagation and transfer) [12]. Although the propagating radicals might be very reactive, once the chain is transferred to the allylic C H, the newly formed radical becomes more − stable due to resonance stabilization and does not readily initiate new chains. In comparison with the soybean monomer, the olive monomer is less involved into the chain transfer reactions (the chain transfer constant CM = 0.015 for OVM while for SBM CM = 0.026). As a result, the homopolymerization of the olive monomer occurs at a higher rate of 12.2–45.3 10 5 mol/(L s) when compared with the more · − · unsaturated soybean monomer 4.3 11.3 10 5 mol/(L s). The molecular weights of the homopolymers − − · − · were determined by gel permeation chromatography. The resulting homopolymers from OVM have higher number average molecular weights (16 800–23 200 g/mol for 2-N-acryloylaminoethyl oleate compared to 13 600–14 300 g/mol for 2-N-acryloylaminoethyl linoleate). The reactivity of the POBMs in chain copolymerization was studied in their reactions with styrene and vinyl acetate. A characteristic feature of the POBMs is the presence of the acryloylamide fragment (CH2=CH–C(O)–NH–CH2–CH2–) in their structure, which determines the monomer reactivity in copolymerization. The composition of the copolymers was determined from 1H-NMR spectroscopy data. Radical copolymerization of the plant oil-based monomers is described with the classical Mayo–Lewis equation. The Alfrey Price Q (0.41–0.51) and e (0.09–0.28) parameters are close for all − POBMs and do not essentially depend on the monomer structure [13]. This is due to the presence of the same acryloylamide moiety in the POBM molecules which determines the monomer reactivity in polymerization reactions. The features of copolymerization are determined by the structure of monomers based on plant oil triglycerides along with the degradative chain transfer by formation of less active radicals. Nevertheless, the growth of macrochains can be described with the conventional features of chain copolymerization, yielding copolymers with a potential to be used in a broad variety of applications. Vinyl monomers from plant oils that have different degrees of unsaturation, soybean, and olive oils, were copolymerized in emulsion with styrene to investigate the kinetics features and feasibility of latex formation. The kinetics of emulsion copolymerization of styrene with the olive and soybean monomers agree with the Smith-Ewart theory since the number of nucleated latex particles is proportional to the surfactant and initiator concentration to the powers 0.58–0.64 and 0.39–0.46, respectively [33]. Copolymerization of styrene with POBMs follows the typical phenomenology for emulsion polymerization of hydrophobic monomers with a micellar nucleation mechanism. When the POBMs were copolymerized in emulsion with significantly more water soluble comonomers, methyl methacrylate and vinyl acetate, latex particle nucleation mainly occurred through homogeneous mode. For the emulsion copolymerization of methyl methacrylate with OVM and SBM, the reaction orders Molecules 2020, 25, 2990 10 of 19 with respect to emulsifier and initiator are 0.33–0.67 and 0.56–0.69, respectively. It was shown that upon adding the highly hydrophobic POBMs into the monomer mixture, the latex polymer particles originating from micellar nucleation essentially increases [15]. Using emulsion and miniemulsion copolymerization of the olive and soybean monomers with styrene or methyl methacrylate, stable aqueous dispersions of polymers with latex particle sizes of 40–210 nm were produced. The content of the POBM units in the macromolecules of the latex polymers is 5–60 wt.%. The average molecular weight of the synthesized polymers varies in the range of 30,000–391,500. It was found that the molecular weight of the latex copolymers decreases with increasing unsaturation degree of the POBMs and their content in the reaction mixture, which is explained by degradative chain transfer to unsaturated fatty acid chains [15,33]. An analysis of the literature shows a rapid development of a new branch in polymer science related to the chemistry of aliphatic and aromatic biobased monomers obtained from renewable plant sources. The synthesis of such monomers allows for producing fully biobased polymers with biocompatible and biodegradable properties which do not pollute the environment. Copolymerization of monomers synthesized from various plant oils, which have different unsaturation, enables formation of copolymers with side branches of the macrochain with different unsaturation degrees. A large variety of the POBMs allows to synthesize polymers having moieties with different unsaturation and to make coatings with adjustable cross-linking degree thereof, including latex copolymers from fully biobased monomer mixtures [24]. Remarkably, copolymerization of the POBMs with commercial vinyl monomers enables synthesis of polymers with enhanced hydrophobicity along with the mechanism of internal plasticization. Synthesized latex polymers and copolymers are prospective candidates for the formation of moisture-/water-resistant polymer coatings with controlled physical and mechanical properties using controlled content of incorporated POBM units with different unsaturation in the latex structure.

4. Preparation of Polymeric Coatings from Plant Oil-Based Monomers As shown by Solomon [34], both crude and modified plant oils are common film-forming materials for the production of paints and varnishes. Despite the emergence of various synthetic polymers based on vinyl and acrylic monomers, crude plant oils are still the basis of some paints for painting the roofs of houses and other outdoor objects. One of the disadvantages of such materials is the slow drying and relatively low moisture resistance. The synthesis of plant oil-based acrylic monomers opens new avenues for producing homo- and copolymers thereof with adjustable physical and mechanical properties (e.g., flexibility, strength, etc.) due to formation of three-dimensional networks with controlled cross-linking density. The development of such coatings was shown to be carried out through oxidative cross-linking of the polymer network [35]. It should be noted that upon POBM application for the synthesis of latex polymers as highly hydrophobic film-forming protective coatings, they form three-dimensional networks with adjustable cross-linking density through the oxidative cross-linking mechanism. Triglycerides of linseed oil contain about 52% of linolenic (cis,cis,cis-9,12,15-octadecatrienoic) acid chains which have three isolated carbon-carbon double bonds in their structure (Figure 10). Other fatty acids in linseed oil are oleic (cis-9-octadecenoic, 22%) and linoleic (cis,cis-9,12-octadecadienoic, 16%) acids. Hence, linolenate is a major constituent of LSM. Oxidative cross-linking of the LSM-based copolymers is a free radical chain process consisting of chain initiation, propagation, and termination steps. Initiation, i.e., the formation of a fatty acid chain radical, can occur by thermal homolytic cleavage of a C–H bond or by a hydrogen atom abstraction from C–H by an initiator free radical. The bond dissociation energy of a bisallylic hydrogen is approximately 42 kJ/mol lower than that of an allylic hydrogen. As a result, linoleates and linolenates are more readily autooxidized and cross-linked in comparison with oleates. Hydrogen atom abstraction from C-11 or C-13 of the linolenate moiety leads to pentadienyl radicals I and II (Figure 10). Subsequent oxygen addition to radicals I and II generates peroxyl radicals Molecules 2020, 25, x FOR PEER REVIEW 11 of 19

CH2 CH CH2 CH CH2 CH Molecules 2020, 25CO, 2990 CO CO 11 of 19 NH NH NH O2 O2 which are able of abstracting a hydrogenΔ atom from a donorΔ such as another linolenate moiety to form conjugatedOtrans,cis-hydroperoxides I–IVO (Figure 10). The hydroperoxidesO undergo decomposition CO CO CO reaction (Figure 11). TheCH last3 three reactions lead to cross-linkingCH3 of the macromoleculesCH3 and formation of a polymer(CH network.2)7 (CH2)7 (CH2)7 Molecules 2020, 25, x FOR PEER REVIEW 11 of 19 . . CH2 CH CH2 CH CH2 CH pentadienyl radical I pentadienyl radical II CO LSMCO unit in CO macromolecule NH NH NH O2 O2 + O , + RH; - R. + O , + RH; - R. 2 Δ Δ 2

O O O

CH2 CH CO CHCH3 2 CH CO CH3CH2 CH CO CHCH32 CH CO(CH2)7 CO (CH2)7 CO(CH2)7 CO NH NH NH NH . .

pentadienyl radical ILSM unit in pentadienyl radical II O O macromolecule O O

CO CH3 . CO CH3 CO CH3 . CO CH3 + O2, + RH; - R + O2, + RH; - R (CH2)7 (CH2)7 (CH2)7 (CH2)7 HOO OOH

CH2 CH CH2 CH CH2 CH CH2 CH CO CO CO CO hydroperoxide I hydroperoxide IV NH NH OOH HOONH NH hydroperoxide II hydroperoxide III Figure 10. Formation of radicals and hydroperoxides during oxidative cross-linking of polymers O O O O from linseed oil-based monomer (LSM). CO CH3 CO CH3 CO CH3 CO CH3 (CH2)7 (CH2)7 (CH2)7 (CH2)7 HOOHydrogen atom abstraction from C-11 or C-13 of the linolenate moiety leads to pentadienylOOH radicals I and II (Figure 10). Subsequent oxygen addition to radicals I and II generates peroxyl

radicals whichhydroperoxide are able I of abstractingOOH a hydrogen atom fromHOO a donor such ashydroperoxide another IVlinolenate moiety to form conjugated trans,cishydroperoxide-hydroperoxides II I–IV (Figurehydroperoxide 10). III The hydroperoxides undergo decomposition reaction (Figure 11). The last three reactions lead to cross-linking of the FigureFigure 10. 10.Formation Formation of radicalsof radicals and and hydroperoxides hydroperoxides during during oxidative oxidative cross-linking cross-linking of polymersof polymers from macromolecules and formation of a polymer network. linseedfrom oil-basedlinseed oil-based monomer monomer (LSM). (LSM).

Hydrogen atom abstraction from C-11 or C-13 of the linolenate moiety leads to pentadienyl ROOH RO.. + OH radicals I and II (Figure 10). Subsequent.. oxygen addition to radicals I and II generates peroxyl radicals which2ROOH are able of abstractingRO + a ROOhydrogen + Hatom2O from a donor such as another linolenate moiety to form conjugated trans,cis-hydroperoxides.. I–IV (Figure 10). The hydroperoxides undergo ROOH + RH RO + R + H2O decomposition .reaction (Figure 11). The last three reactions lead to cross-linking of the macromoleculesRO and + formationR'H of a polymerROH + network. R'. . . RH + OH R + H2O ROOH RO.. + OH R.. + R RR 2ROOH RO.. + ROO + H O RO. + R. ROR 2 ROOH + RH RO.. + R + H O RO.. + RO ROOR 2 RO. + R'H ROH + R'. where RH. and R'H are unaltered. fatty acid chains in macromolecules RH + OH R + H2O Figure 11.11. Oxidative cross-linking of polymers fromfrom linseedlinseed oil-basedoil-based monomermonomer (LSM).(LSM). R.. + R RR TheThe mainmain mechanicalmechanicalRO. + R. characteristicscharacteristicsROR of ﬁlmsfilms fromfrom latexlatex polymerspolymers basedbased onon styrenestyrene oror methylmethyl methacrylatemethacrylate andand thethe POBMsPOBMs werewere determined.determined. TheThe compositioncomposition ofof thethe copolymerscopolymers waswas calculatedcalculated RO.. + RO ROOR fromfrom thethe 11H-NMR spectroscopy data.data. The content of the olive and soybean monomers in the reaction mixturemixture variedvaried fromfromwhere 1010 toRHto 4040 and wt.wt. R'H % forare copolymers unaltered fatty withwith acid methylmethyl chains methacrylatemethacrylate in macromolecules andand fromfrom 2525 toto 6060 wt.wt. % for copolymersFigure with 11. styrene. Oxidative A plasticizingcross-linking of eﬀ polymersect and enhancedfrom linseed hydrophobicity oil-based monomer were (LSM). observed for the

The main mechanical characteristics of films from latex polymers based on styrene or methyl methacrylate and the POBMs were determined. The composition of the copolymers was calculated from the 1H-NMR spectroscopy data. The content of the olive and soybean monomers in the reaction mixture varied from 10 to 40 wt. % for copolymers with methyl methacrylate and from 25 to 60 wt. %

Molecules 2020, 25, 2990 12 of 19 copolymers synthesized from 2-N-acryloylaminoethyl oleate and 2-N-acryloylaminoethyl linoleate as comonomers. The unsaturation degree of the olive and soybean monomers was used as an experimental parameter to control the latex properties. The effect of monomer unsaturation on the cross-linking density of the latex films and, thus, on the physical and mechanical properties of the coatings was demonstrated [35]. The decrease in the glass transition temperature of the latex copolymers (from 105 to 57 ◦C for the copolymers of the olive and soybean monomers with methyl methacrylate and from 100 to 5 ◦C for the copolymers with styrene) indicates that the presence of the OVM and SBM units in the macromolecules affects thermomechanical properties of the resulting latex copolymers. The olive and soybean monomer units impart flexibility to the macromolecules, improve the conditions of film formation, increase the strength in comparison with conventional polystyrene and poly(methyl methacrylate). Moreover, the OVM and SBM units in the macromolecules increase the hydrophobicity of polymeric latex films thus reducing the negative impact of water on the properties of the coatings. Therefore, the incorporation of the hydrophobic fatty acid chains into the macromolecules of latex polymers allows for formation of polymer networks with a controlled cross-linking density along with enhancing the water resistance of the coatings. The copolymers based on the olive and soybean monomers enable the formation of coatings with low surface energy and water-repellent properties.

5. Formation of Micelles from the Complexes of Highly Hydrophobic Plant Oil-Based Monomers with Sodium Dodecyl Sulfate

The synthesized POBMs contain CH2=CH–C(O)–NH–CH2CH2–O–C(O)– as a hydrophilic fragment in their chemical structure and R– as a hydrophobic constituent in the fatty acid chain. Such a monomer structure imparts unique properties to the POBMs associated with the ability to participate in intermolecular (electrostatic and/or van der Waals) interactions to produce complexes (aggregates). The influence of high oleic soybean oil-based (HO-SBM) and olive oil-based acrylic monomers on micellization of sodium dodecyl sulfate (SDS) was studied at different monomer and surfactant concentrations. The obtained data imply that SDS is able to solubilize highly hydrophobic monomer molecules. This leads to development of mixed (SDS/POBM) micelles (Figure 12). Surface activity of a SDS/POBM mixture varies by adding the monomer and, as a rule, is higher than for the surfactant alone [36]. It was also found that monomer molecules replace surfactant counterparts in the mixed micelles. Both the DLS and TEM data allow for conclusion that incorporation of POBM into the mixed micelles facilitates micellar association and development of 25–30 nm structures. Hence, solubilization of monomer molecules by SDS can affect mechanism of emulsion polymerization and reaction kinetics, as well as have an effect on development of latex particles and their morphology. Molecules 2020, 25, x FOR PEER REVIEW 13 of 19

Figure 12. Possible location of the polar “heads” in a di directrect micelle from the SDS molecules and the POBM/SDSPOBM/SDS aggregate.

TheSurfactants feature formof micellization direct micelles of sodium due to dodecyl the interactions sulfate (SDS) between in the hydrocarbon presence of the parts POBMs of their is surfactantmolecules. ability Usually, to solubilize the micelle highly has a hydrophobic layered structure monomer depending molecules onthe and packaging promote development of surfactant ofmolecules. mixed (SDS/POBM) A micelle contains micelles. a hydrocarbon As shown nucleus,by Kingsley a water-hydrocarbon et al. [36], the packing layer, which of surface-active includes 2–3 SDS/POBMmethylene groups, complexes and (aggregates) a layer of hydrated and the polar SDS groups.molecules It should occurs beupon noted micellization. that surfactant In this molecules event, theare freelySDS molecules localized can inthe be micelle.squeezed They out of can the leave micelle the and micelle localized or move at the toa interphase diﬀerent position; reducing they the interfacial tension. Sodium dodecyl sulfate is known to have a micelle aggregation number of 60-70 [38]. It was found that the aggregation number decreases to 10–48 (Table 3) upon micellization of the SDS/POBM complexes. The micellar size depends on the packaging of the surfactants. Their length and packing density in the micelle determine the radius of the hydrocarbon nucleus. The formed colloidal solution simultaneously contains the SDS micelles and the mixed SDS/POBM micelles. It should be noted that their size is 18–38 nm (Table 3, Figure 13) whereas the SDS micellar size is 1.7–3.1 nm.

Table 3. Micellar parameters for SDS and POBM at different concentrations.

SDS + POBM (x,mol: y,mol) Nagg NPOBM I1/I3 d,nm PDI σ, mN/m SDS at 0.02 M 41 0 1.04 3.1 0.006 36.2 + HO-SBM 0.01 M 25 20 0.94 18.2 0.02 34.1 0.02 M 15 25 0.94 23.3 0.05 31.2 0.04 M 12 39 0.92 25.4 0.04 30.4 SDS at 0.05 M 57 0 1.03 1.7 0.003 34.9 + HO-SBM 0.02 M 46 22 0.96 27.3 0.03 31.5 0.04 M 38 34 0.95 28.5 0.05 29.8 SDS at 0.02 M 41 0 1.03 3.1 0.006 36.2 + OVM 0.01 M 27 22 0.95 22.6 0.06 32.4 0.02 M 19 31 0.93 28.7 0.04 31.1 0.04 M 10 33 0.93 37.8 0.04 30.1 SDS at 0.05 M 57 0 1.03 1.7 0.003 34.9 + OVM 0.02 M 48 23 0.95 28.2 0.02 32.6 0.04 M 31 28 0.94 33.9 0.04 30.2

Molecules 2020, 25, x FOR PEER REVIEW 13 of 19

Molecules 2020, 25, 2990 13 of 19

Figure 12. Possible location of the polar “heads” in a direct micelle from the SDS molecules and the can evenPOBM/SDS be engulfed aggregate. into the nucleus, which is determined by the hydrophobicity of the surfactant fragment [37,38]. The feature of micellization of sodium dodecyl sulfate (SDS) in the presence of the POBMs is surfactant abilityability toto solubilizesolubilize highly highly hydrophobic hydrophobic monomer monomer molecules molecules and and promote promote development development of mixedof mixed (SDS (SDS/POBM)/POBM) micelles. micelles. As shown As shown by Kingsley by Kingsley et al. [36 et], theal. packing[36], the of packing surface-active of surface-active SDS/POBM complexesSDS/POBM (aggregates)complexes (aggregates) and the SDS and molecules the SDS occursmolecu uponles occurs micellization. upon micellization. In this event, In this the event, SDS moleculesthe SDS molecules can be squeezed can be squeezed out of the out micelle of the and micelle localized and atlocalized the interphase at the interphase reducing the reducing interfacial the tension.interfacial Sodium tension. dodecyl Sodium sulfate dodecyl is known sulfate to is have known a micelle to have aggregation a micelle aggregation number of 60–70 number [38 ].of It 60-70 was found[38]. It thatwas thefound aggregation that the aggregation number decreases number to decreases 10–48 (Table to 10–483) upon (Table micellization 3) upon micellization of the SDS /POBM of the complexes.SDS/POBM Thecomplexes. micellar The size micellar depends size on thedepends packaging on the of packaging the surfactants. of the Theirsurfactants. length andTheir packing length densityand packing in the density micelle determinein the micelle the radiusdetermine of the the hydrocarbon radius of the nucleus. hydrocarbon The formed nucleus. colloidal The solutionformed simultaneouslycolloidal solution contains simultaneously the SDS micelles contains and the the SDS mixed micelles SDS/ POBMand the micelles. mixed SDS/POBM It should be micelles. noted that It theirshould size be is noted 18–38 that nm (Tabletheir 3size, Figure is 18–38 13) whereasnm (Table the 3, SDS Figure micellar 13) sizewhereas is 1.7–3.1 the SDS nm. micellar size is 1.7–3.1 nm. Table 3. Micellar parameters for SDS and POBM at diﬀerent concentrations. Table 3. Micellar parameters for SDS and POBM at different concentrations. SDS + POBM (x,mol: y,mol) Nagg NPOBM I1/I3 d,nm PDI σ, mN/m SDS SDS+ POBM at 0.02 (x,mol: M y,mol) 41Nagg 0NPOBM 1.04I1/I3 d,nm 3.1 PDI 0.006 σ, mN/m 36.2 + HO-SBMSDS at 0.02 0.01 M M 25 41 20 0 0.94 1.04 18.2 3.1 0.006 0.02 36.234.1 + HO-SBM0.02 M 0.01 M 15 25 25 20 0.94 0.94 23.318.2 0.02 0.05 34.131.2 0.040.02 M M 12 15 39 25 0.92 0.94 25.423.3 0.05 0.04 31.230.4 SDS at0.04 0.05 M M 57 12 0 39 1.03 0.92 25.4 1.7 0.04 0.003 30.434.9 + HO-SBMSDS at 0.05 0.02 M M 46 57 22 0 0.96 1.03 27.3 1.7 0.003 0.03 34.931.5 + HO-SBM0.04 M 0.02 M 38 46 34 22 0.95 0.96 28.527.3 0.03 0.05 31.529.8 0.04 M 38 34 0.95 28.5 0.05 29.8 SDS at 0.02 M 41 0 1.03 3.1 0.006 36.2 + OVMSDS at 0.010.02 M 27 41 22 0 0.95 1.03 22.6 3.1 0.006 0.06 36.232.4 + OVM0.02 M 0.01 M 19 27 31 22 0.93 0.95 28.722.6 0.06 0.04 32.431.1 0.040.02 M M 10 19 33 31 0.93 0.93 37.828.7 0.04 0.04 31.130.1 0.04 M 10 33 0.93 37.8 0.04 30.1 SDS at 0.05 M 57 0 1.03 1.7 0.003 34.9 + OVMSDS at 0.020.05 M 48 57 23 0 0.95 1.03 28.2 1.7 0.003 0.02 34.932.6 + OVM0.04 M 0.02 M 31 48 28 23 0.94 0.95 33.928.2 0.02 0.04 32.630.2 0.04 M 31 28 0.94 33.9 0.04 30.2

Figure 13. TEM micrograph of micelles prepared by mixing SDS (0.02M) and HO-SBM (0.01M) (inset shows morphology of selected individual micelle). Reprinted from Ref. 36, Copyright (2019), with permission from Elsevier.

If the fatty acid chain cannot leave the hydrocarbon nucleus, the polar group can be even drawn into the hydrophobic nucleus [38], which also aﬀects the aggregation number. The authors explain the features of micellization (micellar parameters, size, structure, and surface tension) and the obtained Molecules 2020, 25, x FOR PEER REVIEW 14 of 19

MoleculesIf the2020 fatty, 25, 2990 acid chain cannot leave the hydrocarbon nucleus, the polar group can be even 14drawn of 19 into the hydrophobic nucleus [38], which also affects the aggregation number. The authors explain the features of micellization (micellar parameters, size, structure, and surface tension) and the results with the formation of surface-active SDS/POBM complexes (aggregates) of the following obtained results with the formation of surface-active SDS/POBM complexes (aggregates) of the structure (Figure 14): following structure (Figure 14):

FigureFigure 14.14. Chemical structure ofof plantplant oil-basedoil-based monomermonomer ((AA),), surfactantsurfactant ((BB),), andand schematicschematic ofof POBMPOBM solubilizationsolubilization byby SDSSDS moleculesmolecules ((CC).). Reprinted Reprinted fromfrom [ 36[36].]. CopyrightCopyright (2019),(2019), withwith permission permission fromfrom Elsevier. Elsevier.

TheThe formationformation of of a a water-hydrocarbon water-hydrocarbon layer layer of of the the spherical spherical micelle micelle leads leads to the to localizationthe localization of the of acrylicthe acrylic groups groups of the of POBM the POBM molecule molecule at the interface. at the interface. This opens This up opens new possibilities up new possibilities for the formation for the offormation “core–shell” of “core–shell” morphology, morphology, providing ability providin of POBMg ability to of undergo POBM polymerization.to undergo polymerization. ChemicalChemical structurestructure ofof POBMPOBM andand SDSSDS moleculesmolecules isis similar.similar. TheyThey bothboth havehave hydrophilichydrophilic “head”“head” andand longlong non-polar non-polar “tail” “tail” with with in in average average 17 17 (POBM) (POBM) and and 12 (SDS)12 (SDS) carbon carbon atoms. atoms. It was It suggestedwas suggested that physicalthat physical association association of both polarof both “heads” polar and “heads” hydrophobic and hydrophobic “tails” in water “tails” underlie in water intermolecular underlie interactions.intermolecular The interactions. results indicate The that results surface indicate activity that of a SDSsurface/POBM activity mixture of a is SDS/POBM usually higher mixture than for is theusually surfactant higher and than varies for the by surfactant adding the and monomer. varies by Moreover, adding the structure, monomer. size, Moreover, and micellar structure, parameters, size, observedand micellar changes parameters, upon theobserved addition changes of the upon POBMs. the addition The formed of the POBMs. complexes The canformed open complexes up new opportunitiescan open up for new micellization opportunities and, thus,for micellization new approaches and, to conductingthus, new heterophaseapproaches polymerizationto conducting (e.g.,heterophase conventional polymerization emulsion and(e.g. miniemulsion, conventional polymerization).emulsion and miniemulsion polymerization).

6.6. DualDual RoleRole ofof Methyl- Methyl-ββ-Cyclodextrin-Cyclodextrin in in the the Emulsion Emulsion Polymerization Polymerization of of Highly Highly Hydrophobic Hydrophobic PlantPlant Oil-BasedOil-Based MonomersMonomers TheThe newnew acrylicacrylic monomersmonomers are also capable of of complexation complexation with with cyclodextrins, cyclodextrins, which which play play a adual dual role role in both in both protecting protecting against against allylic allylic termination termination chain transfer chain transfer as well as as improving well as improving monomer monomerpolymerizability. polymerizability. Methyl-Methyl-ββ-cyclodextrin-cyclodextrin (M-(M-ββ-CD), amphiphilicamphiphilic oligosaccharide,oligosaccharide, was utilizedutilized toto enhanceenhance thethe polymerizabilitypolymerizability of highof high oleic soybeanoleic soybean oil-based oil-based and linseed and oil-based linseed monomers oil-based in copolymerization monomers in withcopolymerization styrene. Interactions with styrene. between Interactions M-β-CD andbetween the POBMsM-β-CD leading and the to thePOBMs development leading to of 1:1the “host-guest”development complex of 1:1 “host-guest” were revealed. complex In the were presence revealed. of the In oligosaccharide,the presence of polymerthe oligosaccharide, yield rises whereaspolymer the yield coagulum rises whereas content the decreases coagulum during content the de emulsioncreases polymerizationduring the emulsion of POBMs polymerization with styrene of implyingPOBMs with their styrene improved implying solubility their in improved water. Latex solubility polymers in withwater. a higherLatex polymers molecular with weight a higher were synthesizedmolecular weight in the presence were synthesized of inclusion in complexes.the presence Incorporation of inclusion of complexes. POBM molecules Incorporation into the of M- POBMβ-CD 1 cavitiesmolecules protects into thethe fattyM-β acid-CD chainscavities and protects reduces the chain fatty transfer acid aschains confirmed and reduces by H-NMR chain spectroscopy. transfer as Thisconfirmed effect is by more 1H-NMR pronounced spectroscopy. for more This unsaturated effect is more linseed pronounced oil-based monomer.for more unsaturated linseed oil-basedThese monomer. results are explained by the specific structures of M-β-CD having a hydrophobic cavity and a hydrophilicThese results exterior, are andexplained the POBM by the molecule, specific possessingstructures aof long M-β hydrophobic-CD having a fatty hydrophobic acid chain; cavity this resultsand a hydrophilic in the formation exterior, of an and inclusion the POBM complex molecule, (Figure possessing 15). a long hydrophobic fatty acid chain; this Toresults confirm in the the formation formation of ofan theinclusion inclusion complex complex, (Figure it was 15). used Powder X-ray diffractometry (PXRD) [39]. The PXRD spectra of H-SBM [monomer from hydrogenated (very low degree of unsaturation) soybean oil], M-β-CD, H-SBM/M-β-CD inclusion complex, and the physical mixture are depicted in Figure 16A. The diffractogram of the physical mixture of M-β-CD and H-SBM was the superposition of the monomer and the oligosaccharide implying that there is no interaction between them [40]. The diffraction pattern of the H-SBM/M-β-CD inclusion complex displayed no Molecules 20202020,, 2525,, xx FORFOR PEERPEER REVIEWREVIEW 1515 ofof 1919

To confirm the formation of the inclusion complex, it was used Powder X-ray diffractometry (PXRD)(PXRD) [39].[39]. TheThe PXRDPXRD spectraspectra ofof H-SBMH-SBM [monom[monomer from hydrogenated (very low degree of unsaturation) soybean oil], M-β-CD,-CD, H-SBM/M-H-SBM/M-β-CD-CD inclusioninclusion complex,complex, andand thethe physicalphysical mixturemixture Molecules 2020, 25, 2990 15 of 19 are depicted in Figure 16(A). The diffractogram of the physical mixture of M-β-CD-CD andand H-SBMH-SBM waswas thethe superpositionsuperposition ofof thethe monomermonomer andand thethe oligosaoligosaccharide implying that there is no interaction betweencharacteristic them peaks [40]. thatThe thediffraction pure monomer pattern had.of the These H-SBM/M- data revealβ-CD-CD that inclusioninclusion the self-lattice complexcomplex arrangement displayeddisplayed nono of characteristicthe monomer peaks was changed that the from pure a monomer crystalline had. to amorphous These data state reveal due that to the the H-SBM self-lattice inclusion arrangement into the ofmethyl- the monomerβ-cyclodextrin was changed cavity. from a crystalline to amorphous state due to the H-SBM inclusion into thethe methyl-methyl-β-cyclodextrin-cyclodextrin cavity.cavity.

FigureFigure 15. 15. SchematicSchematic illustration illustration of of the the association association of of free free methylmethyl-β-cyclodextrin-cyclodextrin-cyclodextrin andand POBMPOBM toto formform aa 1:1 inclusion complex. Reprinted Reprinted from [32]. [32]. Co Copyrightpyright (2018), (2018), with with perm permissionissionission fromfrom Elsevier. Elsevier.

Figure 16. PXRD spectra of POBMs, methyl-β-cyclodextrin, their physical mixture, and inclusion Figure 16. PXRD spectra of POBMs, methyl-β-cyclodextrin, their their physical mixture, and inclusion complexescomplexes (( AA)) – – H-SBM, H-SBM, ((B)) –– HO-SBM.HO-SBM.HO-SBM. ReprintedReprintedReprinted fromfromfrom [[32].[32].32]. Copyright Copyright (2018), (2018), with with permission permission fromfrom Elsevier. Elsevier.

TheThe diffractograms diffractograms ofof HO-SBM,HO-SBM, M- M-ββ-CD,-CD,-CD, and andand HO-SBM HO-SBM/M-HO-SBM/M-/M-ββ-CD-CD-CD inclusion inclusioninclusion complex complexcomplex are areare shown shownshown in ininFigure FigureFigure 16B. 16(B).16(B). As both AsAs M- bothbothβ-CD M-M- andβ-CD-CD high andand oleic highhigh soybean oleicoleic soybeansoybean oil-based oil-baoil-ba monomersedsed monomermonomer are non-crystalline areare non-crystallinenon-crystalline substances, substances,substances,the development thethe developmentdevelopment of HO-SBM /ofofM- HO-SBM/M-HO-SBM/M-β-CD inclusionβ-CD-CD complex inclusioninclusion cannot complexcomplex be proven cannotcannot by bebe PXRD. provenproven byby PXRD.PXRD. ToTo thisthis end, end, di fferentialdifferential scanning scanning calorimetry calorimetry [41] was [41] used was to furtherused confirmto further the complexation.confirm the complexation.The DSC thermograms The DSC ofthermograms H-SBM, M- ofβ-CD, H-SBM, H-SBM M-β/M--CD,-CD,β-CD H-SBM/M-H-SBM/M- inclusionβ-CD-CD complex, inclusioninclusion and complex,complex, the physical andand thethemixture physicalphysical are shown mixturemixture in areare Figure shownshown 17. Althoughinin FigureFigure 17.17. the AlthoughAlthough endothermic thethe peaks endothermicendothermic of the monomer peakspeaks ofof werethethe monomermonomer detected inwerewere the detectedDSC curve in ofthe the DSC physical curve of mixture, the physical no peak mixture, in the meltingno peak rangein the ofmelting the monomer range of was the detectedmonomer in was the detectedthermogram in the of thermogram H-SBM/M-β of-CD. H-SBM/M- This confirmsβ-CD.-CD. thatThisThis the confirmsconfirms H-SBM thatthat molecules thethe H-SBMH-SBM are moleculesmolecules entirely included areare entirelyentirely into includedincludedthe oligosaccharide intointo thethe oligosaccharideoligosaccharide cavities and H-SBM cavitiescavities/M- andandβ-CD H-SBM/M-H-SBM/M- inclusionβ-CD-CD complex inclusioninclusion forms. complexcomplex forms.forms. No peak in the melting range of high oleic soybean oil-based monomer was observed in the DSC curves of HO-SBM/M-β-CD inclusion complex and their physical mixture (data not shown). Obviously, this is because the HO-SBM molecules might be able to penetrate into the M-β-CD cavities since the monomer is an oily liquid. This phenomenon is known as the kneading method for the formation of cyclodextrin-guest complexes [42]. Even though PXRD and DSC studies confirmed the transitions from a crystalline to amorphous state of H-SBM upon its interaction with M-β-CD, these analyses neither definitely confirmed inclusion complexation (especially, for HO-SBM) nor determined the complex stoichiometry. Thus, electrospray ionization–mass spectrometry (ESI–MS) [42,43] was used to investigate the complexation of M-β-CD

with POBM. Molecules 2020, 25, x FOR PEER REVIEW 16 of 19

Molecules 2020, 25, 2990 16 of 19

Molecules 2020, 25, x FOR PEER REVIEW 16 of 19

Figure 17. DSC thermograms of hydrogenated soybean monomer, methyl-β-cyclodextrin, their physical mixture, and inclusion complex. Reprinted from [32]. Copyright (2018), with permission from Elsevier.

No peak in the melting range of high oleic soybean oil-based monomer was observed in the DSC curves of HO-SBM/M-β-CD inclusion complex and their physical mixture (data not shown). Obviously, this is because the HO-SBM molecules might be able to penetrate into the M-β-CD cavities since the monomer is an oily liquid. This phenomenon is known as the kneading method for the formation of cyclodextrin-guest complexes [42]. Even though PXRD and DSC studies confirmed the transitions from a crystalline to amorphous state of H-SBM upon its interaction with M-β-CD, these analyses neither definitely confirmed Figure 17.17.DSC DSC thermograms thermograms of hydrogenatedof hydrogenated soybean soybean monomer, monomer, methylmethyl-β-cyclodextrin,β-cyclodextrin, their physical their inclusion complexation (especially, for HO-SBM) nor determined the complex stoichiometry. Thus, mixture,physical andmixture, inclusion and complex.inclusion Reprinted complex. fromReprinted [32]. Copyright from [32]. (2018), Copyright with permission(2018), with from permission Elsevier. electrosprayfrom Elsevier. ionization–mass spectrometry (ESI–MS) [42,43] was used to investigate the complexationThe ESI mass of M- spectraβ-CD with of inclusion POBM. complexes of the monomers with M-β-CD are presented in FigureNo The18 peak. IonsESI inmass detected the spectramelting in theof range inclusion spectrum of high complexes of H-SBMoleic soybean of/M- theβ -CDmonomers oil-based (Figure with monomer 18A) M- areβ-CD attributedwas are observed presented to sodium in in the adductsDSCFigure curves of18. complexes Ionsof HO-SBM/M- detected of stearate-H-SBM in βthe-CD spectrum inclusion withof H-SBM/M-complex M-β-CD andβ having-CD their (Figure 9–13physical methyl18A) mixtureare groups. attributed (data In thetonot sodium ESI shown). mass spectrumObviously,adducts of of thethis complexes HO-SBM is because of/M– stearate-H-SBM βthe–CD HO-SBM inclusion withmolecu complex M-βles-CD (Figure might having 18be B),9–13 able ions methyl to that penetrate correspond groups. Ininto tothe the ESI inclusionM- massβ-CD spectrum of the HO-SBM/M–β–CD inclusion complex (Figure 18B), ions that correspond to the ofcavities oleate-HO-SBM since the monomer by M10-13 is-β an-CD oily (sodium liquid. adducts)This phenomenon are revealed. is known as the kneading method for theinclusion formation of oleate-HO-SBMof cyclodextrin-guest by M10-13 complexes-β-CD (sodium [42]. adducts) are revealed. Even though PXRD and DSC studies confirmed the transitions from a crystalline to amorphous state of H-SBM upon its interaction with M-β-CD, these analyses neither definitely confirmed inclusion complexation (especially, for HO-SBM) nor determined the complex stoichiometry. Thus, electrospray ionization–mass spectrometry (ESI–MS) [42,43] was used to investigate the complexation of M-β-CD with POBM. The ESI mass spectra of inclusion complexes of the monomers with M-β-CD are presented in Figure 18. Ions detected in the spectrum of H-SBM/M-β-CD (Figure 18A) are attributed to sodium adducts of complexes of stearate-H-SBM with M-β-CD having 9–13 methyl groups. In the ESI mass spectrum of the HO-SBM/M–β–CD inclusion complex (Figure 18B), ions that correspond to the inclusion of oleate-HO-SBM by M10-13-β-CD (sodium adducts) are revealed.

Figure 18. ESI mass spectra of H-SBM/M-β-CD (A) and HO-SBM/M-β-CD (B) inclusion complexes. Figure 18. ESI mass spectra of H-SBM/M-β-CD (A) and HO-SBM/M-β-CD (B) inclusion complexes. Reprinted from [32]. Copyright (2018), with permission from Elsevier. Reprinted from [32]. Copyright (2018), with permission from Elsevier.

Thus,Thus, the the M- M-β-CDβ-CD complexation complexation ofof monomermonomer molecules molecules leading leading to to the the 1:1 1:1 complex complex formation formation (Figure 15) was directly confirmed by the ESI–MS data. The emulsion copolymerization of the (Figure 15) was directly conﬁrmed by the ESI–MS data. The emulsion copolymerization of POBMs with styrene in the presence of methyl-β-cyclodextrin was found to allow for the the POBMs with styrene in the presence of methyl-β-cyclodextrin was found to allow for the preservation and protection of fatty acid double bonds (–CH=CH–) and the bisallylic hydrogen preservation and protection of fatty acid double bonds (–CH=CH–) and the bisallylic hydrogen atoms atoms (–CH=CH–CH2–CH=CH–). The inclusion complexation decreases the chain transfer (–CH=CH–CH –CH=CH–). The inclusion complexation decreases the chain transfer contribution contribution by2 protecting the allylic moiety of the monomer fatty acid chains and simultaneously byimproves protecting the the aqueous allylic moietysolubility of and the monomeravailabilityfatty of the acid monomers chains and in the simultaneously emulsion polymerization improves the aqueous solubility and availability of the monomers in the emulsion polymerization process. Therefore, a higher molecular weight of latex polymers from the highly hydrophobic POBMs was achieved with higherFigure monomer 18. ESI conversion mass spectra and of H-SBM/M- lower coagulumβ-CD (A formation.) and HO-SBM/M-β-CD (B) inclusion complexes. Reprinted from [32]. Copyright (2018), with permission from Elsevier. 7. Conclusions MonomersThus, the M- basedβ-CD on complexation various plant oilsof monomer were synthesized molecules through leading a two-step to the 1:1 procedure. complex Aformation one-step process(Figure for15) thewas synthesis directly confirmed of new vinyl by monomersthe ESI–MS by data. the reactionThe emulsion of direct copolymerization transesteriﬁcation of the of plantPOBMs oil with triglycerides styrene within theN -(hydroxyethyl)acrylamidepresence of methyl-β-cyclodextrin was recently was patented. found to Theallow features for the of homopolymerizationpreservation and protection kinetics of for fatty the POBMsacid doub werele determined.bonds (–CH=CH–) The reactivity and the of bisallylic the plant hydrogen oil-based atoms (–CH=CH–CH2–CH=CH–). The inclusion complexation decreases the chain transfer contribution by protecting the allylic moiety of the monomer fatty acid chains and simultaneously improves the aqueous solubility and availability of the monomers in the emulsion polymerization

Molecules 2020, 25, 2990 17 of 19 monomers was studied by radical copolymerization with vinyl monomers. The Alfrey Price Q − (0.41 0.51) and e (0.09 0.28) parameters are close for all POBMs and do not essentially depend on − − the monomer structure. The unique molecular structure of the plant oil-based acrylic monomers is that they simultaneously have a CH2=CH–C(O)–NH–CH2CH2–O–C(O)– polar (hydrophilic) fragment capable of electrostatic interactions and a hydrophobic fatty acid chain (C15–C17) capable of van der Waals interactions. This opens up new opportunities for formation of micelles from the complexes of highly hydrophobic plant oil-based monomers with sodium dodecyl sulfate and new approaches to conducting heterophase polymerization. Preparation of polymeric coatings from the plant oil-based monomers through the incorporation of the hydrophobic fatty acid chains into the macromolecules of latex polymers allows for formation of polymer networks with a controlled cross-linking density along with enhancing the water resistance of the coatings. The copolymers based on the olive and soybean monomers enable the formation of coatings with low surface energy and water-repellent properties. The copolymers based on the olive and soybean monomers enable the formation of coatings with low surface energy and water-repellent properties. The formation of inclusion complexes upon the interaction between the molecules of the plant oil-based acrylic monomers and methyl-β-cyclodextrin leads to a higher molecular weight of latex polymers from highly hydrophobic POBMs with higher monomer conversion and lower coagulum formation. An analysis of the literature shows a rapid development of a new branch in polymer science related to the chemistry of aliphatic and aromatic biobased monomers from renewable plant sources. The synthesis of such monomers allows for producing fully biobased polymers with biocompatible and biodegradable properties which do not pollute the environment. Copolymerization of the biobased monomers with commercial monomers enables formation of copolymers with controlled physical, chemical, and mechanical properties.

8. Patents Biobased Acrylic Monomers US 10,315,985 B2 June 11th, 2019. Biobased Acrylic Monomers and Polymers Thereof US 10,584,094 B2 March 10th, 2020.

Author Contributions: Conceptualization, A.K., S.V., and A.V.; methodology, Z.D., V.K., K.K., and O.S.; investigation, A.K., Z.D., V.K., K.K., and O.S.; writing—original draft preparation, A.K., V.K., and S.V.; writing—review and editing, S.C. and A.V.; project administration, S.C. and A.V.; funding acquisition, A.V. All authors have read and agreed to the published version of the manuscript. Funding: ND EPSCoR RII Track 1 ((IIA-1355466), North Dakota Department of Commerce, North Dakota Department of Agriculture, United Soybean Board. Conﬂicts of Interest: The authors declare no conﬂict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

1. Papageorgiou, G.Z. Thinking Green: Sustainable Polymers from Renewable Resources. Polymers 2018, 10, 952. [CrossRef][PubMed] 2. Sharmin, E.; Zafar, F.; Akram, D.; Alam, M.; Ahmad, S. Recent advances in vegetable oils based environment friendly coatings: A review. Ind. Crops Prod. 2015, 76, 215–229. [CrossRef] 3. Xia, Y.; Larock, R.C. Vegetable oil-based polymeric materials: Synthesis, properties, and applications. Green Chem. 2010, 12, 1893–1909. [CrossRef] 4. Can, E.; Wool, R.P.; Kusefoglu, S. Soybean- and Castor-oil-based thermosetting polymers: Mechanical properties. J. Appl. Polym. Sci. 2006, 102, 1497–1504. [CrossRef] 5. Van De Mark, M.R.; Sandefur, K. Vegetable Oils in Paint and Coatings. In Industrial Uses of Vegetable Oils; Erhan, S.Z., Ed.; AOCS Press: Boca Raton, FL, USA, 2005; pp. 149–168. Molecules 2020, 25, 2990 18 of 19

6. Statista. Available online: https://www.statista.com/statistics/263933/production-of-vegetable-oils- worldwide-since-2000/ (accessed on 25 May 2020). 7. Moreno, M.; Miranda, J.I.; Goikoetxea, M.; Barandiaran, M. Sustainable polymer latexes based on linoleic acid for coatings applications. Prog. Org. Coat. 2014, 77, 1709–1714. [CrossRef] 8. Yuan, L.; Wang, Z.; Trenor, N.M.; Tang, C. Amidation of triglycerides by amino alcohols and their impact on plant oil-derived polymers. Polym. Chem. 2016, 7, 2790–2798. [CrossRef] 9. Moreno, M.; Lampard, C.; Williams, N.; Lago, E.; Emmett, S.; Goikoetxea, M.; Barandiaran, M.J. Eco-paints from bio-based fatty acid derivative latexes. Prog. Org. Coat. 2015, 81, 101–106. [CrossRef] 10. Tarnavchyk, I.; Popadyuk, A.; Popadyuk, N.; Voronov, A. Synthesis and Free Radical Copolymerization of a Vinyl Monomer from Soybean Oil. ACS Sustain. Chem. Eng. 2015, 3, 1618–1622. [CrossRef] 11. Molina-Gutierrez, S.; Ladmiral, V.; Bongiovanni, R.; Caillol, S.; Lacroix-Desmazes, P. Radical polymerization of biobased monomers in aqueous dispersed media. Green Chem. 2019, 21, 36–53. [CrossRef] 12. Demchuk, Z.; Shevchuk, O.; Tarnavchyk, I.; Kirianchuk, V.; Kohut, A.; Voronov, S.; Voronov, A. Free Radical Polymerization Behavior of the Vinyl Monomers from Plant Oil Triglycerides. ACS Sustain. Chem. Eng. 2016, 4, 6974–6980. [CrossRef] 13. Tarnavchyk, I.; Voronov, A. Biobased acrylic monomers. US patent 10,315,985 B2, 11 June 2019. 14. Demchuk, Z.; Shevchuk, O.; Tarnavchyk, I.; Kirianchuk, V.; Lorenson, M.; Kohut, A.; Voronov, S.; Voronov, A. Free Radical Copolymerization Behavior of Plant Oil-Based Vinyl Monomers and Their Feasibility in Latex Synthesis. ACS Omega 2016, 1, 1374–1382. [CrossRef][PubMed] 15. Kingsley, K.; Shevchuk, O.; Kirianchuk, V.; Kohut, A.; Voronov, S.; Voronov, A. Emulsion Copolymerization of Vinyl Monomers from Soybean and Olive Oil: Eﬀect of Counterpart Aqueous Solubility. Eur. Polym. J. 2019, 119, 239–246. [CrossRef] 16. Yuan, L.; Wang, Z.; Trenor, N.M.; Tang, C. Robust Amidation Transformation of Plant Oils into Fatty Derivatives for Sustainable Monomers and Polymers. Macromolecules 2015, 48, 1320–1328. [CrossRef] 17. Harrison, S.A.; Wheeler, D.H. The Polymerization of Vinyl and Allyl Esters of Fatty Acids. J. Am. Chem. Soc. 1951, 73, 839–842. [CrossRef] 18. Chen, F.B.; Bufkin, G. Crosslinkable Emulsion Polymers by Autoxidation. I. Reactivity Ratios. J. Appl. Polym. Sci. 1985, 30, 4571–4582. [CrossRef] 19. Chen, F.B.; Bufkin, G. Crosslinkable Emulsion Polymers by Autoxidation. II. J. Appl. Polym. Sci. 1985, 30, 4551–4570. [CrossRef] 20. Boshui, C.; Nan, Z.; Jiang, W.; Jiu, W.; Jianhua, F.; Kai, L. Enhanced biodegradability and lubricity of mineral lubricating oil by fatty acidic diethanolamide borates. Green Chem. 2013, 15, 738–743. [CrossRef] 21. Chen, R. Bio-based polymeric materials from vegetable oils. PhD Thesis, Iowa State University, Ames, IA, United States, 2014. 22. Voirin, C.; Caillol, S.; Sadavarte, N.V.; Tawade, B.V.; Boutevin, B.; Wadgaonkar, P.P. Functionalization of cardanol: Towards biobased polymers and additives. Polym. Chem. 2014, 5, 3142–3162. [CrossRef] 23. Jaillet, F.; Darroman, E.; Boutevin, B.; Caillol, S. A chemical platform approach on cardanol oil: From the synthesis of building blocks to polymer synthesis. OCL - Oilseeds and fats crops and lipids 2016, 23, 511–518. [CrossRef] 24. Demchuk, Z.; Li, W.S.J.; Eshete, H.; Caillol, S.; Voronov, A. Synergistic Eﬀects of Cardanol- and High Oleic Soybean Oil Vinyl Monomers in Miniemulsion Polymers. ACS Sustain. Chem. Eng. 2019, 7, 9613–9621. [CrossRef] 25. Mhadeshwar, N.; Wazarkar, K.; Sabnis, A.S. Synthesis and characterization of ricinoleic acid derived monomer and its application in aqueous emulsion and paints thereof. Pigment & Resin Technology 2019, 48.[CrossRef] 26. Chatterjee, D.P.; Mandal, B.M. Facile atom transfer radical homo and block copolymerization of higher alkyl methacrylates at ambient temperature using CuCl/PMDETA/quaternaryammonium halide catalyst system. Polymer 2006, 47, 1812–1819. [CrossRef] 27. Çayli, C.; Meier, M.A.R. Polymers from renewable resources: Bulk ATRP of fatty alcohol derived methacrylates. Eur. J. Lipid Sci. Technol. 2008, 110, 853–859. [CrossRef] 28. Tarnavchyk, I.; Voronov, A. Biobased acrylic monomers and polymers thereof. US patent 10,584,094 B2, 10 March 2020. Molecules 2020, 25, 2990 19 of 19

29. Barison, A.; da Silva, C.W.; Campos, F.R.; Simonelli, F.; Lenz, C.A.; Ferreira, A.G. A simple methodology for the determination of fatty acid composition in edible oils through 1H NMR spectroscopy. Magn. Reson. Chem. 2010, 48, 571–659. [CrossRef] 30. Bozell, J.J. Feedstocks for the future—biorefinery production of chemicals from renewable carbon. Clean Soil, − Air, Water 2008, 36, 641–647. [CrossRef] 31. Boskou, D. Olive Oil Chemistry and Technology, 2nd ed.; AOCS Publishing: New York, NY, USA, 2006; 288p. 32. Kohut, A.; Demchuk, Z.; Kingsley, K.; Voronov, S.; Voronov, A. Dual role of methyl-β-cyclodextrin in the emulsion polymerization of highly hydrophobic plant oil-based monomers with various unsaturations. Eur. Polym. J. 2018, 108, 322–328. [CrossRef] 33. Kingsley, K.; Shevchuk, O.; Demchuk, Z.; Voronov, S.; Voronov, A. The features of emulsion copolymerization for plant oil-based vinyl monomers and styrene. Ind. Crops Prod. 2017, 109, 274–280. [CrossRef] 34. Solomon, D.H. The Chemistry of Organic Film Formers; Robert, E., Ed.; Krieger Publishing Co.: Huntington, NY, USA, 1977; 412p. 35. Demchuk, Z.; Kohut, A.; Voronov, S.; Voronov, A. Versatile Platform for Controlling Properties of Plant Oil-Based Latex Polymer Networks. ACS Sustain. Chem. Eng. 2018, 6, 2780–2786. [CrossRef] 36. Kingsley, K.; Shevchuk, O.; Voronov, S.; Voronov, A. Effect of highly hydrophobic plant oil-based monomers on micellization of sodium dodecyl sulfate. Colloids Surf. A Physicochem. Eng. Asp. 2019, 568, 157–163. [CrossRef] 37. Mittal, K.L. Micellization, Solubilization, and Microemulsions, Vols. 1 and 2; Plenum: New York, NY, USA, 1977; 945p. 38. Rusanov, A.I. Micellization in solutions of surfactants (in Russian); Khimiya: St. Petersburg, Russian Federation, 1992; 280p. 39. Michalska, P.; Wojnicz, A.; Ruiz-Nuño, A.; Abril, S.; Buendia, I.; León, R. Inclusion complex of ITH12674 with 2-hydroxypropyl-β-cyclodextrin: Preparation, physical characterization and pharmacological effect. Carbohydr. Polym. 2017, 157, 94–104. [CrossRef] 40. Liao, Y.; Zhang, X.; Li, C.; Huang, Y.; Lei, M.; Yan, M.; Zhou, Y.; Zhao, C. Inclusion complexes of HP-β-cyclodextrin with agomelatine: Preparation, characterization, mechanism study and in vivo evaluation. Carbohydr. Polym. 2016, 147, 415–425. [CrossRef][PubMed] 41. Cabral Marques, H.M.; Hadgraft, J.; Kellaway, I.W. Studies of cyclodextrin inclusion complexes. I. The salbutamol-cyclodextrin complex as studied by phase solubility and DSC. Int. J. Pharm. 1990, 63, 259–266. [CrossRef] 42. Guo, M.Q.; Song, F.; Zhiqiang, L.; Shuying, L. Characterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometry. J. Mass Spectrom. 2004, 39, 594–599. [CrossRef][PubMed] 43. Marangoci, N.; Mares, M.; Silion, M.; Fifere, A.; Varganici, C.; Nicolescu, A.; Deleanu, C.; Coroaba, A.; Pinteala, M.; Simionescu, B.C. Inclusion complex of a new propiconazole derivative with β-cyclodextrin: NMR, ESI–MS and preliminary pharmacological studies. Results Pharma Sci. 2011, 1, 27–37. [CrossRef] [PubMed]

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).