polymers

Article A Feasible Method Applied to One-Bath Process of /Acrylic Blended Fabrics with Novel Heterocyclic Reactive and Application Properties of Dyed

Meihui Wang 1, Xianfeng Wang 1, Chong Guo 1, Tao Zhao 1,2,* and Wenyao Li 3,*

1 College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China; [email protected] (M.W.); [email protected] (X.W.); [email protected] (C.G.) 2 Key Laboratory of Science and Technology of Eco-, Ministry of Education, Donghua University, Shanghai 201620, China 3 College of Material Engineering, Shanghai University of Engineering Science, Shanghai 201620, China * Correspondence: [email protected] (T.Z.); [email protected] (W.L.); Tel.: +86-021-6779-2811 (T.Z.)

 Received: 27 December 2019; Accepted: 17 January 2020; Published: 1 February 2020 

Abstract: Reactive dyes containing cationic groups have great potentiality as novel dyes, which can be applicable to one-bath of wool/acrylic blended fabrics. In this work, four novel heterocyclic reactive dyes containing cationic groups were designed by using m-aminophenyltrimethylammonium salt or N-(2-aminoethyl) pyridinium chloride salt as cationic groups, N, N-diethyl-1,3-benzenediamine as a coupling component, 2-amino-6-methoxybenzothiazole, 2-aminobenzothiazole or 3-amino-5-nitrobenzoisothiazole as diazo components. These dyes based on benzothiazole derivative chromophores not only showed beautiful color, including blue-green and fuchsia, but also had larger tinctorial strength with a high molar extinction coefficient, further reducing the dosage of dyes to achieve same color depth. Factors affecting the dyeability on fabrics, such as pH value, dyeing temperature and concentration were discussed. Excellent dyeing behavior, levelling properties and good fastness on wool/acrylic blended fabric were obtained. What’ more, excellent anti-ultraviolet and antibacterial properties were obtained for textiles with these dyes. The application of these dyes with large molar extinction coefficients presents a wide range of possibilities for the further development of cleaner production and eco-friendly dyeing, even functional textiles.

Keywords: heterocyclic reactive dyes; wool/acrylic blended fabrics; cationic group; one-bath process; levelling properties; anti-ultraviolet; antibacterial activities

1. Introduction The application of blended fabrics greatly confers the complementary properties of fibers and reduces processing costs by combining the advantages of multiple fibers in textile goods. In recent years, the great market demand for wool/acrylic blended fabrics has remained a great impetus in knitwear because of its unique hand feeling, excellent wearing comfort, soft texture, and warmth retention [1,2]. Generally, wool/acrylic blended fabrics are carried out by the two-bath dyeing method. Compared with a conventional two-bath process [3], the one-bath dyeing method is widely applied to wool/acrylic blended fabric dyeing in the aspects of production efficiency improvement and energy saving [4]. However, large amounts of surfactants are used to avoid the reaction between cationic dyes for acrylic and anionic dyes for wool in one-bath dyeing, which has a serious effect on the environment [5]. As we all know, textile wastewater is one of the most important pollution sources in the , causing serious damage to the ecosystem and lives [6,7]. Hence, the development

Polymers 2020, 12, 285; doi:10.3390/polym12020285 www.mdpi.com/journal/polymers Polymers 2020, 12, 285 2 of 18 Polymers 2020, 12, x FOR PEER REVIEW 2 of 18 ofdevelopment dyes applied of fordyes the applied one-bath for processing the one-bath of woolprocessing/acrylic of fabrics wool/acrylic will become fabrics an will active become research an active area inresearch printing area and in dyeing printing as and it reduces dyeing the as it effl reduceuent ands the improves effluent and the improves dyeing eff theectiveness. dyeing effectiveness. InIn ourour previousprevious work,work, itit hashas provenproven promisingpromising toto useuse reactivereactive dyesdyes containingcontaining cationiccationic groupsgroups forfor thethe one-bathone-bath dyeingdyeing ofof woolwool/acrylic/acrylic blendedblended fabricsfabrics [[8–12].8–12]. The reactive group inin thethe molecularmolecular structurestructure ofof dyedye reactsreacts withwith thethe woolwool fiberfiber toto form the covalent bond and the cationic group combines withwith acrylicacrylic fiberfiber viavia thethe ionicionic bond,bond, realizingrealizing thethe one-bathone-bath dyeingdyeing ofof woolwool/acrylic/acrylic blendedblended fabricsfabrics (shown(shown inin FigureFigure1 )[1) 13[13].]. To To date, date, a a series series of of reactive reactive dyes dyes containing containing cationic cation groupsic groups reported reported with with red andred and yellow yellow based based on aniline-based on aniline-based and and anthraquinone anthraquinone as chromophores as chromophores has has been been described described [14 –[14–17]. However,17]. However, most most reactive reactive dyes dyes have have shown shown little substantivitylittle substantivity for wool for wool and acrylic and acrylic fiber atfiber the at same the timesame and time exhibited and exhibited some shortages some shortages in terms in of terms color-deepening, of color-deepening, color fastness, color fastness, and brightness and brightness of shade. Therefore,of shade. Therefore, researchers researchers are still looking are still for looking brighter, for brighter, more eff ective,more effective, and amenable and amenable colorants colorants for this familyfor this with family the with aim the of improving aim of improving the dye-uptake the dye-uptake and the tinctorialand the tinctorial strength strength [18]. [18].

Figure 1. The mechanism between reactive dye with blended fabric. Figure 1. The mechanism between reactive dye with blended fabric. Heterocyclic dyes are well-known compounds that have larger tinctorial strength and brighter colorHeterocyclic than azo dyes dyes based are on well-known aniline-based compounds derivative that [19– have21], and larger have tinctorial attracted strength great interest and brighter among dyecolor chemists than azo in thedyes modern based textile on aniline-based chemistry in recentderivative years [19–21], [22,23]. Commercialand have attracted heterocyclic great dyes interest have beenamong largely dye chemists classified in into the fourmodern major textile classes: chemistry (benzo) in thiazole recent years dyes, [22,23]. (benzo) Commercial isothiazole dyesheterocyclic [24,25], thiadiazoledyes have been dyes largely [26], and classified thiophene into dyes four [27major]. Due classes: to extensive (benzo) delocalizedthiazole dyes,π-systems, (benzo) theseisothiazole dyes showeddyes [24,25], a significant thiadiazole bathochromic dyes [26], and eff ectthio inphene the UV-visibledyes [27]. Due absorption to extensive spectrum delocalized [28]. Green,π-systems, red, bluethese and dyes dark showed tones havea significant been displayed bathochromic on the fabrics. effect in In addition,the UV-visible much workabsorption so far hasspectrum focused [28]. on theGreen, effect red, of theblue aromatic and dark rings tones with have the been substituent displaye groupsd on the [29]. fabrics. Meanwhile, In addition, the development much work of so dyed far fabricshas focused with manyon the functions, effect of suchthe aromatic as anti-ultraviolet rings with performance the substituent [30], antibacterialgroups [29]. activitiesMeanwhile, [31, 32the], anddevelopment sensing applications of dyed fabrics [33,34], with have increasedmany functions, rapidly. Thesuch development as anti-ultraviolet of multifunctional performance dye [30], has alsoantibacterial proven promising. activities To[31,32], the best and of oursensing knowledge, applications only a few[33,34], researches have haveincreased been reported rapidly. about The thedevelopment one-bath dyeingof multifunctional of wool/acrylic dye blendedhas also proven fabrics withpromising. reactive To dyes the best containing of our knowledge, cationic groups only baseda few researches on heterocyclic have chromophores.been reported about The application the one-bath of dyeing these reactive of wool/acr dyesylic based blended on benzothiazole fabrics with derivativereactive dyes chromophores containing cationic not only groups provides based a brighter on heterocyclic color, but chromophores. also reduces the The usage application of dyes toof achievethese reactive same color dyesdepth. based on benzothiazole derivative chromophores not only provides a brighter color,In but the also present reduces paper, the four usage reactive of dyes dyes to achieve containing same cationic color depth. groups based on azo benzothiazole derivativeIn the (shownpresent inpaper, Figure four2) as reactive a diazo dyes component containing have cationic been designed. groups ba Theysed on had azo a widebenzothiazole range of colorderivative shades (shown with ain very Figure better 2) as depth a diazo and componen darker colort have compared been designed. with other They reactive had a dyeswide reportedrange of incolor the shades literature with [18 a ,very35]. Inbetter order depth to reveal and darker the structure–spectra color compared with relationship other reactive between dyes these reported dyes, diinff theerent literature substituted [18,35]. groups In haveorder been to reveal introduced the structure–spectra into molecule structures, relationship and thebetween method these of density dyes, functiondifferent theorysubstituted (DFT) groups was recommended. have been introduc The dyeinged into behaviors molecule of structures, these dyes and were the evaluated method byof determiningdensity function the theory color strength (DFT) was (K /recommended.S) value on wool The/acrylic dyeing fabric behaviors in order of these to further dyes were elucidate evaluated the by determining the color strength (K/S) value on wool/acrylic fabric in order to further elucidate the influence of dyeing conditions, including pH, temperature, and time. The levelling properties and

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Polymers 2020, 12, x FOR PEER REVIEW 3 of 18 influencecolor fastness of dyeing such conditions, as washing, including rubbing, pH, and temperature, light fastness and were time. measured. The levelling What’s properties more, the and anti- color fastnessultraviolet such asperformance washing, rubbing, and antibacterial and light fastness activities were against measured. S. aureus What’s of more, dyed the textiles anti-ultraviolet were performanceinvestigated. and antibacterial activities against S. aureus of dyed textiles were investigated.

FigureFigure 2. 2.Structures Structures ofof thethe synthesizedsynthesized heterocyclic reactive reactive dyes. dyes.

2. Experimental2. Experimental

2.1.2.1. Materials Materials and and Instrumentation Instrumentation CyanuricCyanuric chloride, chloride, 2-amino-6-methoxybenzothiazole 2-amino-6-methoxybenzothiazole and and 2-aminobenzothiazole 2-aminobenzothiazole were were supplied supplied byby the the Tokyo Tokyo Chemical Industry Co., Co., Ltd. Ltd. (TCI,(TCI, Shanghai, China) China) and and used used without without any any further further

Polymers 2020, 12, x FOR PEER REVIEW 4 of 18

Polymerspurification.2020, 12 , 285Further, 3-amino-5-nitrobenzoisothiazole, 3-(N, N-diethylamino) acetanilide 4were of 18 received from Wanfeng Chemical Engineering Co., Ltd (Zhejiang, China). All other reagents were obtained from Shanghai Chemical Reagent Co., Ltd. (Shanghai, China) purification. Further, 3-amino-5-nitrobenzoisothiazole, 3-(N, N-diethylamino) acetanilide were received Wool (265.1 g/m2), acrylic (150 g/m2) and 50/50 wool/acrylic blended fabric (150 g/m2) were from Wanfeng Chemical Engineering Co., Ltd (Zhejiang, China). All other reagents were obtained provided by Donghua University Textile Institute Training Center (Shanghai, China). The fabrics from Shanghai Chemical Reagent Co., Ltd. (Shanghai, China). were pretreated with 2 g/L nonionic detergent at 60 ℃ for 30 min before being rinsed and dried. Wool (265.1 g/m2), acrylic (150 g/m2) and 50/50 wool/acrylic blended fabric (150 g/m2) were Ultraviolet-visible (UV-Vis) absorption spectra of these dyes, dissolved in dimethylformamide provided by Donghua University Textile Institute Training Center (Shanghai, China). The fabrics were solution, were recorded with the U-3310 Spectrophotometer (Hitachi Limited, Tokyo, Japan) using a pretreated with 2 g/L nonionic detergent at 60 °C for 30 min before being rinsed and dried. quartz glass cell at the room temperature. The color strength (K/S) and colorimetric data of the dyed Ultraviolet-visible (UV-Vis) absorption spectra of these dyes, dissolved in dimethylformamide fabrics were determined by Datacolor SF 600X spectrophotometer (Datacolor, Lucerne, Switzerland). solution, were recorded with the U-3310 Spectrophotometer (Hitachi Limited, Tokyo, Japan) using a The topography of different was observed at the optical microscope. A 3D microscope graph quartz glass cell at the room temperature. The color strength (K/S) and colorimetric data of the dyed of fabrics was obtained by Super Depth of Field 3D Microscope VHX-6000 (Keyence, Osaka, Japan). fabrics were determined by Datacolor SF 600X spectrophotometer (Datacolor, Lucerne, Switzerland). Ultraviolet protection factor (UPF) and TUVA% were measured by Labsphere UV 2000F (Labsphere, The topography of different fibers was observed at the optical microscope. A 3D microscope graph North Sutton, NH, USA). of fabrics was obtained by Super Depth of Field 3D Microscope VHX-6000 (Keyence, Osaka, Japan). Ultraviolet2.2. Preparation protection factor (UPF) and TUVA% were measured by Labsphere UV 2000F (Labsphere, North Sutton, NH, USA). These four novel dyes were provided by our research group. The cationic quaternary 2.2.ammonium Preparation salts including N-(2-aminoethyl) pyridinium chloride salt and m- aminophenyltrimethylammonium salt were synthesized according to the reported researches [16,36– These four novel dyes were provided by our research group. The cationic quaternary ammonium 38]. The final products were synthesized by classical condensation and diazotization-coupling salts including N-(2-aminoethyl) pyridinium chloride salt and m-aminophenyltrimethylammonium salt reaction according to the literature [12]. Methanol and dichloromethane (4:1 by volume) as the eluent were synthesized according to the reported researches [16,36–38]. The final products were synthesized system for chromatographic column was used to purified. All the dyes were prepared successfully by classical condensation and diazotization-coupling reaction according to the literature [12]. and investigated by FT-IR, 1H-NMR, and EA. The synthetic process and results can be found in Methanol and dichloromethane (4:1 by volume) as the eluent system for chromatographic column was supplementary materials. used to purified. All the dyes were prepared successfully and investigated by FT-IR, 1H-NMR, and EA. The synthetic process and results can be found in supplementary materials. 2.3. Dyeing and Measure Methods 2.3. Dyeing and Measure Methods 2.3.1. One-Bath One-Step Procedure 2.3.1.All One-Bath dyeing One-Stepof three kinds Procedure of fabrics were carried out using an infrared laboratory dyeing machine (PYROTEC-2001,All dyeing of threeRoaches kinds International, of fabrics were UK) carried using outfour using heterocyclic an infrared reactive laboratory dyes dyeingwith a machineliquor of (PYROTEC-2001,40:1 at different shade Roaches of 1~5% International, (o. w. f). UK)These using dyes four were heterocyclic applied to reactivewool/acr dyesylic blended with a liquor fabric of using 40:1 atthe di ffone-batherent shade dyeing of 1~5% method (o. w.as f).described These dyes in Figure were applied3. After todyeing, wool/acrylic the dyed blended samples fabric were using soaped the one-bathfor 10 min dyeing at 98 °C method in a soap as described solution of in containing Figure3. After 2 g/L dyeing, soap flakes. the dyed samples were soaped for 10 min at 98 ◦C in a soap solution of containing 2 g/L soap flakes.

Figure 3. Dyeing profile of wool/acrylic blended fabric using heterocyclic dyes. Figure 3. Dyeing profile of wool/acrylic blended fabric using heterocyclic dyes.

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2.3.2. Dye Exhaustion The absorbance of the dye solution before and after dyeing was carried out by UV-Vis spectrophotometry at λmax. The percentage of exhaustion (E%) was calculated using Equation (1):

(A0 A ) E% = − 1 100 (1) A0 × where A0 and A1 are the absorbance of the dye solution before and after the dyeing process, respectively.

2.3.3. The Color Strength (K/S) on the Dyed Fabrics In the spectrum visible region, 380–720 nm, the K/S values and color parameters (L *, a *, b *) of the dyed fabric were measured using Datacolor SF 600X spectrophotometer. In order to obtain the correct K/S, five separate points of each tested dyed fabric were selected. The color yield of dyed fabrics was calculated using the Kubelka-Munk equation (Equation (2)).

K (1 R)2 = − (2) S 2R where R is the reflectance of the dyed substrate at λmax, K is the absorption coefficient, and S is the scattering coefficient.

2.3.4. Fabric Strength Test Considering that knitted fabrics were used for dyeing, fabric strength was obtained by bursting strength according to GB/T 19976–2005. The bursting strength of textiles was determined by the steel ball method. The maximum bursting strength of this sample was recorded at a constant rate of extension testing machine (CRE, HD026N-200, Multifunctional electronic fabric strength tester, Nantong Hongda Experiment Instruments CO., LTD, Nantong, China) when the sample was broken. Each kind of fabric was measured at least five times to obtain the mean bursting strength.

2.3.5. Levelling Test Levelling test refers to the uniformity of the color of the fabric after dyeing. Five separate locations on the surface of the dyed fabric were chosen and assessed by Datacolor spectrophotometry [39,40]. Then, the mean color differences value (∆E) between the five locations were calculated using Equation (3). Under normal circumstances, ∆E < 1 means that the color difference is small, and the dyeing uniformity is good. h i12 ∆E = (∆L)2 + (∆a)2 + (∆b)2 (3) where ∆L, ∆a, and ∆b are the differences in the color parameters.

2.3.6. Fastness Testing Fastness testing for the dyed fabrics was performed according to international standards. Fastness to washing was assessed according to ISO 105-C03(2010). Fastness to the light was assessed using ISO 105-B02(2013). Fastness to rubbing was assessed following ISO 105-X12(2001).

2.3.7. Anti-Ultraviolet Testing Anti-ultraviolet testing for the dyed fabric was performed according to AATCC 183: 2014. The UPF and TUVA% of fabrics were measured by Labsphere UV-2000F. Polymers 2020, 12, 285 6 of 18

2.3.8. Antibacterial Testing Staphylococcus aureus (S. aureus) was engaged to perform the antibacterial testing of the dyed fabric according to AATCC100-2009, and the antibacterial rates were calculated by using Equation (4).

Polymers 2020, 12, x FOR PEER REVIEW 6 of 18 (A B) R% = − 100 (4) A × (A − B) R% = A × 100 (4) where R% is the percentage reduction of the bacterium, while A and B are the quantities of bacterial colonieswhere of R% fabrics is the before percentage and afterreduction the dyeing of the bacterium, process, respectively. while A and B are the quantities of bacterial colonies of fabrics before and after the dyeing process, respectively. 3. Results and Discussion 3. Results and Discussion 3.1. Spectral Characterization 3.1. Spectral Characterization In order to investigate the relationship between spectral properties and the dye structures, In order to investigate the relationship between spectral properties and the dye structures, the the reactive dyes bearing different substituted groups were designed. The maximum absorption reactive dyes bearing different substituted groups were designed. The maximum absorption wavelengthswavelengths of the of fourthe four reactive reactive dyes dyes containing containing cationic cationic groups groups with withthe the samesame concentration (0.012 (0.012 g/L) wereg/L) measured were measured in DMF solution.in DMF solution. The strong The absorptionstrong absorption bands bands were observedwere observed in Figure in Figure4 and 4 resultsand of the spectralresults of data the spectral were listed data were in Table listed1. in The Tableλmax 1. Theof λ themmax of werethem were 633.0 633.0 nm withnm with greenish greenish blue blue shade for D-1,shade 536.0, for D-1, 535.0, 536.0, and 535.0, 542.0 and nm 542.0 with nm fuchsia with fuchsia shades shades for D-2, for D-3,D-2, D-3, and and D-4 D-4 in thein the visible visible region, respectively.region, respectively. It is clear to It us is thatclearπ to-π us* transition that π-π* transition would be would facilitated be facilitated with the with increase the increase of the delocalizedof the π-conjugateddelocalized system π-conjugated [41]. The system molar [41]. absorption The molar coe absorptionfficients ofcoefficients these dyes of werethese brilliantdyes were at brilliant the range of at the range of 26,6341 to 55,2471 L·mol−1·cm−1, which was caused by the π-π* transition between the 26,634 to 55,247 L mol− cm− , which was caused by the π-π* transition between the aromatic rings aromatic rings ·and the· azo units. and the azo units.

FigureFigure 4. UV-Vis4. UV-Vis absorption absorption spectra spectra for syntheti syntheticc dyes dyes in inDMF DMF solution solution (0.012 (0.012 g/L). g /L). Table 1. Spectroscopic properties of the azo heterocycle reactive dyes. Table 1. Spectroscopic properties of the azo heterocycle reactive dyes. opt λ λ λ ε −1 λ E Dye λDMFDMF MethanolλMethanol IsopropanolλIsopropanol ɛ (L mol Color λonset g Dye (nm) (nm) (nm) (L mol 1 cm 1) Color (nm) (nm) (nm) (nm) −cm−1)− (nm) (ev)(ev) D-1 633.0 623.0 621.0 26634 greenishgreenish blue 712.0 1.74 D-1 633.0 623.0 621.0 26634 712.0 1.74 D-2 536.0 535.0 532.0 34435 fuchsiablue 614.0 2.02 D-2D-3 536.0 535.0 534.0 535.0 532.0 532.0 55247 34435 fuchsia fuchsia 614.0 626.0 1.98 2.02 D-3D-4 535.0 542.0 539.0 534.0 536.0 532.0 43379 55247 fuchsia fuchsia 626.0 624.0 1.99 1.98 D-4 542.0 539.0 536.0 43379 fuchsia 624.0 1.99

With the common coupling components, the color and depth of hues of these dyes were influenced by the electron effect of the substituent at the diazo components. Due to the introduction

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With the common coupling components, the color and depth of hues of these dyes were influenced Polymersby the electron2020, 12, x FOR effect PEER of theREVIEW substituent at the diazo components. Due to the introduction of -NO7 of 182 substituent group as the electron-withdrawing group, the maximum absorption wavelength of D-1, ofis found-NO2 substituent to demonstrate group a as remarkable the electron-withdrawing bathochromic shift. group, The the dye maximum was obtained absorption by replacing wavelength diazo ofcomponent D-1, is found of D-1 to demonstrate structure with a remarkable 2-amino-6-nitrobenzothiazole, bathochromic shift. whichThe dye still wa hads obtained more bathochromic by replacing diazoshift than component D-2, but itsof λD-1max wasstructure shorter with than 2-amino-6-nitrobenzothiazole, that of D-1. It is known that thewhich slight still hypsochromic had more bathochromicshift effect was shift usually than caused D-2, but by theits λ introductionmax was shorter of electron-attracting than that of D-1. groups It is known into the that “second the slight leg” hypsochromicattached to the shift halotriazine effect was [16 usually]. D-3, m-aminophenyltrimethylammoniumcaused by the introduction of electron-attracting as a substituent groups group into is themore “second hypsochromic leg” attached than D-4, to theN-(2-aminoethyl) halotriazine [16]. pyridinium D-3, m-aminophenyltrimethylammonium as substituent. As observed in Table as 1a, substituentthe maximum group absorption is more of hypsochromic dyes did not shiftthan significantly,D-4, N-(2-aminoethyl) indicating thatpyridinium they did as not substituent. have a strong As observedsolvent dependence. in Table 1, the Meanwhile, maximum the absorption higher the of polaritydyes did of not the shift solvent, significantly, the further indicatingλmax was that shifted they didtowards not have a longer a strong wavelength solvent (bathochromism), dependence. Meanwhile, which can the be attributedhigher the to polarity dye–solvent of the interactions solvent, the by furtherthe dipolar λmax ewasffect shifted [42] and towards intermolecular a longer hydrogen wavelength bonding (bathochromism), forces [43]. which can be attributed to opt dye–solventFurther, interactions the optical band by the gap dipolarEg was effect determined [42] and intermolecular from the onset absorptionhydrogen bonding edge λonset forcesat higher [43]. wavelengthsFurther, the according optical toband Equation gap (5)was [44 ].determined This equation from means the onset that absorption the greater edge the λ E,onset the at furtherhigher wavelengthsλ will toward according hypsochromic to Equation shift. The(5) [44]. electronic This equation transitions means cause that the the dye greater shade the and E, arethe relatedfurther toλ willstimulate toward transition hypsochromic energy [shift.45]. TheThe optical electronic band transitions gap of these cause dyes the can dye be foundshade inand the are Table related1. to stimulate transition energy [45]. The optical band gap of these dyes can be found in the Table 1. opt hc abs Eg =ℎ = 1240/λonset (5) = λabs = 1240/ (5) onset In addition,addition, in in order order to discloseto disclose the structure–spectra the structure–spectra relation relation between between these dyes, these the DFTdyes,/B3LYP the DFT/B3LYPmethod combined method with combined the 6–31 with G (d) the basis 6–31 set G was (d) carriedbasis set out was with carried the Gaussian out with 09. the The Gaussian calculated 09. Theenergy calculated gaps for energy chromophores gaps for chromophores in these dyes werein thes 2.14,e dyes 3.11, were and 2.14, 2.84 3.11, eV respectively,and 2.84 eV respectively, which were whichin agreement were in withagreement their UV-vis with their absorption UV-vis absorpti spectra.on A crudespectra. view A crude of the view processes of the processes can be provided can be providedby HOMO-LUMO by HOMO-LUMO plots [46]. plots As can[46]. be As seen can inbe Figure seen in5, Figure the subtle 5, the changes subtle forchanges molecular for molecular orbitals orbitalsincluding including the HOMO the HOMO and LUMO and LUMO of these of these chromophores chromophores were were observed observed due due to the to the influences influences of ofdi ffdifferenterent substituent substituent groups groups attached attached to to the the heterocyclic heterocyclic ring, ring and, and the the electron electron cloud cloud density density of of D-3 D- 3was was concentrated. concentrated. As As can can been been seen seen with with the molecular the molecular orbital orbital plots ofplots HOMO of HOMO and LUMO and inLUMO different in differentsolvents, solvents, the electron the densityelectron between density between HOMO andHOMO LUMO and were LUMO very were similar, very as similar, evident as inevident Figure in5. FigureIt can be 5. observedIt can be observed that these that dyes these showed dyes a showed weak solvent a weak dependency. solvent dependency.

Figure 5. The HOMOs and LUMOs for dyes’ chromophores with DFT/B3LYP 6–31 G (d) basis. Figure 5. The HOMOs and LUMOs for dyes’ chromophores with DFT/B3LYP 6–31 G (d) basis. 3.2. Dyeing Properties of the Four Reactive Dyes 3.2. Dyeing Properties of the Four Reactive Dyes In the dyeing process, the dye-uptake is a major factor that should be taken into consideration. All kindsIn the of dyeing fabrics process, were dyed the dye-uptake by using an is exhausta major dyeingfactor that process. should The be taken types into of cationic consideration. groups Alland kinds chromophores of fabrics were presented dyed by in using the structures an exhaust of dyeing these dyes process. have The a remarkabletypes of cationic effect groups on dyeing and chromophores presented in the structures of these dyes have a remarkable effect on dyeing performance [30]. As illustrated in Figure 1, on the one hand, covalent bonds could be generated by reactive groups with the amino groups of wool fabric by nucleophilic substitution reaction, on the other hand, cationic group could combined with the carboxyl group of wool fabric and sulfonic acid group of acrylic fabric via ionic bonds.

Polymers 2020, 12, 285 8 of 18 performancePolymers 2020, 12 [30, x ].FOR As PEER illustrated REVIEW in Figure1, on the one hand, covalent bonds could be generated8 of by 18 reactive groups with the amino groups of wool fabric by nucleophilic substitution reaction, on the Table 2 summarizes the percentage dye exhaustion of 1.0% (o. w. f) dyeing range. It was found other hand, cationic group could combined with the carboxyl group of wool fabric and sulfonic acid that high exhaustion of D-1-D-4 could reach over 97% due to the lower solubility and good affinity group of acrylic fabric via ionic bonds. for fibers. Moreover, the exhaustion on acrylic of dye 4 was a little lower than that of dye 3. This Table2 summarizes the percentage dye exhaustion of 1.0% (o. w. f) dyeing range. It was found implies that it’s easier for m-aminophenyltrimethylammonium as a quaternary ammonium salt that high exhaustion of D-1-D-4 could reach over 97% due to the lower solubility and good affinity group to form ionic bonds with acrylic fiber in contrast to the N-(2-aminoethyl) pyridinium salt for fibers. Moreover, the exhaustion on acrylic fiber of dye 4 was a little lower than that of dye 3. group. This implies that it’s easier for m-aminophenyltrimethylammonium as a quaternary ammonium salt group to form ionic bonds with acrylic fiber in contrast to the N-(2-aminoethyl) pyridinium salt group. Table 2. Exhaustion and K/S value of synthesized dyes.

Table 2. Exhaustion and K/S valueAcrylic of synthesizedWool/Acrylic dyes. Wool Fabric Wool Fabric Acrylic FabricFabric WoolBlended/Acrylic Fabric Blended Fabric E% 97.68% 99.94% 97.85% E% 97.68% 99.94% 97.85% D-1 D-1 K/S K/S5.33 5.33 5.05 5.05 6.16 6.16 E% E%99.86% 99.86% 99.75%99.75% 99.44% 99.44% D-2 D-2 K/S K/S16.52 16.52 9.61 9.61 11.18 11.18 E% 99.91% 99.43% 99.97% E% 99.91% 99.43% 99.97% D-3 D-3 K/S K/S29.18 29.18 12.77 12.77 12.29 12.29 E% 99.89% 98.71% 99.91% E% 99.89% 98.71% 99.91% D-4 D-4 K/S K/S28.85 28.85 6.30 6.30 9.10 9.10

OptimizedOptimized structures structures for for the the chromophore chromophore are are shown shown in in Figure Figure6. 6. The The results results show show that, that, for for D-3 D- 3 and D-4, the dihedral angle between the phenyl and the benzothiazole rings is calculated to be and D-4, the dihedral angle between the phenyl and the benzothiazole rings is calculated to be 179.81◦. They179.81°. exhibited They exhibited good planarity good planarity for the chromophore.for the chromophore. The dye The molecules dye molecules with higherwith higher planarity planarity can becan easily be easily immobilized immobilized to the to surface the surface of the of fiber the fiber in a largein a large area [area47]. [47]. This This also furtheralso further explained explained the phenomenonthe phenomenon that thethat exhaustion the exhaustion of dyes of dyes 3 and 3 4and were 4 were a little a little higher higher than than those those of dyes of dyes 1 and 1 2.and 2.

Figure 6. Optimized structure for the chromophore in reactive dyes. Figure 6. Optimized structure for the chromophore in reactive dyes. It is worthwhile to mention that the exhaustion of these dyes on acrylic fabric were higher than thoseIt is worthwhile on wool fabrics, to mention while that the the K exhaustion/S of dyed of acrylic these fabricdyes on was acrylic lower fabric than were those higher on wool than those on wool fabrics, while the K/S of dyed acrylic fabric was lower than those on wool fabrics. This implies that the color yield relates to differences of dye-uptake, dye distribution on fiber, the molecular structures of the dye, and the refractive index of fiber.

Polymers 2020, 12, 285 9 of 18 fabrics. This implies that the color yield relates to differences of dye-uptake, dye distribution on fiber, thePolymers molecular 2020, 12 structures, x FOR PEER of REVIEW the dye, and the refractive index of fiber. 9 of 18

3.3.3.3. E Effectffect of of pH pH Value Value TheThe pH pH value value is is an an important important factor factor for for di differenfferentt kinds kinds of of fabrics fabrics dyeing. dyeing. With With the the exception exception of of D-1,D-1, it it can can be be seen seen from from Figure Figure7 7that that the the K K/S/S of of these these dyes dyes on on wool wool fabric fabric dyeing dyeing slightly slightly increased increased withwith the the increase increase of of the the pH pH value, value, while while it it decreased decreased when when the the pH pH value value exceeded exceeded 6, 6, which which is is related related toto the the isoelectric isoelectric pointpoint ofof wool fabrics (4.2–4.8) (4.2–4.8) an andd the the hydrolysis hydrolysis of of dyes. dyes. When When the the pH pH value value of the of thedyebath dyebath exceeded exceeded its itsisoelectric isoelectric point point of of wool, wool, a ane negativegative charge charge on on the surface ofof thethe woolwool could could formform an an electrostatic electrostatic attraction attraction with with cationic cationic groups groups of of reactive reactive dye. dye. At At the the same same time, time, the the number number of of freefree amino amino groups groups on on the the wool wool was was increased, increased, which which is is favorable favorable for for forming forming a a covalent covalent bond bond with with reactivereactive groups. groups.

Figure 7. Effect of pH on K/S for heterocyclic reactive dyes. (a) Dye 1; (b) Dye 2; (c) Dye 3; (d) Dye 4. Figure 7. Effect of pH on K/S for heterocyclic reactive dyes. (a) Dye 1; (b) Dye 2; (c) Dye 3; (d) Dye 4. As displayed in Figure7, pH 4 was the optimum value for acrylic fabric dyeing. It is well known that cationicAs displayed dyes werein Figure applied 7, pH to 4 thewas acrylic the optimum fiber dyeing value for at pHacrylic 4–5. fabric The dyeing. color yield It is well decreased known duethat to cationic the hydrolysis dyes were of applied the acrylic to the fiber acrylic and thefibe dyer dyeing under athigh pH 4–5. pH valueThe color dyeing yield conditions decreased [ 48due]. Overall,to the hydrolysis as can be of seen the acrylic from Figure fiber and7, for the D-1 dye and under D-2, high the pH color value yields dyeing on theconditions wool /acrylic [48]. Overall, were maximizedas can be seen at pH from 4 of Figure the dyebath, 7, for D-1 but and the maximumD-2, the color color yields yield on for the D-3 wool/acrylic and D-4 were were at pH maximized 6. at pH 4 of the dyebath, but the maximum color yield for D-3 and D-4 were at pH 6. 3.4. Effect of Temperature

3.4. ItEffect can beof Temperature seen in Figure 8 that the low K /S values of dyes was observed below 95 ◦C for acrylic fiber dyeing. However, the K/S increased significantly when the dyeing temperature exceeded the glass It can be seen in Figure 8 that the low K/S values of dyes was observed below 95 °C for acrylic transition temperature of the acrylic fiber (80~90 C), at which temperature the molecular segment fiber dyeing. However, the K/S increased signific◦ antly when the dyeing temperature exceeded the movement was intensified, and the dye molecules were more likely to diffuse into the fiber interior. glass transition temperature of the acrylic fiber (80~90 °C), at which temperature the molecular segment movement was intensified, and the dye molecules were more likely to diffuse into the fiber interior. An increase in the K/S values of dyed wool fabrics was observed with the increase of temperature, which attributed to the dense scale layers on the wool surface. The topography of wool fiber was observed by the optical microscope (Figure 9a). On the one hand, as the temperature

Polymers 2020, 12, 285 10 of 18

Polymers 2020, 12, x FOR PEER REVIEW 10 of 18 An increase in the K/S values of dyed wool fabrics was observed with the increase of temperature, Polymers 2020, 12, x FOR PEER REVIEW 10 of 18 whichascended, attributed the scale to thelayer dense on the scale wool layers surface on the opened, wool surface.and the resistance The topography between of fibers wool fiberand dyes was observed by the optical microscope (Figure9a). On the one hand, as the temperature ascended, the scale ascended,became smaller. the scale On thelayer other on thehand, wool as cansurface be seen opened, in Figure and 9c,the the resistance solubility between of these fibers dyes graduallyand dyes layer on the wool surface opened, and the resistance between fibers and dyes became smaller. On the becameincreased. smaller. On the other hand, as can be seen in Figure 9c, the solubility of these dyes gradually other hand, as can be seen in Figure9c, the solubility of these dyes gradually increased. increased.

Figure 8. Effect of temperature on K/S for heterocyclic reactive dyes. (a) Dye 1; (b) Dye 2; (c) Dye 3; FigureFigure(d) Dye 8.8. 4. EEffect ffect ofof temperaturetemperature onon KK/S/S forfor heterocyclicheterocyclic reactivereactive dyes.dyes. (a) DyeDye 1; ((b)) DyeDye 2;2; ((cc)) DyeDye 3;3; (d) Dye 4. (d) Dye 4. Additionally, the K/S value tended to be smooth and even declined when the temperature Additionally, the K/S value tended to be smooth and even declined when the temperature exceeded exceededAdditionally, 100 °C owing the K/Sto the value hydrolysis tended of to the be dye. smooth As show andn evenin Figure declined 9d, the when heterocyclic the temperature structure 100 C owing to the hydrolysis of the dye. As shown in Figure9d, the heterocyclic structure of D-1 was exceededof D-1◦ was 100 especially °C owing unstable to the hydrolysis under high of temperature. the dye. As show The nresults in Figure indicate 9d, the that heterocyclic 95 °C is the structure suitable especially unstable under high temperature. The results indicate that 95 C is the suitable temperature oftemperature D-1 was especially as a one-bath unstable dyeing under contact high temptemperature.erature on The the results wool/acrylic indicate◦ blended that 95 °Cfabric. is the suitable as a one-bath dyeing contact temperature on the wool/acrylic blended fabric. temperature as a one-bath dyeing contact temperature on the wool/acrylic blended fabric.

Figure 9. Cont.

PolymersPolymers2020 2020,,12 12,, 285 x FOR PEER REVIEW 1111 ofof 1818 Polymers 2020, 12, x FOR PEER REVIEW 11 of 18

Figure 9. (a) The topography of wool fiber; (b) The topography of wool/acrylic blended fiber; FigureFigure 9.9. ((aa)) TheThe topographytopography ofof woolwool fiber;fiber; ((bb)) TheThe topographytopography ofof wool/acrylicwool/acrylic blendedblended fiber;fiber; ((cc)) TheThe (c) The solubility of these dyes under the different temperatures; (d) The absorbance change of D-1 solubilitysolubility ofof thesethese dyesdyes underunder thethe differentdifferent temperatures;temperatures; ((dd)) TheThe absorbanceabsorbance changechange ofof D-1D-1 withwith with temperature. temperature.temperature. 3.5. Dyeing Heat-Rate Curve 3.5.3.5. DyeingDyeing Heat-RateHeat-Rate CurveCurve Dyeing heat-curves of these dyes are described in Figure 10. It is clear that increasing the dyeing Dyeing heat-curves of these dyes are described in Figure 10. It is clear that increasing the dyeing temperatureDyeing and heat-curves time has aof pronounced these dyes are effect described on the K in/S Fi valuegure of10. the It is dyed clear fabric. that increasing This phenomenon the dyeing is temperature and time has a pronounced effect on the K/S value of the dyed fabric. This phenomenon alsotemperature attributed and to thetime fiber has swellinga pronounced and dye effect di ffonusion. the K/S What’s value more, of the thedyed dyeing fabric. heat-rate This phenomenon curves of is also attributed to the fiber swelling and dye diffusion. What’s more, the dyeing heat-rate curves of theseis also dyes attributed were provided to the fiber by comparingswelling and the dye K/S diff valueusion. between What’s three more, types the ofdy fabrics.eing heat-rate curves of thesethese dyesdyes werewere providedprovided byby comparingcomparing thethe K/SK/S valuevalue betweenbetween threethree typestypes ofof fabrics.fabrics.

Figure 10. The dyeing heat-rate curve of the heterocyclic reactive dyes. (a) Dye 1; (b) Dye 2; (c) Dye 3; (FiguredFigure) Dye 10. 4.10. TheThe dyeingdyeing heat-rateheat-rate curvecurve ofof ththee heterocyclicheterocyclic reactivereactive dyes.dyes. ((aa)) DyeDye 1;1; ((bb)) DyeDye 2;2; ((cc)) DyeDye 3;3; ((dd)) DyeDye 4.4. As shown in Figure 10, the dye-uptake on wool increased gradually with dyeing temperature and time,As butAs shownshown the dye-uptake inin FigureFigure on 10,10, acrylic thethe dye-uptakedye-uptake fiber increased onon woolwool sharply increasedincreased at above graduallygradually 90 ◦C, which withwith dyeing candyeing be attributed temperaturetemperature to theandand rapid time, time, motion but but the the ofdye-uptake dye-uptake the chain segmentson on acrylic acrylic above fiber fiber increased theincreased glass transitionsharply sharply at at temperature. above above 90 90 °C, °C, What’whichwhich more,can can be be the attributed attributed dyeing heat-ratetoto thethe rapidrapid curve motionmotion and the ofof K thethe/S value chainchain of segmentssegments these dyes aboveabove on blended thethe glassglass fabric transitiontransition were similar temperature.temperature. to those What’ onWhat’ acrylic more,more, fabric thethe owingdyeingdyeing to heat-rateheat-rate the order curvecurve of dyeing andand thethe diff erentK/SK/S valuevalue fibers ofof [13 thesethese]. dydyeses onon blendedblended fabricfabric werewere similarsimilar toto thosethose onon acrylicacrylic fabricfabric owingowing toto thethe orderorder ofof dyeingdyeing differentdifferent fibersfibers [13].[13].

Polymers 2020, 12, 285 12 of 18

3.6. Build-UpPolymers and 2020 Homochromaticity, 12, x FOR PEER REVIEW of Different Dyed Fabrics 12 of 18

The3.6. build-up Build-Up propertyand Homochromaticity of three kindsof Different of dyed Dyed Fabrics fabrics is significant in terms of dye utilization and production cost [49], as shown in Figure 11. When the dye concentration reaches to 4% (o. w. f), The build-up property of three kinds of dyed fabrics is significant in terms of dye utilization and the K/S valueproduction increases cost [49], slowly, as shown indicating in Figure that 11. When the dyeing the dye tends concentration to be saturated. reaches to The4% (o. K w./S valuef), the of the wool/acrylicK/S value blended increases fabric slowly, locates indicating between that the the single-component dyeing tends to be saturated. fiber with The the K/S same value concentration. of the This canwool/acrylic be explained blended by the fabric fact locate that thes between synergistic the single-component effect of the two fibe fibersr with inthe the same blended concentration. fabric during the exhaustionThis can of be the explained dyes. by the fact that the synergistic effect of the two fibers in the blended fabric during the exhaustion of the dyes.

Figure 11.FigureBuild-up 11. Build-up property property of the of the heterocyclic heterocyclic reactive reactive dyes. (a ()a Dye) Dye 1; ( 1;b) (Dyeb) Dye 2; (c) 2; Dye (c) 3; Dye (d) Dye 3; (d 4.) Dye 4.

The unionThe dyeingunion dyeing property property (k) is(k) an is an important important indexindex to to determine determine the the color color match match between between dyed dyed acrylic andacrylic wool and fabric, wool fabric, which which were were calculated calculated using using EquationEquation (4). (4). K S  k= K K (6) S s k = wool (6)  K  where (K/S)wool and (K/S)acrylic are the K/S values ofs dyedacrylic wool fabric and acrylic fabric, respectively. The parameters (refers to L *, a *, and b * values) of the dyed fabrics at 1.0% (o. w. f) dye concentration are shown in Table 3. The hue variations were observed by combining all parameters. where (K/S)wool and (K/S)acrylic are the K/S values of dyed wool fabric and acrylic fabric, respectively. TheGenerally, parameters the union (refers dyeing to L proper *, a *,ties and were b good * values) in the case of the where dyed k is fabricsclose to 1 at [50]. 1.0% Meanwhile, (o. w. f) dye the low color differences between acrylic and wool fiber can meet the requirements in the practical concentration are shown in Table3. The hue variations were observed by combining all parameters. application. In general, D-1 has more outstanding union dyeing properties than the other dyes. Generally, the union dyeing properties were good in the case where k is close to 1 [50]. Meanwhile, the low color differencesTable between 3. The acrylic union dyeing and performance wool fiber of can wool meet and acrylic the requirementsfabric. in the practical application. In general, D-1Dyes has more Fabrics outstanding L * union a * dyeing b * properties K/S k than the other dyes. wool 39.40 −16.23 −7.43 5.33 D-1 1.06 Table 3. The unionacrylic dyeing 41.49 performance −15.82 of−7.61 wool and5.05 acrylic fabric. wool 28.24 38.15 −0.97 16.52 DyesD-2 Fabrics L * a * b * K/S1.72 k acrylic 32.41 34.80 −6.62 9.61 wool 39.40 16.23 7.43 5.33 D-1 − − 1.06 acrylic 41.49 15.82 7.61 5.05 − − wool 28.24 38.15 0.97 16.52 D-2 − 1.72 acrylic 32.41 34.80 6.62 9.61 − Polymers 2020, 12, 285 13 of 18

Table 3. Cont.

Dyes Fabrics L * a * b * K/S k wool 20.71 24.52 3.82 29.18 D-3 − 2.29 acrylic 28.64 31.32 10.21 12.77 − wool 22.47 32.29 9.20 28.85 D-4 − 4.58 acrylic 28.48 19.64 4.54 6.30 − Polymers 2020, 12, x FOR PEER REVIEW 13 of 18 3.7. Fabric Strength Test wool 20.71 24.52 −3.82 29.18 D-3 2.29 Three fabrics were dyed with a liquoracrylic of28.64 40:1 at31.32 95 ◦C,−10.21 60 min, 12.77 and 1.0% (o. w. f) dye concentration. wool 22.47 32.29 −9.20 28.85 The fabric strength of three fabricsD-4 was shown in Table4. The results showed4.58 that the fabric strength of dyed fabrics was slightly lower thanacrylic those 28.48 of untreated 19.64 − fabric,4.54 6.30 but there was no obvious difference. The decrease3.7. ofFabric fabric Strength strength Test may be caused by temperature. In order to accelerate the diffusion of dyes and motion of the chain segments, a higher temperature was used during the process of dyeing. For this dyeingThree process, fabrics the were damage dyed with of fibera liquor was of caused 40:1 at by95 °C, higher 60 min, temperature, and 1.0% (o. reducing w. f) dye the fabric concentration. The fabric strength of three fabrics was shown in Table 4. The results showed that the strength offabric dyed strength fabrics. of dyed However, fabrics comparedwas slightly lower with than untreated those of fabrics,untreated the fabric, dyeing but there condition was no had little influence onobvious the fabric difference. strength. The decrease of fabric strength may be caused by temperature. In order to accelerate the diffusion of dyes and motion of the chain segments, a higher temperature was used during the processTable 4. ofThe dyeing. fabric For strength this dyeing of three process, fabrics the damage before and of fiber after was dyeing. caused by higher temperature, reducing the fabric strength of dyed fabrics. However, compared with untreated fabrics, the dyeing condition had little influenceWoolFabric on the fabric Acrylicstrength. Fabric Wool/Acrylic Fabric

Untreated fabricTable 4. The fabric 219.1 strength N of three fabrics 331.8 before N and after dyeing. 379.3 N Dyed fabric with D-1 213.5 N 325.3 N 373.1 N Dyed fabrics with D-2 212.8 Wool Fabric N Acrylic 324.6 Fabric N Wool/Acrylic 372.2Fabric N Dyed fabricsUntreated with D-3 fabric 212.5 219.1 N N 331.8 324.7 N N 379.3 N 372.5 N Dyed fabricsDyed withfabric D-4 with D-1 214.6 213.5 N N 325.3 325.5 N N 373.1 N 373.4 N Dyed fabrics with D-2 212.8 N 324.6 N 372.2 N Dyed fabrics with D-3 212.5 N 324.7 N 372.5 N 3.8. Levelling PropertiesDyed fabrics with D-4 214.6 N 325.5 N 373.4 N

The dyed3.8. Levelling wool /Propertiesacrylic blended fabrics at 1.0% (o. w. f) dye concentration were measured by a Datacolor spectrophotometerThe dyed wool/acrylic toblended obtain fabrics the at mean 1.0% (o. color w. f) didyeff erencesconcentration (∆E). were As measured shown by in a Figure 12, these dyedDatacolor fabrics hadspectrophotometer low color di toff erencesobtain the andmean good color differences levelling properties.(ΔE). As shown The in Figure 3D microscope 12, these graph in Figure 13dyed shows fabrics that had low each color fiber differences was evenly and good dyed levelling and viewedproperties. from The 3D the microscope cross-section graph in of the fiber. The two kindsFigure of 13 fibershowsinterweaved that each fiber was and evenly cooperated dyed and withviewed each from otherthe cross-section and the of dyes the fiber. were The transferred two kinds of fiber interweaved and cooperated with each other and the dyes were transferred among among fibers,fibers, achieving achieving the the dyeing dyeing equili equilibrium.brium. The levelling Thelevelling properties propertiesof D-1 and D-2 of were D-1 better and than D-2 D- were better than D-3 and3 and D-4, D-4, which which was was ascribed ascribed to its to similar its similar color strengths. color strengths.

Figure 12. Levelling properties of wool/acrylic blended fabrics with heterocyclic dyes. Figure 12. Levelling properties of wool/acrylic blended fabrics with heterocyclic dyes.

Polymers 2020, 12, x FOR PEER REVIEW 14 of 18 Polymers 2020, 12, x FOR PEER REVIEW 14 of 18 Polymers 2020, 12, x FOR PEER REVIEW 14 of 18

Polymers 2020, 12, 285 14 of 18 Polymers 2020, 12, x FOR PEER REVIEW 14 of 18

Figure 13. 3D microscope graph of wool/acrylic blended fabrics with heterocyclic dyes. Figure 13. 3D microscope graph of wool/acrylic blended fabrics with heterocyclic dyes. 3.9. Fastness Properties of the Dyed Fabrics Figure 13. 3D microscope graph of wool/acrylic blended fabrics with heterocyclic dyes. 3.9. Fastness Properties of the Dyed Fabrics The color fastness properties of the dyed blended fabric with four dyes bearing an azo 3.9. Fastness Properties of the Dyed Fabrics benzothiazoleTheFigure color 13. derivate3D fastness microscope at properties 1.0% graph (o. ofw. of wool f) thedye/acrylic dyedconcentration blended blended fabrics werefabric with summarized with heterocyclic four indyes dyes. Table bearing 5. The anresults azo Figure 13. 3D microscope graph of wool/acrylic blended fabrics with heterocyclic dyes. 3.9. FastnessbenzothiazoleshowedThe Properties that color the derivate fastness ofdry the rubbing Dyed at properties 1.0% Fabrics was (o. good,w. of f) thedyebut dyedwetconcentration ru blenbbingded fastness werefabric summarized waswith poor, four which indyes Table canbearing 5. be The explained anresults azo 3.9. showedbenzothiazolebyFastness the existence Propertiesthat the derivate dry ofof thedye rubbing Dyed atoligomer. 1.0% Fabrics was (o. good,Further,w. f) dyebut D-4 wetconcentration containing rubbing fastness wereN-(2-aminoethyl) summarized was poor, which pyridiniumin Table can 5. be Theas explained cationic results The color fastness properties of the dyed blended fabric with four dyes bearing an azo benzothiazole byshowedgroup the hadexistence that better the dryoflight dye rubbing fastness oligomer. was than good,Further, the other but D-4 wet dyes, containing ru butbbing they fastness Nwere-(2-aminoethyl) grades was poor, 4–5 due whichpyridinium to the can benzothiazole be as explained cationic derivate at 1.0% (o. w. f) dye concentration were summarized in Table5. The results showed that the groupbystructure.The the color hadexistence betterfastness oflight dyeproperties fastness oligomer. thanof theFurther, the dyed other D-4 blendyes, containingded but fabric they Nwerewith-(2-aminoethyl) gradesfour dyes 4–5 duebearing pyridinium to the an benzothiazole azo as cationic dry rubbing was good, but wet rubbing fastness was poor, which can be explained by the existence of benzothiazolestructure.group had derivatebetter light at 1.0% fastness (o. w. than f) dye the concentrationother dyes, but were they summarized were grades in 4–5 Table due 5. to The the results benzothiazole dye oligomer. Further,Table 5. D-4Fastness containing of dyedN wool/acrylic-(2-aminoethyl) blended pyridinium fabrics at 1.0% as cationic (o. w. f) groupdye concentration had better lighta. showedstructure. that the dry rubbing was good, but wet rubbing fastness was poor, which can be explained fastnessby the thanexistence theTable other of 5.dye dyes,Fastness oligomer. but of they dyed Further, were wool/acrylic gradesD-4 containing blended 4–5 due fabrics toN-(2-aminoethyl) the at benzothiazole 1.0% (o. w. pyridinium f) dye structure. concentration as cationic a. Digital Pictures for Blended Rubbing Washing Light group had betterTable light 5. Fastness fastness ofthan dyed the wool/acrylic other dyes, blendedbut they fabrics were grades at 1.0% 4–5 (o. w.due f) todye the concentration benzothiazole a. Samples Fabric RubbingFastness WashingFastness a FastnessLight structure.Table 5. FastnessDigital of dyedPictures wool for/acrylic Blended blended fabrics at 1.0% (o. w. f) dye concentration . Samples Digital Pictures(1%owf)Fabric for Blended DryRubbingFastness Wet SC WashingFastnessSW SA FastnessLight Rubbing Washing Light Digital Pictures(1%owf) for Blended Fabric Fastness Fastness a Fastness SamplesSamplesTable 5. Fastness of dyedFabric wool/acrylic blended fabricsDryFastness at 1.0%Wet (o. w. f) dyeSCFastness concentrationSW SAFastness . (1%owf)(1%owf) Dry Wet SC SW SA Digital Pictures for Blended RubbingDry WetWashing SC SW SA Light SamplesD-1 Fabric Fastness5 4 Fastness4 4 4–5Fastness 4 D-1 (1%owf) Dry 5 Wet 4SC SW4 SA4 4–5 4 D-1D-1 5 44 44 44 4–54–5 4 4

D-1 5 4 4 4 4–5 4

D-2 5 4 4 4 4–5 4–5 D-2D-2 5 44 44 44 4–54–5 4–5 4–5 D-2 D-2 5 5 4 4 4 44 4–54 4–54–5 4–5

D-3D-3 D-3 4–5 4–53–4 3–43–44 444 44–54 4–5 4–5 4–5 4–5 4–5 Polymers 2020, 12, x FOR PEER REVIEW 15 of 18 D-3 4–5 3–4 4 4 4–5 4–5

D-3 4–5 3–4 4 4 4–5 4–5

D-4 4–5 4 4–5 4–5 4–5 4–5 D-4D-4 4–5 44 4–54–5 4–5 4–5 4–5 4–5 4–5 4–5

a SC = staining on ; SW = staining on wool; SA = staining on acrylic a SC = staining on cotton; SW = staining on wool; SA = staining on acrylic. a SC = staining on cotton; SW = staining on wool; SA = staining on acrylic

3.10. Anti-Ultraviolet Properties of Dyed Fabric The effects of dyes on the anti-ultraviolet properties of dyed fabric were investigated and shown in Figure 14. According to the assessment standard of the anti-UV performance of textile, the textiles whose UPF is better than 40 and TUVA% is less than 5% can be called the UV-protection products. Compared with untreated fabric, the UPF of dyed fabrics has been remarkably improved and the TUVA% of these four dyes was less than 0.5%. The data of UPF and TUVA% demonstrate that they exhibited excellent anti-ultraviolet properties. Further, results showed that the UV resistance of dyed wool/acrylic blended fabrics improved with increasing the dosage of four novel heterocyclic dyes owing to the increase of dye adsorption capacity.

Figure 14. Anti-ultraviolet properties of wool/acrylic blended fabrics with these dyes.

3.11. Antibacterial Properties of Dyed Fabric

According to the AATCC-100 antibacterial test method, the antibacterial rate of dyed wool/acrylic blended fabrics against Staphylococcus aureus was evaluated at 5.0% (o. w. f) dye concentration. As can been seen in Table 6, the antibacterial rates of dyed wool/acrylic blend were around 90%. Quaternary ammonium groups in the molecular structure played a major role in the antibacterial activities, which caused the damage of the cell membrane and protein activity [51–53]. At the same time, the free electrons on the surface of N and S atoms in the structures had an auxiliary effect on the antibacterial activities. Such a phenomenon indicates that the dyed fabric possessed effective antibacterial activities. Further, measurements of the effect on hydrocarbon chain length and washing durability of antimicrobial functions are ongoing in our laboratory.

Polymers 2020, 12, 285 15 of 18

Polymers 2020, 12, x FOR PEER REVIEW 15 of 18 3.10. Anti-Ultraviolet Properties of Dyed Fabric 3.10. Anti-Ultraviolet Properties of Dyed Fabric The effects of dyes on the anti-ultraviolet properties of dyed fabric were investigated and shown in FigureThe 14 effects. According of dyes toon the the assessmentanti-ultraviolet standard proper ofties the of anti-UVdyed fabric performance were investigated of textile, and the shown textiles in Figure 14. According to the assessment standard of the anti-UV performance of textile, the textiles whose UPF is better than 40 and TUVA% is less than 5% can be called the UV-protection products. Comparedwhose UPF with is better untreated than fabric,40 and theTUVA UPF% is ofless dyed than fabrics 5% can has be call beened remarkablythe UV-protection improved products. and the Compared with untreated fabric, the UPF of dyed fabrics has been remarkably improved and the TUVA% of these four dyes was less than 0.5%. The data of UPF and TUVA% demonstrate that they TUVA% of these four dyes was less than 0.5%. The data of UPF and TUVA% demonstrate that they exhibited excellent anti-ultraviolet properties. Further, results showed that the UV resistance of dyed exhibited excellent anti-ultraviolet properties. Further, results showed that the UV resistance of dyed wool/acrylic blended fabrics improved with increasing the dosage of four novel heterocyclic dyes wool/acrylic blended fabrics improved with increasing the dosage of four novel heterocyclic dyes owing to the increase of dye adsorption capacity. owing to the increase of dye adsorption capacity.

Figure 14. Anti-ultraviolet properties of wool/acrylic blended fabrics with these dyes. Figure 14. Anti-ultraviolet properties of wool/acrylic blended fabrics with these dyes. 3.11. Antibacterial Properties of Dyed Fabric 3.11. Antibacterial Properties of Dyed Fabric According to the AATCC-100 antibacterial test method, the antibacterial rate of dyed wool/acrylic blendedAccording fabrics againstto the StaphylococcusAATCC-100 antibacterial aureus was evaluatedtest method, at 5.0%the antibacterial (o. w. f) dye rate concentration. of dyed Aswool/acrylic can been seen blended in Table fabrics6, the against antibacterial Staphylococcus rates ofaureus dyed was wool evaluated/acrylic blendat 5.0% were (o. aroundw. f) dye 90%. Quaternaryconcentration. ammonium As can been groups seen inin theTable molecular 6, the an structuretibacterial playedrates of adyed major wool/acrylic role in the blend antibacterial were activities,around 90%. which Quaternary caused the ammonium damage of groups the cell in membrane the molecular and structure protein activityplayed a [51 major–53]. role At thein the same time,antibacterial the free electronsactivities, onwhich the caused surface the of Ndamage and S of atoms the cell in membrane the structures and hadprotein an auxiliaryactivity [51–53]. effect on theAt antibacterial the same time, activities. the free electrons Such a phenomenonon the surface of indicates N and S thatatoms the in dyedthe structures fabric possessed had an auxiliary effective effect on the antibacterial activities. Such a phenomenon indicates that the dyed fabric possessed antibacterial activities. Further, measurements of the effect on hydrocarbon chain length and washing effective antibacterial activities. Further, measurements of the effect on hydrocarbon chain length and durability of antimicrobial functions are ongoing in our laboratory. washing durability of antimicrobial functions are ongoing in our laboratory. Table 6. The antibacterial rates of dyed wool/acrylic blended fabrics. Table 6. The antibacterial rates of dyed wool/acrylic blended fabrics.

TypesTypes Undyed Undyed Fabric fabric D-1D-1 D-2D-2 D-3 D-3 D-4 D-4 AntibacterialAntibacterial rate rate (%) (%) 0 0 88.09 88.09 91.2391.23 94.50 94.50 90.46 90.46

4. Conclusions

Polymers 2020, 12, 285 16 of 18

4. Conclusions Four novel reactive dyes containing cationic groups based on an azo benzothiazole derivative chromophores were designed and applied to wool/acrylic blended fabric by the one-union dyeing. These results demonstrate that these reactive dyes based on heterocyclic chromophores show beautiful color with high molar extinction coefficients. Moreover, these dyes exhibited excellent dyeing properties and fastness on wool/acrylic blended fabric. For wool/acrylic blended fabric dyed with D-1 and D-2, the optimum dyeing conditions were determined at pH 4, 95 ◦C for 60 min. In contrast, pH 6 is suitable for D-3 and D-4 dyes. Further, these dyes possessed excellent anti-ultraviolet properties and antibacterial activities. The present popularity of the reactive dyes containing cationic groups can be ascribed to their application of environmentally friendly functional finishing. This work will open the door for many dye chemists to improve the dye-uptake and color fastness and to enrich the applications of dyes on wool/acrylic textiles.

Supplementary Materials: The following are available online at http://www.mdpi.com/2073-4360/12/2/285/s1. Author Contributions: Data curation, M.W.; Investigation, M.W. and C.G.; Methodology, M.W. and C.G.; Supervision, T.Z. and W.L.; Writing—Original draft, M.W.; Writing—Review & editing, X.W., T.Z. and W.L. All authors have read and agreed to the published version of the manuscript. Funding: This work was funded by “the Fundamental Research Funds for the Central Universities and Graduate Student Innovation Fund of Donghua University” (CUSF-DH-D-2019064), NSFC (No.51602193), Shanghai “Chen Guang” project (16CG63). Conflicts of Interest: The authors declare no conflicts of interest.

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