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Coplymerization of Aleuritic Acid with L-Lactic Acid and Study the Aggregation Behavior in Different Solvents

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Coplymerization of Aleuritic Acid with L-Lactic Acid and Study the Aggregation Behavior in Different Solvents IJRPC 2013, 3(2) Asutosh K Pandey et al. ISSN: 22312781 INTERNATIONAL JOURNAL OF RESEARCH IN PHARMACY AND CHEMISTRY Available online at www.ijrpc.com Research Article COPLYMERIZATION OF ALEURITIC ACID WITH L-LACTIC ACID AND STUDY THE AGGREGATION BEHAVIOR IN DIFFERENT SOLVENTS Asutosh K Pandey and Baijayntimala Garnaik Polymer Science and Engineering Division National Chemical Laboratory Pune, Maharashtra, India. ABSTRACT In this present work, we highlight the copolymerization of L-lactic acid (L-LA with protected aleuritic acid in presence of Lewis acid catalyst using dehyropolycondensation method. The resulted copolymers are pliable, soft, waxy or even viscous liquid copolymers influenced by the aleuritic acid content. The purpose of this study is to investigate the physical properties. In addition, deprotected copolymers focus micelle -like aggregates in various organic solvents and mixed organic solvent at various proportions. INTRODUCTION some host trees. India is the major shellac Aliphatic polyesters constitute an important producing country in the world. Shellac (Lac) is class of polymers because of their known to comprise of several hydroxyl acid biodegradability1, and biocompability2a, b, that unit, aleuritic acid and its esters have great enable their use in drug delivery systems, importance in industrial domain. It is a artificial tissues3a,b, and commodity materials. valuable starting material for preparation of Polyesters are commonly produced through transparent water-clear adhesive, plasticizers9. either condensation or ring opening Aleuritic acid has been used as a raw material polymerization using various catalysts4-6. Self- for the synthesis of macrocyclic musk like organization of condensation polymer is rare in lactones such as ambrettolide, civetone and the literature. Particularly, self-organization of exaltone. There is only one literature report of amphiphilic polymers has resulted in poly aleuritic acid, where aleuritic acid has assemblies such as micelle, vesicles, fibers, been polymerized thermally and resulted helical, superstructures and macroscopic insoluble product10. We demonstrate for the tubes. These materials have potential first time that the linear homopolymer of application in areas ranging from material aleuritic acid (PAA) is obtained from aleuritic science to biological science. Thermo or pH acid (Fig 1). The change in the surface of the sensitive polymer micelles7a, b, and vesicles7c, assembly is the amplified consequence of have been reported in which the nature of the change in molecular level conformation with functionality at the corona changes in each polymer chain due to the presence of 9, response to the stimulus. A little attention has 10-hydroxy group in each monomeric unit. been paid to realize an environment- These polymers with such properties could dependent switch from a micelle-type find use in the applications such as carriers for assembly with a lipophilic corona8. Here, we trafficking drugs and as components of smart report a new class of aliphatic polyester adhesives. PAA is biocompatible and superstructures that exhibit such properties. biodegradable polymer, which could find Shellac is the only known commercial resin of potential use in biological system. animal origin. It is an important natural Block copolymers are often used for a variety resinous product secreted by an insect of supramolecular assemblies, in which the (Laccifer lacca), which lives on the sap of driving force involves the mutual immiscibility 426 IJRPC 2013, 3(2) Asutosh K Pandey et al. ISSN: 22312781 of the block and/or the immiscibility of one of chain show zigzag conformation in the the blocks in the bulk solvent. In case of poly polymer molecule13. (styrene-co-acrylic acid) block copolymers The thermal polymerization of Aleuritic acid exhibit several interesting amphiphilic leads to insoluble product because both intra assemblies11-12. We aimed to synthesize and intermolecular condensation are possible aliphatic polyester by polycondensation. The leading fast to the formation of fusible ethers, hydrophilic 9, 10-hydroxy functionality, the anhydrides, lactones and esters which hydrophobic methylene moiety are stitched in ultimately become infusible and insoluble three the same polymer backbone. The methylene dimensional network structures. group’s greater than five units in a polymeric OH O HO OH OH Aleuritic acid Fig. 1: 9, 10, 16-trihydroxy, palmitic acid (aleuritic acid) These functional polymers can be post Polyesters of glycolic and lactic acids are the modified to crosslink the polymer, or to attach main group of interest due to their long history bioactive molecules such as peptides or drugs of safety. and have shown potential application in drug Lactic acid can be condensed with other delivery systems and scaffold materials. The hydroxyl acids such as 6-hydroxycaproic acid, functional polyesters have tunable mechanical glycolic acid, and hydroxybutyric acid or in the properties with in vivo degradability14. presence of diols, diacids, and diamines. Polyesters syntheses have been explored by Direct condensation usually resulted in low both chemical synthesis and enzymatic molecular weight copolymers that can then be approaches. Several hydroxyl functional further linked to yield high-molecular-weight polyesters15-21, and poly (carbonate esters)22, polymers. In the second step, linking have been synthesized. Polymers with vicinal molecules such as diisocyanates, bis (amino- diols were prepared by chemical ethers), phosgene, phosphate, and anhydrides polymerization of L-lactide with protected takes place33-35. sugars23,24, followed by deprotection25-27. Use There is no report available so far, where the of monomers, initiators with unsaturated bond 9, 10 secondary vicinal diol is protected and enabled the introduction of epoxide groups by the hydroxy and carboxylic acid groups are post modification reaction with m- free to undergo dehydropolycondensation chloroperbenzoic acid (m-CPBA), while reaction to produce a linear high molecular treatment of allylic side chains with NMO/OsO4 weight homopolymer. resulted in dihydroxylation of side chains28. Fatty acids are suitable candidates for the Chemical polymerization of unprotected preparation of biodegradable polymers36,37, as hydroxyl functional caprolactones29, and they are natural body components and they hydroxymethyl substituted 1, 4-dioxan-2-ones are hydrophobic, and thus they may retain an 30,31, resulted in hyper branched structures with encapsulated drug for longer time periods comparable molecular weights and degree of when used as drug carriers. Aleuritic acid (9, branching. 10, 16-trihydroxy palmitic acid) is common The biodegradable polymers are intensively C16 fatty acids with two secondary hydroxyl aliphatic polyester of both natural and groups at 9, 10 positions and a primary synthetic origin. Polyesters can be synthesized hydroxyl group in the 16th position. It is by polycondensation of hydroxyl acids or by produced from resin (Shellac). ring-opening polymerization of cyclic esters The objective of this study is to incorporate (lactones), grafting, chain extension, or aleuritic acid in lactic acid based polymers for transesterification32. A wide range of the purpose of altering its physical properties. monomers has been used to produce The trifunctionality of aleuritic acid (9, 10, 16- biodegradable polyesters. Their trihydroxy palmitic acid) does not allow forming polymerizations can be carried out either in the the linear polymer. Previous study in our bulk or in solution. The most useful monomers laboratory focused on the synthesis aleuritic used for polycondensation are lactic, glycolic, acid (9, 10, 16-trihydroxy palmitic acid) hydroxybutyric acid and hydroxycaproic acids. homopolymer. The homopolymer synthesized 427 IJRPC 2013, 3(2) Asutosh K Pandey et al. ISSN: 22312781 from aleuritic acid by protecting the 9, 10 (Aldrich, USA), sodium sulphate, chloroform hydroxyl groups with dimethoxy propane and methanol (S.D Fine Chemicals, India), (DMP) to make –COOH and 16th position – mesitylene (Aldrich, USA), decaline (Aldrich, OH group free for reaction to make linear USA), and diphenyl ether (Fluka, Germany). polyester38. These copolymers have pendent All solvents were dried by using standard hydroxyl groups for aggregation to form micro procedures for example toluene by distilling scale morphologies. Molecular self-assembly over metallic sodium. All liquids were of organic molecules has generated a wide transferred by syringe under dry argon variety of objects with nanoscale or atmosphere. micrometer-scale morphologies including micelles39,40, vesicles41,42, ribbons43, films44, EXPERIMENTAL fibers45, 46, and tubules47-48. Synthesis of methyl ester of aleuritic acid: Crude aleuritic acid was converted to methyl The copolymerization of L-lactic acid (L-LA ester by using tetraphenyltin (TPT) as a with protected aleuritic acid in presence of catalyst in dry methanol solution at reflux Lewis acid catalyst using temperature. The reaction mixture was dehyropolycondensation method. The refluxed for 9 h, during which reaction was resulted copolymers are pliable, soft, waxy or monitored using TLC (solvent system; even viscous liquid copolymers influenced by chloroform/ methanol 9/1). The ester was the aleuritic acid content. The purpose of this dried using rotavapour and further purified by study is to investigate the physical properties. column chromatography (chloroform/ methanol In addition, deprotected copolymers focus
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