Tunable hydrogel that contained well-defined poly(vinyl alcohol) (PVA), labile lactate groups, and hydrophilic poly(ethylene glycol) (PEG) segments was prepared through a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and esterification reaction. A diol was prepared via the esterification between lactic acid (LA) and PEG. Then the diol was allowed to react with maleic anhydride to produce a diacid. Meanwhile, well-defined PVA was synthesized by the alcoholysis of poly(vinyl acetate) (PVAc) obtained by RAFT polymerization of vinyl acetate. The hydrogels with tailor-made structure were generated by crosslinking PVA with LA-based diacid. The structures and properties of LA-based intermediates and the hydrogels were characterized with Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Both LA-based diol and diacid were semicrystalline and water-soluble, their melting temperature and glass transition temperature were 52 and −51, 54 and −41°C, respectively. The polydispersity indexes of the precursor of PVA samples were within the range of 1.03–1.10. It was found that the thermal stability of hydrogel was higher than that of LA-based diacid. Both the swelling and release properties of the hydrogels depend on the feeding ratio of PVA/LEM and the chain length of PVA, which reflected that the structure and properties of the hydrogels were controllable. POLYM. ENG. SCI., 54:1366–1371, 2014. © 2013 Society of Plastics Engineers

A novel poly(ester-urethane) with tailor-made structure was prepared by using lactic acid (LA) as starting material through a combination of two facile common reactions. First, a diol was prepared via the esterification between LA and poly(ethylene glycol) (PEG) with low molecular weight. Subsequently, the poly(ester-urethane) was synthesized through the addition polymerization of the LA-based diol and toluene 2,4-diisocyanate with 1,4-butanediol as chain extender. The structure, morphology, and properties of intermediate and the poly(ester-urethane) were analyzed with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography (GPC), X-ray diffraction, differential scanning calorimetry, polarizing optical microscopy, and thermogravimetric analysis. The results indicated that the intermediate was a diol of conjugating quite short lactate sequences with PEG oligomer, and the structure of the poly(ester-urethane) was as expected. The thermal transition, thermal decomposition temperature, and crystallinity of the polymer samples depended on the molecular size of PEG. In vitro degradation property of the poly(ester-urethane) also relied on the molecular weight of PEG. The weight loss percentages varied from 11 to 36% after 12-days immersing in phosphate-buffer saline at 37°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A tunable starch-based hydrogel was prepared by crosslinking unsaturated macromonomers in the presence of H₂S. First, well-defined poly(vinyl alcohol) (PVA) was prepared by alcoholysis of poly(vinyl acetate) obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate. Subsequently, carbon-carbon double bonds were incorporated onto PVA through esterification with maleic anhydride. Finally, the hydrogel was formed via concurrent electrophilic addition and thiol-ene reaction between starch maleic half-ester, unsaturated PVA and H₂S using potassium persulfate as initiator at 60 °C. Elemental analysis showed the percentage of sulfur in the gel ranged from 0.86% to 1.73%, depending on the chain length of PVA. The storage modulus, loss modulus and glass transition temperature of the networks varied from 12.7 to 50.9 MPa, from 3.7 to 15.7 MPa and from 57.0 to 71.8 °C, respectively. Both the swelling and release behavior of the gels were also modulated by changing the unsaturated PVA component. © 2012 Society of Chemical Industry

A structure-exact starch-based xanthate agent was prepared and used as chain transfer agent to mediate RAFT polymerization of vinyl acetate, which offered a convenient way to well control the structure and composition of starch-g-poly(vinyl acetate). The structures of the intermediate and the polymer were verified with FTIR and ¹H-NMR. Gel permeation chromatography measurement results indicated that the polymerization was performed as expected. It was found that the relationship between number average molecular weight and monomer conversion was linear. The polydispersity index of grafted side-chain ranged from 1.19 to 1.53 and most of them were around 1.2. There was one more degradation stage appeared on the thermogravimetric analysis profile of starch-g-poly(vinyl acetate) than that of starch. TEM observation exhibited that the product was able to self-assemble into micelles in aqueous solution, which suggested the copolymer was amphiphilic. Both the thermal and amphiphilic properties demonstrated the starch-g-poly(vinyl acetate) was successfully synthesized as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012