A novel temperature responsive copolymer, poly[2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate-co-N-hydroxymethyl acrylamide] [P(MEO₂MA-co-OEGMA-co-HMAM)], was synthesized by atom transfer radical polymerization. pH responsive poly(methacrylic acid) (PMAA) was synthesized by reversible addition-fragmentation chain transfer polymerization. After the hydroxyl groups on P(MEO₂MA-co-OEGMA-co-HMAM) were transformed into azide groups and the carboxyl groups on PMAA were transformed into alkyne groups respectively, a novel temperature and pH responsive hydrogel was fabricated by click chemistry between the azide-P(MEO₂MA-co-OEGMA-co-HMAM) and alkyne-PMAA in the presence of CuSO₄ and sodium ascorbate in aqueous solution. The rheological kinetics of gel formation demonstrated that gelation had commenced within 5 min at 25 °C, since then the storage modulus (G′) was higher than the loss modulus (G″). SEM images of hydrogel morphology and the swelling ratios of hydrogel at different temperatures and pH proved that the formed hydrogel had temperature and pH sensitivities. Bovine serum albumin was used as a model to evaluate the sustained release of the hydrogel; the results indicated that the hydrogel was a promising candidate for controlling protein drug delivery. © 2015 Society of Chemical Industry

Several different composition temperature- and pH-sensitive poly(acrylic acid-g-N-isopropylacrylamide) (P(AA-g-NIPAM)) graft copolymers were synthesized by free-radical copolymerization utilizing macromonomer technique. The phase behavior and conformation change of P(AA-g-NIPAM) in aqueous solutions were investigated by UV–vis transmittance measurements, fluorescence probe, and fluorescence quenching techniques. The results demonstrate that the P(AA-g-NIPAM) copolymers have temperature- and pH-sensitivities, and these different composition graft copolymers have different lower critical solution temperature (LCST) and critical phase transition pH values. The LCST of graft copolymer decreases with increasing PNIPAM content, and the critical phase transition pH value increases with increasing Poly(N-isopropylacrylamide) (PNIPAM) content. At room temperature (20°C), different composition of P(AA-g-NIPAM) graft copolymers in dilute aqueous solutions (0.001 wt %) have a loose conformation, and there is no hydrophobic microdomain formation within researching pH range (pH 3 ∼ 10). In addition, for the P(AA-g-NIPAM) aqueous solutions, transition from coil to globular is an incomplete reversible process in heating and cooling cycles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008