Manipulating the Phase Transition Behavior of Dual Temperature-Responsive Block Copolymers by Adjusting Composition and Sequence

Temperature-responsive polymers have garnered significant attention due to their ability to respond to external stimuli.In this work,dual temperature-responsive block copolymers are synthesized via reversible addition-fragmentation chain transfer polymerization(RAFT)polymerization utilizing zwitterionic monomer methacryloyl ethyl sulfobetaine(SBMA) and N-isopropyl acrylamide(NIPAAm) as monomers.The thermal responsive behaviors can be easily modulated by incorporating additional hydrophobic monomer benzyl acrylate(BN) or hydrophilic monomer acrylic acid(AA),adjusting concentration or pH,or varying the degree of polymerization of the block chain segments.The cloud points of the copolymers are determined by UV-Vis spectrophotometry,and these copolymers exhibit both controlled upper and lower critical solu bility temperatures(LCST and UCST) in aqueous solution.This study analyzes and summarizes the influencing factors of dual temperature responsive block copolymers by exploring the effects of various conditions on the phase transition temperature of temperature-sensitive polymers to explore the relationship between their properties and environment and structure to make them more selective in terms of temperature application range and regulation laws.It is very interesting that the introduction of poly-acrylic acid(PAA) segments in the middle of di-block copolymer PSBMA_(55)-b-PNIPAAm_(80) to form PSBMA_(55)-b-PAA_(x)-b-PNIPAAm_(80) results in a reversal of temperature-responsive behaviors from 'U'(LCST UCST) type,while the copolymer PSBMA_(55)-b-P(NIPAAm_(80)-co-AA_(x)) not.This work provides a clue for tuning the phase transition behavior of polymers for manufacture of extreme smart materials.

Synthesis of a Kind of Temperature-responsive Cell Culture Surface for Corneal Sheet

In this study, acrylic acid （AA） and 4-azidoaniline were used to modify poly （N-isopropylacrylamide） （NIPAAm） in order to fabricate temperature-responsive surface for corneal epithelia cell adhesion and detachment. First, NIPAAm was copolymerized with acrylic acid. Then, the copolymer was coupled with azidoaniline to synthesize AzPhPIA, derivative of p（NIPAAm-co-AA）, which possesses both thermo- and photo-sensitivities. Second, the synthesized copolymer was characterized by high performance liquid chromatography （HPLC）, Fourier transform infrared （FTIR） and a CHN analyzer. The thermo-sensitivity was characterized by temperature reducing experiment, contact angle measurement and low critical solution temperature （LCST） testing. Third, the derivatized copolymer was immobilized by photolithography on a polystyrene plate, and then the surface characterization of AzPhPIA-coated polystyrene plate （PSt） was measured by electron spectroscopy for chemical analysis （ESCA）. The thermo-sensitivity and cytocompatibility of the AzPhPIA-coated PSt were investigated by corneal epithelial cells culture. The results revealed that the AzPhPIA-coated PSt exhibited good cytocompatibility and cell detachability when temperature decreased.