Thermo-responsive poly(N-isopropylacrylamide-co-styrene)[P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and ...Thermo-responsive poly(N-isopropylacrylamide-co-styrene)[P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and polymerization time on particle size and monodispersity were investigated.The results showed that, with increasing initiator dosage,mean diameter increased slightly to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing stirring rate,particle diameter decreased while the monodispersity became worse. When the amount of phase rate increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles hardly changed, and the monodispersity became better gradually. The microspheres prepared under the optimum experimental conditions showed satisfactory particle size and monodispersity.展开更多
以羟丙基甲基纤维素的水溶液为反应介质制备了快速响应的温敏性聚(N-异丙基丙烯酰胺)(PNIPA)水凝胶。利用DSC对其相转变温度进行了表征,利用SEM观察其表面形态,并测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学...以羟丙基甲基纤维素的水溶液为反应介质制备了快速响应的温敏性聚(N-异丙基丙烯酰胺)(PNIPA)水凝胶。利用DSC对其相转变温度进行了表征,利用SEM观察其表面形态,并测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。实验证明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且具有更快的响应速率。例如:该水凝胶在1 m in内失去89%的水,在4 m in内失去大约93%的水,而传统水凝胶在15 m in内仅失去66%左右的水。展开更多
The temperature dependence of the specific refractive index increment d n /d c of aqueous poly( N isopropylacrylamide) solution in the range of 20 ℃ to 35 ℃ were determined by a differential refractometer. The measu...The temperature dependence of the specific refractive index increment d n /d c of aqueous poly( N isopropylacrylamide) solution in the range of 20 ℃ to 35 ℃ were determined by a differential refractometer. The measured d n /d c of the solution decreases regularly and smoothly with increasing temperature until to the specific coil globule transition temperature of PNIPAM (around 32 ℃) and afterwards it increases with increasing temperature on the contrary. This extraordinary phenomenon is successfully explained and treated by a quantitative theory in terms of accompanying solvation desolvation process in the course of coil globule transition of the polymer chain in solution.展开更多
基金国家自然科学基金 (No 2 0 2 0 60 19)教育部留学回国人员科研启动基金 (No [2 0 0 2 ] 2 47)资助项目~~
文摘Thermo-responsive poly(N-isopropylacrylamide-co-styrene)[P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and polymerization time on particle size and monodispersity were investigated.The results showed that, with increasing initiator dosage,mean diameter increased slightly to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing stirring rate,particle diameter decreased while the monodispersity became worse. When the amount of phase rate increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles hardly changed, and the monodispersity became better gradually. The microspheres prepared under the optimum experimental conditions showed satisfactory particle size and monodispersity.
文摘以羟丙基甲基纤维素的水溶液为反应介质制备了快速响应的温敏性聚(N-异丙基丙烯酰胺)(PNIPA)水凝胶。利用DSC对其相转变温度进行了表征,利用SEM观察其表面形态,并测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。实验证明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且具有更快的响应速率。例如:该水凝胶在1 m in内失去89%的水,在4 m in内失去大约93%的水,而传统水凝胶在15 m in内仅失去66%左右的水。
文摘The temperature dependence of the specific refractive index increment d n /d c of aqueous poly( N isopropylacrylamide) solution in the range of 20 ℃ to 35 ℃ were determined by a differential refractometer. The measured d n /d c of the solution decreases regularly and smoothly with increasing temperature until to the specific coil globule transition temperature of PNIPAM (around 32 ℃) and afterwards it increases with increasing temperature on the contrary. This extraordinary phenomenon is successfully explained and treated by a quantitative theory in terms of accompanying solvation desolvation process in the course of coil globule transition of the polymer chain in solution.
