基于互穿网络结构的pH/温度双重刺激响应性微凝胶的研究

室温下采用氧化-还原引发体系,以低交联密度的聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶为种子,通过种子乳液聚合法合成由PNIPAM和聚丙烯酸(PAA)形成的具有互穿聚合物网络结构的微凝胶.傅立叶变换红外光谱分析结果表明微凝胶由PNIPAM和PAA两种聚合物组成,透射电镜表征结果证实微凝胶中PNIPAM和PAA两种聚合物形成了互穿网络结构.用动态激光光散射测试不同温度或pH值水介质中微凝胶的粒径,结果发现微凝胶具有良好的pH/温度双重刺激响应性.在水介质pH值大于5.5的情况下,PAA组分对微凝胶的体积相转变温度没有影响;而在水介质pH值为4.0的情况下,由于PAA与PNIPAM之间的氢键作用,微凝胶的体积相转变温度稍微降低.微凝胶中PAA组分含量越高,其pH刺激响应性越显著.

pH/TEMPERATURE DUAL STIMULI RESPONSIVE MICROGELS BASED ON INTERPENETRATING POLYMER NETWORK STRUCTURE

The microgels with in terpenetrating polymer network(IPN) structure based on poly(N-isopropyl acrylami de)(PNIPAM) and poly(acrylic acid)(PAA) were synthesized by seed-emulsion poly merization,using redox initiator at room temperature and the less crosslinked P NIPAM microgels as seeds.The microgels were determined to be composed of PNIPAM and PAA by Fourier transform infrared spectrometer (FTIR),and the IPN structur e in the microgels was confirmed by transmission electron microscopy(TEM).The results obtained by dynamic laser light scattering(DLLS) showed that the microg els had good pH/temperature dual stimuli responsiveness without any marked inter action.In the case of the pH of the aqueous media >5.5,the PAA component in t h e microgels had no effect on their volume phase transition temperature,but when the pH of the aqueous media was 4.0,their volume phase transition temperature was slightly decreased due to the formation of hydrogen bonds between PNIPAM and PAA.The pH stimuli responsiveness of the microgels was enhanced by the PAA co ntent within the microgels.