School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.
J Colloid Interface Sci. 2010 Mar 1;343(1):168-75. doi: 10.1016/j.jcis.2009.11.047. Epub 2009 Nov 26.
Effects of tannic acid (TA) on the phase transition behaviors of monodisperse poly(N-isopropylacrylamide) (PNIPAM) microgels in aqueous solutions are systematically investigated. Monodisperse PNIPAM microgels are prepared through a microfluidic approach. The isothermal phase transition behaviors of PNIPAM microgels induced by TA in aqueous solutions are studied at 25 degrees C. The results show that there exist significant isothermal phase transition phenomena for PNIPAM microgels induced by TA, and the dynamic phase transition rate and the equilibrium shrinking degree of PNIPAM microgels in TA solutions are dependent on the TA concentration. The higher the TA concentration, the faster the isothermal shrinking rate of PNIPAM microgels induced by TA. There exists a critical TA concentration for the isothermal phase transition behavior, below which the equilibrium shrinking degree of PNIPAM microgels becomes larger with increasing the TA concentration, while above which the equilibrium shrinking degrees of PNIPAM microgels remain almost the same. The adsorption of TA molecules to PNIPAM polymer networks leads to slight shift of the low critical solution temperature to higher temperatures when the TA concentration in solution is lower than 10(-5) mol/L.
系统研究了没食子酸（TA）对单分散聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶在水溶液中相转变行为的影响。通过微流控方法制备了单分散 PNIPAM 微凝胶。在 25°C 下研究了 TA 在水溶液中诱导的 PNIPAM 微凝胶的等温相转变行为。结果表明，TA 诱导的 PNIPAM 微凝胶存在显著的等温相转变现象，TA 溶液中 PNIPAM 微凝胶的动态相转变速率和平衡收缩度取决于 TA 浓度。TA 浓度越高，TA 诱导的 PNIPAM 微凝胶的等温收缩速率越快。存在一个临界 TA 浓度，低于该浓度时，PNIPAM 微凝胶的平衡收缩度随 TA 浓度的增加而增大，而高于该浓度时，PNIPAM 微凝胶的平衡收缩度几乎保持不变。当溶液中 TA 浓度低于 10^(-5)mol/L 时，TA 分子对 PNIPAM 聚合物网络的吸附导致低临界溶液温度略微向高温移动。
