水溶液自由基聚合制备的PNIPA分子特性

摘要

The molecular characteristics of poly(N-isopropylacrylamide) (PNIPA), prepared by free-radical polymerization using an aqueous redox initiator and reaction conditions were investigated by altering the monomer concentration ([NIPA]) and the polymerization temperature (tp) from 0 ℃ to 50 ℃ across the lower critical solution temperature(LCST). When tp ＜ LCST, there was a critical [NIPA] (= n* ) above which PNIPA partially formed gels in the absence of a chemical crosslinker, and the gel fraction increases with increasing [NIPA] and decreasing tp. In addition, the relationships between relative molecular mass (measured by GPC) of soluble PNIPA and monomer concentration were discussed.%采用水溶液自由基聚合方法,制备聚N-异丙基丙烯酰胺(PNIPA),探讨了PNIPA的分子特性与单体浓度、聚合温度(从0℃至50℃)的关系.研究发现,当聚合温度低于最低临界溶解温度(LCST)时,如果单体浓度达到一个临界值(n*),即使不添加任何交联剂,PNIPA分子链之间也会发生向聚合物的链转移反应,从而形成自交联凝胶,并且在提高单体浓度和降低聚合温度时自交联凝胶的含量也随之增加.此外,采用凝胶渗透色谱(GPC)测定未交联PNIPA的相对分子质量及相对分子质量分布,并探讨了它们与单体浓度的关系.