第三单体结构对温敏水凝胶相转变温度的影响

采用乳液聚合法,以N异丙基丙烯酰胺为温敏性主单体,大分子双烯化合物为交联剂,过硫酸铵为引发剂合成温敏性水凝胶。加入疏水性丙烯酸酯类第三单体以调节温敏性水凝胶的低临界溶解温度(lower critical solution temperature,LCST),用不同温度下温敏性水凝胶的粒径变化表征其相转变行为。结果表明:加入疏水性丙烯酸酯类单体能够有效调节温敏性水凝胶的LCST,且质量分数越高则温敏性水凝胶的LCST越低;丙烯酸酯上的α甲基存在与否对温敏性水凝胶体系的LCST无显著影响;丙烯酸酯类结构上的R基对体系的LCST有显著影响,且R基上碳链越长,LCST降低越多;同时,R基的异构化对降低LCST也表现出明显的差异,其中直链烷基可更有效地降低LSCT,而仲碳结构、叔碳结构对降低LCST的作用依次减弱。

Influence of Third Monomer Structure on Phase Transition Temperature of Thermo-sensitive Hydrogel

This paper took N-isopropyl acrylamide as main temperature-sensitive monomer,macromolecular diene compound as crosslinking agent,ammonium persulfate as initiator to synthesize temperature-sensitive hydrogel through emulsion polymerization.Hydrophobic acrylate was added as the third monomer to adjust the lower critical solution temperature(LCST)of thermo-sensitive hydrogel.The phase transition behavior of thermo-sensitive polymers with different structure were characterized by their particle sizes at different temperatures.The results show that the addition of hydrophobic acrylate monomers can regulate the LCST of thermo-sensitive hydrogels effectively,and the higher the mass fraction,the lower the LCST of thermo-sensitive hydrogels.The presence or absence ofα-methyl on acrylate has no significant effect on regulation of LCST in thermo-sensitive hydrogel system.The R radical on the acrylic structure has a significant effect on the LCST in the system,and the longer the carbon chain,the more the LCST decreases.The isomerization of R radical with the same carbon chain shows significant effect in reducing LCST.The linear alkyl structure reduces LSCT more effectively while the effect of the secondary carbon structure and tertiary carbon structure on the reduction of LCST decreases successively.