磺酸基共聚凝胶在混合有机溶剂中的体积相变

Volume Phase Transition of Copolymerized Sulfonic Acid Gels in Mixed Organic Solvents

２－丙烯酰胺基－２－甲基丙磺酸（ＡＭＰＳ）与甲基丙烯酸－２－羟基丙酯（ＨＰＭ）在乙二醇／水（１∶１，质量比）中７０℃下进行共聚，ＡＭＰＳ／ＨＰＭ（８∶２，摩尔比）为该体系的恒比共聚点．在此组成加入交联剂Ｎ，Ｎ－亚甲基双丙烯酰胺２％、３％和５％（摩尔分数）制备了凝胶试样Ｇ０２、Ｇ０３、Ｇ０５．它们在ＤＭＳＯ／ＴＨＦ混合溶剂中ＴＨＦ达５５％～６０％（体积百分数）时发生体积相变；在乙醇／ＴＨＦ混合溶剂中Ｇ０３的体积随ＴＨＦ的加入连续缩小，但不出现体积相变．此现象可用高分子链溶剂化层的变化以及低极性介质中离子对之间的偶极－偶极相互作用来说明．

Radical copolymerization of 2 acrylamido 2 methylpropane sulfonic acid(AMPS) with 2 hydropropyl methacrylate(HPM) was conducted in ethylene glycol/water(1∶1 in weight) at 70 ℃. The azeotropic composition was found at the monomer molar ratio of AMPS/HPM as 8/2. Three sulfonic gels were prepared at this composition with the crosslinker N,N methylene bis(acrylamide) of 2%, 3% and 5%(molar percentage), and referred to as G02, G03 and G05, respectively. As expected from their polyelectrolyte nature, these gels swell in dimethyl sulfoxide(DMSO) but shrink in tetrahydrofuran(THF) at 25 ℃. The volume phase transition takes place in the G02 and G03 swollen in DMSO/THF mixtures when THF content is increased beyond 55%￣60%(volume ratio). In ethanol/THF mixture, however, no volume phase transition was found though the gel still shrunk with increasing THF. The dipole dipole interaction model in less polar medium was adopted to interpret these results with the concept of preferential solvation.