含系列丙烯酸酯链节的N-异丙基丙烯酰胺共聚物温敏性能的研究

Thermo-Sensitivity Behavior of N-IsopropylacrylamideBased Copolymers Containing Different Acrylic Ester Segments

采用溶液聚合法合成了不同配比的N-异丙基丙烯酰胺／丙烯酸甲酯、丙烯酸乙酯或丙烯酸丁酯线型共聚物，红外光谱对它们进行了表征；在远高于试样低临界溶液温度，采用逐步降温法测定了不同线型结构共聚物的溶胀比。研究表明共聚物组分比对共聚物温敏性能有显著影响，提出的临界线型水凝胶形成温度具有与LCST相似的物理意义，两者的差值可以表征聚合物对温度响应的灵敏程度。

Abstract: Linear hydrogels of poly(N-isopropylacrylamide)(PNIPAm) arc commonly acknowledged to be widely useful in many applications. But their study has only made relatively limited progress. In our research, poly (N-isopropylacrylamidc) and its copolymers , which were poly (N-isopropylacrylamide-co-methylacrylate ) , poly ( N-isopropylacrylamide-co-ethylacrylate ) and poly ( N-isopropylacrylamide-co-butylacrylate), were synthesized using solution free radical polymerization at 70℃. We used infrared spectroscopy technology to characterize the segmental structures and monomer's compositions in the three copolymers. We focused on the influence of copolymers' chain structures, different pH values, and concentrations of Nad electrolyte solution on thermo-sensitivc behavior of these polymers. Starting at a temperature far higher than the samples' lower critical solution temperature (LCST), we measured the swelling ratios of both poly (N-isopropylacrylamide) and its three copolymers by lowering swelling temperature gradually under an equilibrium state. We proposed for the first time the concept of a lower critical gel formation temperature ( LCGFT ) for each of the following four polymers; poly (N-isopropylacrylamide) and its three copolymers. We deem that LCGFT is very valuable in practical applications.