Schmaljohann Dirk, Beyerlein Detlev, Nitschke Mirko, Werner Carsten
Welsh School of Pharmacy, Redwood Building, King Edward VII Avenue, Cardiff University, Cardiff, CF10 3XF, Wales, UK.
Langmuir. 2004 Nov 9;20(23):10107-14. doi: 10.1021/la034653f.
Thin films of graft copolymers consisting of poly(N-isopropylacrylamide) (PNiPAAm) or poly(N,N-diethylacrylamide) (PDEAAm) as polymer backbone and poly(ethyleneglycol) as side chains were cross-linked on fluoropolymer substrates by low-pressure plasma treatment. All immobilized polymers exhibit a lower critical solution temperature between 34 and 40 degrees C. The swelling and collapsing of the hydrogels was examined with temperature-dependent spectroscopic ellipsometry. Two time ranges of swelling were observed: a fast 'dynamic' and a slow 'equilibrium' swelling. The dynamic swelling occurs within minutes or less, whereas the equilibrium swelling needs several days to complete. The surface-bound hydrogels show a shift in the transition temperature toward lower temperatures compared with the behavior in solution. Full reversibility of the dynamic swelling/collapsing was found, but the temperature scan exhibits a hysteresis between heating and cooling cycles. The PNiPAAm-containing hydrogels show a sharper transition compared to the PDEAAm-containing hydrogels, which is almost linear over a wide temperature range.
以聚（N-异丙基丙烯酰胺）（PNiPAAm）或聚（N，N-二乙基丙烯酰胺）（PDEAAm）为聚合物主链、聚乙二醇为侧链的接枝共聚物薄膜通过低压等离子体处理交联在含氟聚合物基材上。所有固定化聚合物的低临界溶液温度在34至40摄氏度之间。通过温度相关的光谱椭偏仪研究了水凝胶的溶胀和收缩情况。观察到两个溶胀时间范围：快速的“动态”溶胀和缓慢的“平衡”溶胀。动态溶胀在几分钟或更短时间内发生，而平衡溶胀需要几天才能完成。与在溶液中的行为相比，表面结合的水凝胶的转变温度向更低温度偏移。发现动态溶胀/收缩具有完全可逆性，但温度扫描在加热和冷却循环之间表现出滞后现象。与含PDEAAm的水凝胶相比，含PNiPAAm的水凝胶表现出更明显的转变，在很宽的温度范围内几乎呈线性。
