Wu Kun, Wu Bing, Wang Ping, Hou Yi, Zhang Guangzhao, Zhu Da-Ming
Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China.
J Phys Chem B. 2007 Aug 2;111(30):8723-7. doi: 10.1021/jp073236z. Epub 2007 Jul 11.
Poly(N-isopropylacrylamide) (PNIPAM) physisorbed on gold surfaces in aqueous solutions has been studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption isotherms of the polymer, that is, the adsorbed mass versus the concentration of PNIPAM in solution, show distinctly different behaviors at temperatures below and above a lower critical solution temperature (LCST). Below the LCST, PNIPAM forms a single compact layer in solutions with concentrations up to 100 ppm in weight; above the LCST, much thicker films of PNIPAM form in the same concentration range. Changes in the dissipation factor versus solvent concentration show a behavior similar to those in the isotherms. The difference in the adsorption behavior below and above the LCST can be qualitatively explained in terms of the conformation difference of the polymer in its swelling and collapsed states.
利用具有耗散监测功能的石英晶体微天平（QCM-D），对水溶液中物理吸附在金表面的聚（N-异丙基丙烯酰胺）（PNIPAM）进行了研究。聚合物的吸附等温线，即吸附质量与溶液中PNIPAM浓度的关系，在低于和高于最低临界溶液温度（LCST）时表现出明显不同的行为。在LCST以下，PNIPAM在重量浓度高达100 ppm的溶液中形成单一致密层；在LCST以上，在相同浓度范围内形成更厚的PNIPAM膜。耗散因子随溶剂浓度的变化表现出与等温线类似的行为。LCST上下吸附行为的差异可以根据聚合物在其溶胀和塌陷状态下的构象差异进行定性解释。
