基于电化学方法原位增强离子特异性效应实现对界面两性聚电解质性质的调控

It is known that the intensities of specific ion effects in macromolecular systems are positively related to ionic strength in solutions, so that the ion specificities in macromolecular systems can be simply amplified by increasing the ionic strength in solution. However, this still greatly limits the applications of ionic specificities under low ionic strength circumstances. To solve this conflict, in this project we will choose polyzwitterionic brushes as a model system, which was grafted on a conductive polymer film. By using electrochemical methods to change the charged state of the conductive polymer film, ions can be enriched in the interfacial region of polymer brushes. In this way the ionic strength in this local area can be significantly enhanced even though the ionic strength in solutions is low. Consequently the ion specificities in macromolecular systems will be amplified. This approach can be utilized to explore the applications of specific ion effects in low ionic strength solutions, not only in tuning the basic physicochemical property of polyzwitterionic brushes such as the conformational behavior and the content of hydration, but also in controlling the adsorption of protein or cells, as well as in the purification of protein. The implementation of this project will be useful in expanding the application fields of specific ion effects and in understanding the amplification mechanism of ion specificities, as well as in developing new types of stimuli-responsive interfacial polymeric materials controlled by ion specificities under low ionic strength circumstances.

高分子体系离子特异性效应的强度与溶液离子强度呈正相关。虽然增加溶液离子强度可以增强高分子的离子特异性效应，但这极大限制了离子特异性效应在低离子强度环境中的应用。为了解决这一难题，本项目中拟以两性聚电解质刷作为模型体系，将其接枝于导电聚合物薄膜表面，利用电化学方法改变导电聚合物带电状态，实现离子在界面区域的富集，从而可以在低离子强度环境下显著增加界面区域离子强度，达到增强高分子体系离子特异性效应的目的。此方法不但可以应用于调控低离子强度环境下两性聚电解质刷的构象变化、水化程度等基本物理化学性质，还可以进一步应用于调控蛋白质、细胞在其表面的吸附以及蛋白质纯化等。本项目的实施将极大拓展高分子体系离子特异性效应的应用范围，加深对离子特异性效应增强本质的理解，并为设计低离子强度环境下离子特异性调控的新型界面高分子材料提供研究思路。

对材料在固-液界面上的性质的精确表征及其性质变化过程的有效调控对于充分发挥材料性能、拓展材料应用具有重要意义。在本项目的资助下，我们利用电化学石英晶体微天平等手段原位研究了离子特异性效应对导电聚合物薄膜材料界面性能的影响和调控。具体如下：通过研究不同性质的导电聚合物薄膜在电场作用下发生氧化/还原过程中的离子特异性效应，拓展了导电聚合物薄膜在高离子强度环境中的应用；在此基础上研究了两性聚电解质接枝的导电聚合物薄膜在电场作用下发生氧化/还原过程中的离子特异性效应，阐明该材料在极低离子强度环境中的应用潜力。此外，我们还利用石英晶体微天平研究了通过离子效应赋予强聚电解质刷光响应性及其响应强度调控，硫醇对金表面的刻蚀反应机理及溶液环境对反应动力学的影响，以及电极界面上两性聚电解质吸附层对水凝胶电解质基的超级电容器性能的调控，澄清了相关的作用机制。本项目的实施，为原位表征和调控材料固-液界面性质提供了研究思路，并为设计新型界面高分子材料提供实验依据。