Effect of Counterion Condensation on Polyelectrolytes at the Air-Water Interface

The condensation of counterions on a polyelectrolyte (PE) is a well established phenomenon in aqueous solution and it has important consequences for the properties of PEs in many types of mixture including biological systems. However, very little is known experimentally about its consequences for equilibrium aqueous surfaces. In the case of the air-water interface, there are no experimental results that have been successful and correctly interpreted. This means that there is no sound basis for understanding the surface behavior of mixtures involving a PE as one of the components. We propose to do parallel ST, NR measurements on a perdeuterated sample of NaPSS(MW:~24K) We would regard the experiment as a first stage in trying to elucidate the effect of the dilute-semidilute transition on the surface properties, which requires higher MW or higher concentrations.

聚电解质（polyelectrolyte, PE）上的反离子凝聚是水溶液中已被广泛证实的经典现象，其对包括生物体系在内的各类混合体系中聚电解质的性质具有重要影响。然而，目前针对其对平衡水溶液界面的影响，实验研究仍十分有限。就气液界面而言，目前尚无得到成功实施且正确解读的实验结果，这意味着当前缺乏可靠依据来理解以聚电解质为组分之一的混合体系的表面行为。我们拟对全氘代聚苯乙烯磺酸钠（sodium polystyrene sulfonate, NaPSS，分子量：~24K）样品并行开展ST与中子反射（Neutron Reflectometry, NR）测量。本实验将作为尝试阐明稀溶液-亚浓溶液转变对表面性质影响的第一阶段研究，而该类研究需采用更高分子量或更高浓度的样品。