Viscosity of Ionomer Solutions under High Pressure

采用高压滚球粘度计(S。Sawamura等人，Rev. Sci。Instrum。， 61, 871（1990）。在这些实验中，使用Nafion（杜邦公司）作为离聚体，使用99.5 Vol %乙醇（Nacalai tesque公司）作为极性有机溶剂。制备了8种不同浓度的溶液。测量在25.0ºC和高达300 MPa下进行。在常压条件下，在这些离聚体溶液中观察到在极性有机溶剂的普通聚电解质溶液中常见的聚电解质效应。即稀溶液的粘度随着样品溶液浓度的降低而增加。在高压下也观察到聚电解质效应。然而，随着压力的增加，这种效应被抑制。相似的行为，。也就是说，在常压下的其他离聚体溶液中，加入少量的简单盐可以抑制-聚电解质的效应，这已经被其他工作者报道过。但在本研究中首次观察到离聚体溶液粘度的压力依赖性以及多电解质效应随压力的增加而受到抑制。由于实验刚刚结束，很难描述本研究结果的考虑因素。但证实了以下几点：(1)在高压下观察到聚电解质效应；(2)随着压力的增加，聚电解质效应被抑制。这里观察到的抑制可以用稀释溶液中聚合物离子的形状变化来解释。溶剂的介电常数随着压力的增加而增加，可能对抑制聚电解质效应起重要作用。

Viscosity measurements of ionomer solutions under high pressure were made using a high pressure rolling-ball viscometer(S. Sawamura et al., Rev. Sci. Instrum., 61, 871(1990)). In these experiments, Nafion(Du Pont Inc.)was used as an ionomer, and 99.5 Vol % ethanol(Nacalai tesque Inc.)was used as a polar organic solvent. The 8 kinds of different concentration solutions were prepared. The measurements were carried out at 25.0 ﾟC and up to 300 MPa. Polyelectrolyte effect, which was well known in ordinary polyelectrolyte solutions of polar organic solvent, was observed in these ionomer solutions under atmospheric pressure. Namely, the viscosity of the dilute solution increased with decreasing concentration of the sample solutions. The polyelectrolyte effect was also observed under high pressure. However, the effect was suppressed with increasing pressure. The similar behavior, . that is, the suppression of the- polyelectrolyte effect with adding a small amount of simple-salt was reported already by other workers in the other ionomer solutions under atmospheric pressure. But the pressure dependence of the viscosity of the ionomer solution and the suppression of the polyelectrolyte effect with increasing pressure were first observed in this study.Since the experiments have just finished, it is difficult to describe the considerations of the results of this research. But the followings were confirmed : (1)Polyelectrolyte effect was observed under high pressure, (2)The polyelectrolyte effect was repressed with increasing pressure. The repression observed here may be explained by the shape change of the polymer ions in the dilute solution. And the increment of dielectric constant of the solvent with increasing pressure may play important role for the repression of the polyelectrolyte effect.