小角X光散射表征分散液中Nafion的微观结构

利用小角X光散射研究了全氟磺酸离子聚合物Nafion膜在不同比例的氮甲基甲酰胺和正丁醇混合溶剂中分散形成分散液的微观结构。 研究表明,主链刚性和主-侧链亲疏水性的协同作用使分散液中的Nafion呈典型的棒状胶束结构。 胶束的等效回转半径(R_g)对Nafion质量浓度表现出-0.42的标度,与聚电解质在无盐溶剂中的理论标度一致;而胶束间相关长度对Nafion质量浓度表现出-0.13的标度,与典型的中性聚合物溶液理论标度一致。 极性低的正丁醇促进Nafion主链溶剂化并利于长胶束形成,而极性高的氮甲基甲酰胺则能促进Nafion分散。 该研究将为理解Nafion分散液的性质以及湿法制备Nafion膜的微结构形成提供清晰指导。

Characterization of Microscopic Structure of Nafion in Dispersion Using Small Angle X-Ray Scattering

Small angle X-ray scattering was used to characterize the microscopic structure of Nafion in its dispersion composed by different volume ratios of N-methylformamide and n-butanol. The results show that Nafion forms typical micelle structures in its dispersion, because of the synergistic effect of rigidity of main chain and hydrophobicity/hydrophilicity of main/side chain. The radius of gyration(R_g) of micelles exhibits the scale of -0.42 as the increase of Nafion mass concentration, which is in consistent with the theoretical scale of polyelectrolyte in salt free solvents. The correlation length between micelles shows a scale of -0.13, identical to the theoretical scale of typical neutral polymer solutions. Lower polarity n-butanol promotes the formation of long micelles, while high polarity N-methylformamide promotes the dispersion of Nafion. This study provides a clear guidance for understanding the properties of Nafion dispersions and the formation of micro-structure of Nafion films prepared by wet method.