MOISTURE DIFFUSION INTO POLY-ELECTROLYTE COMPLEX OF POLY-(ACRYLIC ACID)/POLY(4-VINYL-N-ETHYLPYRIDINIUM BROMIDE)

The process of water vapor sorption into the polyelectrolyte complex of poly(acrylic acid)/poly(4-vinyl-N-ethylpyridinium bromide) has been investigated; the complex is classified as being of the weak polyelectrolyte/strong polyelectrolyte type. Films of stoichiometric (1/1 molar ratio) and nonstoichiometric (1/2 molar ratio) complex were employed in the experiments. The successive differential sorptions demonstrated that these complexes have an analogous morphological structure and undergo a very similar structural change during moisture sorption. The structural change is discussed by considering the network structure of the complexes. The integral sorption data indicated that the sorption rate for the 1/2-complex is greater than that for the 1/1-complex. For the present complexes, it has been found that the magnitude of the sorption rate can be interpreted in terms of the ionic character of the materials. The sorption rate was also evaluated from a theory available for non-Fickian processes that has been presented by Long and Richman.