Sorption behavior of water vapor into polyelectrolyte complex of poly(acrylic acid)/poly(4‐vinylpyridine)

The sorption of water vapor into the polyelectrolyte complex of poly(acrylic acid)/poly(4‐vinylpyridine) has been investigated. The sorption isotherm was evaluated on the basis of various theories; BET equation, Flory–Huggins interaction parameter χ1, and cluster function G11/v1. The behavior of the BET plot, χ1, and G11/v1 was considered in terms of the structure of the complex, while the crosslink density and charge density were determined from the carbonyl absorption in IR spectra. The reasonable conclusion drawn from the available data is as follows. The interaction of water with specific polymer sites plays an important role in the sorption. The sorbed water plasticizes this material, and it enables the expansion of the network. The large amounts of water incorporated by the expansion cannot be dispersed homogeneously in the network, and indicate clustering tendency.