Linear hydrogen bonded aggregates of carboxylic acids in crystalline channels of syndiotactic polystyrene

Abstract

Sorption of long aliphatic carboxylic acids (lauric with 12 C atoms and stearic with 18 C atoms) and of an aliphatic dicarboxylic acid (adipic), by amorphous and nanoporous-crystalline δ-form and ε-form films of syndiotactic polystyrene (sPS), is reported. Fourier Transform Infrared (FTIR), Polarized FTIR and Wide Angle X-ray diffraction (WAXD) patterns show that the empty crystalline channels of the ε form are able to host long carboxylic acids as well as dicarboxylic acids. These acids are instead absorbed much more slowly and only from the amorphous phase for δ form sPS films, which exhibit crystalline cavities rather than crystalline channels. This selective and fast uptake of carboxylic acids in the crystalline channels of the sPS ε form is due the formation of hydrogen bonded linear dimers and linear polymers, for monocarboxylic and dicarboxylic acid guests, respectively.