Syndiotactic Polystyrene Aerogels: Adsorption in Amorphous Pores and Absorption in Crystalline Nanocavities

Sorption experiments have been conducted for syndiotactic polystyrene (s-PS) aerogels with different crystalline forms and of different porosities. Nitrogen uptake experiments at 77 K have confirmed that δ-form aerogels present crystalline nanocavities as well as amorphous porosity. The equilibrium uptake of organic molecules, from dilute aqueous solutions, for δ-form aerogels is high (e.g., more than 5 wt % of 1,2-dichloroethane, DCE, from 1 ppm solutions) and independent of aerogel porosity. Gravimetric experiments, as well as FTIR conformational studies on absorbed DCE, clearly indicate that guest absorption from diluted solutions occurs only in the crystalline nanocavities. High-porosity δ-form aerogels (P > 98%) can also exhibit substantial water adsorption from the amorphous porosity, which is favorable to the pollutant absorption kinetics. In fact, apparent guest diffusivity increases of several orders of magnitude, with respect to the corresponding films, have been observed.