Mechanical experiments as a tool for study of swelling-deswelling and structural properties of porous polymers

Abstract

The expansion and structural parameters for a series of crosslinked porous polymers are discussed during their swelling. In the study, commercial Amberlite XAD2, XAD4 XAD16 and XAD7HP resins of varying porosity and polarity were used as model polymers. Videomicroscopy LM is combined with in-situ strain-stress measurements during the process of wetting the polymer with ethanol. The force exerted by the expansion of the spherical polymer particle due to swelling reflects the structural properties of the polymer and is related to the total porosity of a given type of polymer matrix. The pore structure of the samples was characterized by liquid nitrogen adsorption and their swelling degree was assessed by light microscopy. The deswelling curves, represented by strain-stress curves, are stepped for polymers of lower porosity; the first step represents the evacuation of the solvent from the pores. This process is regulated by the external pore openings in a particle; the second, elongated step on the deswelling curve represents the evaporation of the solvent from the polymer network.