Macro- and Nanoscopic Studies of Porous Polymer Swelling

A commercial Amberlite XAD7HP resin was investigated as a typical porous polymer which swells in tetraethoxysilane (TEOS). TEOS appears to be an extremely effective polymer swelling agent; thus, it serves as an easily assimilable silica source in polymer–silica composites. The present study discusses the application of light microscopy (LM) and positron annihilation lifetime spectroscopy (PALS) for the studies of macroscopic and microscopic features during the progress of polymer swelling. LM offers precise information on the swelling in the solvent vapor, especially for the well-defined, spherically shaped particles of the polymer. The swelling of a porous polymer consists of the swelling of pore walls and adsorption of the solvent on the internal surface of the walls. PALS provides an opportunity to recognize the sequence of solvent penetration into porous polymer particles. It allows in situ monitoring of the evolution of every free volume in the sample under study.