Study in adsorption behavior of polymer on molecular sieves by surface and pore properties

A series of polymers including polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polystyrene (PS) were successfully adsorbed on mesoporous silica with tubular structure by adding silica particles directly into polymer solution during stirring. Presence of polymers on silica was confirmed by thermogravimetric analysis, FTIR spectroscopy and transmission electron microscopic images. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after polymer adsorption. BET specific surface area, pore size distribution (PSD), and surface fractal analysis were calculated in traditional BET (Brunauer, Emmett and Teller) method, BJH (Barret, Joyner and Hanlenda), and the thermodynamic method, respectively from the isotherms. We proposed a model for conformation of polymer adsorbed based on such variations, which was further confirmed by transmission electron microscopic results. We found that PVA and PEG with high polarity (due to high content of oxygen atoms both in the chain or hydroxyl groups), could spread their chains into the tubes of molecular sieves except the adsorption outside of the tubes via hydrogen bond, while PS with relatively low polarity could only adsorb randomly on the surface.