The adsorption behavior of polymer mixtures

Abstract

Abstract The interfacial behavior of several mixtures of incompatible polymers has been examined at 24°C using finely divided silica as the adsorbent and trichloroethylene as the solvent. Displacement experiments have shown that poly (ethylene‐vinyl acetate) (EVA) (20.4% by wt. vinyl acetate) completely displaces polystyrene (PS) from silica within 1 hr. while poly (vinyl acetate) (PVAc) displaces ethyl cellulose (EC) within 3 hrs. A given EVA copolymer displaces one of lower vinyl acetate content; EVA (44.2% vinyl acetate) is displaced by EC. EC tends to displace poly (methyl methacrylate) (PMMA), but the process is slow and incomplete. The fraction of adsorbed polymer segments attached directly to silica, as determined by infrared spectroscopy, can be correlated with the displacement results. Experiments with PS/PVAc, PS/PMMA, and polydimethylsiloxane/EVA (20.4% vinyl acetate) mixtures have shown that adsorbance values of the preferentially adsorbed PVAc, PMMA, and EVA are increased by the second polymer, when polymer concentrations which cause phase separation are approached. Increases in adsorbance are accompanied by lower infrared bound fraction values, implying formation of a more extended adsorbed layer.