Some factors affecting the molecular association of poly(ethylene oxide) and poly(acrylic acid) in aqueous solution

Abstract

AbstractInvestigations of the properties of very high molecular weight polymers of ethylene oxide have shown that, while this polymer structure is relatively nonpolar, it displays a high degree of polymer solvent interaction in aqueous systems. A unique application of the hydrogen bonding affinity of the ether oxygens in the poly(ethylene oxide) chain has been found in the molecular association complexes formed between this polyether and polymeric acids such as poly(acrylic acid). Interest in the properties of these complexes has prompted a more detailed study of the mechanism of association which occurs in solution. In this study the effects of pH, of composition and concentration, and of temperature on solution viscosity are examined in order to define the stoichiometry of the intermolecular association. A wide range of polymer molecular weights has been studied, ranging in the case of poly(ethylene oxide) from low molecular weight waxes to very high molecular weight polymers. The molecular complex of poly(ethylene oxide) and poly(acrylic acid) appears to be an association between ether oxygens and carboxyl groups through hydrogen bonding which approaches 1:1 stoichiometry. While at low pH this association is sufficient to cause phase separation, at higher pH the complex exists in solution. In neutral solution there also appears to be an interaction between the two polymer species.