Association of organic quaternary ammonium cations with polyacrylates. Conductivity and viscosity measurements

The association of series of alkyl and aryl quaternary ammonium cations with polyacrylate and acrylate copolymers (with acrylamide, butyl acrylate, and styrene) was studied by combined conductivity and viscosity measurements on the organic ammonium polysalts. The degree of counterion binding in the low molecular weight alkyl trimethylammonium polysalts is basically determined—as with small organic counterions—by the distance between the carboxylate groups on the polyion backbone, i.e., electrostatic effects predominate with these cations. However, the counterion-polyion interaction decreases significantly with increase in counterion size and steric effects from tetramethyl- to hexyltrimethylammonium cation. In the octyl- and decyltrimethyl ammonium polysalts, van der Waals' effects become more effective and the degree of association then increases with increase in counterion size. Phenyl- and naphthyltrimethylammonium cations behave similarly to the lower alkyl homologs. Pyridine- and quinolinemethonium cations interact more markedly with polyacrylates, especially with the butyl acrylate and styrene copolyacrylates. Van der Waals' interaction between the organic sections of counterion and polyion backbone is indicated with these cations: the estimated free energy due to this effect (with these cations) is 0.2–0.5 RT cal./g. mole.