Investigation of pH-Induced Changes in a Methacrylate Terpolymer Chain Conformation Using Dilute Solution Viscometry

In this study, pH-induced changes in chain conformation of a methacrylate terpolymer i.e., poly(dimethylaminoethyl methacrylate-co-methyl methacrylate-co-butyl methacrylate) is followed as a function of mono (acetic acid) or dicarboxylic acids concentration. The polymer was dissolved in a solvent mixture comprising acetone, ethanol and 1-propanol. Dicarboxylic acids were also selected as a homologous series including oxalic, succinic and adipic acid. Reduced viscosities were determined using a capillary viscometer and used to determine chain conformation parameters using Fuoss model. It was observed that using acetic acid, tertiary amine functional groups on the polymer backbone was protonated by reducing pH values to values lower than 7.28 which in turn cause an increment in repulsive forces induced by electrostatic charges. These repulsive forces will expand the polymer coil helix. Intramolecular crosslinking was observed using dicarboxylic acids when polymer concentrations were much lower than C* values.