Dilute Solution Properties of Styrene-Methyl Methacrylate Copolymers with Different Architecture

Abstract

The results of an extensive study on solution properties of alternating, statistical and block copolymers of styrene and methyl methacrylate with nearly equimolar composition are described, by placing emphasis upon their dependence on the sequential arrangement of monomers. The θ temperatures are determined in cyclohexanol by a phase-equilibrium method. Measurements of intrinsic viscosity are made in six different solvents, which are chosen to differ in their behavior toward the parent homopolymers. All data are examined on the basis of current two parameter theories.The short-range interactions, as given by the characteristic ratios, are expressed for the block copolymers as a composition average of those of the parent homopolymers, whereas for the alternating and statistical copolymers they show a positive deviation from the average. The deviation is roughly proportional to the population of the dyads of unlike monomers in the copolymer chain, i.e., to the run number. The long-range interactions are interpreted by assuming dyads as copolymer segments. Thus, the interaction parameters of the statistical and block copolymers may be expressed as a function of composition and run number in terms of the three parameters each characterizing the interaction of the parent homopolymers and the alternating copolymer with the pure solvent.