Dilute solution properties and molecular characterization of poly(butyl methacrylate-co-styrene)

Abstract

Dilute solution properties of fractionated poly(butyl methacrylate-co-styrene) PBMAS prepared by bulk polymerization, have been investigated by means of light scattering, viscometry, and osmometry. As the composition heterogeneity was narrow, the characterization of the copolymer was effected in a single solvent by light scattering. Infrared and nuclear magnetic resonance spectra were used to determine the composition and sequence distribution of monomer units of the copolymer. The molecular weight dependence of the limiting viscosity number and of the root-mean-square end-to-end distance have been established. The Mark-Houwink relation showed that methylethyl ketone is a good solvent compared with cyclohexane. The validity of various extrapolation procedures that have been proposed to calculate the unperturbed dimensions have been examined. Root-mean-square end-to-end distances have been calculated from the Debye-Bueche and Kirkwood-Riseman methods and compared with the experimental values. The molecular weight dependence of the second virial coefficient agreed well with that calculated from the Orofino-Flory equation. The value of the steric hindrance parameter s for the copolymer has been found to be 2.27 compared to 2.05 for poly(butyl methacrylate) and 2.22 for polystyrene, which indicates that PBMAS is a stiffer chain in solution than those of the constituent homopolymers.