Dipole moments and molecular structure of copolymers. I. Dipole moment of methyl methacrylate–styrene copolymers

Abstract

AbstractThe dielectric properties of methyl methacrylate–styrene copolymers in benzene solution have been measured, and in a theoretical treatment it has been attempted to evaluate the effective dipole moment of the methyl methacrylate group in relation to the distribution of polar group sequences in the copolymer molecule. If it is assumed that the polar groups in a polar (A)–nonpolar (B) copolymer molecule can be classified into three types such that the nearest neighbors along the chain are (I) two polar groups A, (II) a polar group A and a nonpolar group B, and (III) two nonpolar groups B (the molecular polarizations of which are denoted by PAA, PAB, and PBB, respectively), then the average molecular polarization of polar group A in the copolymer molecule, Pav, can be written in the form Here fAA and fAA2 are the probabilities of an AA sequence and a double AA sequence arising in the copolymer molecule, respectively. The values of fAA and fAA2 can be calculated from the reactivity ratios of the two monomers and the composition of the initial monomer mixture. The measurements were made on six samples of different compositions. It has been shown that the experimental values of Pav agreed satisfactorily with the values calculated from the above equation, over the whole range of copolymer composition. This seems to indicate that only the nearest neighbors in the polymer chain affect the effective dipole moment of the polar group in the copolymer molecule.