Random-Coil Dimensions and Dipole Moments of p-Chlorostyrene Chains

Abstract

Mean-square dimensions and dipole moments of p-chlorostyrene chains CH3–[CH(p-C6H4Cl)–CH2–] xH have been calculated as a function of their stereochemical structure, degree of polymerization x, and temperature. Theoretical arguments and experimental evidence indicate that p-chlorostyrene and styrene chains differ little in conformational energy. Therefore, the present investigation employs conformational energies of styrene chains recently obtained by Flory and co-workers from analysis of the stereochemical equilibrium compositions of styrene dimers and trimers. The calculations indicate that at large x the dimensions of p-chlorostyrene, or styrene, chains and the dipole moments of p-chlorostyrene chains should increase with increasing isotacticity and decreasing temperature. The marked differences in the configurational characteristics of p-chlorostyrene and vinyl chloride chains are shown to result from the large difference in size between p-C6H4Cl groups and Cl atoms. Theoretical results calculated for large x are, in general, in satisfactory agreement with published experimental results on poly (p-chlorostyrene). Several experimental results, as yet unconfirmed, seem however to evade interpretation in terms of the present model. Additional experimental investigations would be required to resolve this discrepancy and to provide a more definitive test of the calculated results.