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

Abstract

Mean‐square dimensions and dipole moments of p‐chlorostyrene chains CH 3 –[ CH (p ‐C 6 H 4 Cl )– CH 2 –] x H have been calculated as a function of their stereochemical structure, degree of polymerizationx, 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.