Angular correlations in linear copolymers from the compositional dependence of their dipole moments. III. Experimental: Poly(4-chlorostyrene, 4-methylstyrene) copolymers

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Abstract
The complex dielectric constants ε*=ε′−jε″ of members of a set of ten poly(4‐chlorostyrene, 4‐methylstyrene) copolymers, P(4CS,4MS), that spans the whole composition range and includes the homopolymers P4CS and P4MS, have been measured at temperatures ranging from about 450 °K downwardly to their glass transition temperatures at about 390 °K. The compositional dependence of the effective dipole moment per structural unit μ2e, as determined from these measurements is analyzed by methods developed in Papers I and II of this series, but as modified for applications to copolymers having nearly random ordering of sequences of chemical types of structural units. The analysis presupposes knowledge of the compositional dependence of the condtional probabilities Pαβ that a structural unit of type β immediately follows one of type α, where α,β=0,1. The analysis is done with the help of a series expansion of the compositional dependence of μ2e, the terms of which are linearly independent functions of composition with constant coefficients. The coefficients are linear combinations of products μαμβηαβks, where ηαβks is twice the average cosine of the angle between the dipole moments μα and μβ of a pair of structural units, lying in the same chain and separated by k intervening units that are arranged in a sequence of chemical types as designated by the index s. The first few coefficients of the expansion are evaluated for P(4CS,4MS) copolymers and are used as a basis of both qualitative and quantitative discussions of the magnitudes and the nature of those localized angular correlations that contribute to μ2e. Possibilities are considered for obtaining more detailed analyses, either by choosing appropriate copolymer systems that meet certain requirements, or by using specified additional information from independent sources.