Dielectric relaxation spectrum of undiluted poly(4-chlorostyrene), T≳T g

Abstract

Dielectric relaxation characteristics of undiluted, atactic poly(4‐chlorostyrene), P4CS, have been determined at temperatures 406 K⩽T⩽446 K from measurements made at frequencies 0.2 Hz⩽f⩽0.2 MHz. After effects of electrical conductivity are subtracted, it is found that the normalized complex dielectric constant K^*=K′−i K″ can be represented quantitatively by the Havriliak–Negami (H–N) equation K^*=[1+(iωτ₀)^1‐α]^−β, 0⩽α, β⩽1, except for a small, high frequency tail that appears in measurements made near the glass transition temperature, T_g. The parameter β is nearly constant, and α depends linearly on log τ₀, where τ₀ is a characteristic relaxation time. The parameters α and β extrapolate through values obtained from published data from P4CS solutions, and extrapolation to α=0 yields a value of τ₀ which compares favorably with a published value for crankshaft motions of an equivalent isolated chain segment. These observations suggest that β may characterize effects of chain connectivity and α may describe effects of interactions of the surroundings with the chain. Experimental results are compared with alternative empirical and model‐based representations of dielectric relaxation in polymers.