Molecular Dynamics in Poly(ethene-alt-N-alkylmaleimide)s As Studied by Broadband Dielectric Spectroscopy

Broadband dielectric spectroscopy has been used to analyze the molecular dynamics in a set of nine poly(ethene-alt-N-alkylmaleimide)s. The polymers were studied in the frequency range from 0.1 Hz to 10 MHz and at temperatures between 120 and 500 K. The alternating maleimide copolymers possess alkyl side chains varying in length from methyl to octadecyl. Four relaxation processes are observed:  (i) a (secondary) β-relaxation corresponding to librational fluctuations of the terminal end group of the alkyl side chain, (ii) the α‘-relaxation being assigned to a relaxation of the side chain, (iii) the dynamic glass transition (α-relaxation), being designated to motions of the succinimide ring, and (iv) the α_s-relaxation reflecting cooperative fluctuations of an ensemble of about 2−3 maleimide rings in an underlying helical superstructure. This model is supported by calorimetric measurements and published nuclear magnetic resonance data.