Dielectric relaxation of specially prepared polystyrene terminated with rigid polar groups

Two polystyrenes terminated withp-cyanobenzyl andp-cyanobiphenyl groups (=labels) were prepared and their complex dielectric constants were measured in the glass transition region in the frequency range 10^–2–10⁶ Hz. The glass temperaturesT _g (DSC) were considerably different, 92 and 97.5°C, resp., although their molecular weights were very similar (11 000 and 10 000 g/mol, resp.). Their relaxation behavior showed that the cyano groups relax cooperatively with the polymer segments. The cyanophenyl groups were found to relax with shorter relaxation times than the cyanobiphenyl groups. The measured relaxation strengths showed that there was no association between the dipoles. The relaxation mechanisms of the cyano groups in both labels seemed to be different although the only difference between them was an additional phenyl group in the case of the second label.