RELAXATION BEHAVIOR OF SEMIFLEXIBLE POLYMERS AT VERY-LOW FREQUENCIES

The dielectric activity of poly(monocyclohexylmethylene itaconate) (PM CI) and poly(dicyclohexylmethylene itaconate) (PDCI) in the glassy reg ion and in the glass-rubber transition is studied by thermostimulated discharge current (TSDC) techniques. The spectra obtained by global TS DC experiments show a prominent alpha-glass-rubber relaxation peak wit h maxima located at 97 and 55 degrees C for PMCI and PDCI, respectivel y, following in decreasing order of temperature for a well developed b eta absorption and a comparatively low intensity relaxation. Better re solution of the relaxation behavior of these polymers in the glassy re gion is obtained by calculating the components of the complex dielectr ic permittivity epsilon at extremely low frequencies from partial TSD C experiments. The ac spectra thus obtained suggest that the beta abso rption is composed by two relaxations, each of them presumably associa ted with the motions of a side group. The differences observed in thes e spectra with those reported for the beta mechanical relaxation repor ted for these polymers in the literature are interpreted in terms of t he restrictions that the side groups produce in the conformational spa ce of phase of the backbone. These restrictions also explain the small changes in enthalpy in the glass-rubber transition which preclude the possibility of obtaining the glass-rubber transition temperature of t hese polymers by differential scanning calorimetric techniques. (C) 19 97 American Institute of Physics.