Enthalpy relaxation of comb-like polymer analysed by combining activation energy spectrum and TNM models

In the enthalpy relaxation of poly(cyanobiphenyl ethylacrylate) (PCB2A), the decrease in enthalpy was measured as a function of ageing time and ageing temperature with DSC technique. Obtained data was analysed at first with the activation energy spectrum (AES) model, then compared with the prediction of a multiparameter phenomenological model which follows the evolution of the configurational entropy (SC) of the sample during the whole thermal history. In AES model, the decrease in enthalpy is controlled by molecular processes whose energies are distributed over a continuous spectrum. The spectrum gives the relation between the number and energy of processes. In consequence, AES of a single peak was obtained. The energy at which the peak maximum was located decreased with the increase in ageing temperature, which is a well-known behaviour as a distribution of relaxation processes. Furthermore, cp(T), the heat capacity data obtained by the calculation based on SC model reproduced the experimental cp(T) curve. Model parameters found in the calculation was discussed in relation to the energy value of AES maximum.

► For the enthalpy relaxation of PCB2A, time–temperature reducibility can be applied. ► TNM model has the prediction power for cp(T) curve sufficiently. ► The energy value at the maximum of AES peak is discussed in terms of the model parameter.