A description of the physical ageing and annealing processes in poly (N-vinyl carbazole) using differential scanning calorimetry and two-dimensional correlation mapping analysis

Both physical ageing and annealing processes have a remarkable effect on mechanical properties of polymers. In the present work, the physical ageing and annealing processes of poly (N-vinyl carbazole) (PNVC), which encompasses phase separation on purification and thermal annealing, have been followed by differential scanning calorimetry (DSC) at different temperatures. The thermal responses were analysed by both generalized two-dimensional correlation mapping (2D-CM) and multiple-perturbation 2D correlation mapping. The asynchronous correlation cross-peak at (233, 211) °C was a measure of the phase separation of the two stereoforms that contributed to each process. Its intensity was a measure of the effect of holding time on the phase separation, and this was decreased with increasing the holding temperature, which indicated that the occurrence of phase separation was faster at higher holding temperature. The negative values of the correlation peaks indicated that the two relaxation processes changed on the opposite direction. A step change in the correlation intensity with a reflection temperature around 240 °C was observed. The later temperature is interestingly, consistent with the lower critical solution temperature of PNVC reported elsewhere. 2D-CM and its valuable tools provide new routines for DSC thermal responses analysis to extract useful information from complicated polymer systems.