On the plasticization of poly(2,6‐dimethyl phenylene oxide) by CO2

Change in the glass transition temperature, Tg, of poly(2,6‐dimethyl phenylene oxide), PPO, due to the dissolved CO2 has been measured as a function of the gas pressure, p, using a high‐pressure DSC cell. At 61.2 atm, the highest pressure studied, Tg is depressed by 31.6°C. The depression in Tg is found to be linear with pressure, with dTg/dp of −0.5°C atm−1. The experimental results are in fair agreement with those calculated from a quasilattice solid‐solution model for polymer‐diluent systems. The present results, however, differ markedly from a recent investigation on PPO‐CO2 system which reported a depression in Tg of 226°C at 60 atm and a dTg/dp of −3.8°C atm−.