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

Change in the glass transition temperature, T g , of poly(2,6‐dimethyl phenylene oxide), PPO, due to the dissolved CO 2 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, T g is depressed by 31.6°C. The depression in T g is found to be linear with pressure, with dT g /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‐CO 2 system which reported a depression in T g of 226°C at 60 atm and a dT g /dp of −3.8°C atm − . © 1994 John Wiley & Sons, Inc.