Effects of polymer molecular weight and chemical modification on the gas transport properties of poly(2,6-dimethyl-1,4-phenylene oxide)

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) of different intrinsic viscosi ties has been studied to understand the effect of polymer molecular weight on the permeability and permeability ratio of CO2/CH4 and O-2/N-2 gas pairs . The increase in permeability of dense films prepared from higher molecula r weight PPO was explained in terms of increased free volume. Gas permeabil ity for the high molecular weight was further improved by attaching bulky b romine groups to the phenyl ring of the PPO backbone. Permeability ratio of PPO was greatly improved by attaching polar groups such as -COOH or -SO3H. The loss in permeability because of the presence of the polar groups was c ompensated by using PPO that was brominated and sulfonated. (C) 2000 John W iley & Sons, Inc.