Dual‐phase polyphenylene oxide membranes with copolyimide branched modifiers

Abstract

AbstractPoly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) membranes are attractive due to high permeability for gases; however, the selectivity of these membranes is insufficient. In this work, the gas selectivity was improved without significant loss of the permeability. For this purpose, PPO was modified via incorporation of the branched copolyimide filler–grafted copolyimide (PI‐g‐PMMA) with polymethyl methacrylate (PMMA) side chains. Two series of mixed self‐supporting PPO/PI‐g‐PMMA films (with variation of the filler content) were prepared and studied as gas separation membranes. The length of the polymide (PI) chain and the density of PMMA grafting were the same in both series, however, in one series the grafted chains contained 50 MMA units, and in the other 150 units. The intermolecular interactions between the PPO matrix and the PI‐g‐PMMA fillers were investigated using viscometry, infrared (IR) spectroscopy, and scanning electron microscopy. The compatibility of the polymer components is limited; however, for both series, the contents of the respective filler are found, which ensures phase segregation only in a microscale. Therefore, the mechanical properties of the films allow their use as gas separation membranes. It is shown that the degree of the segregation as well as the mechanical and gas transport properties of the membranes depend on the length of the PMMA chains, and the membranes with filler‐containing shorter branches (50 MMA units) show better selectivity.