Preparation and properties of polybenzoxazole-based gas separation membranes: A comparative study between thermal rearrangement (TR) of poly(hydroxyimide) and thermal cyclodehydration of poly(hydroxyamide)

This comparative study focuses on the cyclodehydration reaction of poly(hydroxyamide)s (PHAs) and the thermal rearrangement (TR) reaction of aromatic poly(hydroxyimide)s (APIs) to produce poly-benzoxazoles (PBOs) for application as gas separation membranes. Systematic comparisons between the two routes showed that PHA cyclodehydration can produce fully converted PBO membranes at a temperature more than 100 degrees C lower than the API-TR route. Gas separation performance of PHA-PBOs is comparable to API-TR polymers, and PHA-PBOs are considerably more mechanically robust. More importantly, PBO films can be produced equally well in both air and inert atmospheres via the PHA cyclodehydration route. The PHA-PBOs formed in air have statistically the same physical and transport properties as those formed in N-2. The present study provides fundamental information regarding the PHA-to-PBO cyclodehydration process. (C) 2015 Elsevier Ltd. All rights reserved.