(346g) Triptycene-Containing Polybenzoxazole (PBO)-Based Membranes: New Synthesis and Gas Transport Properties

¹Shuangjiang Luo, ¹Ashish Kushwaha, ²Junyi Liu, ²Haiqing Lin, ¹Ruilan Guo* (rguo@nd.edu)

¹Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556-5637

²Department of Chemical and Biological Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260-4200

Polybenzoxazole (PBO)-based membranes, such as thermally rearranged (TR) polymers, hold great promise for gas separation that unite high gas permeability and high selectivity. It has been shown that gas separation performance of these thermally converted PBO membranes are largely determined by the precursor structures and the thermal treatment protocols. Herein we report the preparation and transport properties of two new series of PBO-based polymer membranes that were thermally derived from triptycene-containing o-hydroxy polyimide and polyamide precursors via thermal rearrangement (TR) process and thermal cyclodehydration (TC) process, respectively. Incorporation of triptycene units into poly(hydroxyimide) precursor structures led to significant increase of fractional free volume and created ultrafine microporosity in the converted PBO-based TR membranes, which enabled both high gas permeabilities and high selectivities. Although TC process of poly(hydroxyamide) precursor led to moderate improvement in the separation performance of the resulting triptycene-containing PBO membranes as compared to TR process, the PBO films converted via TC process exhibited excellent mechanical properties that are superior to many other TR membranes previously reported in the literature as well as the triptycene-containing TR membranes in this study. In particular, the PBO film thermally rearranged at 450 ^oC showed H₂ pure gas permeability of 807 barrer, CO₂ permeability of 269 barrer, and CO₂/CH₄ and H₂/CH₄ selectivities of 67 and 202, respectively, at 35 ^oC and 11 atm, which are far beyond the upper bound limits. In this talk, synthesis and characterization of these new PBO membranes will be presented. Fundamental transport properties including pure gas permeation data (with H₂, N₂, CO₂, and CH₄) will be discussed to illustrate the fundamental relationship between microscopic structures with macroscopic transport properties for these new triptycene-containing PBO membranes.