Engineering substructure morphology of asymmetric carbon molecular sieve hollow fiber membranes

In this study, a novel pre-pyrolysis treatment is developed to restrict the morphology collapse in asymmetric carbon molecular sieve (CMS) hollow fiber membranes. The technique is referred as V-treatment, due to the use of a sol-gel crosslinking reaction between an organic-alkoxy silane (vinyltrimethoxysilane) and moisture. The V-treatment technique enables restricting the microscale morphology collapse in asymmetric CMS membranes without having a chemical reaction with the polymer precursor material. The effect of V-treatment is reported on two different polyimide precursors: Matrimid® and 6FDA:BPDA-DAM. For both the CMS V-treated Matrimid® and 6FDA:BPDA-DAM hollow fibers, a significant reduction up to 5-6-fold in apparent membrane skin thickness is observed compared to the CMS from untreated precursors. This improvement translates to an increase in gas separation productivities for both pure and mixed gas feeds in CMS V-treated Matrimid® and 6FDA:BPDA-DAM hollow fiber membranes. Moreover, several characterization analyses and transport results for V-treatment method using 100% VTMS are reported herein.