CARBON MOLECULAR SIEVE (CMS) MEMBRANES STRUCTURE-PROPERTY RELATIONSHIPS
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The goal of this work is to develop a framework to understand the material science options to fabricate novel, high performing separation CMS membranes. The transport and sorption properties of CMS membranes formed by pyrolysis under argon at 550 oC for four novel polyimide precursors referred to as 6FDA/DETDA, 6FDA:BPDA(1:1)/DETDA, 6FDA/DETDA:DABA(3:2) and 6FDA/1,5-ND:ODA(1:1) were reported and compared. The 6FDA/DETDA:DABA(3:2) derived CMS membranes showed the highest permeability and offered the greatest practical potential. The effects of pyrolysis conditions, including pyrolysis temperature; O2 doping; and precrosslinking, on the separation performance of 6FDA/DETDA:DABA(3:2) derived CMS membranes were reported and compared. The temperature dependence of both energetic and entropic selectivity and their contributions to overall diffusion selectivity of various types of CMS membranes are discussed in detail in this study. Finally, the viability of extending the promising separation performance obtained from 6FDA/DETDA:DABA(3:2) CMS dense film into hollow fiber morphology was also explored in this work.