Polyimides modifications and carbon molecular sieves derived from polyimides for gas separation

Abstract

Membranes have been widely used in gas separation over the past decades and experienced rapid development in recent years. Membranes with both high permeability and selectivity are preferred to effectively separate gas mixtures for industrial applications. This study has discovered a series of novel multi-functional cross-linking agents, namely polypropylenimine tetraamine (DAB-AM-4; G1), polypropylenimine octaamine (DAB-AM-8; G2), polypropylenimine octaamine (DAB-AM-16; G3) dendrimers, 1,3-cyclohexanebis(methylamine) (CHBA) and ethylenediamine (EDA) to cross-link polyimides at room temperature and enhance their separation performance. Furthermore, the chemically modified polyimides were thermally treated to enhance their anti-plasticization characteristics. Besides, 6FDA-durene (Tg :425 a??)polyimide with a higher Tg, was applied to study the Tga??s effect on the evolution of physicochemical and transport properties of membranes from polymeric, intermediate to carbon stages. In the last part, gas transport properties of different morphological 6FDA/PMDA-TMMDA films and their derived carbon molecular sieve membranes (CMSMs) were studied.