2020-Thermally rearranged polymer membranes containing highly rigid biphenyl ortho-hydroxyl diamine for hydrogen separation
作者：XiaofanHu Won Hee Lee Jiayi Zhaob Ju Sung Kim ZhenWang Jingling Yan Yongbing Zhuang Young Moo Leea
關(guān)鍵字：Thermally rearranged polymer membranes
論文來(lái)源：期刊
具體來(lái)源：Journal of Membrane Science
發(fā)表時(shí)間：2020年
A novel bulky and rigid ortho-hydroxyl diamine,
3,3′-diamino-5,5′,6,6′-tetramethyl-[1,1′-biphenyl]-2,2′-diol (TMBDA),
was synthesized for gas separation membranes in this study. The chemical
structure of TMBDA with four methyl groups and a fixed twist biphenyl
center was rationally designed, and consequently presented a superior
energy barrier of rotation, which efficiently suppressed chain motion
and enhanced polymer rigidity. Four types of TMBDA-based polyimides
(PIs) were prepared with two commercially available dianhydrides, i.e.,
4,4''''-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and
pyromellitic dianhydride (PMDA), from two different synthetic routes,
azeotropic and chemical imidization. Thermally rearranged (TR) polymers
were obtained from TMBDA-based PIs by thermal treatment at various
temperatures. Thermal properties and physicochemical characteristics of
TMBDA-based PIs and TR polymers were investigated. The resulting
polymers exhibited high glass transition temperatures (Tg) and contorted backbone structures with three discrete d-spacing values, where the smallest interchain d-spacing was located between the kinetic diameters of H2 and CH4 molecules. Moreover, TMBDA-based TR polymers showed outstanding performances in hydrogen separation with comparable H2 permeability and higher selectivity than reported TRs. For instance, 6F-TM-Ac-425 exhibited a H2 permeability of 325 Barrer with H2/CH4 and H2/N2 selectivities of 50 and 39, respectively, approaching to the 2008 Robeson upper bound.