二胺
气体分离
玻璃化转变
部分
分子
材料科学
选择性
侧链
扩散
化学工程
聚酰亚胺
高分子化学
吊坠组
膜
化学
有机化学
聚合物
工程类
物理
催化作用
生物化学
图层(电子)
热力学
作者
Caili Zhang,Pei Li,Bing Cao
标识
DOI:10.1016/j.memsci.2017.02.030
摘要
Abstract Three spirobichroman-based diamines, FSBC, SBC and MSBC, with different substituted groups (-CF3, -H, and -CH3) were synthesized. The diamines were reacted with 4,4′-hexafluoroisopropylidene bisphthalic dianhydride (6FDA) to form 6FDA-FSBC, 6FDA-SBC, and 6FDA-MSBC polyimides, respectively. The organosolubilities, molecular weights (Mn), densities, glass transition temperature (Tg), thermal stabilities, fractional free volume (FFV), d-spacing and gas separation properties of the spirobichroman-based polyimides were systematically studied. The three spirobichroman-based polyimides had high Mn and Tg, excellent thermal stabilities, and good solubilities in a wide range of organic solvents. 6FDA-FSBC exhibited the highest gas permeability which could be attributed to its insufficient chain packing conditions rooting from the incorporation of spriobichroman backbone with the spiro and non-coplaner nature, and the bulky CF3 substituting group that increased the polymer FFV and decreased the polymer chain flexibility. 6FDA-MSBC had the highest H2/CH4 selectivity due to the present of the CH3 group in the diamine moiety which had the turnstile-like rotary thermal motion that inhibited the diffusion of large molecules like CH4 but had little effect on the diffusion of small molecules like H2.
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