Abstract
Although the molecular design of polyimide has been extensively investigated, the role of monomer's atomic configuration in controlling the structure of polyimide membrane hence its gas transport behaviors remains relatively uncertain. Therefore, a series of polyimides with different monomer combinations were synthesized to determine the crucial features of monomer that can impose great influence on membrane properties such as the fractional free volume (FFV). The results showed that the polyimide chain length (M-w) depended strongly on the monomer reactivity, which was primarily controlled by the steric hindrance of monomers' substituent instead of their electronic nature. In addition, the polarity and atomic configuration of monomer were found to be the two dominant factors in governing the membrane FFV. A polyimide model was also constructed and validated by molecular dynamics simulation to predict the gas transport behaviors (solubility and diffusivity) of copolyimide membranes. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46073.