The spirobichroman-based polyimides with different side groups: from structure–property relationships to chain packing and gas transport performance

Abstract

Effect of substituents on the dihedral angle and chain packing plays a critical role in the enhancement in the gas separation performance of polymer membranes.

Highly soluble fluorinated polyimides with promising gas transport performance and optical transparency

“…Hence, –CF 3 led to 6FDA posing strong steric hindrance, resulting in the neighbouring polymer chains being more loosely packed. 54–56 For 6FDA-BASA and BPADA-BASA, the change of smaller d -spacing can be attributed to flexible groups (–O– and –C(CH 3 ) 2 ) resulting in closer packing and thus fewer void spaces. The increased d -spacing was mainly attributed to the bulky –C(CF 3 ) 2 and corresponded to an increase in FFV, which further improved the gas permeability of the polymer.…”

“…In the study of polyimide materials for the gas separation membrane, 6FDA polyimide-containing –C(CF 3 ) 2 has attracted much attention. 25–28…”

“…In the study of polyimide materials for the gas separation membrane, 6FDA polyimide-containing -C(CF 3 ) 2 has attracted much attention. [25][26][27][28] The sulfone group (-SO 2 ) is another important structure, which can increase the interaction between the main chain and gas molecules to improve the sorption coefficient of gases, 29 and could increase the chain spacing with a larger free volume fraction. 30 Ronova et al 31 studied the use of sulfone-substituted polyimide amino fragments as a methylene bridge and found that the introduction of a sulfone group into the amine component of polyimide leads to an increase in the glass transition temperature and the permeability coefficient of the polymer membrane.…”

Design, synthesis and characterization of novel fluorinated polyimide membranes with bulky pendant for gas transport

“…[6][7][8] As a class of comprehensive performance material, aromatic polyimides (PIs) have outstanding thermal properties, mechanical strength, structural diversity as well as good gas selectivity. [9][10][11][12][13] Thus, they have attracted extensive attention of and been widely studied by researchers in the field of gas separation. In general, ideal polymer membranes require high gas permeability and selectivity.…”