Preparation Of Thermally Rearranged Membranes Containing Aryl Imidazole Structures And Their Application Gas Separation

With the acceleration of industrialization,the problem of air pollution is becoming increasingly serious.The use of gas membrane separation technology to separate,recover,and reuse pollutants has shown unique technological advantages.Membrane materials are the core of membrane separation technology,and the development of new membrane materials to improve gas separation efficiency has always been a research hotspot in the field of gas separation.In particular,the thermally rearranged（TR）polymer membranes derived from hydroxyl-containing polyimide（HPI）as the precursors have attracted extensive attention of researchers due to their unique microporous structures.Therefore,in this work,two novel diamine monomers containing tetraaryl imidazole structures were designed and synthesized,and the structure and performance of the membrane materials were regulated through homo-or copolymerization methods,resulting in good gas separation performance.The research content of this dissertation includes the following four parts:（1）A new diamine monomer 4,4’-[4,5-diphenyl-（3-hydroxy-4-aminophenoxy）phenyl]imidazole（PMAPPP）was synthesized and polymerized with five kinds of dianhydrides,respectively.Five kinds of polyimide precursors containing o-hydroxy groups based on tetraarylmidazole structures（PI）were prepared,and further thermal rearrangement reactions were carried out to prepare corresponding thermal rearrangement polymer membranes.The results showed that the TR-6FDA had the best gas separation performance,with permeation fluxes of H₂（284.34 Barrer）,CO₂（269.31 Barrer）,O₂（62.75 Barrer）,and N₂（10.67 Barrer）,and selectivity of CO₂/N₂（25.24）,O₂/N₂（5.88）,and H₂/N₂（26.59）,respectively.（2）Copolymer membranes with different molar ratios were prepared by copolymerization of 9,9’-bis（3-amino-4-hydroxyphenyl）fluorene（BAHPF）,PMAPPP,and hexafluorodianhydride（6FDA）.Then,through thermal rearrangement reaction at450°C,the corresponding thermal rearrangement copolymer membranes were obtained.Gas permeation data showed that the gas flux of co TR（PMAPPP-BAHPF-6FDA）-（4:6）is the highest,with H₂（272.12 Barrer）,CO₂（265.98 Barrer）,O₂（50.11Barrer）,and N₂（5.01 Barrer）,respectively,with ideal selectivity of CO₂/N₂（52.44）and O₂/N₂（9.88）.（3）A novel diamine monomer 4,4’-（4,5-diphenyl-（3-hydroxy-4-aminophenyl））imidazole（DMAP）was synthesized.Two types of copolymers TS（PI-DF）-8:2 and HT（PI-DF）-8:2 were prepared by copolymerization of DMAP,6FAP,and 6FDA using different methods（two-step method,one-step high-temperature method）at the same copolymerization ratio.After thermal rearrangement at 450°C,copolymer membranes TS（TR-DF）-8:2 and HT（TR-DF）-8:2 were obtained.（4）Co PI（PMAPPP-DAPP-6FDA）membranes with different molar ratios were prepared by copolymerization of 3,3’-diaminophenolphthalein（DAPP）,PMAPPP,and 6FDA.The corresponding thermal rearrangement polymer membrane co TR（PMAPPP-DAPP-6FDA）was obtained through further thermal rearrangement reaction at 450°C.Among them,the co TR（PMAPPP-DAPP-6FDA）-（6:4）displays the best gas separation performance,with gas permeabilities of H₂（318.8 Barrer）,CO₂（220.4 Barrer）,O₂（49.20 Barrer）,and N₂（7.28 Barrer）,respectively.