含四芳基咪唑结构的热重排气体分离膜的制备与性能研究

Preparation and Performance of Thermally Rearranged Gas Separation Membranes Containing Tetraarylimidazole Structure

合成了一种新型含四芳基咪唑结构的二胺单体4,4’-(4,5-二苯基-(3-羟基-4-氨基苯氧基)苯基)咪唑(PMAPPP),然后分别与5种二酐单体聚合,经热酰亚胺化处理得到含羟基聚酰亚胺(HPI)薄膜.接着,对这些薄膜进行450℃热处理,得到相应的热重排(TR)膜材料,并对薄膜进行了结构与性能表征.结果表明,刚性大体积四芳基咪唑结构的引入使HPI膜表现出优异的热性能和力学性能,玻璃化转变温度在263~361℃,拉伸强度在98.4~118.3 MPa.热重排后,TR膜的气体分离性能得到了显著提高.其中,TR(PMAPPP-6FDA)的气体渗透性能最佳,即H_(2)(269.31 Barrer)、CO_(2)(284.25 Barrer)、O_(2)(62.75 Barrer)和N_(2)(10.67 Barrer),CO_(2)/N_(2)和O_(2)/N_(2)的理想选择性分别为25.24和5.88,且O_(2)/N_(2)的分离性能超过2008 Robeson上限.因此,将四芳基咪唑结构引入到HPI分子结构中,可以获得一类气体分离性能优异的TR膜材料.

In recent years,the thermal rearrangement(TR)membrane materials derived from hydroxyl-containing polyimides(HPI)as precursors have received extensive attention in the field of gas separation.In this study,the dihydroxy compound 4,4'-(4,5-diphenyl-(4-hydroxyphenyl))imidazole(PMOPPP)containing rigid and bulky tetraarylmidazole structure was first synthesized,and then reacted with 5-fluoro-2-nitrophenol to produce a dinitro compound 4,4'-(4,5-diphenyl-(3-hydroxy-4-nitrophenoxy)phenyl)imidazole(PMNPPP).After reduction treatment,a new kind of diamine monomer 4,4'-(4,5-diphenyl-(3-hydroxy-4-aminophenoxy)phenyl)imidazole(PMAPPP)was obtained.Then,the diamine PMAPPP was separately polymerized with five kinds of dianhydride monomers,followed by thermal imidization treatment to obtain HPI membranes.Subsequently,these membranes were further thermally treated at 450℃for 1 h to obtain the corresponding TR membranes,and the structure and performance of these membrane materials were characterized.The testing results showed that the introduction of rigid and large volume tetraarylimidazole structure resulted in excellent thermal and mechanical properties of five HPI membranes,and the glass transition temperatures(Tg)were in the range of 263‒361℃and the tensile strength ranged from 98.4 MPa to 118.3 MPa.Compared to HPI membrane materials,the gas separation performances of TR membranes were significantly improved.Among them,the TR(PMAPPP-6FDA)exhibited the highest gas permeabilities,namely H_(2)(269.31 Barrer),CO_(2)(284.25 Barrer),O_(2)(62.75 Barrer)and N_(2)(10.67 Barrer).Moreover,the ideal selectivities of CO_(2)/N_(2),O_(2)/N_(2) and H_(2)/N_(2) were 25.24,5.88 and 26.64,respectively,and the O_(2)/N_(2) separation performance was beyond the 2008 Robeson upper bound.