Preparation And Properties Of Fluorene Based Polyimide And Thermally Rearranged Polymer

Polyimides(PI)are widely used in many fields due to their excellent comprehensive performance.However,the traditional polyimides have some drawbacks,such as insoluble,low transparency,bad heat resistance and poor gas permeability.In this dissertation,in order to overcome these problems,the fluorenyl group was introduced to the backbone of polyimides,and the relationship between structure and properties was studied.On this basis,the thermally rearranged(TR)polymers were prepared by further thermal treatment of fluorene based polyimides,and the TR polymers demonstrated excellent gas separation performance.Then,the influence of thermal atmosphere and temperature on TR polymer of properties was investigated.The dissertation consists of two parts:(1)preparation and properties of fluorene based polyimides;(2)preparation and properties of thermally rearranged polymers.(1)Firstly,two kinds of fluorene containing diamines were synthesized,and their structures were characterized by FT-IR and 1H NMR.The melting points of diamines were determined by DSC.Secondly,a series of homopolyimides and copolyimides were synthesized by self-made diamines,9,9'-bis(3-amino-4-hydroxyphenyl)fluorene(BAHF),9,9'-bis[4-(4-amino-2-hydroxybenzoxyl)phenyl]fluorene(BAHOPF),9,9'-bis(4-aminophenyl)fluorene(BAF)and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA).The structures and properties of these PIs were characterized by FT-IR,TGA,DSC,universal tensile tester and solubility testing.The experimental results showed that the fluorene containing diamines and the corresponding polyimides were prepared successfully.These PIs showed good thermal stability.The glass transition temperature(Tg)of PIs were about 350 o C,and the highest5% weight loss temperature was 505 o C.In addition,the PI membranes showed good optical transparency and light color.In the UV-visible region,the transmittance of PIs was over 85%,and the transmittance at 450 nm was more than 80%.These PIs also demonstrated good mechanical properties.Besides,the solubility of PIs was excellent,they easily dissolved in the polar solvent,such as DMAc,DMF and NMP.Meanwhile,the PIs are of good chemical resistance.(2)A series of TR polymers were prepared by the thermal treatment of CPI-BAHF-BAF-5-5.The influence of thermal treatment atmosphere and temperature on TR polymers was studied.The experimental results showed that under N2 atmosphere,the PIs underwent an obvious thermal rearrangement.However,the air atmosphere hindered the thermal rearrangement due to the thermal crosslinking.Nomatter with the atmosphere,the thermally treated membranes exhibited a high Tg value.With the temperature increasing,the gas permeabilities of the membranes were improved.It was worth noting that the membrane treated at 480? in N2 showed excellent gas permeability,the gas permeabilities of H2,CO2,O2,N2 and CH4 were1908.26,5087.49,678.63,212.78,and 245.45 barrer,respectively.