Research On The Modification Of Thermoplastic Polythioetherimide By Copolymerization

Polyimides, a kind of high-temperature polymeric materials, have been widely applied inmany fields such as aerospace，military, electronic industry, mechanical and chemical industryowning to their excellent comprehensive properties. However, many of these polymers areinsoluble and infusible, because of their rigid backbones and strong interactions betweenintermolecular and intramolecular, which limit their processing and applications. To solve thisproblem and improve their processablity, researchers are devoting to develop novel meltprocessablethermoplasticpolyimides.It has been demonstrated that polythioetherimide synthesized from mixture of three isomericdiphenylthioether dianhydrides (m-TDPA) is one type of thermoplastic polyimide with excellentsolubility, thermal properties and melt processability in our previous reports. But its properties likethermal properties, toughness and melt processability have yet to be further improved, while thecosts of preparation could be further reduced. How to optimize and control the price/performanceratio of polythioetherimide through appropriate means is an important research topic.Copolymerization is one of most important ways to develop novel thermoplastic polyimides, andit’s convenient to control the properties of polymer by intruducing different monomers. Adoptingcopolymerization, wemayachievetheaimofperformanceimprovementsandcostreduction.However, previous modification researches of polythioetherimide by copolymerization ismainly focused on introducing diamines to copolymerize, while the introduction of dianhydrides tocopolymerize has not beeninvestigated deeply andlack ofsystemicresearch.In this study, a series of copolymers is synthesized by introducing different dianhydrides tothe polythioetherimide, in order to investigate the influence of introducing dianhydrides withdifferent structures on the polymer thermal properties, solubility, mechanical properties and meltprocessability.Thisstudy mainly focuseson as followingthreeaspects:1. To investigate the influence of introducing long chain dianhydride (3benzene rings)copolymerization on the properties of polythioetherimide, a series of molecular-weight-controlledcopolyimides were synthesized from mixture of three isomeric diphenylthioether dianhydrides (m-TDPA),1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and4,4′-oxydianiline (4,4′- ODA) with phthalic anhydride (PA) as an end-capper. It was found that with the increase of theHQDPA components content, the copolyimides had lower glass-transition temperature (Tg) meltviscosity, while their thermal stability, solvent resistance, melt processability and transparency areimproved.2. To investigate the influence of bridged dianhydride (2benzene rings) copolymerization onthe properties of polythioetherimide, a series of molecular-weight-controlled copolyimides weresynthesized from mixture of three isomeric diphenylthioether dianhydrides (m-TDPA),3,3’,4,4’-Biphenyltetracarboxylic dianhydride (BPDA) and4,4′-oxydianiline (4,4′-ODA) with phthalicanhydride (PA) as an end-capper. It was found that with the increase of the BPDA componentscontent, the Tgof copolymers increase slightly, thermal stability are improved, while solubility andmelt fluidity become poorer. By introducing appropriate proportion of BPDA, it can achieve bothwellmeltprocessability and highTg.3. To investigate the influence of dianhydride with one benzene ring (PMDA)copolymerization on the properties of polythioetherimide, a series of molecular-weight-controlledcopolyimides were synthesized from mixture of three isomeric diphenylthioether dianhydrides (m-TDPA),1,2,4,5-Benzenetetracarboxylic anhydride (PMDA) and4,4′-oxydianiline (4,4′-ODA) withphthalic anhydride (PA) as an end-capper. It was found that with the increase of the PMDAcomponents content, Tgs of the polymers increase obviously, thermal stability of copolymers areimproved,whilethesolubilitiesbecomepoorer.