Synthesis and properties of polyetherimide copolymers based on AB-type monomer
A series of polyetherimides PEI-ABx[x is the dosage of 3-amino-5,6,9,10-tetrahydro-[5]helicene-7,8-dicarbonyl-dicarboxylic anhydride(ATHDA),based on the total mass of 4,4'-(4,4'-isopropylidenediphenyloxy)bis-(phthalic anhydride)(BPADA)and 4,4'-diaminodiphenyl ether(ODA),the same below]were synthesized from AB-type monomer ATHDA,BPADA and ODA by high-temperature one-step method.The obtained polymers were then characterized by FTIR,1HNMR,DSC,DMA and TGA,and analyzed for their mechanical properties and solubility.The results showed that PEI-ABx exhibited inherent viscosity of 0.60～0.87 dL/g,good film-forming property and excellent solubility in common organic solvents such as N,N-dimethylacetamide and N-methylpyrrolidone.Meanwhile,the polymers displayed glass transition temperatures(Tg)obtained from DMA analysis of 228～256℃,and 5%thermal mass loss temperature(T5%)of 505～536℃in N2 atmosphere,indicating excellent thermal stability.Moreover,the PEI-ABx showed good mechanical properties with tensile strength,Young's modulus and elongation at break of 41.7～88.1 MPa,1.7～2.7 GPa and 3.3%～4.8%,respectively.In addition,the tetrahydro-[5]helicene structure in polymer chains could be dehydrogenated to form more rigid aromatic structure.Compared with those of PEI-AB20,the Tg and T5%of PEI-AB20 after aromatization were increased from 256℃to 283℃and 531℃to 557℃,respectively,showing improved heat resistance of the polymers after dehydrogenation.
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