Synthesis and characterization of phenylethynyl-terminated polyimide oligomers derived from 2,3,3′,4′-diphenyl ether tetracarboxylic acid dianhydride and 3,4′-oxydianiline

With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride (PEPA)-terminated imide oligomers prepared by the reaction of 2,3,3′,4′-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA) and 3,4′-oxydianiline (3,4′-ODA) with different molecular weights (degree of polymerization: n = 1–9) were formed. The resultant oligomers with different molecular weights were characterized for their chemical architecture, cure behavior, thermal properties, solubility in organic solvents and rheological characteristics. Besides, the thermal properties and tensile test of cured polyimide films were also evaluated. The imide oligomer (degree of polymerization: n = 1) has some somewhat crystalline phase, and imide oligomers (degree of polymerization: n = 2–9) showed excellent solubility (40 wt%) in N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) at room temperature. Furthermore, the rheological properties of imide oligomers showed very low melt viscosity and wider processing window. The cured films exhibited good thermal properties with the glass transition temperatures of 282–373 °C and 5 wt% thermal decomposition temperatures higher than 551 °C in nitrogen atmosphere. The elongation at break of the prepared films was found to be high (almost > 9.3%).