Thermal and Mechanical Properties of Phenylethynyl-Containing Imide Oligomers Based

Abstract: In order to further improve both processability of imide oligomers containing pendent or/and ter-minal phenylethynyl groups and their cured Tg values without sacrificing mechanical properties, isomeric dianhydrides, 2,2,3,3-biphenyltetracarboxylic dianhydride (3,3-BPDA) or 2,3,3,4-biphenyl tetracar-boxylic dianhydride (3,4-BPDA), were introduced into main chain. The rigid and bent structure of the isomeric BPDAs can provide a good combination of melt flow while maintaining a high Tg. Phenylethynyl containing oligoimides were prepared from the reaction of isomeric dianhydrides (3,3-BPDA, 3,4-BPDA and 4,4-BPDA), 4,4-oxydianiline (4,4-ODA), 3,5-diamino-4-phenylethynyl benzophenone (DPEB) and 4-phenylethynylphthalic anhydride (4-PEPA) or phthalic anhydride (PA) at an approximate number aver-age molecular weight of 2500 and 5000 g mol1. The imide oligomers from 3,3-BPDA and 3,4-BPDA exhibited good processability. The 3,3-BPDA-based imide oligomers exhibited slightly lower melt vis-cosity and the cured resins exhibited similar Tg values compared with those from 3,4-BPDA. OI-7 and OI-8 each with a molecular weight of 2500 g mol1 had lower melt viscosities of 25 Pa s (342 C) and 178 Pa s (344 C) and higher cured Tg at 367 C and 365 C. The cured films from OI-7, OI-8 showed good tensile properties and the elongations at break were around 10%. The neat resins from OI-7 and OI-8 had higher compressive strengths of 200 and 190 MPa. G827/OI-7 and G827/OI-8 exhibited com-parable mechanical properities: flexural strengths of 1714 and 1826 MPa, flexural modulus of 130 and 124 GPa, and interlayer shear strengths of 95 and 101 MPa, respectively. Key Words: Isomeric imide oligomers biphenyltetracarboxylic dianhydride phenylethynyl group 1