Interpenetrating polymer networks derived from ethynyl-terminated imide oligomers and cyanate ester

Ethynyl-terminated oligomers (BETI) with different degrees of polymerization were synthesized using 2, 3, 3', 4'-biphenyltetracarboxylic dianhydride and 2, 2'-bis(trifluoromethyl) benzidine as the monomers and ethynylphthalic anhydride as the end-capper; modified cyanate ester resins were then formulated by dissolving BETI in bisphenol A dicyanate, and the properties of the blends and the resulting Interpenetrating Polymer Networks (IPNs) were investigated in terms of curing behavior, and thermal, mechanical, and dielectric properties. The results indicate that the trimerization of-OCN functionality could be catalyzed by the incorporation of BETI, as evidenced by significantly reduced curing temperatures and shorter gelation time. Moreover, IPNs show improved thermal and mechanical properties compared to pure polycyanurate. especially, when 30% weight BETI with the polymerization degree 19 was blended in pure cyanater ester resin, the class transition temperature, 5% weight loss temperature, tensile strength, and impact strength of the IPNs were increased from 297℃ to 309℃, 425℃ to 431℃, 76 MPa to 94 MPa, and 24 kJ/m² to 31 kJ/m², respectively. The dielectric constants of the IPNs are slightly higher than that of pure polycyanurate. The BETI-modified cyanate ester resins could be potentially used as matrix resin in aerospace industry due to their improved processability and material properties.