Preparation of phthalonitrile resins containing siloxane linkages with improved processability

To improve the processability of biphenyl phthalonitrile resin, a flexible siloxane structure was introduced into the phthalonitrile monomer through molecular design, which was then blended with a biphenyl monomer to prepare phthalonitrile alloy resins. When the ratio of phthalonitrile monomer containing flexible siloxane to biphenyl phthalonitrile monomer was 1:1, the processing window widened from 58 to 110°C, as compared to that of biphenyl phthalonitrile. Due to the introduction of the biphenyl structure into the phthalonitrile alloy resins, the initial decomposition temperature of the silicon-containing phthalonitrile resin increased from 385 to 516°C. More importantly, the phthalonitrile alloy resin exhibited a high bending strength (66 MPa) and bending modulus (3762 MPa), indicating that it could be potentially applied as high temperature structural composite matrices. Furthermore, it provides a new strategy for processing phthalonitrile resins with a high melting point and narrow processing window.