Low-melting siloxane-bridged phthalonitriles for heat-resistant matrices

New low-melting phthalonitrile monomers were obtained by introduction of different flexible siloxane bridges such as -O-SiPh2-O- and -O-SiPhMe-O-. In spite of the presence of the siloxane groups the considered monomers were separated as single compounds by column chromatography with good yields (up to 90%). The synthesized monomers possessed T-g = 12-27 degrees C which were by a decade lower than it had been reported for phthalonitrile monomers before and even lower than the lowest T-g = 41 degrees C detected for phtalonitrilic oligomers. The cured monomers demonstrated high thermal and thermooxidative stabilities at the same level as described earlier for that type of polymer matrices. Thus a significant decrease of the T-g of the suggested monomers dramatically expands the processing window for the whole class of phthalonitrile matrices for reinforced plastics. (C) 2015 Elsevier Ltd. All rights reserved.