Studies of polycyanurates based on phenoxy-substituted cyclic phosphazenes: synthesis of the monomer and a preliminary study of its thermal properties in binary blends

The four-step preparation of a new monomer, 1,2,3-tris(4-cyanatophenoxy)-,3’,5,5-tris-phenoxy2,4,6-[1,3,5,2,4,6]-triazatriphosphinine, is reported. Characterization of the monomer is undertaken using spectroscopic and chromatographic methods and elemental analysis and the data are in agreement with the proposed structure (as a mixture of isomers). The thermal polymerization of the monomer and its behaviour within selected blends containing 2,2-bis(4cyanatophenyl)propane (AroCy B10) are studied using differential scanning calorimetry. The blends appear to melt sharply at ca. 80oC onset of polymerization (corresponding to the melting point of the commercial dicyanate) before commencing polymerization directly thereafter. Typical exothermic peak maxima at ca. 135 oC are observed, whilst the cure is apparently concluded by 200oC under the scanning conditions. On rescan, the cured samples display glass transition values 2 in the region of 160-190 oC, depending on composition with the higher values reflecting increasing amounts of the new material. The cured polycyanurate of the tricyclophosphazene is also analysed using thermogravimetric analysis and displays a mass loss of 5% at approximately 381oC in air and 366oC in nitrogen. When 1,2,3-tris(4-cyanatophenoxy)-,3’,5,5-tris-phenoxy-2,4,6[1,3,5,2,4,6]-triazatriphosphinine is combined with AroCy B10, the cured copolymers (containing between 10 and 30 wt% of the tricyclophosphazene) show disappointing thermal stability with a progressive reduction in the onset of degradation with increasing phosphazine content; this may be a result of incomplete cure. Author