Studying the effect of the chloral group on the thermal and physical properties of aromatic cyanate esters

Two cyanate ester monomers: 2,2-bis(4-cyanatophenyl)propane (1) and l,l-dichloro-2,2-(4-cyanatophenyl)ethylidene (2) are formulated with copper(II) acetylacetonate (200 ppm) in dodecylphenol (1% w/v active copper suspension) and cured (2 K/min to 150 °C + 1 h; 2 K/min to 200 °C + 3 h) followed by a post cure (2 K/min to 260 °C + 1 h). The polymerisation enthalpy for the thermal polymerisation of monomer (2) was recorded as 87.6 ± 0.75 kJ/mol. OCN (75.0 ± 0.80 kJ/mol. OCN following catalysis) and 99.4 ± 1.86 kJ/mol. OCN, 85.8 ± 4.03 kJ/mol. OCN following catalysis for (1). Formulated monomers show little advancement in cure during storage at a several temperatures (ambient, -5 °C and -20 °C) over a period of 2 months. TGA measurements conducted on cured 'puck' sample3s reveal char yields of 38% at 800 °C in the case of (1) and 54% for (2). Pyrolysis-GC shows only minor similarities in the species detected implying that the two polymers undergo significantly different degradation pathways under the analysis conditions, but the low incidence of polynuclear aromatics present (aside from substituted fluorenes, biphenyls and anthracenes) is probably due to the rapidity of heating a short residence times involved.