Synthesis of Biphenylated Cyanate Esters: Thermomechanical Resin Comparisons Within Two Isomeric Series

Three isomeric tetraaryl cyanate esters containing biphenyl moieties {bis-[4-(4'-cyanatophenyl)phenyl] propane, 2,2-bis-[4-(3'-cyanatophenyl)phenyl]propane, and 2,2-bis-[4-(2'-cyanatophenyl)phenyl]propane} and three isomeric triaryl cyanate esters {2-(4'-hydroxyphenyl)-2-[4'-(4-hydroxyphenyl)phenyl]propane, 2-(4'-hydroxyphenyl)-2-[4'-(3-hydroxyphenyl)phenyl]propane, and 2-(4'-hydroxyphenyl)-2-[4'-(2-hydroxyphenyl)phenyl]propane} were synthesized from their corresponding bisphenols. The structures of the monomers were confirmed with IR and H-1-NMR spectroscopy. The curing behavior was investigated with differential scanning calorimetry. Cyanate esters were cured thermally in the absence of a catalyst and were characterized by dynamic mechanical analysis. The results were compared to the properties of commercial bisphenol A polycyanurate. Of the three tetraaryl isomers, 2,2-bis-[ 4-(2'-cyanatophenyl)phenyl]propane had the highest melting point, and its corresponding resin had the lowest glass-transition temperature (T-g). The para isomer displayed the highest T-g value of the three novel tetraaryl resins. The triaryl dicyanate isomers were low-melting solids, with the ortho and meta isomers existing as liquids at room temperature. The T-g value of the paratriaryl isomer was the highest of the three triaryl isomers and was about the same as that of bisphenol A polycyanurate. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 756-763, 2011