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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 1H-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 (Tg). The para isomer displayed the highest Tg 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 Tg value of the para-triaryl isomer was the highest of the three triaryl isomers and was about the same as that of bisphenol A polycyanurate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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