Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins

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AbstractAn efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol‐A‐monocyanate monoglycidyl ether 3, has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol‐A 2, was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8, but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12, depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2‐allylphenyl cyanate 16, has also been synthesized and characterized. Like 3, 2‐allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2‐allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19. Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.