Effect of Segmental Configuration on Properties of n-Propyl-Bridged Polycyanurate Networks

The effect of the chemical configuration of network segments on the physical properties, cure properties, mechanical performance, and chemical stability of polycyanurate networks was investigated via synthesis, network formation, and characterization of an isomeric series of n-propyl-bridged cyanate ester monomers. Configurations that provide cyanurate oxygen atoms with either nearby methyl groups or nearby bridge groups exhibited decreased moisture uptake by up to 50%, along with a roughly 20–40 °C reduction in the loss in glass transition temperatures due to hydrolysis, for networks immersed in 85 °C water for 96 h. In ortho,para-linked aryl cyanates, dry glass transition temperatures of cured networks were reduced compared to analogous para,para-linked networks by only about 10 °C, compared to a reduction of 30 °C in ortho-methylated cyanate ester networks, leading to higher “wet” glass transition temperatures in the ortho,para-linked networks. Neither methyl groups nor bridge groups in a position orth...