Synthesis and characterization of a renewable cyanate ester/polycarbonate network derived from eugenol

A homogenous polycarbonate/cyanate ester network has been prepared from a renewable, eugenol-derived bisphenol. The pure polycarbonate exhibited a Tg of 71 °C, Mn = 8360, and polydispersity of 1.88. An 80:20 blend of cyanate ester: polycarbonate was prepared and thermally cured. The presence of the polycarbonate had no significant effect on the cure behavior of the cyanate ester. Small Angle Laser Light Scattering (SALLS) and DSC were used to analyze the blend and no phase separation was observed either during or after cure, suggesting that a homogenous network was generated. TMA of the resulting composite material revealed a single Tg of 132 °C (tan δ), roughly 55 °C lower than the Tg of the pure polycyanurate and 60 °C higher than the polycarbonate. A solvent extraction study showed that the polycarbonate could be quantitatively separated from the thermoset matrix after cure. This result proved that no chemical grafting occured under the cure conditions employed. The excellent miscibility of the polycarbonate and cyanate ester coupled with the efficient cure of the blend to a homogenous network suggests that these types of blends may have applications for fabrication of toughened composite structures.