Synthesis and Characterization of Novel Betti Type Cyanate Esters

Several aromatic diols bearing amino benzyl linkage in the main chain have been synthesized through high yield Betti reaction, which involves the reaction of an aldehyde with p-amino phenol and 8-hydroxy quinoline. Five different aldehydes have been used to prepare five new bisphenols. These bisphenols were converted to their corresponding cyanate esters by the treatment of cyanogen bromide in the presence of triethyl amine. The structures of the diols and dicyanate esters were confirmed by FT-IR, ¹H-NMR, ¹³C-NMR spectral studies and elemental analysis. The cyclotrimerization reactions of cyanate esters have been studied by differential scanning calorimetry (DSC). The maximum curing temperatures of these cyanate esters are in the range of 186-201^oC. T_gvalues of the polycyanurate networks are above 270^oC. Thermogravimetric analysis (TGA) shows that the 10% weight loss of all the cured cyanate esters is above 400^oC in N₂ atmosphere. The char yield is in the range of 66-73%. The flame retardancy of the cyanate ester resins have been studied using Limiting Oxygen Index (LOI) value which is in the range of 43.9-46.7% at 700^oC.