Synthesis and characterization of dicyanate monomers containing methylene spacers

The bisphenols containing methylene spacer were prepared by treating eugenol/2‐allyl phenol with 2,6‐dimethyl phenol/guiacol/o‐cresol in the presence of AlCl₃. All the bisphenols were converted to their respective cyanate esters by treating with CNBr. The structural confirmation was done by FTIR, ¹H NMR, ¹³C NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the T_g is in the range of 208–239°C. The T_g is highest for the cyanate ester Cy(b) with symmetric structure. The T_g of the cured network depends on the length and symmetry of the monomer, T_g being higher for shorter and the para‐substituted monomers. The T₁₀ values are in the range of 364–381°C. The char yield is in the range of 47–53%. From the char yield, the limiting oxygen index (LOI) value was determined, which is used to confirm the flame retardancy of the cyanate ester resins. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008