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 confiramtion was done by FTIR, H-1 NMR, C-13 NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the Tg is in the range of 208-239 C. The Tg 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 T-10 values are in the range of 364-381 degrees 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. (c) 2008 Wiley Periodicals, Inc.