A series of new bisphenols containing sulfoxide has been prepared from various substituted phenols and thionyl chloride using AICI(3) as catalyst. These bisphenols were converted to their respective cyanate esters by reacting with cyanogen bromide. The structures of all the five bisphenols and cyanate esters have been confirmed by FTIR, H-1 NMR, and C-13 NMR spectral methods and elemental analysis. The thermal properties of cyanate ester resins were studied by DSC and TGA. The glass transition temperature of the cured sulfoxide bridged cyanate esters are in the range of 181-236 degrees C. The Cy(e) cyanate ester shows high thermal stability due to linked interpenetrating polymer networks formed by allyl functionality. The initial thermal degradation temperature starts above 340 degrees C. The char yield is in the range of 38-54%. The limiting oxygen index value is the range of 32.7-39.1. POLYM. ENG. SCI., 49:889-895, 2009. (C) 2009 Society of Plastics Engineers