A 2,6-dimethyl phenol-dicyclopentadiene novolac (DCPDNO) was synthesized from dicyclopentadiene and 2,6-dimethyl phenol, and the resultant DCPDNO was reacted with cyanogen bromide into 2,6-dimethyl phenol-dicyclopentadiene cyanate ester (DCPDCY). The structures of the novolac and cyanate ester were confirmed with Fourier transform infrared spectroscopy, elemental analysis, mass spectrometry, (MS), and nuclear magnetic resonance. For the purpose of increasing the mobility of residual DCPDCY during the final stage of curing and achieving a complete reaction of cyanate groups, a small quantity of a monofunctional cyanate ester, 4-tert-butylphenol cyanate ester (4TPCY), was added to DCPDCY to form the cyanate ester copolymer. The synthesized DCPDCY was then cured with 4TPCY at various molar ratios. The thermal properties of the cured cyanate ester resins were studied with dynamic mechanical analysis, dielectric analysis, and thermogravimetric analysis. These data were compared with those of the commercial bisphenol A cyanate ester system. Compared with the bisphenol A cyanate ester system, the cured DCPDCY resins exhibited lower dielectric constants (2.52-2.67 at 1 GHz), dissipation factors (0.0054-0.0087 at 1 GHz), glass-transition temperatures (261-273 degreesC), thermal stability (5% degradation temperature at 406-450 degreesC), thermal expansion coefficients (4.5-5.78 x 10(-5)/degreesC before the glass-transition temperature), and moisture absorption (0.8-1.1%). (C) 2004 Wiley Periodicals, Inc.