A novel resin is formed by the copolymerization of vinylethynylbenzene and diethynylbenzene. Polymerization is carried out under conditions which result in the retention of both unreacted vinyl groups from the vinylethynylbenzene component and unreacted ethynyl groups from the diethynyl component, both of which are then susceptible to crosslinking. The polymer is useful in the formation of high-performance carbon-carbon composites, producing an unusually high char yield with advantageous handling and processing characteristics.