Disclosed is a circuit material, including dielectric substrate or a circuit subassembly further comprising a conductive layer, that is formed from a precursor composition, wherein the precursor composition comprises, based on the total weight of the precursor composition, thermosetting resin or thermoplastic polymer, optionally monomeric triallyl isocyanurate or triallyl cyanurate, dispersed particles of poly(triallyl isocyanurate) or poly(triallyl cyanurate), and optionally inorganic filler, wherein the circuit material has a Df of less than 0.0060 at 10 GHz. Also disclosed is a method of manufacturing such a circuit material in which emulsion polymerized particles of poly(triallyl isocyanurate) or poly(triallyl cyanurate) are dispersed in a thermosetting or thermoplastic resin.