High-Tg, Low-Dielectric Epoxy Thermosets Derived from Methacrylate-Containing Polyimides.

Three methacrylate-containing polyimides (Px⁻MMA; x = 1⁻3) were prepared from the esterification of hydroxyl-containing polyimides (Px⁻OH; x = 1⁻3) with methacrylic anhydride. Px⁻MMA exhibits active ester linkages (Ph⁻O⁻C(=O)⁻) that can react with epoxy in the presence of 4-dimethylaminopyridine (DMAP), so Px⁻MMA acted as a curing agent for a dicyclopentadiene-phenol epoxy (HP7200) to prepare epoxy thermosets (Px⁻MMA/HP7200; x = 1⁻3) thermosets. For property comparisons, P1⁻OH/HP7200 thermosets were also prepared. The reaction between active ester and epoxy results in an ester linkage, which is less polar than secondary alcohol resulting from the reaction between phenolic OH and epoxy, so P1⁻MMA/HP7200 are more hydrophobic and exhibit better dielectric properties than P1⁻OH/HP7200. The double bond of methacrylate can cure at higher temperatures, leading to epoxy thermosets with a high-Tg and moderate-to-low dielectric properties.