A copolymer composition including a copolymer having repeat units of structural formula I: ##STR1##

where X is selected from —CH₂—, —CH₂—CH₂— and O; m is an integer from 0 to 5; and each occurrence of R¹-R⁴ are independently selected from H; C₁ to C₂₅ linear, branched, and cyclic alkyl, aryl, aralkyl, alkaryl, alkenyl and alkynyl that can include one or more hetero atoms selected from O, N, and Si; a group that contains an epoxy functionality; —(CH₂)_nC(O)OR⁵; —(CH₂)_nC(O)OR⁶; —(CH₂)_nOR⁶; —(CH₂)_nOC(O)R⁶; —(CH₂)_nC(O)R⁶; —(CH₂)_nOC(O)OR⁶; and any combination of two of R¹, R², R³, and R⁴ linked together by a linking group. A portion of the repeat units having structural formula I contain at least one epoxy functional pendant group. The copolymer composition can be included with a material that photonically forms a catalyst in a photodefinable dielectric composition, which can be used to form a photodefinable layer on a substrate.