Epoxy- and cyclopropane-functional copolymers: Synthesis, thermal properties and photocrosslinking behavior

Abstract

Copolymers bearing both epoxy and cyclopropane groups were syn­thesized by free-radical copolymerization of glycidyl 2-(4-vinylphenyl)cyc­lo­propanecarboxylate (GVPCC) with methyl methacrylate (MMA) using AIBN at 343 K, in bulk and in benzene under inert atmosphere. Copolymer compositions were determined by spectroscopy and copolymerization parameters were eval­uated by the Fineman–Ross method. The reactivity ratios were r₁(GVPCC) = 0.68±0.05 and r₂(MMA) = 0.51±0.07; their product (r₁r₂ = 0.35) indicates random copolymerization with a tendency toward alternation. Alfrey–Price par­ameters (Q₁ = 0.96, e₁ = −0.63; Q₂ = 0.74, e₂ = 0.40) confirm strong comonomer interactions and pronounced polar effects. For a 50/50 copolymer, the intrinsic viscosity was 0.66 dL g^-1 (benzene, 25 °C). Thermogravimetric analysis showed composition-dependent stability with T₅ 250–320 °C, increasing with GVPCC content, alongside improved adhesion (up to 5.6 MPa) and Vicat softening temp­erature (121 °C). UV irradiation produced efficient crosslinking and negative-tone photoresist behavior (resolution with depth of penetration, D_p 0.25–0.35 μm; cri­tical exposure energy, Ec, 14.5–16.4 mJ cm^-2; sensitivity, S, 61–69 cm² J^-1), dem­onstrating potential for UV-patternable microfabrication materials.