Tuning of the electron beam sensitivity of acrylate copolymers by compositional effects

Complete text of publication follows. The chemical effects of high-energy radiation onto homopolymers is relatively well understood, but the radiation chemistry of copolymers is still a vast field of investigation. The reactivity under electron beam (EB) irradiation of two families of copolymers with well-defined structure and composition was examined and quantified by applying the Charlesby-Pinner formalism to the variations of the resulting gel fraction as a function of the absorbed dose. A first series of copolymers with various compositions were prepared from n-butyl acrylate (BuA) and methyl methacrylate (MMA), two comonomer units known to exhibit antagonistic effects, MMA units favoring scission, whereas BuA units tend to crosslink the chains. The second series was prepared by side-chain functionalization of poly(butyl acrylate) by transesterification with alcohols bearing selected chemical groups (branched alkyl, unsaturated or heteroatomic functions). The differential contributions of infinitesimal amounts of functional comonomer units on the variation of G-values for scission and for crosslinking are discussed in terms of intrinsic chemical reactivity. Additional physical effects are also invoked for higher contents in comonomer that induce variations of polymer segments mobility in the bulk state. The results of this study were applied to acrylate-based lateces whose reactivity under radiation, assessed by gel dose measurements after filmification, is significantly enhanced by judicious composition adjustments