Electron beam sensitivity of butyl acrylate copolymers: effects of composition on reactivity

Abstract

Partial transesterification of poly(butyl acrylate) (PBuA) was developed and used as a novel method for obtaining acrylate copolymers possessing the same distribution of the degree of polymerization (DP) as that of the parent PBuA and bearing various organofunctional side groups with olefinic unsaturations or heteroatoms. The series of copolymers exposed to accelerated electron beams exhibited radiation sensitivity expectedly dependent on chemical composition. The copolymer reactivity was examined and quantified by applying the Charlesby-Pinner formalism to the gel fraction content as a function of the absorbed dose. The modifications of reactivity for small variations of the copolymer composition were determined by comparing the values of radiochemical yields for scission G(S) and for crosslinking G(X) of the slightly modified polymers with that of the parent homopolymer. The resulting differential contributions of infinitesimal amounts of functional comonomer units are discussed in terms of intrinsic chemical reactivity. Additional physical effects are also invoked for higher contents in the comonomer that induce variations of polymer segments mobility in the bulk state.