Tracer techniques for the determination of monomer reactivity ratios. I. A direct counting technique applied to the styrene–methacrylate copolymerization

Abstract

Abstract A direct counting technique has been evaluated and used for the determination of monomer reactivity ratios. Windowless gas‐flow counting of polymer samples plated directly on planchets gave reproducible counting rates and nearly linear self‐absorption curves in the 8–25 mg./planchet range. Copolymer composition data obtained by radioactivity assay on a series of styrene C 14 /methyl methacrylate copolymers gave monomer reactivity ratios of r 1 = 0.48, r 2 = 0.46 at 60° and r 1 = 0.60, r 2 = 0.55 at 132°; these values are in good agreement with previously recorded values.