Tracer techniques for the determination of monomer reactivity ratios. III. Ionization chamber assay and the reactivity ratios for the styrene/p‐methylstyrene copolymerization

Abstract Monomer reactivity ratios for the copolymerization of styrene (M1)with p‐methylstyrene (M2)using labeled styrene and an ionization chamber assay technique gave values of r1 = 0.83 and r2 = 0.96. These values are believed to be more reliable than those obtained by direct counting techniques (r1 = 0.99 and 0.94). There is a possibly significant difference between these values and those for this monomer pair in the aluminumtrialkyl–titanium chloride‐initiated copolymerization (r1 ∼ r2 ∼ 1.0), which requires further evaluation.