Copolymerization studies. II. Effect of high pressures on monomer reactivity ratios

Abstract

Abstract Studies of the effect of pressure on comonomer reactivity ratios in the styrene—acrylonitrile and methyl methacrylate—acrylonitrile systems show that the values of r 1 and r 2 increase in both cases and that the relative activation volumes (Δ V 11 ‡ − Δ V 12 ‡ ) are −9.8 and −9.5 cc./mole respectively, where acrylonitrile is monomer 2. The product r 1 r 2 increases toward unity in both systems. A study of the effect of temperature on these reactivity ratios shows that (Δ H 11 ‡ — Δ H 12 ‡ ) is essentially zero for methyl methacrylate—acrylonitrile, but 500 cal./mole for styrene—acrylonitrile. Within the pressure range studied, it has been found that the e values for the two monomer pairs are dependent upon pressure, tending to become equal, the higher the pressure, while the Q values are relatively unaffected by pressures up to 1000 atm.