Effect of reaction medium on copolymerization of acrylonitrile and sodium allyl sulfonate

The copolymerization of acrylonitrile (AN) with sodium allyl sulfonate (SAS) in dimethyl sulfoxide (DMSO) at pH 7, aqueous DMSO solution (6% H2O), DMSO at pH 1.5, and aqueous solution at pH 7 has been investigated. Monomer reactivity ratios at 45°C. for AN and SAS are found to be r1 = 1.00 ± 0.01, r2 = 0.38 ± 0.02 in DMSO at pH 7; r1 = 1.25 ± 0.01, r2 = 0.28 ± 0.02 in aqueous DMSO; r1 = 1.85 ± 0.01, r2 = 0.43 ± 0.01 in DMSO at pH 1.5. From these values Price Q and e values, respectively, calculated for SAS were 0.19 and 0.22 in DMSO at pH 7, 0.14 and 0.18 in aqueous DMSO, and 0.18 and 0.70 in DMSO at pH 1.5. The large differences in reactivity of SAS may be attributed to the different electron distributions in SAS in each solvent which are caused by the poor solvating power of dimethyl sulfoxide and by the addition of protons. In copolymerization in aqueous solution, the physical condition depends upon the content of SAS in the monomer feed, and SAS is copolymerized to only a small extent in the range of heterogeneous systems, whereas SAS is copolymerized rather well in the range of homogeneous systems. Homopolymerization of SAS shows a first‐order dependence on initiator concentration and a three‐halves‐order dependence on monomer concentration; this is attributed to degradative chain transfer of SAS. Rates of copolymerization of AN and SAS decrease with increasing SAS content.