Copolymerization of acrylonitrile and p‐sodium styrene sulfanate

Abstract The copolymerization of acrylonitrile (AN) with sodium p‐styrenesulfonate (SSS) in aqueous solutions (of pH 3 and pH 7) has been investigated. Monomer reactivity ratios at 45°C. for AN and SSS are found to be r1 = 0.10 ± 0.02, r2 = 1.20 ± 0.10 at pH 3 and r1 = 0.05 ± 0.01, r2 = 1.40 ± 0.04 at pH 7, from which Price Q and e values for SSS of 0.76 and −0.26 at pH 3 and of 1.25 and −0.43 at pH 7 are calculated. Initial rates of copolymerization at 45°C. with ammonium persulfate (APS) as initiators were determined over the entire range of composition from pure AN to pure SSS, and it has been found that there is a sharp rise in copolymerization rates within 0.2–5 mole‐% monomer feed, sometimes being eight times larger than those in the neighboring range. The copolymerization in SSS monomer feed of 0.2–5 mole‐% occurs in the transition phase from homogeneous to heterogeneous, and the system is very viscous and slightly cloudy. From the investigation of the effect of initiator concentration on the copolymerization rate and the direct observation by an electron microscope, the sharp rise in copolymerization rates may reasonably be interpreted in terms of the emulsion copolymerization mechanism.