ESR Studies of Copolymerization of Water-Soluble Monomers with Acrylonitrile

Abstract

Copolymerization of water-soluble unconjugated monomers (M1) with acrylonitrile (AN) has been studied by ESR using a flow system.The M1-monomers studied were maleic anhydride (MA), sodium allyl sulfonate (SAS), sodium methallyl sulfonate (SMAS), allyl alcohol (AA), sodium vinyl sulfonate (SVS), allyl acetate (AAc), with vinyl acetate (VAc) as reference standard. The initiation reactions and the addition of AN units to monomer radicals (M1·) at pH 1.4 and 7.0 were studied. The addition of small amounts of AN to M1 monomers caused a sharp decrease in the concentration of monomer radicals (M1·), whereas the concentration of allylic monomer radicals (in the cases of AA and SAS), AN· and, especially, the co-polymer radicals M1—AN· formed from M1· increased. The reactivity of sulfonic acid monomer radicals, such as SVS and SMAS, increased almost to double upon changing pH from 1.4 to 7.0. All results show the very low reactivity of water-soluble unconjugated monomers and their radicals. The M1—AN· copolymer radicals are characterized by lower aHβ-values than the AN monomer radical. This is interpreted as due to restricted rotation caused by steric hindrance from the M1 units attached to the β-carbon of the AN radicals.