Correlation of reactivity ratios, transition-metal salts and ester hydrolysis to radical polymerization of electron-deficient comonomers with 2-(N,N-dimethylamino)ethyl methacrylate as the inimer

Abstract

The radical copolymerization of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA, M1) as the inimer and electron-deficient monomers (M2, including methyl methacrylate (MMA), acrylamide (AAm) and N,N-dimethylacrylamide (DMAAm)) with transition-metal salts (such as copperII and ironIII) as the oxidizing agent was correlated to their reactivity ratios (r1 and r2), counterions to transition-metal salts and ester hydrolysis of DMAEMA with an objective to obtain high-molecular weight (MW) branched polymers. As r1 ≈ r2 ≈ 1.0, primary chain initiation occurred even at high MMA conversion during CuSO4-DMAEMA redox-initiated radical polymerization of MMA, and thus the polymerization failed to form high-MW branched PMMA free from linear analogues. As r1 > 1.0 > r2, DMAEMA was preferentially converted into -DMAEMA- units during Fe(NO3)3-DMAEMA redox-initiated aqueous radical polymerization of AAm/DMAAm, but N,N-dimethylaminoethanol formed via hydrolysis led to lower-MW chains. Under optimal conditions with minimum hydrolysis, FeCl3-DMAEMA redox-initiated aqueous radical polymerization of DMAAm proceeded via redox-initiated reverse atom transfer radical polymerization (ATRP) generating DMAEMA-terminated chains with a carbon-chloride terminal. FeII-catalyzed self-condensing ATRP led to high-MW branched PDMAAm even under aerobic conditions.