Statistical n-butyl acrylate-sulphonatopropylbetaine copolymers: 1. Synthesis and molecular characterization

Abstract

Radical copolymerization of n-butyl acrylate (A) and 1,1-dimethyl-1-(3-methacrylamidopropyl)-1-(3-sulphopropyl)ammonium betaine (B) initiated by 4,4′-azobis-4-cyanovaleric acid (ACVA) was studied in ethanol solution at 50°C: [ A + B] ⋍ 1–2.9 mol l −1 (molar fraction of monomer B, f B ⩽ 0.65), [ACVA] = 1 × 10 −3 mol l −1. The copolymerization process apparently obeys the terminal unit model over the whole composition range ( r A = 0.42, r B = 6.0), and the reliability of these reactivity ratios was checked through the analysis of the monomer unit distribution in the chain by 13C nuclear magnetic resonance spectroscopy (carbonyl pattern). For constant concentrations in monomers and initiator, the transition from a homogeneous to a heterogeneous system for f B = 0.1 leads to a twofold increase in the average degree of polymerization with respect to pure poly(n-butyl acrylate). The B units slightly increase the sensitivity of the copolymer to thermal degradation (initial degradation temperature of 300°C under nitrogen).