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Inverse emulsion polymerization of acrylamide. II. Synthesis and characterization of copolymers with methacrylic acid

1987; Wiley; Volume: 25; Issue: 4 Linguagem: Inglês

10.1002/pola.1987.080250418

1099-0518

В. В. Глухих, C. Graillat, Christian Pichot,

Polymer Science and PVC

Abstract Inverse emulsion copolymerization studies of acrylamide (Am) with methacrylic acid (MAA) are reported. Aqueous monomer solutions were emulsified in toluene with a blend of two surfactants (sorbitan sesquioleate and C18‐terminated acrylamide oligomers). Polymerization kinetics in presence of an oil‐soluble initiator (AIBN) were determined at 40°C as a function of methacrylic acid content and aqueous‐phase pH. Polymerization rates were found to be faster at basic pH than at acidic pH, which appeared to be related to the actual concentration of methacrylic acid in the aqueous phase. Monomer reactivity ratios have been derived as r A‐M = 0.58 ± 0.02 and r M‐A = 4.0 ± 0.10 at pH 4, r A‐M = 0.56 ± 0.005 and r M‐A = 0.15 ± 0.03 at pH 10. These differences were found to have an effect on the molecular characteristics of the copolymers. Initial emulsions and final inverse latexes displayed the same broad size distribution; under basic pH the particle size is relatively insensitive to the ionic comonomer concentration. Poor latex stability is characteristic of copolymer latexes prepared under acidic conditions. Based on these experimental results, some aspects of the polymerization mechanism are discussed.