Amphiphilic gradient poly(styrene- co-acrylic acid) copolymer prepared via nitroxide-mediated solution polymerization. Synthesis, characterization in aqueous solution and evaluation as emulsion polymerization stabilizer

• Published in: Polymer (Guilford) 2006-03, Vol.47 (6), p.1935-1945
• Main Authors: Lefay, Catherine, Charleux, Bernadette, Save, Maud, Chassenieux, Christophe, Guerret, Olivier, Magnet, Stéphanie
• Format: Article
• Language: English
• Subjects: Acrylic acid; Amphiphilic copolymer; Applied sciences; Chemical Sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Styrene
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2006.01.034

A well-defined, amphiphilic poly(styrene- co-acrylic acid) copolymer was synthesized in a single step by nitroxide-mediated controlled free-radical copolymerization of styrene and acrylic acid, without protection of the acid groups: M n=6500 g mol −1, M w/ M n=1.5 and a composition of F AA=0.70±0.03 in acrylic acid. In addition to the good control over molar mass and molar mass distribution, the copolymer exhibited a narrow composition distribution with a slight gradient. Such copolymer was an efficient stabilizer for the emulsion polymerizations of styrene and of mixtures of methyl methacrylate and n-butyl acrylate, until 45 wt% solids. A low amount (typically 3–4 wt% based on the monomer(s)) was needed for a good stabilization. This is approximately a decade lower than the required amount of random, amphiphilic copolymers prepared via conventional free-radical polymerization. The performances were, however, below those of analogous diblock copolymers, but the great advantage is the very easy synthetic procedure.