Nitroxide-Mediated Controlled Free-Radical Emulsion Polymerization Using a Difunctional Water-Soluble Alkoxyamine Initiator. Toward the Control of Particle Size, Particle Size Distribution, and the Synthesis of Triblock Copolymers

A novel dialkoxyamine bearing two carboxylic acid groups was synthesized by the addition of a high dissociation rate constant alkoxyamine onto tri(ethylene glycol) diacrylate. This dialkoxyamine was first successfully used as an initiator for the bulk polymerizations of n-butyl acrylate and styrene. Then the sodium salt counterpart was used as a water-soluble initiator in the emulsion polymerizations of n-butyl acrylate and styrene via a multistep process. Owing to its unique structure with two carboxylate salts remaining covalently bound to the chain and hence locked at the particle surface, very stable latexes were recovered with, for the first time, small particles and narrow particle size distributions. The emulsion process was successfully applied to the synthesis of well-defined poly(n-butyl acrylate) and polystyrene homopolymers as well as polystyrene-b-poly(n-butyl acrylate)-b-polystyrene triblock copolymer. This work represents the first successful attempt of the synthesis of a complex architecture together with the control of average diameter and particle size distribution in nitroxide-mediated polymerization in emulsion, which is of high industrial and academic interest.