Stable Free-Radical Emulsion Polymerization

Abstract

Polymerizations of styrene under emulsion stable free-radical polymerization conditions are reported. Precipitation of an acetone solution of a low molecular weight TEMPO-terminated polystyrene into an aqueous solution of poly(vinyl alcohol) enables the formation of emulsion particles that can be swollen with monomer and subsequently polymerized. The polymerizations proceed in a living manner, yielding polymers that show an incremental increase in molecular weight with time and have narrow molecular weight distributions. Plots of number-average molecular weight versus conversion are linear, indicating a controlled polymerization. The resulting latexes are colloidally stable, and particle size distributions are Gaussian with an average particle diameter of 450 nm. These results constitute the first successful example of an SFRP emulsion process in which the product is not contaminated with a conventionally produced broad molecular weight distribution polymer.

Nitroxide‐Mediated Controlled Free‐Radical Emulsion Polymerization of Styrene and n‐Butyl Acrylate with a Water‐Soluble Alkoxyamine as Initiator

“…[7] Consequently, the real challenge in nitroxide-mediated emulsion polymerization is first to select an appropriate water-soluble alkoxyamine initiator, and second to find the appropriate conditions to form a stable latex with sufficiently high solids content. [9] The very few reports on nitroxide-mediated ab initio emulsion polymerization have mainly concerned the application of a water-soluble radical initiator in conjunction with free nitroxide, either TEMPO [9][10][11] or SG1. [12] Marestin et al [10] are the only group to report the use of a TEMPObased water-soluble alkoxyamine in a diluted emulsion polymerization of styrene.…”

Recent advances in controlled/living radical polymerization in emulsion and dispersion

“…14). 200 Recently, the nanoprecipitation method was also applied to RAFT 201 and ATRP 202,203 emulsion polymerization systems, producing well-controlled homo and block copolymers in stable latex particles.…”

Application of Stable Radicals as Mediators in Living‐Radical Polymerization

“…218 A preformed TEMPO-terminated oligomer, which serves as both a macroinitiator and particle stabilizer, dissolved in acetone, is precipitated in an aqueous solution of poly(vinyl alcohol). Removal of acetone and subsequent heating of the remaining aqueous phase in the presence of styrene yields stable latexes with particles of ∼500 nm.…”