Polymerizations of n-butyl acrylate under stable free radical polymerization (SFRP) conditions, using TEMPO as the nitroxide mediator, are reported at reaction temperatures between 133 and 135 °C. The polymerizations proceed in a living manner under both bulk and miniemulsion conditions with polydispersities of around 1.3. Plots of number-average molecular weight vs conversion and ln([M]0/[M]) vs time are linear, indicating a controlled polymerization. It is argued that the ability of a particular nitroxide to control the polymerization of n-butyl acrylate is not only due to a favorable equilibrium constant (K) between the dormant and active polymeric species in the system but also due to the amount of excess nitroxide that is present. In these experiments excess TEMPO is controlled by the continuous addition of a dilute solution of ascorbic acid or an ascorbic acid derivative, leading to successful n-butyl acrylate polymerizations. Chain extension of a homopoly(n-butyl acrylate) prepared under miniemulsion conditions is demonstrated.

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.

The stable free radical polymerization (SFRP) of styrene, initiated with benzoyl peroxide in the presence of TEMPO, under bulk conditions, is demonstrated to proceed rapidly without the need for any rate enhancing additives such as camphorsulfonic acid, 2‐fluoro‐1‐methyl pyridinium p‐toluenesulfonate, or acetic anhydride. Monomer conversions as high as 70% can be achieved in 5 h or less while maintaining polydispersity indexes of 1.15. These results stand in stark contrast to earlier reactions that required 70 h to achieve similar conversions. This study demonstrates that the single largest factor governing the rates of polymerization is the molar concentration of excess TEMPO remaining in solution after initiation. A reduction in the TEMPO to BPO ratio is required when large amounts of BPO are used to target low molecular weight polystyrenes. However, when a lower molar amount of BPO is used to obtain high molecular weight polystyrenes, a higher TEMPO to BPO ratio is required. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5487–5493, 2007

Polymerizations of styrene under emulsion reversible‐addition fragmentation chain transfer polymerization conditions are reported. Using a recently developed nanoprecipitaiton process, emulsion particles were formed by the precipitation of an acetone solution of a macroRAFT agent into an aqueous solution of poly(vinyl alcohol). The particles were then swollen with monomer and subsequently polymerized. Emulsion polymerizations were performed at 65 and 75 °C in which either KPS, BPO, or a combination of both was used as an initiating source. Reactions were also performed at temperatures over 100 °C in which the thermal initiation of styrene was used as an initiating source. In all cases, the polymerizations proceeded in a living manner, yielding polymers that showed an incremental increase in molecular weight with time and had narrow molecular weight distributions. Plots of number‐ average molecular weight versus conversion were linear, indicating a controlled polymerization. The resulting latices were colloidally stable and gave particle size distributions with a typical average particle diameter in the 150 nm range. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5708–5718, 2006

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