TEMPO-mediated n-butyl acrylate polymerizations

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 degreesC. 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.