RAFT polymerisation in water-borne organic dispersions
Two different approaches to achieving controlled reversible addition-fragmentation chain transfer polymerisation in water-borne dispersions have been attempted, both giving reasonable control over molar mass evolution. Molar mass increased linearly with conversion, and the colloidal instability that has sometimes been observed in similar systems (e.g. [de Brouwer, H.; Monteiro, M. J.; Tsavalas, J. G.; Schork, F. J. Macromolecules 2000, 33, 9239]) was avoided. The similarity of results for the two quite different approaches can largely be reconciled utilising the theory of Luo et al. [Luo, Y.; Tsavalas, J.; Schork, F. J. Macromolecules 2001, 34, 5501] The average number of radicals per particle, in terms of both propagating and RAFT intermediate radicals were compared, using two current models in the literature for the ratio of propagating to intermediate species. [Barner-Kowollik, C.; Quinn, J. F.; Morsley, D. R.; Davis, T. P. J. Polym. Sci. Part A: Polym. Chem. 2001, 39, 1353; Monteiro, M. J.; de Brouwer, H. Macromolecules 2001, 34, 349; Kwak, Y.; Goto, A.; Tsujii, Y.; Murata, Y.; Komatsu, K.; Fukuda, T. Macromolecules 2002, 35, 3026] Possible implications for water-borne dispersions under such conditions are that the maximum value of the average number of propagating radicals per particle may be significantly lower than 0.5, depending on the dominant mechanism for radical loss.