I. Capek et V. Juranicova, Microemulsion polymerization of butyl acrylate. Effect of radical scavenger and formation of primary radicals, POLYM J, 32(2), 2000, pp. 91-96
Microemulsion polymerizations of butyl acrylate initiated by dibenzoyl pero
xide in the presence of a radical scavenger (RS){stable radicals : an oil s
oluble RS : 4-stearoyloxy-2,2,6,6-tetramethyl piperidine-1-oxyl (STPO) and
water soluble RS : 4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl (HTPO)}w
ere investigated. STPO and HTPO decreased the rate of polymerization and th
e decrease was more pronounced with STPO. Inorganic salts and organic addit
ives decreased the rate of polymerization. The shift of the maximum rate of
polymerization to lower conversion by increasing temperature and addition
of several additives was attributed to increase of particle number and decr
ease of monomer concentration at the reaction loci. The decrease of the pal
-tide size in the presence of RS is attributed to retardation of particle g
rowth. A close packed structure at the droplet surface promoted by current
additives acts as a barrier for entering radicals. The larger overall activ
ation energy in runs with STPO is discussed in terms of a depressed entry o
f radicals into microdroplets.