Inverse microemulsion copolymerization of butyl acrylate and acrylamide: kinetics, colloidal parameters and some model applications

The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water-soluble initiator, and stabilized by anionic emulsifiers sodium bis-2ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants kdes (cm 2 s−1) and kdes (s−1) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O’Toole (I), Nomura (II) and Gilbert (III) models. The value of kdes (s−1) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for kdes (cm 2 s−1): the Ugelstad/O’Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in kdes with increasing SDS concentration.  2006 Society of Chemical Industry