Emulsion Polymerization of Styrene Using a Reactive Surfactant and Its Polymeric Counterpart:  Kinetic Studies

Abstract

Emulsion polymerizations of styrene using the reactive surfactant sodium dodecyl allyl sulfosuccinate (TREM LF-40) and its polymeric counterpart, poly(TREM), were studied. The critical micelle concentrations (cmc) and the adsorption behaviors on polystyrene latex particles were determined. The polymerization kinetics obtained via reaction calorimetry showed that the emulsion polymerization of styrene using the reactive surfactant behaved similarly to those reported for the conventional surfactant sodium lauryl sulfate (SLS) in that the rate of polymerization (Rp) profiles showed the same three distinct regions: a rapid rise in rate, attributed to micellar nucleation (interval I); a moderate rise in rate to a maximum where droplets disappear, attributed to homogeneous nucleation (stage 2); and the decreasing rate period (interval III). However, with varying TREM LF-40 concentration (constant initiator concentration), Rp was not found to be proportional to the first power of Np as reported for the SLS system, but 0.7 instead (i.e., Rp ∝ Np0.67). In contrast, by varying the initiator concentration, the kinetics were found to have the same dependencies as the conventional surfactant (Rp ∝ Np1.0 ∝ [I]0.4). These differences are attributed to the participation of the surfactant in the reaction. The kinetics using poly(TREM) differed from those of the reactive counterpart in several ways. The Rp profiles indicated a longer homogeneous nucleation stage 2 in comparison to interval I. Larger (fewer) particles were produced for equivalent weights of the surfactants. This was expected. Although Rp was found to be proportional to the first power of Np, the dependencies on the surfactant and initiator concentrations varied depending on concentration of the component held constant (Rp ∝ Np1.0 ∝ [E]0.2-0.5 and Rp ∝ Np1.0 ∝ [I]0.4-0.8). The lower dependencies on the surfactant concentration and higher dependencies on the initiator concentration are attributed to the ionic strength and the longer nucleation period.