The effect on the polymerization kinetics of predissolving polystyrene polymers that have various molecular weights and end groups in styrene miniemulsions prepared using hexadecane as costabilizer was studied. It was noted that the rate of polymerization and number of droplets nucleated were affected by the molecular weight of the polymer that was predissolved. This dependence was attributed to a change in the number of droplets formed during homogenization as the molecular weight of the polymer was varied. However, the end group of the predissolved polymer did not have an affect on the kinetics. In all cases, predissolving polymer into a miniemulsion stabilized using hexadecane as costabilizer resulted in a much lower degree of enhancement in the kinetics compared to similar miniemulsion systems using cetyl alcohol as costabilizer. Since droplet sizes in miniemulsions containing hexadecane have been shown to be stable with time, unlike miniemulsions containing cetyl alcohol, these experiments were taken as evidence that the dominant cause for “enhanced droplet nucleation” is the preservation of droplet number prior to the addition of initiator.

The utility of the growth mechanism to influence relative particle growth is investigated in a semi-batch reactor. A dynamic competitive growth model is developed and used to simulate the growth of two monodisperse polystyrene particle populations (bidisperse system) at 50 °C. Validation of the model with on-line density and on-line particle diameter measurements demonstrates that radical absorption into particles is more likely to occur by a collision mechanism than either by a propagation or diffusion mechanism. Experimental and simulation results show that relative narrowing of the bidisperse system increases as the weight fraction polymer inside the particles (W p) decreases. It is concluded that the ability to alter W p in a semi-batch reactor makes this mode of operation attractive for particle size distribution control.

Seeded emulsion polymerizations of styrene were conducted with various ratios of the anionic surfactant sodium lauryl sulfate and the nonionic surfactant Triton X-405 adsorbed on the polystyrene latex particles. The polymerization kinetics were monitored utilizing the Mettler RC1 reaction calorimeter and subsequently analyzed to determine the effects of the adsorbed surfactants on the entry of free radicals into the particles and the desorption of radicals from the particles. All the reactions were run in interval III at 50 °C, and “zero−one” conditions were determined to exist in order to analyze the data by the “slope−intercept” method. Using the RC1, the start of the polymerization could be determined within 4 s. No significant effect of the surfactant ratio (40% surface coverage) was noted on the pseudo-first-order entry rate coefficients within experimental error. Larger experimental errors were noted in the determination of the pseudo-first-order exit coefficients with no discernible effect of the surfactant ratio being observable.

The emulsion polymerization of styrene using the homopolymer of sodium dodecyl allyl sulfosuccinate as a polymeric surfactant (poly(TREM)) was studied in terms of the polymerization kinetics, the nucleation mechanisms, and the properties of the final latexes. It was found that the relationship between the maximum rate of polymerization and the final number of polymer particles was one-to-one under all experimental conditions (Rp ∝ Np 1.0 ). The dependencies of these on the initiator and polymeric surfactant concentrations varied, depending on experimental conditions (Rp ∝ NpThese variations were attributed to the increased ionic strength effects with increasing concentration of poly(TREM), a polyelectrolyte, and its properties as a polymeric surfactant. It was inferred from the polymerization kinetics (Rp vs time) that homogeneous nucleation was dominant using poly(TREM) even with concentrations exceeding its critical micelle concentration. This differs from the monomeric TREM LF-40 surfactant. Characterization of the amount of poly(TREM) bound to the polymer particles was carried out by serum replacement studies and ion exchange/conductometric titration measurements. Evidence is given that more than half of the poly(TREM) was bound to the polymer particles, either by grafting of the poly(TREM) and/or irreversible adsorption. The amount of bound poly(TREM) increased with increasing surfactant concentration and increasing initiator concentration (i.e., decreasing particle diameter). Contact angles of water measured on films formed from the latexes showed that the poly(TREM) does not migrate significantly to the surface of the films, which is consistent with the latex surface characterization results.