Experimental and theoretical study of the reaction locus during the dispersion polymerization of methyl methacrylate in a nonpolar hydrocarbon solvent at low temperature

Abstract

The dispersion polymerization of methyl methacrylate (MMA) has been studied in a nonpolar hydrocarbon solvent at low temperature using N,N‐dimethylaniline (DMA) and lauroyl peroxide (LPO) as redox initiation system. To explain the heterogeneous kinetic characteristics of the polymerization process, the reaction locus has been experimentally and theoretically investigated. The evolutions of monomer conversion, polymer molecular weight distribution (MWD), and particle morphology were measured throughout the polymerization. It was found that the significant preferences of LPO and DMA to accumulate in the polymer‐rich phase after the system phase separation are mainly responsible for both the uniformity of particle sizes and the broad polymer MWDs. It was observed that particle agglomeration and breakup mechanisms were enhanced under agitation, thus promoting the formation of broader particle size distributions. The observed kinetics and thermodynamics of the low‐temperature polymerization were also examined through a mathematical model where the distributions of initiators, solvent, and monomer between phases were considered. A good agreement between the experimental and theoretical results was observed and the model was used to estimate the conditions that promote bimodal MWDs. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Investigating the Effectiveness of Reactive Dispersants in Non‐Aqueous Dispersion Polymerization

“…Although the above studies are relevant, the particle sizes are generally larger than those required for coatings applications, with the objective of many of the studies to synthesize micron‐sized particles with a very narrow size distribution for applications such as electrophoretic displays, support of biological materials, and for chromatographic applications . Thus, the research has little concern for optimizing the usage of the dispersant in the system and for robustly producing dispersions with high polymer content and controlled viscosity, of paramount interest for automotive coating applications.…”

Modeling of Phase Inversion and Particle Stability in the Dispersion Polymerization of Methyl Methacrylate in a Non‐polar Hydrocarbon Solvent

“…Dispersion polymerization in either polar or non‐polar solvents has been used to synthesize highly monodisperse polymer particles and the polymerization kinetics has been the subject of active research over the last 40 years 1–12. The use of polar media has received much attention because smaller particles with narrower size distributions can be produced 13–18.…”

“…In a polar medium, however, monomer and initiator tend to accumulate preferentially in the precipitating polymer particles, thus reducing the homogeneous nucleation after the phase separation point and yielding very narrow particles size distributions. Interestingly, choosing appropriate initiators that accumulate preferentially in the precipitating polymer particles, the non‐instantaneous homogeneous nucleation can be also prevented when using non‐polar solvents 12…”

“…Common azo‐ and peroxide‐initiators are used at 50–90 °C 1, 3–11. When low reaction temperatures are desired (e.g., 10–35 °C), gamma‐irradiation,19–21 photoinitiators,22 and redox pairs12 can be used to initiate the dispersion polymerization of MMA. For instance, in our recent study, the dispersion polymerization of MMA in the presence of n ‐hexane has been studied at 30 °C using lauroyl peroxide (LPO) and dimethylaniline (DMA) as redox initiation system 12.…”

“…When low reaction temperatures are desired (e.g., 10–35 °C), gamma‐irradiation,19–21 photoinitiators,22 and redox pairs12 can be used to initiate the dispersion polymerization of MMA. For instance, in our recent study, the dispersion polymerization of MMA in the presence of n ‐hexane has been studied at 30 °C using lauroyl peroxide (LPO) and dimethylaniline (DMA) as redox initiation system 12. It was found that uniform PMMA particles of about 2–3 µm can be produced using relatively high solvent/monomer ratios varying between 0.58 and 1.12 (weight‐based).…”