Mass Transfer in Miniemulsion Polymerisation

Monomer Equilibrium and Transport in Emulsion and Miniemulsion Polymerization

The dual concepts of monomer equilibrium and monomer transport in emulsion and miniemulsion polymerization are discussed in depth. The concepts must be considered together since, first, dispersed-phase polymerizations (in this case emulsion and miniemulsion polymerizations) are by their nature multiphase systems that function only due to interphase mass transfer; and second, because phase equilibrium determines the driving force for monomer transport in these (and all heterophase reaction) systems. Concepts of polymer particle swelling are reviewed, and the question first addressed by Paul Flory in the 1950s: Are emulsion polymerizations transport or reaction limited? is revisited in detail.

Designed incorporation of semi-crystalline domains into structured latex particles via solvent-aided emulsion polymerization

We describe an emulsion polymerization route towards the design of structured latex particles containing semi-crystalline domains with improved mechanical properties.

Kinetic Analysis of Ultrasound-Induced Oil Exchange in Oil-in-Water Emulsions through Contrast Variation Time-Resolved Small-Angle Neutron Scattering

Ultrasound is one of the most commonly used methods for synthesizing and processing emulsion systems. In this study, the kinetics of acoustically induced emulsion oil exchange was examined using contrast variation time-resolved small-angle neutron scattering (CV-SANS). A custom-built sample environment was used to deliver acoustic forces while simultaneously performing CV-SANS experiments. It was observed that the oil exchange rate was significantly accelerated when sonicating at high acoustic pressures, where violent cavitation events can induce droplet coalescence and breakup. No significant oil exchange occurred at acoustic pressures below the cavitation threshold within the short time scales of the experiments. It was also observed that the oil exchange kinetics was deterred when emulsions were stabilized by surfactants. In addition, oil exchange rates varied nonlinearly with the concentration of surfactant, and exchange was slowest when the emulsions were stabilized by an intermediate concentration. It is hypothesized that emulsion size, electrostatic repulsion, and Gibbs elasticity of the oil-water interface play significant roles in the observed trends. The observed trends in oil exchange rates versus surfactant concentration coincide well with theoretical models for the fluctuation of the elasticity of the interface. Acoustically induced oil exchange was most inefficient when the interfacial elasticity was at its maximum value.