Nucleation disperse-phase mass

Of particular interest is the case of a heterogeneous mixture with small volume content of the disperse phase W 1. In this case we can assume that the disperse phase exerts a weak influence on the continuous phase. Then fields of velocity, pressure, temperature and other parameters of the continuous phase could be determined by using one-velodty model, and then, for given distributions of parameters, one can determine the behavior of disperse phase. If the disperse phase represents a discrete system of inclusions (solid particles, drops, bubbles, macromolecules), it can be characterized by a distribution n V, t, P) of inclusions over volumes V at a point of space P. Inclusions can exchange mass (due to evaporation, condensation, fusion etc.) with the continuous phase, and also interact between themselves, - they can collide, coagulate, coalesce, break, form the inclusions of various size and shape. In addition, a phase can nucleate in conditions of mixture super-saturation and then increase in size due to a phase transition. The... 

As suggested by Barrett (2), it is assumed that following the particle nucleation stage, the polymerization proceeds in the particle (monomer/polymer) phase with no mass transfer limitation. Therefore, the dispersion polymerization is similar to a mass or suspension polymerization, and kj can not be assumed to be constant even at isothermal conditions, since kp and even kp are dependent on the degree of polymerization because of a gel effect. (2., ,D However, since the application of the model is for a finishing step, with polymer molecular weight and viscosity fairly well established, further changes in kp and kp should be minimal. 

Since mass is conserved during transport, the continuous contribution Gp is due to mass transfer from the fiuid to the solid phase. Likewise, the discontinuous term 5m might appear due to nucleation of particles with nonzero mass from the fluid phase. For systems with no mass transfer between the disperse and continuous phases, the right-hand side of Eq. (4.64) will be null. 

Micro-emulsion polymerization In micro-emulsion polymerization, the initial system is microemulsion which consist of monomer droplets (varying from 10 to 100 nm) dispersed in water with the aid of a classical emulsifier (e.g. sodium dodecyl sulfate, SLS) and a "cosurfactant" such a low molar mass alcohol (pentanol or hexanol). Micro-emulsions are thermod3mamically stable and optically one-phase solution. There is an excessive amount of emulsifier in these emulsions. Therefore, they are concentrated systems of micelles and the micelles exist throughout the reaction. One of the most interesting aspects of these micelles is their ability to accommodate monomer molecules. Furthermore, their high total surface area relative to nucleated particles implies the monomer-swollen micelles preferentially capture primary radicals generated in the continuous aqueous phase. Then the probability... 

Miniemulsion polymerization is advantageous for the production of complex colloidal polymer dispersions since, due to droplet nucleation, no mass transfer through the aqueous phase is needed. Therefore, it allows the synthesis of a broad range of materials not obtainable by the means of... 

---