Size Kinetic Effects during Aerosol Polymerization

Abstract

Size effects during chemical transformations in aerosols can lead to a shift in chemical equilibrium and a significant change in reaction rates. The most sensitive to them are polymerization processes, in which both the reaction rate and the degree of polymerization can depend on the number of monomers in a droplet. For the reversible polycondensation reaction, a kinetic equation is formulated based on the assumption that in a small volume, as conversion increases, the equilibrium molecular weight distribution (Flory distribution normalized to a finite number of monomers) is continuously reproduced. Kinetic curves were plotted to demonstrate the influence of droplet size on monomer conversion, degree of polymerization, and evolution of molecular weight distribution. The kinetics of polycondensation was modeled using the example of lactic acid polycondensation and compared with experimental patterns. The model demonstrates that a decrease in droplet size leads to a significant (power-law dependence on the radius) acceleration of the polymerization process and a decrease in the number-average mass of the polymer.