Study for Understanding and Formulation of the Kinetics and Mechanisms of Radical Polymerizations Taking Place inside Dispersed Nano-Size Monomer Droplets

点击翻译按钮获取中文摘要

In radical polymerizations taking place inside dispersed nano-size monomer droplets, the rate of polymerization is well known to be affected by both radical entry into and radical desorption from these droplets irrespective of the site of radical generation (continuous or droplets phases).It was recognized that there is no universal theory that can explain the kinetics and mechanisms of radical polymerization taking place inside these nano-size monomer droplets.In order to clarify the effect of droplet-size on the rate of polymerization, we carried out radical polymerizations with changing the size of monomer droplets by using Microfluidizer and water-insoluble monomers, where the particle growth via Ostwald ripening was negligible.However, it was found that the change in droplet-size via coagulation was inevitable.As an alternative system having dispersed nano-size monomer droplets, we employed a polymerization system having nano-size monomer-swollen polymer particles, which were prep … More ared via onventional emulsion polymerization.This is the so-called "seeded polymerization".In order to generate radicals in the monomer-swollen particles, a representative oil-soluble initiator, 2, 2'-azobis(isobutyronitrile) was used.From the results obtained, it was indicated that(1)most of pair radicals generated inside the particles instantaneously terminated bimolecularly, and hardly contribute to polymerization1 and(2)the ratio of the rate of adical desorption to the rate of radical termination depends on the size of the particles.These experimental results suggest us that quantification of the rates of radical desorption and radical termination taking place inside the nono-size droplets is a key factor to have a universal theory for adical polymerization consisting of dispersed nano-size monomer droplet. Furthermore, we carried out, radical polymerization in much finer nano-size monomer droplets(microemulsion droplets)prepared by adding a larger amount of emulsifier, and could predict the size distribution of resultant polymeric particles by the mechanistic model taking the above-mentioned knowledge into consideration. Less