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

在自由基聚合发生在分散的纳米级单体液滴中，聚合速率受到自由基进入和自由基从这些液滴中解吸的影响，而不管自由基产生的位置（连续相或液滴相）。人们认识到，目前还没有普遍的理论可以解释这些纳米单体液滴内部发生自由基聚合的动力学和机理。为了阐明液滴大小对聚合速度的影响，我们利用微流控器和不溶于水的单体，通过改变单体液滴的大小进行自由基聚合，其中通过奥斯特瓦尔德成熟的颗粒生长可以忽略不计。然而，我们发现液滴大小的改变是不可避免的。作为一种具有分散的纳米单体液滴的替代体系，我们采用了一种具有纳米单体膨胀聚合物颗粒的聚合体系，该聚合体系通过常规的乳液聚合制备了更多的聚合物颗粒。这就是所谓的“种子聚合”。为了在单体膨胀颗粒中生成自由基，采用了具有代表性的油溶性引发剂2,2′-偶氮（异丁腈）。结果表明：(1)粒子内部产生的对自由基大部分是瞬间终止的双分子，对聚合几乎没有贡献；(2)自由基解吸速率与自由基终止速率的比值取决于粒子的大小。这些实验结果表明，自由基解吸速率和自由基终止速率的定量是对由分散的纳米单体液滴组成的自由基聚合有一个普遍理论的关键因素。此外，我们在加入更大量乳化剂制备的更细的纳米单体液滴（微乳液液滴）中进行了自由基聚合，并根据上述知识通过机理模型预测了聚合所得聚合物颗粒的粒径分布。少

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