高浓度窄分布无皂高分子纳米粒子胶乳的制备

在微波辐照和丙酮存在下，进行了苯乙烯(ST)和甲基丙烯酸甲酯(MMA)的无皂乳液聚合.当丙酮的含量在50％以下时，可以得到稳定的窄分布的纳米粒子胶乳.丙酮的含量由0增加到50％，粒子的平均水化半径由278nm降低到35.4nm.在一定的浓度范围内，固定引发剂过硫酸钾（KPS）的用量，则粒子的平均水化半径与单体的浓度成正比；当单体浓度一定时,随着引发剂浓度的增加，粒子平均水化半径从25nm减少到22nm然后又增大.考虑到引发剂既是粒子表面电荷的来源，又增加了体系的离子强度，在粒子形成过程中，起着稳定和絮凝的双重作用，我们得到了一个简单的公式用以描述粒子的平均水化半径

Preparation of High Content Surfactant-free Narrowly Distributed Macromolecule Nanoparticle Latex

Emulsifier-free emulsion polymerization of styrene in acetone-water medium has been carried out using microwave irradiation. Below acetone content of 50％ , narrowly distributed nanoparticles stable in water were obtained. The average particle hydrodynamic radius is decreased from 278 to 35.4 nm with an increase in acetone content in the range 0-50 ％ .When the initiator amount is kept constant, the value is increased and is proportional to the monomer concentration, in the range from 1.2 to 7.0％ . When the monomer concentration is kept costant and the initiator concentration is decreased (from 0.27 to 0.027 ％ ) the value is decreased from 25 to 22 nm and then increased. On the basis that the initiator, potassium persulfate (KPS), acts as a source of surface charge and ionic strength, both has the stabilizing and coagulating effects in the polymerization process, we have successfully found a simple formula to describe the relationship between the particle size and mass ratio (mmonomer / minitiator). Adding a few amount of methyl methacrylate(MMA) monomer, the size of the copolymer particles remarkably decreases from 35.4 to 16.0 nm. It has been shown that the increased stability of the resulted dispersion is due to the increase of surface hydrophilicity of latex particles. The stability and uniformity of the final latex does not change any more before and after the vacuum distillation of the acetone from the dispersions.Consequently, we can get a high concentration latexes very conveniently by simply distill out the acetone from the latex solution.