【摘要】 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<Rh>和单体 引发剂质量比(mm/mi)之间的关系.加入少量的MMA单体 ,则共聚物粒子的体积明显减少 ,<Rh>从35.4减少到16.0nm.这表明增加粒子表面的亲水性 ,使得分散体系变得稳定.用减压蒸馏的办法可以除去体系中的丙酮 ,蒸馏前后粒子的大小和分布都不变.本方法很方便地得到了高浓度窄分布的无皂分子纳米胶乳.更多还原

【Abstract】 Emulsifier free emulsion polymerization of styrene in acetone water medium has been carried out using microwave irradiation. Below acetone content o f 50％, narrowly distributed nanoparticles stable in water were obtained. The av erage particle hydrodynamic radius <Rh> 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 <Rh> value is increased and is proportional to the monomer c oncentration, 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 <Rh> 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 char ge and ionic strength, both has the stabilizing and coagulating effects in the p olymerization process, we have successfully found a simple formula to describe t he relationship between the particle size <Rh> and mass ratio (mmonomer / miniti ator). 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 th e 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 concentratio n latexes very conveniently by simply distill out the acetone from the latex sol ution.更多还原