分散共聚法制备特殊形态高分子微球的研究

以聚乙二醇 (PEG)大分子单体为反应性稳定剂 ,在丙烯腈的分散共聚反应中添加少量苯乙烯以形成疏水性核 ,制备得到了亚微米级高分子微球 .透射电子显微镜研究表明 ,该高分子微球具有特异的形态结构 .同时研究了分散共聚体系中各种反应因素对微球形态和直径的影响 ,结果表明 ,苯乙烯单体的添加量、PEG大分子单体的浓度及分子量、混合溶剂的组成对微球直径和形态均有明显的影响 .X 射线光电子能谱 (XPS)研究结果表明 ,微球表面聚集有亲水性PEG链 ,核为疏水的聚 (丙烯腈 苯乙烯 ) ,即形成的特异形态的PEG接枝高分子微球亦为复合型结构

PREPARATION OF POLYMER PARTICLE WITH UNUSUAL FORM BY DISPERSION COPOLYMERIZATION

PEG macromonomer with one methacryloyl end group for per polymer chain was selected as reaction stabilizer.PEG grafted poly(acrylonitrile/styrene) particles with sub micron to nano sizes were prepared by dispersion copolymerization of acrylonitrile with styrene using 2,2′ azobisisobutyrnitrile (AIBN) as a free radical initiator in the presence of PEG macromonomer in ethanol/water (Vol/Vol=7/3) mixed solvents at 60℃ for 24 h.The nanoparticles having narrow size distribution were observed based on the studies of transmission electron microscopy (TEM) and laser light scattering (LLS).The surfaces of the nanoparticles have unusual structures which can be control by changing molecular weight of PEG macromonomer and other reaction conditions.The dynamic diameter of the nanoparticles can be controlled in range from 110 to 920?nm by changing reaction factors such as solvent composition,concentration of PEG macromonomer or styrene.X ray photoelectron spectroscopy analysis shows PEG segments were covered into the surfaces of the nanoparticles.The structure of the freeze dried nanoparticles was investigated by XRD.XRD pattern of any particles showed a distinct diffraction peak at 2 θ =22 6° corresponding to a spacing of 0 39?nm and some small peaks in the 2 θ range of 5～30°,indicating that the particles are crystallized.