草莓型PMMA/SiO_2有机-无机复合微球的合成与表征

在纳米二氧化硅水分散介质中,借助于正离子单体甲基丙烯酰氧乙基三甲基氯化铵(MTC)与未改性纳米二氧化硅颗粒之间的电荷作用,通过MTC与甲基丙烯酸甲酯(MMA)的自由基共聚合,制备了草莓型的PMMA/SiO2复合微球.整个制备反应过程中,纳米二氧化硅无需表面处理,体系中无需另外加入乳化剂或助乳化剂,微球表面吸附的纳米二氧化硅对颗粒起稳定作用.详细讨论了纳米二氧化硅初始添加量、MTC浓度对复合微球的平均粒径、复合微球中二氧化硅含量及微球形态的影响.动态光散射粒度分布仪(DLS)测得复合微球粒径在180~300 nm之间,热重分析(TGA)表明复合微球中二氧化硅含量介于16.4%~40.8%之间.透射电镜(TEM)显示所得复合微球具有草莓型结构,二氧化硅于表面富集.

SYNTHESIS AND CHARACTERIZATION OF RASPBERRY-LIKE PMMA/SiO2 ORGANIC-INORAGNIC COMPOSITE PARTICLES

Waterborne raspberry-like PMMA/SiO_2 composite microspheres were synthesized by a soapless one-step method in the presence of aqueous silica sols and cationic monomer(2-(methacryloy)ethyltrimethylammonium) chloride(MTC).MTC was copolymerized with MMA via radical polymerization and then nanosilica particles were deposited onto the surfaces PMMA particles in the aqueous medium through electrostatic interaction between negatively charged nanosilica particles and positively charged MTC.The whole process neither required surface treatment for nanosilica particles nor additional surfactant or stabilizer.TEM indicated that electrostatic interaction between silica and MTC was strong enough for the formation of long-stable nanocomposite microspheres with raspberry-like morphology.The average particle sizes of the obtained composite microspheres ranged from 180～300?nm,depending on the precise formulation.Thermogravimetric analysis indicated silica content in the nanocomposite microspheres ranged from 16.4%～40.8%.Some influencing parameters such as initial silica amount and MTC amount on the diameter,silica contents and morphologies of the composite microspheres were investigated in detail.A possible formation mechanism of the raspberry-like composite microspheres was proposed.