【作者】 刘晓云；

【导师】 查刘生；

【作者基本信息】 东华大学 ， 材料加工工程， 2006， 硕士

【摘要】 本文采用种子乳液聚合法制备内核为二氧化硅、壳层为具有交联结构的聚甲基丙烯酸叔丁酯的核壳复合微粒,目的是想通过水解,使聚甲基丙烯酸叔丁酯转变为聚甲基丙烯酸,最后得到壳层为交联聚甲基丙烯酸的无机/有机核壳复合微粒。该微粒壳层具有pH敏感性,能响应环境pH值的变化发生溶胀或收缩,相应地其亲疏水性也会发生变化,因此该微粒作为催化剂或酶的载体能起到根据环境pH值控制它们的活性的作用。 首先采用两种不同工艺的溶胶—凝胶法合成了SiO₂胶体粒子。在一次加料的溶胶—凝胶法中,通过改变反应体系中水的浓度,合成了三种粒径大小不同的SiO₂胶体粒子。用TEM和SEM观察到SiO₂胶体粒子的形状为球形,随着粒径增大,粒子球形形状越来越规整,单分散性也越来越好。在多次间隙加料的溶胶-凝胶法中,维持二氧化硅种子的数目不变,通过改变加料次数合成了粒径大小不同的、单分散性良好的SiO₂胶体粒子,在4h内可使SiO₂胶体粒子粒径从120nm增长到550nm,粒子增长速度明显快于一次加料法。 用甲基丙烯酸-3-（三甲氧基硅基）丙酯（MPS）对SiO₂胶体粒子表面进行修饰,使其表面接枝能参与自由基聚合反应的碳碳双键基更多还原

【Abstract】 The aim to synthesize the composite microparticles based on silica as core and crosslinked poly(tert-butylmethacrylate) as shell in this work, is to prepare the inorganic/organic core/shell composite microparticles whose shells are composed of crosslinked poly(methacrylic acid) by transforming poly(tert-butylmethacrylate) into poly(methacrylic acid) by hydrolysis. Since the crosslinked poly(methacrylic acid) shells are pH-sensitive and can swell or shrink in response to the environmental pH change, the microrparticles are expected to used as carriers for catalysts or enzymes, which activity can be controlled by environmental pH value.Silica colloid particles were firstly synthesized by two different sol-gel processes. By means of batch sol-gel process, three kinds of silica colloid particles with different particle sizes were prepared by changing the water amount in the reaction feed. The spherical shape of the silicacolloid partices was observed by TEM or SEM, and as their particle sizes increased, their shape became more and more spherical and their monodispersity was improved. In the semi-batch sol-gel process, monodisperse silica colloid particles of different particle size were prepared by changing the feed times under maintaining constant number of silica seeds. The silica particle size increased from 120 nm to 550 nm within 4 hours in the semi-batch prcess, and the particle growth rate was much higher than that in the batch process.Then the silica colloid particles were modified by 3-(trimethoxysilyl)propyl methacrylate (MPS) to graft C=C groups on their surfaces. The MPS-modified silica colloid particles were characterized by elemental analysis, contact angle, FTIR, 29Si NMR and 13C NMR spectroscopy;and the results showed that the C=C groups were successfully grafted on the surface of the silica colloid particles. The mechanism of grafting of MPS on the surface of the silica particles may be as follows: MPS was firstly hydrolyzed, and the hydrolysis substance was polymerized by condensation reaction to form the oligomers;these oligomers were adsorbed on the surface of silica particles by hydrogen bonding, and then the linkage between the oligomers and the particles occurred by the condensation reaction between the hydroxyl of the oligomers and the hydroxyl on the surface of the silica particles.Silica/crosslinked poly(tert-butylmethacrylate) core/shell composite microparticles were prepared via seed emulsion polymerization method using the MPS-modified silica colloid particles as seeds, SDS as emulsifier, tert-butylmethacrylate as monomer and ethyleneglycol dimethacrylate as crosslinker. It was evidenced by the investigation of the effect of the factors on the morphological structure of the composite microparticles that, the formation of pure poly(tert-butylmethacrylate) colloid particles in the process of see-emulsion polymerization could be avoided by controlling the solid content of the silica seed emulsion;pure poly(tert-butylmethacrylate) colloid particles were tended to be formed under large amount of SDS used, while the core/shell composite microparticles were readily flocculated under small amount of SDS used;their shell thickness was enhanced as the amount of the monomer and crosslinker used was increased, but the excessive amount of the monomer and crosslinker used was helpful to the formation of pure poly(tert-butylmethacrylate) colloid particles and the flocculation of the formed core/shell composite microparticles. The morphological structure of the core/shell composite microparticles was confirmed by TEM. The fact that the silica cores of the composite microparticles were enwrapped by polymer was confirmed by contact angle measurements, and the microparticles were identified to be composed of silica and poly(tert-butylmethacrylate) by NMR and FTIR.更多还原