种子乳胶粒表面修饰法制备核壳结构PSt/TiO_2复合微球

PREPARATION OF PSt/TiO_2 CORE-SHELL COMPOSITE MICROSPHERES VIA SURFACE MODIFICATION OF PSt SEED LATEX PARTICLES

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360 nm的单分散聚苯乙烯(PSt)乳液,并利用聚乙烯亚胺(PEI)在25℃下对PSt乳胶粒表面进行修饰,得到了表面带有正电荷的PSt种子乳液;然后以乙醇和水的混合物为反应介质,采用种子乳液加入法,使钛酸正丁酯(TBT)在修饰后的乳胶粒表面进行水解与缩合,制备出了核壳结构PSt/TiO2复合微球,利用电镜对复合微球的结构形态进行了表征.结果表明,PSt乳液改性时体系的zeta电位随着PEI用量的增加而升高,当PEI用量为PSt聚合物重量的15%时,体系的zeta电位从原来的-40.3 mV升高到了38.3 mV,达到对PSt乳胶粒表面改性的最佳值;在制备PSt/TiO2复合微球时,TiO2包覆量随着反应时间的延长而增加,反应7 h时达到90.2%的最大值;随介质中水含量的增加,吸附到复合微球表面上的TiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比为100/6.0时,得到结构均一、壳层厚度为29 nm的核壳结构PSt/TiO2复合微球.

A negatively charged monodisperse PSt seed emulsion was first synthesized via batch emulsifier-free emulsion polymerization,and then polyethyleneimine（PEI） was added to modify the particle surface at 25℃ to prepare the positively charged PSt seed particles.Finally,the core-shell PSt/TiO2 composite microspheres were obtained by adding the diluted modified PSt seed emulsion into the medium of ethanol with certain amount of tetrabutyl titanate（TBT） under neutral condition.Influence of PEI amount on zeta potential of PSt seed emulsion,and influences of reaction time,addition models and EtOH/H2O mass ratio on the morphology of PSt/TiO2 composite microspheres were investigated.Results showed that zeta potential of PSt seed emulsion increased with the increase of PEI amount,and reached its optimum value of 38.3 mV from-40.3 mV when the amount of PEI was increased to 15 wt% of PSt seed weight.In the preparation of core-shell PSt/TiO2 composite microspheres,the encapsulation ratio of TiO2 onto the modified PSt particles increased with the increasing reaction time,and a maximum value of 90.2% achieved when the reaction time prolonged to 7 h.With the decrease of EtOH/H2O,the number of TiO2 nanoparticles absorbed onto the composite microspheres decreased,and the uniform core-shell PSt/TiO2 composite microspheres with the shell thickness of about 29 nm were obtained in the medium with EtOH/H2O mass ratio of 100/6.0.