种子表面改性法制备核壳结构PSt/SiO_2复合微球

PSt/SiO_2 CORE-SHELL COMPOSITE MICROSPHERES PREPARED BY PSt SEED SURFACE MODIFICATION

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360nm的单分散聚苯乙烯(PSt)种子乳液,并以EtOH/H2O混合物为分散介质,利用γ-氨丙基三乙氧基硅烷(KH-550)在25℃下对PSt微球表面进行改性,得到了表面硅烷化并带有正电荷的改性PSt种子乳液,然后在碱性条件下加入原硅酸乙酯(TEOS)使其和微球进行共水解与共缩聚,制备出了核壳结构PSt/SiO2复合微球,并利用电镜对复合微球的结构形态进行了表征.研究表明,PSt种子乳液改性时体系的zeta电位随着KH-550用量的增加而升高,当KH-550用量为PSt种子重量的1/3时,体系的zeta电位从原来的-34.5mV升高到了38mV,达到对PSt微球表面改性的最佳值;在制备PSt/SiO2复合微球时,TEOS水解缩聚形成的SiO2包覆到改性微球上的量随着反应时间的延长而增加,反应24h时达到97.9%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SiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比降低到60/28.5时,得到结构均一、壳层厚度为35nm的核壳结构PSt/SiO2复合微球。

A negatively charged PSt seed latex was first synthesized via batch emulsifier-free emulsion polymerization,and the PSt particles were then dispersed into the medium of ethanol and water,and γaminopropyltriethoxysilane（KH-550） was added to modify the particle surface at 25℃ to prepare the positively charged and silylated PSt particles.Finally,the core-shell PSt/SiO2 composite microspheres were obtained by dropwise adding tetraethoxysilane（TEOS） into the above system under alkaline condition.Influences of KH-550 amount on zeta potential of PSt seed latex,and influences of reaction time and EtOH/H2O ratio on the morphology of PSt/SiO2 composite microspheres were investigated.Results showed that zeta potential of PSt seed latex increased with increasing the KH-550 amount,and reached its optimum value of 38 mV from-34.5 mV when the amount of KH-550 was increased to 1/3 of PSt seed weight.In the preparation of core-shell PSt/SiO2composite microspheres,the encapsulation ratio of SiO2 onto the modified PSt particles increased with the increasing reaction time,and maximum value of 97.9% achieved when the reaction time prolonged to 24 h;With the decrease of EtOH/H2O,the number of SiO2 nanoparticles absorbed onto the composite microspheres decreased,and the uniform core-shell PSt/SiO2 composite microspheres with the shell thickness about 35 nm were obtained in the medium with EtOH /H2O weight ratio of 60/28.5.