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首先用聚乙烯亚胺(PEI)对粒径为360 nm的单分散无皂聚苯乙烯(PSt)乳胶粒进行修饰,得到表面荷正电的PSt种子乳液,然后将其滴加到溶有钛酸正丁酯(TBT)的乙醇与水的混合介质中,通过溶胶-凝胶(sol-gel)法制备出了核壳结构PSt/TiO2复合微球,系统研究了体系pH和TBT用量对复合微球结构形态的影响.研究表明,酸性条件不利于核壳结构PSt/TiO2复合微球的形成;当体系pH值为7.2时,可得到包覆完整、TiO2壳层厚度均一的PSt/TiO2复合微球,此后随着体系pH值的升高,包覆厚度逐渐提高;当pH值升高到11.0时,壳层厚度达到最大,但出现了包覆层不完整的复合微球.在固定聚合体系pH为8.5,EtOH/H2O质量比为100/6,表面修饰PSt种子乳液用量为0.5 g(固含量为4%)的条件下,随着TBT用量从0.01 g增加到0.16 g,复合微球壳层厚度从约0 nm逐渐增加到60 nm;当TBT用量增加到0.32 g时,壳层厚度迅速降至12nm,微球表面变得粗糙,并出现大量未包覆微粒;此后随着TBT用量的增加,包覆层厚度逐渐减少,未包覆微球逐渐增多.结果显示,当复合微球中TiO2包覆层达到一定厚度时,经煅烧后才能得到形貌完整的TiO2中空微球.
Polyethyleneimine (PEI) was used to modify the PSt latex particles with a particle size of 360 nm to obtain a PSt seed emulsion with positive surface charge, which was then added dropwise to a solution of titanium (PSt / TiO2) composite microspheres with core-shell structure were prepared by sol-gel method in a mixed medium of ethanol and water with n-butyl acetate (TBT) The results show that the acidic conditions are not conducive to the formation of PSt / TiO2 composite microspheres with core-shell structure. When the pH value of the system is 7.2, the PSt / TiO2 composite coating with uniform thickness of the TiO2 shell can be obtained The thickness of the microspheres increased with the increase of the pH of the system, and the shell thickness reached the maximum when the pH was increased to 11.0, however, the composite microspheres with incomplete coating appeared. With the pH value of 8.5, the mass ratio of EtOH / H2O of 100/6 and the amount of surface-modified PSt seed emulsion of 0.5 g (solid content 4%), the amount of TBT increased from 0.01 g to 0.16 g, The shell thickness increased from about 0 nm to 60 nm gradually. When the amount of TBT increased to 0.32 g, the shell thickness rapidly decreased to 12 nm and the surface of the microsphere became rough , And a large number of uncoated particles appeared.Furthermore, with the increase of TBT content, the thickness of the coating gradually decreased, and the number of uncoated microspheres gradually increased.The results showed that when the TiO2 coating in the composite microspheres reached a certain thickness, Calcined to get the morphology of TiO2 hollow microspheres.