单分散SiO_2微球的制备及疏水改性研究

采用改进的凝胶-溶胶法制备了200~800 nm的单分散SiO_2微球,并通过真空冷冻干燥法得到不易团聚的单分散SiO_2粉体,采用乙醇超临界方法对制备的SiO_2微球进行疏水改性。通过扫描电镜和氮吸附-脱附分析仪对SiO_2微球的表面形貌、粒径以及孔径分布进行表征;用傅里叶红外变换测试和测量接触角对疏水改性的SiO_2微球进行分析。结果表明SiO_2微球粒径随二次加入TEOS体积增加呈先增大后减小。经过乙醇超临界处理,SiO_2微球表面成功接枝上了疏水烷基,微球尺寸越小,疏水性越好,其接触角高达149°,单次SiO_2微球处理量对结果无明显影响。采用本方法可以单次处理12 g以上的SiO_2微球,接触角均在140°左右,可充分满足实验室使用需求。经过真空冷冻技术和乙醇超临界技术得到疏水单分散SiO_2微球粉体,具有不易团聚及单分散性良好的优点,能够作为胶体晶体原料和三维有序材料(3-DOM)模板剂进行广泛应用。

Preparation and Hydrophobic Modification of Monodisperse SiO2 Nanospheres

Monodispersed SiO 2 nanospheres with diameters of 200-800 nm were prepared by improved St?ber method where the tetraethyl silicate ( TEOS ) , deionized water and ethanol were used as the raw materials.To avoid aggregation , the obtained wet nanospheres were dried by vacuum freeze drying technique afterward .The supercritical ethanol was used to modify the surfaces of the SiO 2 nanospheres as hydrophobic .The morphologies and sizes of the nanosphers were investigated by the scanning electron microscope ( SEM ) . And the size distribution of the pores was investigated by N 2 absorption and desorption measurement .The hydrophobic properties of the particles were characterized by measuring their contact angle to water .Fourier transform infrared spectroscopy ( FTIR ) was used to detect the chemical groups on the surfaces of the particles . The results show that the diameter of the SiO 2 nanospheres initially increase and then decrease as the amount of the second addition of TEOS increase . The FTIR results show that by supercritical ethanol treatment , the surface of SiO 2 nanospheres was grafted with alkyl groups successfully , which make the particles show hydrophobic properties .The smallest treated particles show the best hydrophobic performance , with their contact angle to water as high as 149 °.The amount of the treated particles has no obvious influence on the result .With this method , more than 12 g particles could be treated as hydrophobic ( contact angle to water as high as 140°) in one batch , which meet the laboratory-scale demand quite well .Since the hydrophobic SiO 2 nanospheres prepared by us are easy to be dispersed and had the advantage of monodispersity , they would have a potential application in the field of 3-DOM.