聚合物模板微球表面电性对中空二氧化硅微球形貌的影响

分别以过硫酸钾和偶氮二异丁基脒盐酸盐为引发剂,以聚乙烯吡咯烷酮(PVP)为分散剂,在水中引发苯乙烯聚合制备了2种表面分别带负电性和正电性基团的聚苯乙烯(PS)模板微球.在氨水催化下,利用正硅酸乙酯的水解缩合,形成PS/SiO_2复合微球,去除模板后得到中空SiO_2微球,并对其进行FTIR、电子显微镜、TGA以及氮气吸附等分析表征.结果表明,PS模板微球表面的电性决定了OH-的分布,从而导致PS模板微球表面SiO_2壳层不同的形成机制.当以表面带负电的PS微球为模板时,可得到树莓状的中空SiO_2微球;而以表面带正电的PS微球为模板时,得到是表面光滑的,具有介孔结构的中空SiO_2微球.

Influence of the Surface Electrical Property of Polymer Template Microspheres on the Morphology of Hollow Silica Microspheres

We prepared two kinds of monodispersed polystyrene (PS) microspheres with different surface electrical properties from the polymerization of styrene in water using different initiators.The PS microspheres prepared with potassium persulfate (KPS) as the initiator (PS-a) have negative zeta potential in water,and those prepared with 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) as the initiator (PS-c) have positive zeta potential in water.Next,PS-a and PS-c microspheres were respectively used as the templates to prepare hollow SiO2 microspheres through a sol-gel process of tetraethoxysilane (TEOS) in an ethanol/ammonia medium.Based on the analysis on the products by FTIR,SEM,TEM,TGA,and N2 adsorption-desorption isotherms,it was found that the distribution of OH-in the system depended on the surface electrical property of the PS template microspheres,which would lead to different formation processes of the silica shell on the template microspheres.When the PS-a microspheres were used as the template,the OH-ions were repulsed from the negative surface of the PS-a template microspheres,due to the electrostatic repulsion interaction.Thus,the SiO2 nanoparticles with a size of several tens of nanometers were firstly formed by hydrolysis and condensation of TEOS in the medium,and then adsorbed and packed on the surface of PS-a template microspheres through the polar interaction,resulting in the formation of a raspberry-like silica shell with macropores.After the PS-a template microspheres etched by toluene,the raspberry-like hollow silica microspheres were obtained.However,when PS-c template microspheres were used as the template,the OH-ions were adsorbed on the positive surface of the template microspheres.Then,a smooth and dense silica layer was grown directly from the surface of the template microspheres through the hydrolysis and the condensation of TEOS catalyzed by the adsorbed OH-ions.After calcination at 600 ℃ for 8 h,hollow silica microspheres with a smooth and mesoporous silica shell were produced.This work indicates that the morphology of the hollow silica microspheres can be controlled through the surface electrical property of the template microspheres.This study may lead to more applications of hollow silica microspheres in the area of control-release materials,drug carriers,and absorbents.