树枝状核壳结构聚苯乙烯/介孔氧化硅纳米粒子的可控合成与结构调控

Controlled synthesis and structural regulation of dendritic polystyrene/mesoporous-silica nanoparticles with core-shell structure

以无皂乳液聚合法制备的单分散聚苯乙烯(PS,经二乙烯基苯交联处理)微球为内核,借助油/水两相界面自组装过程在PS内核表面原位包覆树枝状介孔氧化硅(Dendritic mesoporous silica,D-mSiO2),制备具有完整核壳包覆结构的PS/D-mSiO2纳米粒子。红外光谱、X射线衍射、扫描电镜、透射电镜和氮气吸附脱附等分析结果显示:所制备纳米粒子壳层中富含树枝状开放孔道,且基本垂直于内核表面呈车辐放射状;其平均孔径在6.1~8.4 nm,但内部孔道缺乏长程有序性。在本实验条件下,随反应搅拌速率的增大,最终产物的粒径尺寸(或包覆层厚度)呈先增大后减小的变化规律,且过快或过慢的搅拌速率均不利于所得产物包覆结构完整性和孔径均匀性的提高。这可能与剪切力对于界面乳化、自组装以及动态漏斗式梯度生长过程的影响有关。

The monodispersed polystyrene(PS)spheres were obtained via a soap-free emulsion polymerization method using divinylbenzene as a crosslinker.The cross-linked PS cores were uniformly coated with dendritic mesoporous silica(D-mSiO2)shells via a developed St?ber method accompanied by the self-assembly of CTAB micelles with TEOS in terms of an oil-water biphase system,and the PS/DmSiO2nanoparticles with a well-defined core/shell structure were prepared.The obtained hybrids were characterized by Fourier transform infrared spectroscopy,low-angel X-ray diffraction,transmission electron microscopy,field emission scanning electron microscopy and nitrogen adsorption-desorption measurement.The results show that the silica shells are composed of abundant dendritic and three-dimensional mesopores,and the radial meso-channels(6.1?8.4 nm)are perpendicular to the surfaces of PS cores.As confirmed by low-angle XRD,the meso-channles in the silicashells are not in long-range order.For a given PS core,the particle size(or shell thickness)of composites increases firstly and then decreases as the stirring rate increasing.Under the experimental conditions,an appropriate stirring rate contributes to the improvement of the structural integrity and pore size uniformity of the final products.The possible formation mechanism involves the interfacial emulsion to form oil-water hemimicelles,exclusive composite micelles on the solid nuclei,funneling gradient assembly,and growth of the mesochannels.