磁性SiO_2/PSt中空复合微球的细乳液法制备及表征

Preparation and Characterization of Magnetic SiO_2/PSt Hollow Composite Microspheres via Miniemulsion Polymerization

采用双原位细乳液聚合工艺,将疏水改性的磁性纳米粒子(MNP)加入到细乳液反应体系的油相中,利用增长的聚合物和单体TEOS之间的相分离原理,实现了聚合物的生成和TEOS的水解缩合同步进行,一步获得了磁性SiO2/PSt中空复合微球.通过红外光谱(FTIR)、透射电镜(TEM)、热重差热分析(TGA/DSC)和振动磁强计(VSM)对中空复合微球进行了表征.结果表明,制备的SiO2/PSt中空复合微球的尺寸范围为300～600 nm,当加入磁性纳米粒子后,得到的磁性SiO2/PSt中空微球保持了原来的中空结构,中空复合微球内腔的大小可以通过改变单体TEOS的加入量来控制.SiO2/PSt中空微球对磁性纳米粒子的包封率达到了86%.磁性SiO2/PSt中空复合微球具有超顺磁性,饱和磁强度值为14.7 emu/g.

In this work,a facile method was presented for the preparation of magnetic SiO 2 /PSt hollow composite microspheres via double in situ miniemulsion polymerization.Our approach was based on the in situ miniemulsion polymerization of organic monomers and in situ formation of silica from precursor（tetraethoxysilane,TEOS） within miniemulsion monomers droplets simultaneously.Firstly,monodisperse hydrophobic magnetic nanoparticles were synthesized by coprecipitation method as the literature reported.Then the as-prepared magnetic nanoparticles（MNP） were added in the mixtures of styrene（St）,divinyl benzene（DVB）,TEOS,and γ-methacryloxypropyl trimethoxy silane（MPS） to be used as the oil phase.Magnetic nanoparticles were restricted in miniemulsion microreactor droplets via the miniemulsification process by sodium dodecyl sulfate（SDS） aqueous solution as a water phase.After the monomers polymerized,TEOS phase is compressed and restricted as a liquid core due to phase separation between TEOS and the growing polystyrene.When the ammonia was added,silica was in situ formed by the hydrolysis-condensation of TEOS under basic conditions.Because the volume of TEOS decreased dramatically,the original TEOS phase shrank into silica and led to the formation of hollow structure.Hollow composite microspheres were characterized by Fourier-transformed infrared spectrum（FT-IR）,transmission electron microscopy（TEM）,thermogravimetry and differential analyses（TGA/DSC） and vibrating sample magnetometer（VSM）,respectively.The results showed that in the absence of magnetic nanoparticles SiO 2 /PSt hollow composite microspheres with particle sizes in range of 300～600 nm were prepared successfully.With the addition of hydrophobic magnetic nanoparticles,the magnetic SiO 2 /PSt composite microspheres were fabricated conveniently with magnetic nanoparticles embedded in the polymeric shell,which remained the same hollow structure as the SiO 2 /PSt hollow composite microspheres.The inner void size of composite microspheres could be easily controlled by using varied TEOS contents in the miniemulsion formulation.The entrapment efficiency of magnetic nanoparticles in SiO 2 /PSt composite microspheres reached up to 86%.The magnetic SiO 2 /PSt hollow composite microspheres were superparamagnetic and their saturation magnetizations were 14.7 emu/g.The magnetic hollow composite microspheres may provide a very promising vehicle for drug delivery,catalysis,and photoelectric materials.