Preparation Of Hollow And Bowl-shaped Polysilsesquioxane Particles And The Application In Controlled Release

Recently, considerable research has concentrated on micro/nanometer-scale hollow spheres based on organic and inorganic materials. The polymeric hollow microspheres with interior spaces have attracted intense attention due to their broad application in control released, catalysis, sensors, absorber, micro-reactors, biomedicines, and many others.Polysilsesquioxanes (PSQ) is a class of organic-norganic hybrid materials with excellent physical and chemical properties, with applications in coatings, optics, fabrication of fiber materials for photoconductors, and chromatography. Polysilsesquioxanes are among the most promising materials for preparing spheres of narrow size distributions that contain functional groups. Recently, functional polysilsesquioxanes spheres (including mercapto, epoxy, amine, vinyl, or isocyanate) were mostly studied, which prepared by hydrolytic co-condensation of a mixture of organoalkoxysilanes. However, a few studies have examined about polysilsesquioxanes materials with hollow structures and other novel structures.Bowl-shaped sub-micrometer polymer particles represent an interesting platform for many potential applications owing to their specific concave structure, interior cavity, high surface area, etc. The presence of an inner compartment makes such particles interesting as nano-containers, which could be ideal for the entrapment of nano-sized catalysts, nano-particles, or other guest molecules and used as a perfect sub-micrometer chemical reactor. They show special optical properties and effective surface-enhanced Raman scattering due to their bowl-shaped concavity.The work of this paper is based on the above research background. A facile and controllable sol-gel polymerization procedure was developed to precisely fabricate bowl-shaped polysilsesquioxane particles, the formation mechanism was explored, this section is the key of our study. Furthermore, we prepared polysilsesquioxane/avermectin drug-loaded microspheres, and the controlled release of drug-loaded microspheres was studied.The main work and results as follow:(1) Based on sol-gel technology, we prepared hollow polysilsesquioxane microspheres through oil in water suspension polymerization using trifunctional silane monomer as precursors and organic solvent (toluene) as soft templates. Based on this method, a controllable sol-gel polymerization procedure was developed to precisely prepare bowl-shaped polysilsesquioxane particles. The morphology of particles can be fine-tuned by judiciously adjusting the amount of the two precursors, methyltriethoxylsilane (MTES) and phenyltriethoxysilane (PTES). We discussed the effect of the different experimental conditions (monomer ratio, the ratio of the monomer and solvent, catalytic reaction time and stirring speed) on the bowl-shaped particle. The morphology of the particles were characterized by the TEM and SEM, the result show that the different condition can affect the final morphology of the bowl-shaped, the addition of the phenyltriethoxysilane (PTES) help to form the bowl-shaped particle.(2) We explored the formation mechanism of bowl-shaped polysilsesquioxane particles with a kippah structure. The flexibility of the shell and osmotic pressure in combination with centrifugal force should be the key factors to the formation of a bowl-shaped structure.(3) we prepared polysilsesquioxane/avermectin drug-loaded microspheres by suspension polymerization based on sol-gel technology, and the controlled release of drug-loaded microspheres was studied, the effect of drug-loading amount, released medium and temperature on the release behavior of polysilsesquioxane/avermectin composite drug delivery system was investigate. Moreover, models of mass transfer based on Ritger Peppas law were employed to analyze the results of the in vitro drug release experiments.