Study On The Mechanism Of Mesoporous Silica With Complex Structure Prepared By Dynamic Self-Assembly

Since mesoporous materials were discovered,due to its high specific surface area,large pore volume,ordered mesoscopic structure and continuously adjustable mesoporous pores and other structural characteristics,which has shown great development potential in the fields of optics,catalysis,adsorption,separation and biomedicine.All of these are inseparable from the mesoscopic structure and morphology of the mesoporous materials.Therefore,this paper will mainly take mesoporous silica as an example,and summarize the theoretical knowledge involved in mesoporous materials,and then carry out research on the preparation of mesoporous silica with complex structure by dynamic self-assembly method.The mesoscopic structure,morphology and formation mechanism of the synthesized mesoporous materials were characterized by use transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,X-ray diffraction（XRD）and nitrogen adsorption and desorption.This paper will be divided into the following three parts:（1）Hollow nano-structures,known as nanocapsules,have been the preferable candidates in the drug-delivery and control-release applications.So as to enhance the adherence and penetration into biological hosts for efficient drug delivery,constructing multiple pods on the hollow structure to form a tribulus-like branched architecture has been proven an effective strategy.However,the synthesis is challengeable due to the simultaneous control of branched podal morphology,hollow architecture and the mesophase structures at the nanometer scale.Here,a region-selective control strategy by rationally constructing local micro-environment was designed to grow branched architecture of ordered mesoporous silica on polymer spheres.Branched multipodal mesoporous silica hollow spheres were obtained after removing these organic templates（the polymer spheres and surfactants）by calcination.The ordered tubular mesopores were along the central axis direction of the hexagonal-prism-like pods,which connected inside and outside of the hollow spheres.Significantly,the number of the branched pods could be easily tuned at the range of one to more by facilely adjusting the amounts of reagent or synthetic temperature to indirectly affect the diffusion of carboxyl groups/protons from the gaps or weak parts of the thin layer,which will open up plentiful room for precise control synthesis of a variety of complex nano-structures with advanced functions（2）The mesoporous silica material can be used as a carrier for drug release and can achieve spontaneous degradation in the body.Among them,mesoporous silica hollow spheres are particularly prominent in this aspect due to their low density,large hollow structure,and high specific surface area.In this paper,a relatively economical and environmentally friendly bubble generated by high-pressure CO₂ gas as a template was used to synthesize the hollow spheres through the synergistic effect of anionic surfactants,silane coupling agents and inorganic precursors to steadily wrap CO₂ that is always in dynamic change.The hollow sphere had a thin spherical shell,relatively concentrated particle size,good dispersity,and uniform amino groups on the surface of the mesochannel.Based on the structure and functional characteristics of the synthesized materials,it was applied to the efficient adsorption of CO₂,the rapid release of drugs and the efficient catalysis of Knoevenagel polycondensation reaction.（3）Due to the excessive burning of fossil fuels,the global greenhouse gas CO₂emissions are rapidly increasing,resulting in many ecological and environmental problems.Therefore,the capture,storage and utilization of CO₂ gas are very urgent.In this regard,this chapter proposes a variety of methods for direct or indirect utilization of CO₂.In the synthesis of materials,CO₂ gas,which exhibits a weak acidity in an aqueous solution,was used for the first time to replace the traditional strong acid as an acidity regulator to adjust the interaction between anionic surfactant and silane coupling agent.Finally,amino-functionalized mesoporous silica nanoparticles with two-dimensional hexagonal ordered mesoporous channels were synthesized by a co-structure-oriented method.The prepared mesoporous material adsorbent not only had the order mesostructure,high specific surface area and large pore volume of the traditional mesoporous materials,but also improved the loading of amino groups on the surface of mesoporous channels in the material.In terms of application,it is first used for CO₂adsorption.The final test results showed that the synthetic adsorbent can not only efficiently adsorb CO₂,but also have good stability.Due to the uniform distribution of amino groups on the surface of its pores,it was also used to catalyze the Knoevenagel polycondensation reaction and also shows a good catalytic effect.