Preparation And Structure Evolution Research Of Silica Nanoparticle Based Necklace-Like And Porous Nanofibers

Nanosilica has been widely applicated in photovoltaic energy, biomedical and filtration barrier field because it has many advantages, such as specific surface area, strong adsorptive force, high chemical stability and good biological compatibility. However, due to a large number of polar hydroxyl groups in the surface and poor interfacial binding force with polymer matrix, how to modified nanosilica by chemical method has become a research hotspot. This research aimed to fabricate silica nanofibers with different morphologies via chemical modified nanosilica and electrospinning.First of all, SiO2 nanospheres with different particle size was prepared with ethyl silicate (TEOS), ammonia and ethanol by Stober method, then the SiO2 nanospheres would be subsequently amination and bromide step by step. In the last step, the PMMA polymer shells with different molecular weights were grafted onto SiO2 nanosphere cores by Atom Transfer Radical Polymerization (ATRP) method. By characterization of FTIR, SEM, TEM, TGA and GPC, SiO2-PMMA with obvious core-shell structure have been demonstrated and prepared successfully. Based on the theory of electrospinning, SiO2-PMMA nanofibers could be prepared feasibly without polymer matrix. And the effects of electrospinning solution concentration, PMMA shell molecular weight and SiO2 nanosphere core size on the structure and morphology of obtained nanofibers were systematically investigated in details. The experimental results proved that the nanofiber with bigger SiO2 particle size, smaller concentration in the solution and smaller molecular weight of PMMA, tend to form necklace-like nanofiber. When all the ingredients are well tailored, SiO2-PMMA nanospheres stacked one-by-one in a line and formed perfect 1D necklace-like structures.SiO2-NH2 was prepared based on Stober method and amino modified. Then selecting PMMA as pore forming agent and polyacrylonitrile (PAN), porous silica nanofibers with different conditions have been prepared by sol-gel method, combined with electrospinning and high temperature sintering, and they were characterised by SEM, TEM, XRD, BET nitrogen adsorption desorption testing. The results showed that silica nanofibers with porous structure have been successfully prepared. The factors influenced the morphology of porous silica nanofibers were investigated in details. It can be proved that the silica particle size size and content affected the morphologies of nanofiber, besides, the proportion of PMMA higher, the porosity and pore diameter in porous nanofiber would be more obvious. Then porous silica nanofibers were successfully loaded drug metoprolol tartrate, and were placed in the simulated intestinal fluid and simulated gastric environment. The results showed that porous silica nanofibers could be successful drug loaded and achieved sustained release effect, which could be potential in adsorption field.