Fabrication Of Honeycomb Porous Polymeric Materials By Self-assembly During Electrospinning

Self-assembly is a process by which components spontaneously form ordered structures. Self-assembly can occur for both the microscopic and macroscopic objects from molecules, particles, to milimeter scale,if only appropriate conditions meet. Nanoscience and nanotechnology have attracted worldwide interest with the potential to make a global technological and industrial revolution. Amongst different nano fabrication techniques, electrospinning is a very simple and versatile method for the fabrication of continuous nanofibers. Through plenty of experiments, we find that the electrospun products in liquid state can self-assemble into honeycomb structure. In this dissertation, we investigated the factors influencing the self-assembled of the honeycomb porous structures, including concentration, applied voltage, ambient humidity, molecular weight, polarity of molecules.Similar to the previous reports, the electrospun products evolve from spherical or spindal-like particles to nanofibers with the increasing concentration of the PEO solution. For PEO with molecular weight of 100000, the diameter of the electrospun products changed from 200 to 500 nm with increasing PEO solution concentration from 8% (w/v) to 20% (w/v). These particles aggregated into walls and formed honeycomb structures with size ranging from 15 to100μm. In contrast PEO with molecular weight of 500000, the diameter of the electrospinning particles changes from 400 to 500 nm with increasing PEO solution concentration from 6% (w/v) to 12% (w/v). These particles self-assemble into the porous honeycomb strucures of size ranging from 40 to100μm. For PEO with molecular weight of 100000, the diameter of the electrospinning products are changing from 200-500 nm with increasing PEO solution concentration from 8% (w/v) to 20% (w/v). These particles aggregated into wall structures and formed honeycomb structures of size ranging from 15 to100μm. The effect of ambient humidity is investigated as well. It is found that ambient humidity has also some effects on the self-assembly of the honeycomb porous structures. Appropriate control of the humidity is necessary for the self-assembly of the honeycomb structures. The effect of substrate nature was also investigated. Formation of the honeycomb structure on glass substrate is earlier than that on aluminum substrate. The difference in the morphology of the honeycomb structures grown on aluminum and glass substrates seems to be due to the difference in electrical conductivities.