The Study Of Controlling Electrospinning Of PPV And PPV-N Bulk-Heterojunction Nanofibers And Their Properties

One-dimensional (1D) semiconductor nanomaterials, which represent a unique system for exploring phenomena at the nanometer scale, are opening up substantial opportunities for novel photonic and electronic nanodevices. A large number of synthetic and fabrication methods have already been demonstrated for generating 1D nanostructures in the form of fibers, wires, rods, belts, tubes, spirals, and rings from various materials. Among these methods, electrospinning (a drawing process based on electrostatic interactions) seems to provide the simplest approach to nanofibers with both solid and hollow interiors that are exceptionally long in length, uniform in diameter, and diversified in composition. The high surface area-to-volume ratio of the electrospun fibers makes them suitable for many applications such as filtration, sensing, catalysis, tissue engineering, and protective clothing. Currently, more than 50 different polymers have been electrospun into ultrafine fibers in solvent solution or in melt form. Many conjugated polymers are difficult to be directly electrospun as limited by their molecular weights and/or solubilities.Among the conjugated polymers, poly(p-phenylene vinylene) (PPV) is particularly attractive in that the polymer exhibits excellent photo- and electroluminescence, photovoltaic, photoconductive, and nonlinear optical properties. Additionally, the performance of photovoltaic devices based on PPV can be enhanced by incorporating of inorganic nanoparticles. Therefore, PPV could be one of the most interesting organic materials in nanoscience and technology if it is possible to fabricate PPV into well-aligned and highly ordered architectures. PPV can be fabricated into nanofibers by electrospinning its polyelectrolyte precursor solution and subsequently with thermal conversion. However, the electrospinning precursor jets undergo intense instability due to its polyelectrolyte nature. In this work, we describe the controlling electrospinning of PPV nanofibers, witch including the controllment of the morphology and compositon of PPV nanofibers. In addition, we prepared PPV/Fe3O4 and PPV/CdSe nanofibers, and assembled them into devices. The properties of these fibers and devices were investigated. The deep investigation and the preparation of individual fiber devices based on other components (such as PPV/TiO2) are under way.Detailed content:(1) The precursory PPV solutions in ethanol with different concentration were synthesized from alpha, alpha's-dichloro-p-xylene and tetrahydrothiophene. Moreover, in order to establish basic for preparing composite nanofibers, the physical parameters (concentration, conductivity, surface tension, etc.) affecting the morphology of ultrafine fibers was explored. As a result, the relational information about the effect of solutions'physical properties on the morphology of nanofibers was opened out.(2) By tuning precursor solution properties (viscosity, conductivity and surface tension) and processing variables (voltage, distance between the tip and collector, the kind of collector), we obtained uniform PPV fibers with various morphologies, such as yarns, helix and linear. In addition, by modifying the electrospinning process, we obtained the PPV fiber arrays and core-shell fibers. The individual electrospinning nanofibers were obtained, and were assembled into devices directly.(3) The fiber samples were characterized by using modern analysis and testing means (SEM, TEM, PL, etc.). In addition, the tropism mechanism and affecting factors of the morphology and properties of the fibers were researched completely. Simultaneously, the basic science problems obout the design and preparation of polymer nanofibers, as well as theluminescence and photoelectricity conversion in practical applications were opened out.(4) We prepared PPV/Fe3O4 and PPV/CdSe nanofibers, and assembled them into devices. The properties of these fibers and devices were investigated. Our results indicated that PPV-based nanofibers can be directly assembled into photoconductor devices using the simple and low-cost method.