Nanostructured carbon from well-defined polyacrylonitrile (co)polymers obtained by controlled/living radical polymerizations: From synthesis and characterization to devices

This thesis describes a novel, low-cost and controlled route to well-defined nanostructured carbon materials based on the pyrolysis of block copolymer precursors containing polyacrylonitrile (PAN) and a sacrificial block ( e.g., poly(n-butyl acrylate)) with tailored molecular weight and low polydispersity. By this method, the carbon nanostructure is templated after the nanostructure of the PAN domains formed through the self-assembly driven by phase separation between PAN and the sacrificial block. Upon pyrolysis, PAN domains are converted into increasingly partially graphitic carbon, whereas the sacrificial phase is volatilized. The prerequisite for this approach is the ability of the PAN domains to retain their nanostructure upon thermal treatment. The necessary stabilization is achieved by heating up to 300°C under oxidative atmosphere, causing PAN precursor to fore cyclic, ladder and eventually cross-linked species. Well-defined PAN (co)polymers were synthesized using controlled/living radical polymerization (CRP), particularly atom transfer radical polymerization (ATRP). These systems include PAN diblock copolymers, shell crosslinked micelles containing PAN cores, molecular brushes with PAN block copolymer side chains and PAN-grafted silica hybrids. Using these materials as precursors, bulk, thin film, and discrete carbon nanostructures were prepared. In addition, a novel directional casting technique was introduced to prepare long-range ordered PAN block copolymers which were then converted into anisotropic carbon. Many techniques have been used to characterize these block copolymers and resulting carbon materials, including Differential Scanning Calonmetry (DSC, Thermogravimetric Analysis (TGA), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Small Angle X-ray Scattering (SAXS), Grazing Incidence SAXS (GISAXS) and Nitrogen Adsorption. Nanostructured carbons derived through this novel route hold considerable promise in many areas such as: field emitters, supercapacitors and photovoltaic cells. Electrical properties of the nanostructured carbons and their application in field emission arrays are described.