A Route to Stable Nanostructures in Conjugated Polymers

Copper nanoparticles with an average diameter of 32 nm were used as a template to nanostructure a conjugated polymer based on a soluble polythiophene. Mixtures of the polymer and the copper nanoparticles were processed into thin films and subjected to a thermal treatment whereby the solubilizing side chains of the polymer are eliminated, leaving an insoluble high-Tg conjugated polythiophene film with included copper nanoparticles. The copper nanoparticles were then removed using a copper-specific solubilizing agent, leaving voids in the polythiophene film that could be filled with small spherical molecules such as soluble fullerene derivatives, specifically 1-(3-(methoxycarbonyl)propyl)-1-phenyl[6,6]C61 (trivially named phenyl-C61-butyric acid methyl ester = PCBM). X-ray scattering techniques (grazing incidence wide-angle X-ray scattering (GIWAXS), grazing incidence small-angle X-ray scattering (GISAXS), reflectometry) and electron microscopy (SEM, TEM) were used for the characterization of the morphology and crystalline structure. A porosity of <20% could be achieved. In terms of application, the technique was applied to create nanostructures in a conjugated polymer based on the copper nanoparticle template. Bulk heterojunctions of the nanostructured polymer were studied. Copper nanoparticles with an average diameter of 32 nm were used as a template to nanostructure a conjugated polymer based on a soluble polythiophene. Mixtures of the polymer and the copper nanoparticles were processed into thin films and subjected to a thermal treatment whereby the solubilizing side chains of the polymer are eliminated, leaving an insoluble high-Tg conjugated polythiophene film with included copper nanoparticles. The copper nanoparticles were then removed using a copper-specific solubilizing agent, leaving voids in the polythiophene film that could be filled with small spherical molecules such as soluble fullerene derivatives, specifically 1-(3-(methoxycarbonyl)propyl)-1-phenyl[6,6]C61 (trivially named phenyl-C61-butyric acid methyl ester = PCBM). X-ray scattering techniques (grazing incidence wide-angle X-ray scattering (GIWAXS), grazing incidence small-angle X-ray scattering (GISAXS), reflectometry) and electron microscopy (SEM, TEM) were used for the characterization of the morphology and crystalline structure. A porosity of <20% could be achieved. In terms of application, the technique was applied to create nanostructures in a conjugated polymer based on the copper nanoparticle template. Bulk heterojunctions of the nanostructured polymer were studied.