Synthesis and self-organization of PPV-based block copolymers for photonic applications

Rod-coil block copolymers have been synthesized with the objective of enhancing the photovoltaic efficiency by the incorporation of both donor and acceptor components in a molecular architecture that is self-structuring. Block copolymers were obtained by using an end-functionalized rigid-rod block of poly(2,5-dioctyloxy-1,4-phenylenevinylene) (PPV) as a macroinitiator for the nitroxide-mediated controlled radical polymerization of a flexible, styrene-based block. Under suitable conditions the formation of honeycomb structures by PPV-block-polystyrene (PPV-b-PS) is observed. The honeycomb structure consists of a 2-dimensional array of spherical air holes with an inner diameter of 3 - 5 mum in a polymeric film, which results in similar to 6.5 million hexagonally packed holes per square centimeter. The application of these structures as templates for highly ordered functional patterns is demonstrated by evaporating aluminum on this regularly structured surface and subsequently washing away the polymer.