New methods in the synthesis of functionalized polyolefins and solar cell donor materials

Functionalized olefin block copolymers are a highly sought after class of materials with enormous potential. We demonstrate three methods of preparing these types of material starting from the alpha-iminocarboxamide Ni(II) catalyst system. First, by functionalizing the benzyl group of the Ni(II) catalyst with a free radical initiator, we prepare end-functionalized polyolefins. Subsequent controlled free radical polymerization is then used to prepare block copolymers of ethylene and styrene, and ethylene and n-butylacrylate. Second, by taking advantage of the quasi-living copolymerization behavior of the alpha-iminocarboxamide Ni(II) catalyst system, pseudo-tetrablock copolymers of ethylene and a functionalized comonomer are prepared. Third, we prepare a bimetallic catalyst system that is capable of polymerizing ethylene and a functionalized comonomer in an inside-out fashion yielding triblock-like copolymers. The mechanical properties of the latter two materials are examined to assess their potential as thermoplastic elastomers.;The need for alternative energy sources has spawned a great deal of interest in solar energy. Plastic solar cells are emerging as a low cost alternative to traditional inorganic photovoltaics. Device performance in plastic solar cells can be highly dependent on the molecular weight of the conjugated polymer donor material in the active layer, yet efficient methods for preparing some classes of conjugated polymers do not exist. Work herein describes the development of a method for the preparation of low band gap copolymers. The method relies upon microwave-assisted Stille coupling using a stoichiometric adjustment procedure. Several high molecular weight copolymers are prepared via this method. These materials have good hole mobilities and HOMO and LUMO energy levels that are near optimal for employment in fullerene-based bulk heterojunction (BHJ) devices. Solar cells prepared from these materials demonstrated high power conversion efficiencies (PCE), with one of the polymers approaching 5.8%. This is among the highest PCE's reported to date for a BHJ device.