Vinyl-type polynorbornenes with pendant PCBM: a novel acceptor for organic solar cells.

Vinyl addition homo- and copolymerization of norbornene monomer (M1) functionalized with a PCBM moiety using a Pd(II) catalyst in combination with a 1-octene chain transfer agent efficiently produces polynorbornenes with side-chain PCBM groups. Characterization by NMR spectroscopy and elemental analysis reveals that the copolymers constitute a well-defined polymer structure with controlled incorporation of M1. Although the homopolymer is insoluble in organic solvents, the copolymers containing 62 mol% (P2) and 50 mol% (P3) of the PCBM moiety are soluble in chlorinated solvents such as o-dichlorobenzene. The bulk-heterojunction organic photovoltaic devices fabricated based on the P3HT:P3 blends show that P3 can adequately function as an electron acceptor, leading to a cell with a power conversion efficiency of 1.5%, which is outstanding among the polymeric rivals.

Novel chlorotitanium complexes containing chiral tridentate schiff base ligands for ring-opening polymerization of lactide.

The selective synthesis of tri- and dichlorotitanium species containing chiral tridentate Schiff base ligands, derived from (1R,2S)-(-)-1-aminoindanol, was achieved by changing the solvent. Single-crystal X-ray analyses reveal that chlorotitanium complexes are monomeric and octahedral with the meridional occupation of the Schiff base. Although the chlorotitanium complexes lack typical initiating groups such as alkoxides or amides, they are effective catalysts for the controlled ring-opening polymerization of L-lactide (L-LA) as shown by the linearity of the molecular weight vs [L-LA]/[Ti] ratio plot as well as very narrow polydispersity index values.

Novel synthetic strategy for developing an isospecific unbridged metallocene system for propylene polymerization.

New unbridged zirconocenes functionalized with a Lewis base, [{1-(E-C(6)H(4))-3,4-Me(2)C(5)H(2)}(2)ZrCl(2)] (E = p-NMe(2) (3); p-OMe (4); p-SMe (5)) were prepared and their propylene polymerization behavior was examined. Under methylaluminoxane (MAO) activation at atmospheric monomer pressure, these complexes afford mixtures of polymers exhibiting multimelting transition temperatures and broad molecular weight distribution, whereas they produce completely atactic polypropylenes under [Ph(3)C][B(C(6)F(5))(4)] activation. Stepwise solvent extraction of the polymer mixtures reveals that the polymers consist of amorphous, moderately isotactic, as well as, highly isotactic portions and the weight ratio of each portion is dependent upon reaction temperature. The generation of rigid rac-like cationic active species in situ by the interaction between basic sites of catalysts and acidic sites of the [Me-MAO](-) counter anion is considered to be the origin of the observed isospecificity. Further investigation of bulk polymerization in liquid propylene shows not only a considerable increase of the isotactic portion of the obtained polypropylenes but also apparent isospecificity of 4 and 5/MAO systems even at high temperature. Variation of the Lewis basic center leads to a dramatic change in stereoselectivity of the catalyst in the decreasing order of 3>4>>5, in spite of their structural similarity.