Precision synthesis of regioregular poly(3‐hexylthiophene) with low dispersity using a zincate complex catalyzed by nickel with the ligand of 1,2‐bis(dicyclohexylphosphino)ethane

Regioregular poly(3‐hexylthiophene) (P3HT) has been a commonly used p‐type semiconducting material for solution processable organic electronics. To establish a living system of “Negishi‐type catalyst‐transfer polycondensation (NCTP)” using zincate complex as a synthetic method for well‐defined P3HT having predictable molecular weight (MW) and low dispersity (?), the ligands of Ni catalyst were optimized. As a result, a ligand of 1,2‐bis(dicyclohexylphosphino)ethane produced P3HTs with highly controlled number average MWs (1650–32,800) and very low ? values (1.03–1.17). The polymerization results were strongly influenced by steric hindrance based on the factors of cone angle and bite angle of Ni catalysts, and/or electron‐donating ability of phosphine ligands. In addition, we succeeded in the two‐stage polymerization of P3HT and the synthesis of P3HT‐b‐poly(3‐octadecylthiophene), the latter of which is the first demonstration by NCTP using zincate complex. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2287–2296     

A geometric view of Krylov subspace methods on singular systems

We give a geometric framework for analysing iterative methods on singular linear systems A x = b and apply them to Krylov subspace methods. The idea is to decompose the method into the ?(A) component and its orthogonal complement ?(A)^?, where ?(A) is the range of A. We apply the framework to GMRES, GMRES(k) and GCR(k), and derive conditions for convergence without breakdown for inconsistent and consistent singular systems. The approach also gives a geometric interpretation and different proofs of the conditions obtained by Brown and Walker for GMRES. We also give examples arising in the finite difference discretization of two‐point boundary value problems of an ordinary differential equation. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,Optical Properties,and Electronic Structures of Tetrakis(pentafluorophenyl)tetrathiaisophlorin Dioxide

The synthesis, structure, optical and redox properties, and electronic structure of tetrakis(pentafluorophenyl)tetrathiaisophlorin dioxide ( 12 ) are reported. Oxidation of tetrakis(pentafluorophenyl)tetrathiaisophlorin ( 11 ) with dimethyldioxirane afforded the oxidized product, which was the tetrathiaisophlorin with two thiophene 1‐oxide moieties ( 12 ). More significant nonplanarity and greater bond length alternation in 12 than those of 11 were observed by X‐ray structural analysis. The absorption spectrum of 12 contains two bands at λ=348 and 276 nm, with a weak tail that extends to λ≈650 nm. Analysis of the magnetic circular dichroism spectrum of 12 , based on Michl's 4N‐perimeter model and molecular orbital calculations, indicate that the broad band at λ=348 nm appears to contain N₂ and P₂ bands, and 12 is classified as a 4nπ system, similar to 11 . The nuclear‐independent chemical shift values and ¹H NMR spectroscopy data indicate that 12 has more antiaromatic character than 11 .     

Oleic acid-enhanced dissolution of cellulose in high-temperature water

This paper reports, for the first time, the enhanced dissolution of cellulose in subcritical water by addition of a fatty acid. Simply adding oleic acid dramatically promoted the dissolution of cellulose. High-pressure in-situ observation showed that cellulose dissolved in high-temperature water at approximately 500 K, which is 70 K lower than without oleic acid. The yield of oligo and monosaccharides with oleic acid at 473 K was seven times higher than without oleic acid.