Multinuclear cobalt–salen complexes with phenylene linker for epoxide polymerizations

Di‐ and trinuclear cobalt (Co)–salen complexes with a benzene ring as a rigid linker were explored for epoxide polymerizations. The dinuclear Co–salen complex with a 1,2‐phenylene linker showed higher catalytic activity than the dinuclear Co–salen complex with a 1,3‐phenylene linker and the trinuclear Co–salen complex with a 1,3,5‐benzenetriyl linker for the copolymerization of propylene oxide (PO) with carbon dioxide. A combination of the absolute configuration of the two Co–salen moieties was found to affect its catalytic activity. The optimized dinuclear Co–salen complex with a heterochiral combination demonstrated highest activity and maintained its catalytic activity under a low catalyst concentration. The heterochiral dinuclear Co–salen complex also showed high activity for the copolymerization of PO with cyclic anhydride. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2150–2159     

Synthesis and light‐emitting properties of carbazole‐based copolymers bearing cyano‐substituted arylenevinylene chromophore

Two arylenevinylene compounds bearing the cyano group at α‐position ( 6 ) and β‐position ( 9 ) from the dialkoxylphenylene unit were synthesized, in which the molecular termini were functionalized with 3‐bromocarbazole. The Suzuki coupling copolymerization of these compounds with 1,4‐bis[(3′‐bromocarbazole‐9′‐yl)methylene]‐2,5‐didecyloxybenzene and 9,9‐dihexylfluorene‐2,7‐bis(boronic acid) was carried out to obtain copolymers ( cp67 and cp97 ) containing the cyano‐substituted arylenevinylene fluorophore of 7 mol %. Model compounds ( 6 ′ and 9 ′) corresponding to the arylenevinylene fluorophore were also prepared. The UV spectra of copolymers resembled that of homopolymer hp with no arylenevinylene segment in both CHCl₃ solution and thin film. The emission maxima of copolymers in CHCl₃ (394 nm) agreed with that of homopolymer indicating that the emission bands originated from the carbazole‐fluorene‐carbazole segment. The emission maximum wavelength of copolymer cp67 in thin film (477 nm) indicated fluorescence from the cyano‐substituted arylenevinylene fluorophore because of the occurrence of fluorescence resonance electron transfer. In contrast, copolymer cp97 showed fluorescence at 528 nm to suggest the formation of a new emissive species such as a charge‐transfer complex (exciplex). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 91–98, 2010     

Synthesis of microspheres stabilized sterically with two-component grafted chains by dispersion copolymerizations using mixture of two macromonomers in nonaqueous media

The polymer microspheres were synthesized by dispersion copolymerization of divinylbenzene (DVB) with two vinylbenzyl-terminated poly(ethylene glycol methylether) (PEG)/poly(t-butyl methacrylate) (PBMA) macromonomer blends in methanol. In these systems of two macromonomer blends as the emulsifier, the polymer microspheres formed had a very narrow particle size distribution. Two macromonomers formed comicelles with DVB monomer and acted not only as the comonomer but also as the stabilizer. Such polymer microspheres were stabilized sterically with two-component grafted chains, such as PEG and PBMA, in methanol.     

An assembled complex of palladium and non-cross-linked amphiphilic polymer: a highly active and recyclable catalyst for the Suzuki-Miyaura reaction

An insoluble and assembled catalyst of palladium and a non-cross-linked amphiphilic polymer were developed. In the presence of 50-500 ppm mol equiv of catalyst, the Suzuki-Miyaura reaction proceeded efficiently under organic solvent-free conditions. The catalyst was reused 10 times without any decrease in activity and was recycled without any special treatment.[structure: see text]     

Memory effect on the glass transition in vulcanized rubber

The memory effect upon glassification is studied in the glass-to-rubber transition of vulcanized rubber with the strain as a controlling parameter. A phenomenological model is proposed, taking the history of the temperature and the strain into account, by which the experimental results are interpreted. The data and the model demonstrate that the glassy state memorizes the time course of strain upon glassification, not as a single parameter but as the history itself. The data also show that the effect of irreversible deformation in the glassy state is beyond the scope of the present model.     

Surface modification without desorption: recycling of Cl on Si(100)-(2 x 1)

We demonstrate chlorine-induced modification of Si(100)-(2 x 1) under conditions where Cl is recycled rather than desorbed as SiCl2. A dimer with 2 Cl atoms, 2SiCl, converts to SiCl2+Si, allowing the bare Si atom to escape onto the terrace. At temperatures below the desorption threshold, the SiCl2 unit decays through Cl diffusion, allowing the second Si atom to escape. The result is a dimer vacancy, terrace regrowth structures, and Cl that is able to participate in another pitting event. Access to this unexpected roughening pathway is controlled by the Cl concentration and temperature. This previously overlooked process represents an important component of Si(100) surface processing.     

Local approximation of the correlation energy functional in the density matrix functional theory

A local approximation formula of the correlation energy functional E(c) in terms of the first-order reduced density matrix (1-RDM) is presented. With the contracted Schr?dinger equation the principal dependence of E(c) on the natural occupation numbers n(i) is identified. Using the effective mass theory, E(c) is expressed as a functional of the local density and the local variable, J = SUM (i)[square root of (n(i)(1-n(i))] /phi(i)/(2), where phi(i) are the natural spin orbitals. This local approximation satisfies the homogeneous coordinate scaling relation, gives the exact result for a one-electron system, and is almost free from the exchange energy error. It reproduced about 90% of the correlation energies of atoms and molecules.