Effect of branched alkyl chains attached at sp3 silicon of donor–acceptor copolymers on their morphology and photovoltaic properties

We study the degree of π?π interactions in two copolymers composed of 2‐octylbenzotriazole and dialkyldithienosiloles with linear hexyl (P1) and branched 2‐ethylhexyl groups (P2). Although the branched ethyl group can be positioned above the π‐plane of dithienosilole to bring disadvantage to stack among the polymers, the solid‐state absorption spectra of the polymers reveal that P2 possesses stronger interchain interactions than P1. We also evaluate the photovoltaic properties of each polymer with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

On partial regularity of suitable weak solutions to the Navier–Stokes equations in unbounded domains

Consider the nonstationary Navier–Stokes equations in Ω × (0, T), where Ω is a general unbounded domain with non-compact boundary in R ³. We prove the regularity of suitable weak solutions for large |x|. It should be noted that our result also holds near the boundary. Our result extends the previous ones by Caffarelli–Kohn–Nirenberg in R ³ and Sohr-von Wahl in exterior domains to general domains.     

Stereospecific Synthesis of Enantiopure [6]Helicene Containing a Seven-Membered Ring and [7]Helicene by Acid-Promoted Stepwise Alkyne Annulations of Doubly Axial-Chiral Precursors**

Enantiopure [6]helicene containing an embedded seven-membered ring and carbo[7]helicene (>99 % ee) with opposite helicity were simultaneously and quantitatively (>99 %) synthesized with a perfect stereospecificity through stepwise acid-promoted intramolecular alkyne annulations of doubly axial-chiral cyclization precursors. The helical handedness of the [6]- and [7]helicenes was fully stereocontrolled by the doubly axial chirality of the precursors as a result of complete axial-to-helical chirality transfer. The cyclizations proceeded in a stepwise manner; the first six-membered ring formation was followed by the kinetically controlled seven- or six-membered ring formation with or without helix-inversion of a [4]helicene intermediate generated during the first cyclization step, thus quantitatively producing enantiopure circularly polarized luminescent [6]- and [7]helicenes with opposite helicity.     

Photoinduced electron transfer in thin layers composed of fullerene-cyclic peptide conjugate and pyrene derivative

A bilayer structure was constructed on gold by Langmuir-Blodgett deposition of a fullerene (C 60)-cyclic peptide-poly(ethylene glycol) (PEG) conjugate and thereafter a pyrene derivative from the air/water interface. The cyclic peptide moiety acts as a scaffold to prevent the fullerenes from self-aggregation and accordingly makes the monolayer homogeneous and stable. In addition to this gold/C 60-cyclic peptide-PEG/pyrene bilayer, a pyrene monolayer, a gold/C 60-PEG conjugate/pyrene bilayer (lacking the peptide scaffold), and a gold/pyrene/C 60-cyclic peptide-PEG bilayer (with the opposite order of layers) were also prepared, and their anodic photocurrent generation were studied in an aqueous solution containing a sacrifice electron donor. The most efficient photocurrent generation was observed in the gold/C 60-cyclic peptide-PEG/pyrene bilayer. It is considered that the C 60 unit acts not only as sensitizer but also as an electron acceptor facilitating the electron transfer from the excited pyrene unit to gold, and that the fullerene layer suppresses quenching of the excited pyrene unit by energy transfer to gold. Furthermore, the cyclic peptide scaffold helps the fullerenes disperse without aggregation in the membrane and seems to protect their redox properties or inhibit self-quenching of their excited state. It is thus concluded that a bilayer structure with desired orientation of functional units is important for efficient photoinduced electron transfer and that a cyclic peptide scaffold is useful to locate hydrophobic functional groups properly in a thin layer.     

Effect of benzothiophene on tetralin hydrogenation over supported rhodium catalyst in supercritical carbon dioxide solvent

The hydrogenation behavior of tetralin in the presence and absence of benzothiophene was studied over a charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent. The catalyst activity, as well ascis-decalin selectivity, decreased in the presence of benzothiophene.     

Homochiral laminar europium metal-organic framework with unprecedented giant dielectric anisotropy

Hydrothermal (deuteratothermal) reaction of L-ethyl lactate (Lig-Et) with Eu(ClO(4))(3)6 H(2)O gives colorless block crystals of [Eu(Lig)(2)(X(2)O)(2)][ClO(4)] (1, X=H; 2, X=D) both of which possess a two-dimensional laminar homochiral framework. Single-crystal dielectric measurements reveal that 1 and 2 display a giant dielectric anisotropy approximately exceeding 100 and large isotopic effect with about 54 % enhancement along the a axis. Their ferroelectric features further confirm this respect. Crystal parameters: 1, C(6)H(14)ClO(12)Eu, M(r)=465.58, monoclinic, C(2), a=8.6786(6), b=8.3965(6), c=10.2153(7) A, beta=92.040(1) degrees , V=743.92(9) A(3), Z=2, rho(calcd)=2.079 Mg m(-3), R(1)=0.0508, wR(2)=0.1239, mu=4.448 mm(-1), S=1.043; Flack=0.04(5). 2: C(6)H(10)D(4)ClO(12)Eu, M(r)=469.61, monoclinic, C(2), a=8.689(2), b=8.410(2), c=10.224(3) A, beta=92.057(4) degrees , V=746.7(3) A(3), Z=2, rho(calcd)=2.089 Mg m(-3), R(1)=0.0465, wR(2)=0.1150, mu=4.432 mm(-1), S=1.058; Flack=0.02(5).     

Supramolecular polymerization and polymorphs of oligo(p-phenylene vinylene)-functionalized bis- and monoureas

Bis- and monoureas hybridized with the oligo(p-phenylene vinylene) (OPV) pi-electronic segment and 3,4,5-tridodecyloxyphenyl wedge were synthesized and their supramolecular polymerization in diluted solution, gel formation in concentrated solution, and liquid crystallinity in bulk state were investigated. Bisurea 1a featuring a hexamethylene linker showed the highest supramolecular polymerization ability and formed tapelike nanofibers that can gelate various organic solvents. On the other hand, bisurea 1b featuring a dodecamethylene linker and monourea 2 showed a lower degree of supramolecular polymerization, resulting in gel formations in a smaller variety of solvents. These results clearly reflect a high level of cooperativity between the two urea sites and the two OPV segments of 1a upon hydrogen-bonding and pi-pi stacking interactions, respectively. When the gels of 1a, 1b, and 2 were dried, all the compounds self-organized into multilamellar superstructures. Thermal treatment of these lamellae at high temperatures induces columnar liquid-crystalline mesophases as a result of microsegregation between the rigid OPV parts and the molten aliphatic wedges. These results demonstrate that the present molecular constituent is very useful for fabricating dye-based functional assemblies providing nanoscale pi-electronic fibers, and solvent-incorporated and bulk soft materials.     

Representation theory of $\mathcal{W}$-algebras

We study the representation theory of the -algebra associated with a simple Lie algebra at level k. We show that the “-” reduction functor is exact and sends an irreducible module to zero or an irreducible module at any level k∈ℂ. Moreover, we show that the character of each irreducible highest weight representation of is completely determined by that of the corresponding irreducible highest weight representation of affine Lie algebra of . As a consequence we complete (for the “-” reduction) the proof of the conjecture of E. Frenkel, V. Kac and M. Wakimoto on the existence and the construction of the modular invariant representations of -algebras. Mathematics Subject Classification (1991)  17B68, 81R10     

Vertical and directional insertion of helical peptide into lipid bilayer membrane

A novel helical hexadecapeptide carrying a poly(ethylene glycol) (PEG) chain at the N terminal was synthesized. The N and C terminals of the compound are labeled with a fluorescein isothiocyanate (FITC) group and an N-ethylcarbazolyl group (ECz), respectively. An octapeptide carrying the same groups and a hexadecapeptide without a PEG chain were also synthesized and used as control. A mixture of the peptide and dimyristoylphosphatidylcholine was sonicated in a buffer to prepare the liposome. The orientation as well as direction of the helical segment in the lipid bilayer were analyzed by quenching experiments of the FITC and the ECz fluorescence. The results clearly indicated that the helical segment of the peptide penetrated into the lipid bilayer with vertical orientation in both the gel and liquid crystalline states of the lipid bilayer. Notably, the bulky N terminal was left behind in the outer aqueous phase of liposome, meaning that the C terminal of the peptide points to the inner aqueous phase of liposome. The insertion mode of the helical peptide into a bilayer membrane is therefore well-regulated in terms of the orientation and the directionality by designing the balance between the PEG chain and the helix length. The methodology presented here will initiate a way to construct artificial functional molecular systems that can induce vectorial transport phenomena as seen in biological systems.     

Phase transition of alkylsilane monolayers studied by temperature-dependent grazing incidence X-ray diffraction

The phase transition of organosilane monolayers on Si-wafer substrate surfaces prepared from octadecyltrichlorosilane (OTS) or docosyltrichlorosilane (DOTS) was investigated on the basis of grazing incidence X-ray diffraction (GIXD) at various temperatures. The OTS monolayer was prepared by a chemisorption method. The DOTS monolayer was prepared by a water-cast method (DOTS). The GIXD measurement clarified that the OTS monolayer also changed from hexagonal phase to amorphous state above a melting point of otadecyl groups. The GIXD measurements also clarified that the molecular aggregation state of the DOTS monolayer changes from an anisotropic phase to an isotropic phase with an increase in temperature. An estimated linear thermal expansion coefficient of the lattice lengths of a and b of the DOTS monolayer in the rectangular crystalline state assigned a similar value to those of bulk polyethylene with an orthorhombic crystalline lattice. The setting angle of the ab plane of the rectangular DOTS monolayer also showed similar behavior to that of the ab plane of bulk polyethylene.