Synthesis of new vinyl ether functionalized silica for UV-patterning

We report a new ORganically MOdified SILicates (ORMOSILs) stable sol based on vinyl ether function which can be deposited as a layer and structured by mean of UV radiation through a mask or by direct laser writing. Silica matrix is synthesized by sol–gel process and organic network is formed by photopolymerization. One of the potential applications is the fabrication of integrated optical circuits. [2-(3,4 epoxycyclohexyl ethyltrimethoxysilane)] has already used for the fabrication of such devices and to develop microstructures on an organic substrate by cationic polymerization. Obtained results show some weakness such as an important contribution of OH and aliphatic CH groups to the attenuation at 1550 nm wavelength and low conversion rate of organic polymerization involving poor mechanical properties. This work treats on the design of a new generation of hybrid materials with a very high reactivity and low amount of groups involved in the attenuation. We have chosen vinyl ether function as reactive organic part for her highest polymerization rate via cationic way. The new synthesized molecule is 4-vinylether phenyltriethoxysilane. Sol–gel kinetic reactions were monitored by liquid ²⁹Si-NMR spectroscopy. In order to obtain the highest reactive multifunctional oligomers and the lowest OH groups, hydrolysis and polycondensation reactions were followed as a function of time, temperature and pH of the water involved in the hydrolysis conditions. Finally, we show the feasibility to microstructure films deposited with this sol.     

Inflow conditions for inhomogeneous turbulent flows

A cost‐effective method to generate inflow conditions for direct numerical simulations of wall‐bounded flows is presented. The method recycles a finite‐length time series of instantaneous velocity planes extracted from a precursor simulation and has earlier proved efficient for free shear layers. Now a spatially developing plane channel flow is considered. Different durations t_s of the time series are tested and compared. Excellent agreement with fully developed channel flow statistics is observed when t_s equals or exceeds the large‐eddy turnover time scale. The present results are more realistic than those obtained with synthetic turbulence generation and at the same time substantially cheaper than running an auxiliary simulation in parallel. Copyright © 2008 John Wiley & Sons, Ltd.     

Nanostructuring of Self‐Assembled Porphyrin Networks at a Solid/Liquid Interface: Local Manipulation under Global Control

Molecules of (5,10,15,20‐tetraundecylporphyrinato)‐copper(II) [(TUP)Cu] can self‐assemble into four different polymorphs at the interface between highly oriented pyrolytic graphite and 1‐octanoic acid. Scanning tunneling microscopy (STM) reveals that it is possible to combine the global control over monolayer structure, provided by the composition and concentration of the supernatant solution, with local control, from nanomanipulation by the STM tip. In the initially formed monolayer, with a polymorph composition governed by the concentration of (TUP)Cu in the supernatant solution, the exchange of molecules physisorbed at the solid/liquid interface with those in the liquid is very limited. By using a nanoshaving procedure at the tip, defects are created in the monolayer, and these serve as local manipulation sites to create domains of higher or lower molecular density, and to incorporate a second molecular species, (TUP)Co into the monolayer of (TUP)Cu.     

Formation of an Inclusion Complex of a New Transition Metal Ligand in β-Cyclodextrin

The inclusion complex of a new transition metal ligand, 2,4,9-trithia-tricyclo[3.3.1.1^3,7]decane-7-carboxylic acid (2,4,9-trithia-adamantane-7-carboxylic acid, TPCOOH) in β-cyclodextrin was studied by ¹H NMR, 2D NOESY NMR spectroscopy, host-induced CD spectroscopy, and tandem mass spectrometry. ¹H NMR, MS–MS and NOESY data show that the TPCOOH guest forms a 1:1 inclusion complex with the host β-cyclodextrin. The NOESY experiments also show that TPCOOH is oriented in the complex with the thioketal end preferentially located at the larger opening of β-cyclodextrin. The orientation of the guest in the host molecule is also confirmed by the induced CD of the ligand, which shows a positive Cotton effect. An association constant of 660±20?M^?1 was determined by ¹H NMR titration for the complex at room temperature in D₂O.     

The morphology of poly(vinylidene fluoride) crystallized from blends of poly(vinylidene fluoride) and poly(ethyl acrylate)

A combined optical and electron microscopical study has been carried out of the crystallization habits of poly(vinylidene fluoride) (PVF₂) when it is crystallized from blends with noncrystallizable poly(ethyl acrylate) (PEA). The PVF₂/PEA weight ratios were 0.5/99.5,5/95, and 15/85. Isothermal crystallization upon cooling the blends from the single-phase liquid region was carried out in the range 135–155°C, in which the polymer crystallizes in the α-orthorhombic unit cell form. The 0.5/99.5 blend yielded multilayered and planar lamellar crystals. The lamellae formed at low undercoolings were lozenge shaped and bounded laterally by {110} faces. This habit is prototypical of the dendritic lateral habits exhibited by the crystals grown from the same blend at high undercoolings as well as by the constituent lamellae in the incipient spherulitic aggregates and banded spherulites that formed from the 5/95 and the 15/85 blends, respectively. In contrast with the planar crystals grown from the 0.5/99.5 blend, the formation of the aggregates grown from the 5/95 blend is governed by a conformationally complex motif of dendritic lamellar growth and proliferation. The development of these aggregates is characterized by the twisting of the orientation of lamellae about their preferential b-axis direction of growth, coupled with a fan-like splaying or spreading of lamellae about that axis. The radial growth in the banded spherulites formed from the 15/85 blend is governed by a radially periodic repetition of a similar lamellar twisting/fan-like spreading growth motif whose recurrence corresponds to the extinction band spacing. This motif differs in its fan-like splaying component from banding due to just a helicoidal twisting of lamellae about the radial direction. © 1993 John Wiley & Sons, Inc.     

Little exchange at the liquid/solid interface: defect-mediated equilibration of physisorbed porphyrin monolayers

The transition from low to high density 2D surface structures of copper porphyrins at a liquid/solid interface requires specific defects at which nearly all exchange of physisorbed molecules with those dissolved in the supernatant occurs.     

Multiple photosynthetic reaction centres composed of supramolecular assemblies of zinc porphyrin dendrimers with a fullerene acceptor

Multiple photosynthetic reaction centres have successfully been constructed using supramolecular complexes of zinc porphyrin dendrimers [D(ZnP)(n): n = 4, 8, 16] with fulleropyrrolidine bearing a pyridine ligand (C(60)py). Efficient energy migration occurs completely between the ZnP units of dendrimers prior to the electron transfer with increasing the generation of dendrimers to attain an extremely long charge-separation lifetime.