Synthesis and characterization of a polyfluorene containing carbazole and oxadiazole dipolar pendent groups and its application to electroluminescent devices

We have synthesized a blue‐light‐emitting polyfluorene (PF) derivative ( PF‐CBZ‐OXD ) that presents bulky hole‐transporting carbazole and electron‐transporting oxadiazole pendent groups functionalized at the C‐9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF‐CBZ‐OXD and its analogue PF‐TPA‐OXD with a red‐light‐emitting iridium phosphor for use as components of phosphorescent red‐light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF‐CBZ‐OXD , in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2925–2937, 2007     

Self‐assembly of amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers

Amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers consisting of one polystyrene block and two poly(N‐isopropylacrylamide) blocks were prepared by the “arm‐first” method in which RAFT polymerization and nonconvalent ligand–metal complexation were employed. The prepared amphiphilic star‐shaped metallopolymers are able to form micelles in water. The size and distribution of the micelles were studied by dynamic light scattering and transmission electron microscopy techniques. Preliminary studies indicate that the polymer concentration and the hydrophilic poly(N‐isopropylacrylamide) block length can affect the morphologies of the formed metal‐interfaced core–shell micelles in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4204–4210, 2007     

Reply to Nathan: How to reconstruct the causal argument

Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that, on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination, that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that, properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a modified mechanism for hallucinations is implausibly ad hoc.     

An improved numerical simulator for multiphase flow in porous media

In basin modelling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from an equation of state and the Gibbs equality constraints. In this article we present a novel implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods, with and without cross derivative terms between components, are based on a preconditioned Newton‐GMRES scheme for each time‐step with analytical computation of the derivatives. These new algorithms reduce significantly the numerical effort for the computation of the molar masses, and we illustrate the behavior of these methods with numerical computations. Copyright © 2004 John Wiley & Sons Ltd.     

LES of turbulent heat transfer: proper convection numerical schemes for temperature transport

Large eddy simulations of two basic configurations (decay of isotropic turbulence, and the academic plane channel flow) with heat transfer have been performed comparing several convection numerical schemes, in order to discuss their ability to evaluate temperature fluctuations properly. Results are compared with the available incompressible heat transfer direct numerical simulation data. It is shown that the use of regularizing schemes (such as high order upwind type schemes) for the temperature transport equation in combination with centered schemes for momentum transport equation gives better results than the use of centred schemes for both equations. Copyright © 2004 John Wiley & Sons, Ltd.     

Attenuation of electromagnetic waves in a semiconductor superlattice in a magnetic field

Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.