Synthesis and evaluation of a series of novel 2-substituted poly(allylalcohol) side chain liquid crystalline oligomers exhibiting ferroelectricity

Abstract

The recently published Baylis-Hillman methodology has been used to prepare a number of side chain liquid crystalline poly(allylalcohols) incorporating a ferroelectric mesogenic side chain. These poly(allylalcohols) exhibited wide range S?_C phases and, in the case of two of these materials, low glass transition temperatures. The transition temperatures and phase behaviour of the SCLC poly(allylalcohols) were compared to acrylate and methacrylate SCLC oligomers containing a similar mesogenic side chain. The response times for two poly(allylalcohols) exhibiting low glass transition temperatures were also measured over a wide temperature range. Although the poly(allylalcohols) had comparable response times to the analogous acrylate and methacrylate SCLCP, they showed the greater temperature dependence of the response time. However, at 39°C one of the SCLC poly(allylalcohols) showed a response time of 65 ms.     

Time-of-flight flow imaging of two-component flow inside a microfluidic chip

Here we report on using NMR imaging and spectroscopy in conjunction with time-of-flight tracking to noninvasively tag and monitor nuclear spins as they flow through the channels of a microfluidic chip. Any species with resolvable chemical-shift signatures can be separately monitored in a single experiment, irrespective of the optical properties of the fluids, thereby eliminating the need for foreign tracers. This is demonstrated on a chip with a mixing geometry in which two fluids converge from separate channels, and is generally applicable to any microfluidic device through which fluid flows within the nuclear spin-lattice relaxation time.     

THE HADAMARD INEQUALITY FOR CONVEX FUNCTION VIA FRACTIONAL INTEGRALS

In this paper, we establish several inequalities for some differantiable mappings that are connected with the Riemann-Liouville fractional integrals. The analysis used in the proofs is fairly elementar...     

Enterfernung und Wiedergewinnung von Phenolen aus Industrieabw?ssern mit polymeren Amberlit XAD-Adsorbentien

Ohne Zusammenfassung     

Kinetics of immunoassays with particles as labels: effect of antibody coupling using dendrimers as linkers

In this article, we report on poly(amidoamine) dendrimers (PAMAM) as coupling agents for recombinant single-chain (ScFv) antibodies to nanoparticle (NP) labels, for use in immunoassay. We present a simple theory for the kinetics of particle capture onto a surface by means of an antibody-antigen reaction, in which the important parameter is the fraction of the particle surface that is active for reaction. We describe how increasing the generation number of the linking dendrimers significantly increased the fraction of the NP surface that is active for antigen binding and consequently also increased the assay kinetic rates. Use of dendrimers for conjugation of the NP to the antibody resulted in a significantly higher surface coverage of active antibody, in comparison with mono-valent linker chemistry. As a direct consequence, the increase in effective avidity significantly out-weighed any effect of a decreased diffusion coefficient due to the NP, when compared to that of a molecular dye-labelled antibody. The signal to noise ratio of the G4.5 dendrimer-sensitised nanoparticles out-performed the dye-labelled antibody by approximately four-fold. Particle aggregation experiments with the multi-valent antigen CRP demonstrated reaction-limited aggregation whose rate increased significantly with increasing generation number of the dendrimer linker.     

On the role of the definition of potential models in Gibbs ensemble phase equilibria simulations of the H2S-pentane mixture

The effect of treating explicitly the coulombic and polarization interactions is investigated through the calculation of the coexistence curve of the pentane-H₂S binary mixture. In this work, potential models have been developed for hydrogen sulphide and pentane, which include electrostatic sites—estimated from ab initio calculations—and polarizable sites—estimated from experimental data—in addition to Lennard-Jones sites. Compared to existing models, these new models have the same number of fitting parameters to experimental thermodynamic data. They are shown to correctly describe the coexistence curve of the pure compounds. When applied to the case of mixtures, together with Lorentz-Berthelot combining rules, they allow one to obtain a more accurate prediction of the coexisting compositions of the mixture. Furthermore, it is shown that the interaction energy in this kind of mixture cannot be properly described by using effective potential models usually considered for pure compounds.     

Rotational viscosity of uniaxial molecules

Non-equilibrium molecular dynamics (NEMD) are used to calculate the vortex or rotational viscosity of fluids composed of uniaxial molecules. It is shown that the NEMD homogeneous spin flow algorithm proposed by Edberg, R., Evans, D. J., and Moriss, G. P., 1987, Molec. Phys., 62, 1357 considerably underestimates the vortex viscosity. A modified version of this algorithm is proposed and applied to liquid chlorine and nitrogen. The results are in good agreement with previous work using equilibrium or other NEMD methods, and also show that at high spin rates the vortex viscosity decreases with increase in magnitude of the external torque used to drive the spin flow.     

Light on dark laser addressed smectic liquid crystal projection displays

Two techniques for producing dense uniform bulk scattering in cells containing smectic A liquid crystals have been examined for use in a large area liquid crystal projection display. Textures obtained using both thermal pulses and by dynamic scattering in the smectic A phase were evaluated for their uniformity and scattering density. The conditions required for optimum scattering are described in terms of the electrical characteristics of the scattering pulses used, the effects of different surface alignment treatments and of the nematic bandwidth of the materials employed. The two techniques are compared with respect to their suitability for large area, high information content, white on black, laser addressed liquid crystal light valves.     

Hydroxy schiff base-oxazolidine tautomerism: Apparent breakdown of baldwin''s rules

The tautomerism between hydroxy Schiff bases, X-C₆H₄CR=NCMe₂CH₂OH (R=H, Me, C₆H₅; X is a range of substituents) and X-C₆H₄,CR=NC₆H₄ (o-CH₂OH), and the corresponding ring closed systems, oxazolidines and dihydrobenzoxazines, has been investigated. In all cases where equilibria can be determined the process is shown to be extremely facile, despite the fact that Baldwin's rules are contravened. Information about the structure of some of these molecules in the crystalline state is provided by solid state NMR. Previous work on the equilibration of 1-methyl-1,3-oxazolidine and its iminium tautomer in trifluoroacetic acid is shown to be complicated by trifluoroacetate formation, but the overall conclusion that this 5-$\text{endo}$-$\text{trig}$ process is also rapid, appears to be correct. Some mechanistic consequences of these deductions are discussed.