Liquid-crystalline and glass-forming dimers derived from 1-aminopyrene

A homologous series of symmetric dimeric liquid crystals has been synthesized and its phase behaviour investigated. All members of the series were found to form glassy phases above room temperature.     

Material Highlights: Liquid Crystal Polymers

Abstract

A key issue in the area of side chain liquid crystal polymers concerns the conformation of the backbone within the mesophase. In order to resolve this matter, Noirez and co-workers (Liquid Crystals, 1995, 18 129) have studied a wide range of polymers exhibiting both nematic and smectic behaviour using small angle neutron scattering. Their results combined with a survey of those in the literature reveal that if the polymer is solely nematogenic, then the backbone adopts a prolate conformation in which on average it lies along the director. By contrast, in a smectic phase the backbone adopts an oblate shape and on average lies perpendicularly with respect to the director. This arises from a microphase separation in which the backbones are distributed between the mesogenic layers. However, the backbones can cross the mesogenic layers although their ability t o do so depends on, amongst other factors, the degree of polymerization. If the polymer exhibits both nematic and smectic behaviour, then in the nematic phase the backbone adopts a slightly oblate shape resulting from smectic fluctuations.     

Quantitative analysis and characterization of biofunctionalized fluorescent silica particles

A strategy for the production and subsequent characterization of biofunctionalized silica particles is presented. The particles were engineered to produce a bifunctional material capable of both (a) the attachment of fluorescent dyes for particle encoding and (b) the sequential modification of the surface of the particles to couple oligonucleotide probes. A combination of microscopic and analytical methods is implemented to demonstrate that modification of the particles with 3-aminopropyl trimethoxysilane results in an even distribution of amine groups across the particle surface. Evidence is provided to indicate that there are negligible interactions between the bound fluorescent dyes and the attached biomolecules. A unique approach was adopted to provide direct quantification of the oligonucleotide probe loading on the particle surface through X-ray photoelectron spectroscopy, a technique which may have a major impact for current researchers and users of bead-based technologies. A simple hybridization assay showing high sequence specificity is included to demonstrate the applicability of these particles to DNA screening.     

Liquid-crystalline cyclic trimers derived from benzene-1,3,5-tricarboxylic acid

A new class of structurally complex materials whose constituent molecules are composed of three rod-like units, each attached to a central disc-like unit via a flexible spacer have been synthesized and their phase behaviour investigated. They are found to exhibit a rich and unusual liquid-crystalline polymorphism.     

Communication and Cooperation in Public Network Situations

This paper focuses on sharing the costs and revenues of maintaining a public network communication structure. Revenues are assumed to be bilateral and communication links are publicly available but costly. It is assumed that agents are located at the vertices of an undirected graph in which the edges represent all possible communication links. We take the approach from cooperative game theory and focus on the corresponding network game in coalitional form which relates any coalition of agents to its highest possible net benefit, i.e., the net benefit corresponding to an optimal operative network. Although finding an optimal network in general is a difficult problem, it is shown that corresponding network games are (totally) balanced. In the proof of this result a specific relaxation, duality and techniques of linear production games with committee control play a role. Sufficient conditions for convexity of network games are derived. Possible extensions of the model and its results are discussed. The research of Jeroen Suijs has been made possible by a fellowship of the Royal Netherlands Academy of Arts and Sciences.     

The 2012 Luckhurst–Samulski Prize

Abstract

This article describes the state of and progress in experimental studies of liquid crystals of naturally occurring nucleic acids and synthetic polynucleotides. The areas considered in this review include: (i) the liquid-crystalline phase of nucleic acids in aqueous salt solutions, (ii) the liquid-crystalline phase of nucleic acids in aqueous polymer solutions, (iii) the liquid-crystalline phase of nucleic acids in living systems. Some unsolved problems which are of interest from both a physicochemical and a biological point of view are discussed.     

The Chiral Twist-Bend Nematic Phase (N*TB)

The twist-bend nematic, N_TB, phase has been observed for chiral materials in which chirality is introduced through a branched 2-methylbutyl terminal tail. The chiral twist-bend nematic phase, N*_TB, is completely miscible with the N_TB phase of the standard achiral material, CB6OCB. The N*_TB phase exhibits optical textures with lower birefringence than those observed for the achiral N_TB phase, suggesting an additional mechanism of averaging molecular orientations. The N*−N*_TB transition temperatures for the chiral materials are higher than the N_TB−N transition temperatures seen for the corresponding racemic materials. This suggests the double degeneracy of helical twist sense in the phase is removed by the intrinsic molecular chirality. A square lattice pattern is observed in the N* phase over a temperature range of several degrees above the N*_TB–N phase transition, which may be attributed to a non-monotonic dependence of the bend elastic constant.