T-shaped molecules with a rod-like aromatic core and a flexible side chain form liquid crystal honeycombs with aromatic cell walls and a cell interior filled with the side chains. Here, we show how the addition of a second chain, incompatible with the first (X-shaped molecules), can form honeycombs with highly complex tiling patterns, with cells of up to five different compositions ("colors") and polygonal shapes. The complexity is caused by the inability of the side chains to separate cleanly because of geometric frustration. Furthermore, a thermoreversible transition was observed between a multicolor (phase-separated) and a single-color (mixed) honeycomb phase. This is analogous to the Curie transition in simple and frustrated ferro- and antiferromagnets; here spin flips are replaced by 180° reorientations of the molecules.
of the original manuscript:Ungar, G.; Tschierske, C.; Abetz, V.; Holyst, R.; Bates, M.A.; Lui, F.; Prehm, M.; Kieffer, R.; Zeng, X.; Walker, M.; Glettner, B.; Zywocinski, A.: Keywords: columnar liquid crystals, polygonal honeycombs, polyphiles, miktoarm star terpolymers, simulation, Langmuir films, rod-coil molecules, surface alignment Abstract: This article reviews the diversity of phase morphologies observed recently in starbranched liquid crystalline and polymeric compounds containing at least three immiscible segments. Bolaamphiphiles and facial amphiphiles with a rod-like aromatic core, two endgroups and one (T-shape) or two chains (X-shape) attached laterally to the core form numerous honeycomb-like liquid crystal phases, as well as a variety of novel lamellar and 3D-ordered mesophases. Molecular self-organization is described in bulk phases and in thin films on solid and liquid surfaces, as well as in Langmuir-Blodgett films. The remarkably reversible formation of mono-and tri-layer films is highlighted. In the bulk, T-shaped "rod-coil" molecules without the appended end-groups form predominantly lamellar phases if the core is a straight rod, but the bent-core variety forms hexagonal honeycombs. Furthermore, selfassembly of "Janus"-type molecules, such as those with Y-shaped star mesogens bearing different mutually incompatible side-groups, is discussed. Also covered is the diversity of morphologies observed in miktoarm star terpolymers i.e. polymers with three different and 3 incompatible arms of well-defined lengths. A range of bulk phases with 3D or 2D order are observed, combining layers, cylinders and cocontinuous networks. Similarities and differences are highlighted between the liquid crystal morphologies on the 3-15 nm scale and the polymer morphologies on the scale 10-100 nm. A separate section is dedicated to computer simulations of such systems, particularly those using dissipative particle and molecular dynamics. Of special interest are the recently synthesised X-shaped tetraphilic molecules, where two different and incompatible side-chains are attached at opposite sides of the rod-like core. The tendency for their phase separation produces LC honeycombs with cells of different compositions that can be represented as paving a plane with different color tiles. Self-Assembly at Different Length Scales: Polyphilic StarBranched Liquid Crystals and Miktoarm Star CopolymersThe independent variation of chain length and "color" creates the potential for developing a considerable range of complex new 2d-and 3d soft nanostructures. Analogous X-shaped rodcoil compounds with unequal side groups are also of considerable interest, forming tubular lyotropic structures capable of confining strings of guest molecules.
The CALICE Semi-Digital Hadronic Calorimeter (SDHCAL) prototype, built in 2011, was exposed to beams of hadrons, electrons and muons in two short periods in 2012 on two different beam lines of the CERN SPS. The prototype with its 48 active layers, made of Glass Resistive Plate Chambers and their embedded readout electronics, was run in triggerless and power-pulsing mode. The performance of the SDHCAL during the test beam was found to be very satisfactory with an efficiency exceeding 90% for almost all of the 48 active layers. A linear response (within ± 5%) and a good energy resolution are obtained for a large range of hadronic energies (5-80 GeV) by applying appropriate calibration coefficients to the collected data for both the Digital (Binary) and the Semi-Digital (Multi-threshold) modes of the SDHCAL prototype. The Semi-Digital mode shows better performance at energies exceeding 30 GeV.
A large prototype of 1.3 m 3 was designed and built as a demonstrator of the semi-digital hadronic calorimeter (SDHCAL) concept proposed for the future ILC experiments. The prototype is a sampling hadronic calorimeter of 48 units. Each unit is built of an active layer made of 1 m 2 Glass Resistive Plate Chamber (GRPC) detector placed inside a cassette whose walls are made of stainless steel. The cassette contains also the electronics used to read out the GRPC detector. The lateral granularity of the active layer is provided by the electronics pick-up pads of 1 cm 2 each. The cassettes are inserted into a self-supporting mechanical structure built also of stainless steel plates which, with the cassettes walls, play the role of the absorber. The prototype was designed to be very compact and important efforts were made to minimize the number of services cables to optimize the efficiency of the Particle Flow Algorithm techniques to be used in the future ILC experiments. The different components of the SDHCAL prototype were studied individually and strict criteria were applied for the final selection of these components. Basic calibration procedures were performed after the prototype assembling. The prototype is the first of a series of new-generation detectors equipped with a power-pulsing mode intended to reduce the power consumption of this highly granular detector. A dedicated acquisition system was developed to deal with the output of more than 440000 electronics channels in both trigger and triggerless modes. After its completion in 2011, the prototype was commissioned using cosmic rays and particles beams at CERN.
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