Soft Matter Blog

Liquid crystals (LCs) can form polygonal cylinder arrays through self-assembly of polyphilic molecules of a rod-like core, two polar end groups and flexible lipophilic lateral chains. Although LC phases are highly dynamic fluid structures, they have the ability to form 2D lattices over large areas because of the self-healing ability and self-assembling. Understanding these process allows for the practical applications of these complex LC phases in organising π-conjugated aromatic in functional organic emitting devices.

In this hot paper, Cheng, Tschierske and co-workers report the synthesis of a series of new 5,5′-diphenyl-2,2′-dithiophene based bolaamphiphiles and their self-assembling into LC honeycombs. The authors show a transition from triangular/rhombic cylinders to a square honeycomb goes through a disordered isotropic state upon reaching a critical lateral chain length of the dithiophene.

Dithiophene based X-shaped bolaamphiphiles: liquid crystals with single wall honeycombs and geometric frustration
Soft Matter, 2012, 8, 10921.  DOI: 10.1039/c2sm26575c (free to read for a short time)

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The in vitro application of the self-organisation process of ‘active self-organisation (AcSO)’, in which a steady state non-equilibrium structure is maintained by a constant supply of energy, is attracting more and more attention in the production of complex structures on various scales. In this hot paper, featured on the front cover of issue 42 of Soft Matter, Kakugo, Gong et al. report the assembly process of microtubules at an air-buffer interface. Using the AcSO method in the presence of ATP resulted in ring-shaped structures. The team introduce an air–buffer interface control system, which combined with the inert chamber system, shows direct in situ observation of the assembly processes.

Formation of ring-shaped assembly of microtubules with a narrow size distribution at an air–buffer interface
Soft Matter, 2012, 8, 10863.  DOI: 10.1039/c2sm26441b (free to read for a short time)

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This Highlight by Silvia Corezzi and colleagues reviews a series of recent numerical studies that evidence the analogies between reversible and irreversible gelation in small functionality particles. These studies also investigate the crossover from chemically controlled to diffusion-controlled aggregation. The authors suggest that these results will be a useful guide for the interpretation of the kinetic in real systems. They use an example of measuring the extent of reaction in epoxy-resin systems to show this.

Chemical and physical aggregation of small-functionality particles
Soft Matter, 2012, 8, 11207.  DOI: 10.1039/c2sm26112j (free to read for a short time)

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Stimuli-responsive materials have received much attention recently because of their ability to switch their physical and chemical properties in response to external environmental conditions such as irritation with light, temperature or pH. Layer-by-layer multilayer films have been studied because they can be quite sensitive to external stimuli such as pH, temperature and ionic strength. Most studies have focussed on the formation of multilayer films on supporting porous templates or deposition with micro-sized pores. Nano-sized cylindrical porous membranes with tunable pore diameters by external stimuli are important in understanding molecular translocation through membranes by stimuli-responsive porous membranes.

In this hot paper, Char and colleagues from Seoul National University deposited pH sensitive multilayer films on the sidewalls of pores with diameter sub-100 nm. The authors carefully control the molecular weight of the polyelectrolytes during the deposition and use multivalent salts. It is suggested that this approach can be applied to stimuli-driven gating devices that mimic living membranes.

Layer-by-layer assembled stimuli-responsive nanoporous membranes
Soft Matter, 2012, 8, 10271.  DOI: 10.1039/c2sm26562a (free to read for a short time)

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Ionic liquid crystals (ILCs) are closely related to ionic liquids. They have one key different feature compared to ionic liquids in that they consist of at least one long alkyl chain. This also differentiates them from liquid crystals where the alkyl chains are usually short and must contain a rigid core. The applications of ILCs tend to exploit their anisotropic ion conductivity, and they have been used as ordered reaction media or templates for the synthesis of mesoporous materials. A clear understanding of the many molecular factors influencing the ionic mesophases from experimental efforts is lacking.

In this hot paper, Saielli uses molecular dynamics stimulations (coarse-grained force fields) to give a semi-quantitative description of the mesomorphic behaviour of 1-hexadecyl-3-methylimidazolium nitrate. The author shows that coarse-grained force fields can be tuned to better reproduce the thermal range of stability of the mesophase.

MD simulation of the mesomorphic behaviour of 1-hexadecyl-3-methylimidazolium nitrate: assessment of the performance of a coarse-grained force field
Soft Matter, 2012, 8, 10279.  DOI: 10.1039/c2sm26376a (free to read for a short time)

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The dynamics in protein folding on the slower and larger length scale are facilitated by atomic fluctuations in the pico- and nano-second time scale. To understand the complexity of biomacromolecular materials the details of the structure-dynamics-function relationships at these scales must be analysed.

In this hot paper communication Telling and colleagues report the systematic study of macromolecular dynamics in green fluorescent protein, superoxide dismutase and insulin. The authors use neutron spectroscopy as a non-destructive and selective technique in the study, specifically elastic fixed window scattering and the newly developed technique of inelastic fixed window scattering. They find that the proteins show very different structures, but have similar methyl group compositions.

Lyophilised protein dynamics: more than just methyls?
Soft Matter, 2012, 8, 9529.  DOI: 10.1039/c2sm26540k (free to read for a short time)

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Pickering emulsions are currently a ‘hot topic’ in the field because of their applications in cosmetics, foodstuffs, waste-water treatment and energy. Emulsification is regulated by two fundamental steps: coalescence and fragmentation. Emulsions can be stabilised by solid particles which impede coalescence.

This hot paper by the Striolo group from the University of Oklahoma, describes the coalescence of droplets stabilised by solid particles. The authors use dissipative particle dynamics simulations to study water (oil) droplets dispersed in oil (water) in the presence of various nanoparticles. The droplets are forced to coalesce and the process is observed at the molecular level. The results could be used to help design more stable Pickering emulsions.

Mechanistic study of droplets coalescence in Pickering emulsions
Soft Matter, 2012, 8, 9533.  DOI: 10.1039/c2sm26416a (free to read for a short time)

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This review by Marcel Utz, Jan G. Korvink and colleagues describes the use of the common analytical technique, nuclear magnetic resonance (NMR) spectroscopy in connection with soft matter research. The authors discuss the developments in the technique comparing the performance of various microscale NMR detectors. Applications of microscale NMR in soft matter research are also described.

Microscale nuclear magnetic resonance: a tool for soft matter research
Soft Matter, 2012, 8, 10583.  DOI: 10.1039/c2sm26065d (free to read for a short time)

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Droplet-based microfluidics is an effective tool for the miniaturisation and automation of biological assays in many applications. For reliable function, the droplets must be stable against coalescence; must be biocompatible and their components must remain encapsulated. These conditions are all controlled by the surfactant molecules. Understanding the transport of molecules between dispersed microcontainers is highly relevant for many encapsulation systems such as drug delivery systems and applications related to emulsion polymerisation or cell physics.

This hot paper by Taly, Baret and colleagues, addresses the dynamics of molecular exchange between droplets in a mixed emulsion. The authors link microscope exchange between two adjacent droplets and macroscopic kinetics of experimentally measured relaxation of concentration differences in an emulsion. The system uses droplets with two different concentrations of a fluorescent dye.

This article features on the front cover of the Soft Matter principles of microfluidics themed issue.

Dynamics of molecular transport by surfactants in emulsions
Soft Matter, 2012, 8, 10618.  DOI: 10.1039/c2sm25934f (free to read for a short time)

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Biomolecular motors can be found everywhere in nature from the rotary motor enzyme ATP synthase to kinesin and dynein motor proteins. In recent decades, scientists have been able to produce a wealth of synthetic molecular machines such as switches, shuttles, gears, wheels and artificial muscles.

This Review by Lensen and Elemans from the Institute for Molecules and Materials at Radboud University surveys the study of synthetic molecular rotors and motors on surfaces using scanning tunnelling microscopy (STM). This technique allows imaging at the atomic scale and in recent years, has enabled visualisation of molecular motion.

Artificial molecular rotors and motors on surfaces: STM reveals and triggers
Soft Matter, 2012, 8, 9053.  DOI: 10.1039/c2sm26235e (free to read for a short time)

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