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Soft Matter

Kimio Yoshimura, Yue Zhao, Akihiro Hiroki, Yoshihiro Kishiyama, Hideyuki Shishitani, Susumu Yamaguchi, Hirohisa Tanaka, Satoshi Koizumi, Judith E Houston, Aurel Radulescu, Marie-Sousai Appavou, Dieter Richter, Yasunari Maekawa
We found unprecedented reverse relationships in anion-exchange membranes (AEMs) for Pt-free alkaline fuel cell systems, i.e., the increase in hydrophobicity increased water uptake and susceptibility to hydrolysis. AEMs with graft copolymers that composed of anion-conducting 2-methyl-N-vinylimidazolium (Im) and hydrophobic styrene (St) units were employed. We characterized two new structures in these AEMs using a small-angle neutron scattering with a contrast variation method. (1) The distribution of graft polymers in conducting (ion channel) or non-conducting (hydrophobic amorphous poly(ethylene-co-tetrafluoroethylene) (ETFE)) phase was evaluated in a quantitative manner...
September 20, 2018: Soft Matter
Neda Ojaghlou, Hooman V Tafreshi, Dusan Bratko, Alenka Luzar
Quantifying the detachment behavior of a droplet from a fiber is important in many applications such as fog harvesting, oil-water separation, or water management in fuel cells. When the droplets are forcibly removed from hydrophilic fibers, the ease of detachment strongly depends on droplet volume and the rate of the process controlled by the applied force. Experiments, conducted on a ferrofluid under magnetic force, as well as continuum level calculations from fluid mechanics have so far been unable to resolve the time-dependent dynamics of droplet detachment and, most importantly, to assess the role of the applied force as the key determinant of the volume of the droplet residue remaining on the fiber after detachment...
September 20, 2018: Soft Matter
Makoto Asai, Dan Zhao, Sanat K Kumar
Understanding and predicting the mechanisms underpinning the self-assembly of polymer-grafted nanoparticles (PGNPs) are important for controlling the engineering applications of these novel materials. The self-assembly of these materials is driven by their surfactancy, i.e., by the fact that the (inorganic) nanoparticles energetically dislike the (organic) polymer tethers. In previous work we developed a model in which a grafted polymer chain was treated as a rigid equivalent sphere (ES) which was impenetrable to the NPs, but completely penetrable to other ESs...
September 19, 2018: Soft Matter
Sutapa Roy, Anna Maciołek
We study the non-equilibrium coarsening dynamics of a binary liquid solvent around a colloidal particle in the presence of a time-dependent temperature gradient that emerges after a temperature quench of a suitable coated colloid surface. The solvent is maintained at its critical concentration and the colloid is fixed in space. The coarsening patterns near the surface are shown to be strongly dependent on the colloid surface adsorption properties and on the temperature evolution. The temperature gradient alters the morphology of the binary solvent near the surface of the colloid as compared to the coarsening proceeding at a constant temperature everywhere...
September 19, 2018: Soft Matter
Ryan C Maloney, Carol K Hall
Self-assembly of binary mixtures that contain anisotropic, interacting colloidal particles have been proposed as a way to create new, multi-functional materials. We simulate binary mixtures of dipolar rods and dipolar discs in two-dimensions using discontinuous molecular dynamics to determine how the assembled structures of these mixtures differ from those seen in single component systems. Two different binary mixtures are investigated: a mixture of an equal number of dipolar rods and dipolar discs ("equal number"), and a mixture where the area fraction of dipolar rods is equal to the area fraction of dipolar discs ("equal area")...
September 19, 2018: Soft Matter
John S Biggins, L Mahadevan
We consider meniscus instabilities in thin elastic layers perfectly adhered to, and confined between, much stiffer bodies. When the free boundary associated with the meniscus of the elastic layer recedes into the layer, for example by pulling the stiffer bodies apart or injecting air between them, then the meniscus will eventually undergo a purely elastic instability in which fingers of air invade the layer. Here we show that the form of this instability is identical in a range of different loading conditions, provided only that the thickness of the meniscus, a, is small compared to the in-plane dimensions and to two emergent in-plane length scales that arise if the substrate is soft or if the layer is compressible...
September 19, 2018: Soft Matter
Nandita Basu, Rabibrata Mukherjee
We report the evaporative drying of an aqueous droplet containing a dilute solution of sodium chloride (NaCl) on a hydrophobic substrate made of cross-linked poly-dimethyl siloxane (PDMS). The salt concentration Cn was varied between 0.08 molar (M) and 2.0 M. The contact line of the evaporating droplets shows significant initial retraction for all Cn, before they get pinned. While the final morphology comprises a few small NaCl crystals deposited around the pinned contact line, in droplets with a low Cn (<0...
September 19, 2018: Soft Matter
Monika Gosecka, Malgorzata Urbaniak, Maciej Mikina, Mateusz Gosecki, Artur Rozanski
We present an unexpected self-assembly of a glycoluril clip-poly(ε-caprolactone) conjugate in chloroform. The conjugate forms homodimer aggregates due to supramolecular interactions between glycoluril moieties, which was confirmed with MALDI-TOF-ms and 1H NMR. TEM revealed the formation of multilayered nanosized prism-shaped objects resembling tree bark in nature.
September 18, 2018: Soft Matter
Ryota Tamate, Ryoji Usui, Kei Hashimoto, Yuzo Kitazawa, Hisashi Kokubo, Masayoshi Watanabe
A photo/thermoresponsive ABC triblock copolymer-based ion gel exhibiting photoinduced structural transitions accompanied by significant rheological changes is newly developed. The ABC triblock copolymer comprises an ionic liquid (IL)-phobic A block, an IL-philic B block, and a photo/thermoresponsive C block containing azobenzene moieties. The IL-phobic A block forms a rigid micellar core in an IL over a wide temperature range and the photo/thermoresponsive C block undergoes upper critical solution temperature (UCST)-type phase transition in ILs...
September 17, 2018: Soft Matter
Guo-Jun Liao, Sabine H L Klapp
We perform Brownian dynamics simulations in two dimensions to study the collective behavior of circle swimmers, which are driven by both, an (effective) translational and rotational self-propulsion, and interact via steric repulsion. We find that active rotation generally opposes motility-induced clustering and phase separation, as demonstrated by a narrowing of the coexistence region upon increase of the propulsion angular velocity. Moreover, although the particles are intrinsically assigned to rotate counterclockwise, a novel state of clockwise vortices emerges at an optimal value of the effective propulsion torque...
September 17, 2018: Soft Matter
Yumo Wang, Joelle Frechette
The dynamic of contact formation between soft materials immersed in a fluid is accompanied by fluid drainage and elastic deformation. As a result, controlling the coupling between lubrication pressure and elasticity provides strategies to design materials with reversible and dynamic adhesion to wet or flooded surfaces. We characterize the elastic deformation of a soft coating with nanometer-scale roughness as it approaches and contacts a rigid surface in a fluid environment. The lubrication pressure during the approach causes elastic deformation and prevents contact formation...
September 17, 2018: Soft Matter
Yuki Tabata, Hirotaka Uji, Tomoya Imai, Shunsaku Kimura
A novel cyclic hexapeptide composed of l-α-naphthylalanine, d-α-anthrylalanine, and four β-alanines (CP6) is synthesized and its molecular assembly into peptide nanotubes (PNTs) and the electronic properties arising from one-dimensional arrays of aromatic groups along the PNTs were investigated. CP6 with a combination of l- and d-α-amino acids is designed to self-assemble into PNTs with them stacking on top of each other under the constraint of maximizing the number of intermolecular hydrogen bonds between the cyclic peptides...
September 14, 2018: Soft Matter
Yen-Chih Huang, Chun-Jen Su, Nikolay Korolev, Nikolay V Berezhnoy, Sai Wang, Aghil Soman, Chun-Yu Chen, Hsin-Lung Chen, U-Ser Jeng, Lars Nordenskiöld
In eukaryotes, the compaction of chromatin fibers composed of nucleosome core particles (NCPs) connected by a linker DNA into chromosomes is highly efficient; however, the underlying folding mechanisms remain elusive. We used small angle X-ray scattering (SAXS) to investigate the influence of linker DNA length on the local structure and the interparticle interactions of the NCPs. In the presence of the linker DNA of 30 bp or less in length, the results suggest partial unwrapping of nucleosomal DNA on the NCP irrespective of the linker DNA length...
September 14, 2018: Soft Matter
Niki Baccile, Lisa Van Renterghem, Patrick Le Griel, Guylaine Ducouret, Martha Brennich, Viviana Cristiglio, Sophie L K W Roelants, Wim Soetaert
A bio-based glycolipid bolaamphiphile (glyco-bolaamphiphile) has recently been produced (Van Renterghem et al., Biotechnol. Bioeng., 2018, 115, 1195-1206) on a gram scale by using the genetically-engineered S. bombicola strain Δat Δsble Δfao1. The glyco-bolaamphiphile bears two symmetrical sophorose headgroups at the extremities of a C16:0 (ω-1 hydroxylated palmitic alcohol) spacer. Its atypical structure has been obtained by redesigning the S. bombicola strain Δat Δsble, producing non-symmetrical glyco-bolaamphiphile, with an additional knock out (Δfao1) and feeding this new strain with fatty alcohols...
September 13, 2018: Soft Matter
Robert M Elder, Tyler R Long, Erich D Bain, Joseph L Lenhart, Timothy W Sirk
We use molecular simulations and experiments to rationalize the properties of a class of networks based on dicyclopentadiene (DCPD), a polymer with excellent fracture toughness and a high glass transition temperature (Tg), copolymerized with 5-norbornene-2-methanol (NBOH). DCPD is a highly non-polar hydrocarbon, while NBOH contains a hydroxy group, introducing polar functionality and hydrogen bonds (H-bonds). NBOH thus represents a possible route to improve the chemical compatibility of DCPD-based networks with less-hydrophobic materials...
September 13, 2018: Soft Matter
Yoshiharu Dogishi, Yota Sakai, Woon Yong Sohn, Kenji Katayama
The controlled motion of a liquid crystalline active droplet was demonstrated in a surfactant solution and by irradiation with UV light. The droplet could be induced to roll on a glass substrate toward the UV light source. This was explained by the Marangoni flow induced by the UV-induced desorption of surfactants.
September 13, 2018: Soft Matter
Nerea Sebastián, Christophe Contal, Antoni Sánchez-Ferrer, Marco Pieruccini
The influence of structural constraints on the relaxation dynamics of three polyurea networks with a varying degree of crosslinking, has been studied by means of a thorough analysis of broadband dielectric spectroscopy measurements. Two different relaxation processes are observed, namely, a fast process involving the soft poly(propylene oxide) chains, and a slower and much broader process associated with the immediate surroundings of the hard crosslinkers. Microphase separation in soft and hard domains characterizes the systems in the presence of hydrogen bonding...
September 13, 2018: Soft Matter
Yifei Min, Prashant K Purohit
We develop a model to explain discontinuities in the increase of the length of a DNA plectoneme when the DNA filament is continuously twisted under tension. We account for DNA elasticity, electrostatic interactions and entropic effects due to thermal fluctuation. We postulate that a corrugated energy landscape that contains energy barriers is the cause of jumps in the length of the plectoneme as the number of turns is increased. Thus, our model is similar to the Prandtl-Tomlinson model of atomic scale friction...
September 13, 2018: Soft Matter
Jing-Jing Liao, Xiao-Qun Huang, Bao-Quan Ai
Rectification of interacting active particles is numerically investigated in a two-dimensional time-oscillating potential. It is found that the oscillation of the potential and the self-propulsion of active particles are two different types of nonequilibrium driving, which can induce net currents with opposite directions. For a given asymmetry of the potential, the direction of the transport is determined by the competition of the self-propulsion and the oscillation of the potential. There exists an optimal oscillating angular frequency (or self-propulsion speed) at which the average velocity takes its maximal positive or negative value...
September 13, 2018: Soft Matter
Chiara Scognamiglio, Francesco Magaletti, Yaroslava Izmaylov, Mirko Gallo, Carlo Massimo Casciola, Xavier Noblin
Numerous scenarios exist for a cavitation bubble growing in a liquid. We focus here on cavitation phenomena within water under static tension in a confined environment. Drawing inspiration from the natural materials in plants, we design a novel experimental setup where a micrometric volume of water is confined by a hydrogel-based material. We show that, submerging the sample in a hypertonic solution, the water within the cavity is placed under tension and the acoustic emission produced by the resulting bubble nucleation is precisely detected...
September 12, 2018: Soft Matter
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