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Soft Matter

Hossein Sojoudi, Hadi Arabnejad, Asif Raiyan, Siamack A Shirazi, Gareth H McKinley, Karen K Gleason
Ice formation and accumulation on surfaces can result in severe problems for solar photovoltaic installations, offshore oil platforms, wind turbines and aircrafts. In addition, blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases has safety and economical concerns in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Practical adoption of icephobic/hydrate-phobic surfaces requires mechanical robustness and stability under harsh environments...
March 16, 2018: Soft Matter
Matthieu Fumagalli, Julien Berriot, Benoit de Gaudemaris, Anne Veyland, Jean-Luc Putaux, Sonia Molina-Boisseau, Laurent Heux
Rubber materials with well-dispersed fillers and large mechanical reinforcement have been obtained by melt-processing a diene elastomer matrix and tailored nanocellulose powders having both a high specific surface area and a modified interface. Such filler powders with a specific surface area of 180 m2 g-1 and 100 m2 g-1 have been obtained by freeze-drying suspensions of short needle-like cellulose nanocrystals (CNCs) and entangled networks of microfibrillated cellulose (MFC) in tert-butanol/water, respectively...
March 16, 2018: Soft Matter
Brendan Dyett, Hao Hao, Detlef Lohse, Xuehua Zhang
The coalescence between growing droplets is important for the surface coverage and spatial arrangements of droplets on surfaces. In this work, total internal reflection fluorescence (TIRF) microscopy is utilized to in situ investigate the formation of nanodroplets around the rim of a polymer microcap, with sub-micron spatial and millisecond temporal resolution. We observe that the coalescence among droplets occurs frequently during their growth by solvent exchange. Our experimental results show that the position of the droplet from two merged droplets is related to the size of the parent droplets...
March 16, 2018: Soft Matter
Anne-Laure Fameau, Fabrice Cousin, Romain Derrien, Arnaud Saint-Jalmes
Thermoresponsive foams that refer to foams for which the stability can be switched between the stable and unstable state have recently attracted growing interest due to their possible industrial applications. Our approach to design such foams is based on the use of fatty acids, with various counterions and molar ratios. It is the first example of foams with a temperature threshold of destabilization which can be continuously set between 20 °C and 75 °C.
March 15, 2018: Soft Matter
Di Du, Elaa Hilou, Sibani Lisa Biswal
Swimming at low Reynolds number is typically dominated by a large viscous drag, therefore microscale swimmers require non-reciprocal body deformation to generate locomotion. Purcell described a simple mechanical swimmer at the microscale consisting of three rigid components connected together with two hinges. Here we present a simple microswimmer consisting of two rigid paramagnetic particles with different sizes. When placed in an eccentric magnetic field, this simple microswimmer exhibits non-reciprocal body motion and its swimming locomotion can be directed in a controllable manner...
March 15, 2018: Soft Matter
Zhao Pan, Floriane Weyer, William G Pitt, Nicolas Vandewalle, Tadd T Truscott
Inspired by the huge droplets attached on cypress tree leaf tips after rain, we find that a bent fibre can hold significantly more water in the corner than a horizontally placed fibre (typically up to three times or more). The maximum volume of the liquid that can be trapped is remarkably affected by the bending angle of the fibre and surface tension of the liquid. We experimentally find the optimal included angle (∼36°) that holds the most water. Analytical and semi-empirical models are developed to explain these counter-intuitive experimental observations and predict the optimal angle...
March 15, 2018: Soft Matter
S Kaiser, S V Radl, J Manhart, S Ayalur-Karunakaran, T Griesser, A Moser, C Ganser, C Teichert, W Kern, S Schlögl
The present work aims at the preparation of dry adhesives with switchable bonding properties by using the reversible nature of the [4πs+4πs] cycloaddition of anthracenes. Photo-responsive hydrogenated carboxylated nitrile butadiene rubber with photo-responsive pendant anthracene groups is prepared by one-pot synthesis. The formation of 3D networks relies on the photodimerization of the anthracene moieties upon UV exposure (λ > 300 nm). Controlled cleavage of the crosslink sites is achieved by either deep UV exposure (λ = 254 nm) or thermal dissociation at 70 °C...
March 15, 2018: Soft Matter
Rui Zhang, Qianlei Zhang, Youxin Ji, Fengmei Su, Lingpu Meng, Zeming Qi, Yuanfei Lin, Xueyu Li, Xiaowei Chen, Fei Lv, Liangbin Li
Fibrillation and the complexation reaction between poly(vinyl alcohol) (PVA)-iodine (i) complexes have been studied with in situ synchrotron radiation small- and wide-angle X-ray scattering (SAXS and WAXS) during the uniaxial stretching of PVA films in KI/I2 aqueous solution. SAXS results show that stretching induces the formation of nanofibrils, which pack periodically in the later stage of stretching with an average inter-fibrillar distance of around 10 nm. The onset strains for fibrillation and the appearance of periodicity of nanofibrils are located at the beginning and the end of the stress plateau, and decrease with increasing iodine concentration...
March 14, 2018: Soft Matter
Zhijie Zhang, Quan Chen, Ralph H Colby
Current progress in understanding the dynamics of associating polymers is reviewed, with examples including both ionic and hydrogen bonding associations. A particular emphasis is placed on quantification of the strength of the interaction that sets the association lifetime. Knowledge of the interaction energy and the number density of associating groups allows a rational understanding of the linear viscoelastic response of many associating polymers.
March 14, 2018: Soft Matter
Ankush Checkervarty, Marco Werner, Jens-Uwe Sommer
We study pore formation in models of lipid bilayer membranes interacting with amphiphilic copolymers mimicking anti-microbial peptides using Monte Carlo simulations and we rationalize our results by a simple brush-model for the fluid membrane. In our study a weak tension on the membrane is required to observe pore-formation induced by the adsorption of flexible amphiphilic copolymers. The copolymers enhance the pore stability by decreasing the line tension due to weak adsorption along the rim of the pore. Pore formation is enhanced with increasing length of copolymers or stronger stretching of the membrane...
March 14, 2018: Soft Matter
Victoria J Cunningham, Emma C Giakoumatos, Melissa Marks, Steven P Armes, Erica J Wanless
High-speed video analysis has enabled the interaction between a pair of millimetre-sized air bubbles to be studied in aqueous solution. The bubbles were grown in the presence of either poly(glycerol monomethacrylate)-poly(benzyl methacrylate) (PGMA-PBzMA) diblock copolymer spheres or poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) (PGMA-PHPMA-PBzMA) triblock copolymer worms prepared by polymerisation-induced self-assembly (PISA). A reduction in interfacial tension relative to air bubbles grown in the absence of nanoparticles indicated the adsorption of nanoparticles at the air-water interface...
March 14, 2018: Soft Matter
Ruike Zhao, Shaoting Lin, Hyunwoo Yuk, Xuanhe Zhao
Structures of thin films bonded on substrates have been used in technologies as diverse as flexible electronics, soft robotics, bio-inspired adhesives, thermal-barrier coatings, medical bandages, wearable devices and living devices. The current paradigm for maintaining adhesion of films on substrates is to make the films thinner, and more compliant and adhesive, but these requirements can compromise the function or fabrication of film-substrate structures. For example, there are limits on how thin, compliant and adhesive epidermal electronic devices can be fabricated and still function reliably...
March 14, 2018: Soft Matter
Emily E Pocock, Richard J Mandle, John W Goodby
Liquid crystalline phases with a spontaneous twist-bend modulation are most commonly observed for dimers and bimesogens with nonamethylene spacers. In order to redress this balance we devised a simple chemical intermediate that can be used to prepare unsymmetrical bimesogens; as a proof of concept we prepared and studied eleven novel materials with all found to exhibit the twist-bend phase and exhibit a linear relationship between TN-I and TTB-N. A computational study of the conformational landscape reveals the octamethyleneoxy spacer to have a broader distribution of bend-angles than the nonamethylene equivalent, leading to reductions in the thermal stability of the TB phase...
March 12, 2018: Soft Matter
Daniel Salgado-Blanco, Carlos I Mendoza, Marco A Chávez-Rojo, José A Moreno-Razo, Enrique Díaz-Herrera
Molecular dynamics simulations were performed for a Gay-Berne discotic fluid confined in a slab geometry for two different anchorings: homeotropic (face-on) and planar (edge-on), and for two different confinement lengths. Our results show that the behaviour of the more confined system in the temperature region of the isotropic-nematic transition is critically influenced by the presence of the walls: the growth of the solid-liquid crystal interface spans over the entire width of the cell, and the character of the transition is changed from first order to continuous...
March 12, 2018: Soft Matter
Naohito Urakami, Takehiro Jimbo, Yuka Sakuma, Masayuki Imai
We investigated the effects of lipid geometry on vesicle division using coarse grained molecular dynamics simulations. When the vesicle is composed of zero and negative spontaneous curvature lipids (ZSLs and NSLs), the difference in their molecular spontaneous curvatures destabilizes the neck of the limiting shape vesicle. In the vesicle division pathway, the neck developed into the stalk intermediates. The stalk was broken when the NSLs were expelled from the stalk. Free energy analysis shows that the coupling between the lipid geometry and the Gaussian rigidity is responsible for the observed vesicle division...
March 8, 2018: Soft Matter
Avinash Y Gahane, Pritish Ranjan, Virender Singh, Raj K Sharma, Neeraj Sinha, Mandeep Sharma, Rama Chaudhry, Ashwani K Thakur
In the quest for new antimicrobial materials, hydrogels of Fmoc-protected peptides and amino acids have gained momentum due to their ease of synthesis and cost effectiveness; however, their repertoire is currently limited, and the mechanistic details of their function are not well understood. Herein, we report the antibacterial activity of the hydrogel and solution phases of Fmoc-phenylalanine (Fmoc-F) against a variety of Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Fmoc-F, a small molecule hydrogelator, reduces the bacterial load both in vitro and in the skin wound infections of mice...
March 8, 2018: Soft Matter
R C Picu, A Sengab
Adhesion plays an important role in the mechanics of nanoscale fibers such as various biological filaments, carbon nanotubes and artificial polymeric nanofibers. In this work we study assemblies of non-crosslinked filaments and characterize their adhesion-driven structural evolution and their final stable structure. The key parameters of the problem are the network density, the fiber length, the bending stiffness of fibers and the strength of adhesion. The system of fibers self-organizes in one of three types of structures: locked networks, in which fibers remain in the as-deposited state, cellular networks, in which fibers form bundles and these organize into a larger scale network, and disintegrated networks, in which the network of bundles becomes disconnected...
March 8, 2018: Soft Matter
Jiahe Huang, Jiexin Liao, Tao Wang, Weixiang Sun, Zhen Tong
Dopamine-containing hydrogels were synthesized by copolymerization of dopamine methacrylamide (DMA), N,N-dimethylacrylamide (DMAA), and an N,N'-methylenebisacrylamide (BIS) crosslinker in a mixed solvent of water and DMSO. The association of DMA was formed by simply immersing in water to facilely reinforce the hydrogel due to the introduction of the second physical crosslinking. The tensile strength of the hydrogels was increased greatly and regulated in a wide range from 200 kPa to over 2 MPa. The association of DMA was destroyed upon immersing in DMSO...
March 7, 2018: Soft Matter
Duanduan Wan, Sharon C Glotzer
We calculate the configurational entropy of hard particles confined in a cavity using Monte Carlo integration. Multiple combinations of particle and cavity shapes are considered. For small numbers of particles N, we show that the entropy decreases monotonically with increasing cavity aspect ratio, regardless of particle shape. As N increases, we find ordered regions of high and low particle density, with the highest density near the boundary for all particle and cavity shape combinations. Our findings provide insights relevant to engineering particles in confined spaces, entropic barriers, and systems with depletion interactions...
March 7, 2018: Soft Matter
Whitney S Loo, Xi Jiang, Jacqueline A Maslyn, Hee Jeung Oh, Chenhui Zhu, Kenneth H Downing, Nitash P Balsara
It is known that the addition of salts to symmetric block copolymers leads to stabilization of ordered phases and an increase in domain spacing; both trends are consistent with an increase in the effective Flory-Huggins interaction parameter between the blocks, χ. In this work, we show that the addition of salt to a disordered asymmetric block copolymer first leads to the formation of coexisting ordered phases which give way to a reentrant disordered phase at a higher salt concentration. The coexisting phases are both body centered cubic (BCC) with different domain spacings, stabilized by partitioning of the salt...
March 7, 2018: Soft Matter
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