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Soft Matter

Zijian Zheng, Fanzhu Li, Jun Liu, Raffaele Pastore, Guido Raos, Youping Wu, Liqun Zhang
The dispersion of solid nanoparticles within polymeric materials is widely used to enhance their performance. Many scientific and technological aspects of the resulting polymer nanocomposites have been studied, but the role of the structural and chemical heterogeneity of the nanoparticles has just started to be appreciated. For example, simulations of polymer films on planar heterogeneous surfaces revealed unexpected, non-monotonic activation energy to diffusion on varying the surface composition. Motivated by these intriguing results, here we simulate via molecular dynamics a different, fully three-dimensional system, in which the heterogeneous nanoparticles are incorporated in a polymer melt...
January 19, 2018: Soft Matter
Zhizhao Che, Omar K Matar
The impact of droplets on liquid films is a ubiquitous phenomenon not only in nature but also in many industrial applications. Compared to the widely-studied impact of droplets on films of identical fluids, the impact of droplets on immiscible films has received far less attention. In the present work, we show using high-speed imaging that immiscibility has a profound effect on the impact dynamics. The impact of a water droplet on an oil film leads to the formation of a compound crown followed by a central jet, whereas that of an oil droplet on a water film results in rapid spreading on the film surface driven by a large, positive spreading factor...
January 19, 2018: Soft Matter
Lin Feng, Danhua Xie, Binglei Song, Jiayu Zhang, Xiaomei Pei, Zhenggang Cui
Innovations in surfactant structure are a feasible way to probe molecular self-assembly principles. Herein, the solution behaviour of a newly synthesized Gemini surfactant derived from dehydroabietic acid, abbreviated R-(EO)-E-R, was investigated using surface tension, fluorescence, isothermal titration calorimetry (ITC), rheology, freeze-fracture transmission electron microscopy (FF-TEM) and cryogenic transmission electron microscopy (cryo-TEM) methods. R-(EO)-E-R has two large, rigid hydrophobic groups. At low concentrations, R-(EO)-E-R forms micelles with an aggregation number of approximately 10, which is smaller than those of Gemini surfactants containing flexible alkyl tails...
January 19, 2018: Soft Matter
Liana Vaccari, Daniel B Allan, Nima Sharifi-Mood, Aayush R Singh, Robert L Leheny, Kathleen J Stebe
Correction for 'Films of bacteria at interfaces: three stages of behaviour' by Liana Vaccari et al., Soft Matter, 2015, 11, 6062-6074.
January 19, 2018: Soft Matter
K S Jayaprakash, A K Sen
We report the continuous splitting of aqueous droplets at the interface between two co-flowing immiscible oil streams in a microchannel. The aqueous droplets initially present in a primary continuous stream (CP1) migrate into a secondary continuous stream (CP2) when the ratio of the non-inertial lift force to the interfacial tension force exceeds a critical value (K. S. Jayaprakash, U. Banerjee and A. K. Sen, Langmuir, 2016, 32, 2136-2143). Here, experiments were performed to understand the droplet splitting phenomenon and demonstrate the splitting of droplets encapsulating microbeads and cells...
January 19, 2018: Soft Matter
Yasemin Tamer, Biqiong Chen
In this study, a series of covalently crosslinked, l-lysine based poly(beta-aminoester urethane) (LPBAEU) networks with good biodegradability and pH sensitivity was reported. The effect of hydrophilic/hydrophobic characteristics and diacrylate/amine molar ratio on the structure, swelling and degradation behaviour of the networks was investigated. The water transport mechanism and dynamic swelling behavior of the LPBAEU networks were strongly affected by medium pH, and swelling amounts up to 252.2% and 148.7% were observed at pH 5...
January 19, 2018: Soft Matter
Jonas Grimm, Maxim Dolgushev
We investigate the dynamics of fractals and other networks in a viscoelastic and active environment. The viscoelastic dynamics is modeled based on the generalized Langevin equation, where the activity is introduced to it by means of the exponentially correlated noise. The intramolecular interactions are taken into account by the bead-spring picture. The microscopic connectivity (studied in the form of Vicsek fractals, of dual Sierpiński gaskets, of NTD trees, and of a family of deterministic small-world networks) reveals itself in the multiscale monomeric dynamics, which shows vastly different behaviors in the active and passive baths...
January 19, 2018: Soft Matter
Sergey V Pyrlin, Nicholas D M Hine, Arjan W Kleij, Marta M D Ramos
The recently-observed self-assembly of certain salphen-based compounds into neuron-like networks of microrings interconnected with nano-thin strings may suggest a new highly-potent tool for nanoscale patterning. However, the mechanism behind such phenomena needs to be clarified before they can be applied in materials design. Here we show that, in contrast with what was initially presumed, the emergence of a "rings-and-rods" pattern is unlikely to be explained by merging, collapse and piercing of vesicles as in previously reported cases of nanorings self-assembly via non-bonding interactions...
January 19, 2018: Soft Matter
V Meester, D J Kraft
We investigate the mechanisms underlying the reconfiguration of random aggregates of spheres through capillary interactions, the so-called "colloidal recycling" method, to fabricate a wide variety of patchy particles. We explore the influence of capillary forces on clusters of deformable seed particles by systematically varying the crosslink density of the spherical seeds. Spheres with a poorly crosslinked polymer network strongly deform due to capillary forces and merge into large spheres. With increasing crosslink density and therefore rigidity, the shape of the spheres is increasingly preserved during reconfiguration, yielding patchy particles of well-defined shape for up to five spheres...
January 19, 2018: Soft Matter
Anže Lošdorfer Božič
The importance of electrostatic interactions in soft matter and biological systems can often be traced to non-uniform charge effects, which are commonly described using a multipole expansion of the corresponding charge distribution. The standard approach when extracting the charge distribution of a given system is to treat the constituent charges as points. This can, however, lead to an overestimation of multipole moments of high order, such as dipole, quadrupole, and higher moments. Focusing on distributions of charges located on a spherical surface - characteristic of numerous biological macromolecules, such as globular proteins and viral capsids, as well as of inverse patchy colloids - we develop a novel way of representing spherical surface charge distributions based on the von Mises-Fisher distribution...
January 18, 2018: Soft Matter
Gaojian Lin, Qiuting Zhang, Cunjing Lv, Yichao Tang, Jie Yin
We studied the wetting behavior of multiscale self-similar hierarchical wrinkled surfaces. The hierarchical surface was fabricated on poly(dimethylsiloxane) (PDMS) substrates by manipulating the sequential strain release and combined plasma/ultraviolet ozone (UVO) treatment. The generated structured surface shows an independently controlled dual-scale roughness with level-1 small-wavelength wrinkles (wavelength of 700-1500 nm and amplitude of 50-500 nm) resting on level-2 large-wavelength wrinkles (wavelength of 15-35 μm and amplitude of 3...
January 18, 2018: Soft Matter
Xinlu Zhou, Kongshuang Zhao
A dielectric spectroscopy study on a polyelectrolyte in aqueous solutions, which contains hydrophobic groups in part of the side chains poly(acrylic acid)-graft-poly(ethylene oxide)-graft-dodecyl (PAA-g-PEO-g-dodecyl) is reported. A refined double layer polarization model was proposed to analyze the double dielectric relaxations in the dielectric spectra. Various electrical and structural parameters of the copolymers were obtained. Besides the crossover concentration, another turning point around 4 mg mL-1 was identified through the analysis of all the dielectrical parameters including dielectric increment, relaxation time and correlation length...
January 18, 2018: Soft Matter
L Dorogin, B N J Persson
Adhesion between a glass ball and a polydimethylsiloxane (PDMS) sample is dependent on the PDMS cross-link density, and the transformation of the material from the uncrosslinked liquid state to the fully crosslinked solid state is investigated in this study. The physical picture reflected a gradual transition from capillary forces driven contact mechanics to the classical Johnson-Kendall-Roberts (JKR)-type contact mechanics. PDMS was produced by mixing the base fluid and a cross-linker at a ratio of 10 : 1 and allowed to slowly cross-link at room temperature with simultaneous measurement of the ball-PDMS interaction force...
January 18, 2018: Soft Matter
Naisheng Jiang, Mani Sen, Wenduo Zeng, Zhizhao Chen, Justin M Cheung, Yuma Morimitsu, Maya K Endoh, Tadanori Koga, Masafumi Fukuto, Guangcui Yuan, Sushil K Satija, Jan-Michael Y Carrillo, Bobby G Sumpter
Here we report a link between the interfacial structure and adhesive property of homopolymer chains physically adsorbed (i.e., via physisorption) onto solids. Polyethylene oxide (PEO) was used as a model and two different chain conformations of the adsorbed polymer were created on silicon substrates via the well-established Guiselin's approach: "flattened chains" which lie flat on the solid and are densely packed, and "loosely adsorbed polymer chains" which form bridges jointing up nearby empty sites on the solid surface and cover the flattened chains...
January 17, 2018: Soft Matter
Irma Liascukiene, Gabriel Amselem, Deniz Z Gunes, Charles N Baroud
Foams can be stabilized for long periods by the adsorption of solid particles on the liquid-gas interfaces. Although such long-term observations are common, mechanistic descriptions of the particle adsorption process are scarce, especially in confined flows, in part due to the difficulty of observing the particles in the complex gas-liquid dispersion of a foam. Here, we characterise the adsorption of micron-scale particles onto the interface of a bubble flowing in a colloidal aqueous suspension within a microfluidic channel...
January 17, 2018: Soft Matter
Shenglu Deng, Jianxi Zhao
Herein, homogeneous solutions of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethyldodecylammonium bromide), referred to as 12-s-12 where s = 2, 4, 6, 8, and 10, in cyclohexane have been prepared with the help of sodium hexanoate (SH) or sodium laurate (SL). These surfactants self-assembled in cyclohexane to form various aggregating structures, which were characterised by small-angle X-ray scattering (SAXS) together with polarised microscopy observations. The results showed that 12-2-12/SH, where the gemini had the shortest spacer among this series, formed an inverse micellar cubic liquid crystalline phase of the Fd3m structure...
January 17, 2018: Soft Matter
Hongyu Guo, Gheorghe Stan, Yun Liu
Nanoparticles typically have an inherent wide size distribution that may affect the performance and reliability of many nanomaterials. Because the synthesis and purification of nanoparticles with desirable sizes are crucial to the applications of nanoparticles in various fields including medicine, biology, health care, and energy, there is a great need to search for more efficient and generic methods for size-selective nanoparticle purification/separation. Here we propose and conclusively demonstrate the effectiveness of a size-selective particle purification/separation method based on the critical Casimir force...
January 17, 2018: Soft Matter
Tenghao Yin, Danming Zhong, Junjie Liu, Xiangjiang Liu, Honghui Yu, Shaoxing Qu
The tunable diffracted pattern (Debye ring) of the well-ordered close-packed 2D photonic crystal (PC) is achieved via large deformation of the dielectric elastomer (DE) membrane for the first time. Two deformation models are proposed, the in-plane deformation driven by voltage and the out-of-plane deformation actuated by pressure. Both experimental and theoretical analyses are conducted to explore the tunability of the DE stretch on the Debye ring of the 2D PC, by voltage and pressure. An excellent agreement is found between the experimental and analytical results...
January 17, 2018: Soft Matter
A P Zakharov, L M Pismen
We describe reshaping of active textiles actuated by bending of Janus fibres comprising both active and passive components. A great variety of shapes, determined by minimising the overall energy of the fabric, can be produced by varying bending directions determined by the orientation of Janus fibres. Under certain conditions, alternative equilibrium states, one absolutely stable and the other metastable coexist, and their relative energy may flip its sign as system parameters, such as the extension upon actuation, change...
January 17, 2018: Soft Matter
Cunlu Zhao, Chun Yang
In this work, we report an effective microfluidic technique for continuous-flow trapping and localized enrichment of micro- and nano-particles by using induced-charge electrokinetic (ICEK) phenomena. The proposed technique utilizes a simple microfluidic device that consists of a straight microchannel and a conducting strip attached to the bottom wall of the microchannel. Upon application of the electric field along the microchannel, the conducting strip becomes polarized to introduce two types of ICEK phenomena, the ICEK flow vortex and particle dielectrophoresis, and they are identified by a theoretical model formulated in this study to be jointly responsible for the trapping of particles over the edge of the conducting strip...
January 16, 2018: Soft Matter
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