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Soft Matter

M A Ayer, S Schrettl, S Balog, Y C Simon, C Weder
While azo compounds are widely employed as radical initiators, they have rarely been used as stimuli-responsive motifs in macromolecular constructs. In this study, an azo-based cross-linker was prepared and reacted with poly(vinyl alcohol) to afford a series of stimuli-responsive organogels. Irradiation of these materials with UV light causes de-cross-linking and triggers a solid-to-liquid phase transition. Model adhesives with de-bonding-on-demand capability based on this design were explored.
May 26, 2017: Soft Matter
Rui-Bin Zhang, Goran Ungar, Xiangbing Zeng, Zhihao Shen
Using 2D X-ray diffraction and AFM we studied the configuration, in cylindrical confinement, of hexagonal columnar phases that anchor homeotropically, i.e. with the columns normal to the pore wall. A wide range of pore diameters, from 20 nm to 100 μm, were explored by employing anodic alumina membranes and glass capillaries. The compounds used were a small discotic, hexakis(hexyloxy)triphenylene (HAT6), a large discotic hexa-peri-hexabenzocoronene (HBC), and a T-shaped bolaamphiphile, forming a honeycomb-type columnar phase...
May 26, 2017: Soft Matter
Mingfeng Pu, Huijun Jiang, Zhonghuai Hou
Recent studies showed substantial evidence of dynamic clustering and phase separation in active particle systems, but the role of anisotropic interaction between the particles has not been addressed yet. Here we investigate the phase separation of active particles that experience an anisotropic Janus interaction with tunable strength in two dimensional space by using Langevin dynamics simulations. Interestingly, we find that phase separation shows a re-entrance behavior with variation of the Janus interaction strength: while small Janus interaction can enhance the formation of living clusters and phase separation, large Janus interaction would destroy the large cluster...
May 26, 2017: Soft Matter
Benjamin A Kowalski, Vincent P Tondiglia, Tyler Guin, Timothy J White
Monomeric mixtures formulated to prepare a liquid crystal polymer network (LCN) or elastomer (LCE) can be "programmed" by surface alignment to retain complex and arbitrary spatial distributions of the director orientation upon polymerization. The localized control of orientation in a given volume (voxel) within these materials is the subject of intense research, currently motivated by the prospect of distinctive mechanical responses (both active and passive). Here, we report on a rapid and scalable photopatterning method to prepare alignment surfaces with a throughput of 10 mm(2) s(-1), using a commercial spatial light modulator and projection optics...
May 25, 2017: Soft Matter
Hiroshi Noguchi, Jean-Baptiste Fournier
The assembly of banana-shaped rodlike proteins on membranes and the associated membrane shape transformations are investigated by analytical theory and coarse-grained simulations. The membrane-mediated interactions between two banana-shaped inclusions are derived theoretically using a point-like formalism based on fixed anisotropic curvatures, both for zero surface tension and for finite surface tension. On a larger scale, the interactions between the assemblies of such rodlike inclusions are determined analytically...
May 25, 2017: Soft Matter
Wei You, Wei Yu, Chixing Zhou
Currently, it is a great challenge to characterize the dispersion quality of nanoparticles in nanocomposites through experimental techniques. In this work, we suggest a new rheological method based on the strain rate amplification effect to determine the cluster size distribution in polymer nanocomposites. The dispersion exponents of nanoparticles from this rheological method are in good agreement with the cluster analysis of transmission electron microscope (TEM) images. We also obtain a critical value of the dispersion exponent from the effective specific surface area of clusters, which separates the well-dispersed state and the phase-separated state...
May 25, 2017: Soft Matter
S V Kredentser, M M Kulyk, V M Kalita, K Y Slyusarenko, V Yu Reshetnyak, Yu A Reznikov
Here we report a study of chain formation and the magnetic anisotropy induced by them in suspensions of slightly anisotropic Fe3O4 nanoparticles in water and in aqueous V2O5 suspensions. An investigation into the magnetization of the fluid and frozen suspensions, the application of dynamic light scattering techniques and the observation of the magnetic anisotropy in the frozen magnetically aligned samples allowed us to confirm the existence of chains of Fe3O4 in both suspensions. Our study shows that the magneto-induced anisotropy appearing in magnetic fields in colloids with Fe3O4 particles is mainly due to many particle (chain) magneto-induced anisotropy, but not due to single particle magneto-induced anisotropy connected with particle shape anisotropy...
May 24, 2017: Soft Matter
Xiao-Jun Kuang, Ali Wajahat, Wei-Tao Gong, Manivannan Kalavathi Dhinakaran, Xiao-Han Li, Gui-Ling Ning
A novel C3-symmetric benzene-1,3,5-tricarboxamide (BTAs) decorated with three identical pillar[5]arene tails was designed, synthesized and characterized. The compound can gelate acetonitrile at low concentration (0.2 wt%) upon sonication at room temperature, but a precipitate was obtained by a conventional heating-cooling process. Scanning electron microscopy revealed that the gel and precipitate were constructed by entangled, high-aspect-ratio flexible bundles of nanofibrils. UV-vis spectroscopy, circular dichroism, Fourier transform infrared microscopy and powder X-ray diffraction showed that the compound formed chiral, elongated, columnar aggregates with nanofiber morphology by a combination of intermolecular hydrogen bonding between the N-H and C[double bond, length as m-dash]O of amides, π-π stacking (H-aggregates) and hydrophobic interactions of peripheral groups...
May 24, 2017: Soft Matter
Ting Su, Kwon Ho Hong, Wannian Zhang, Fei Li, Qiang Li, Fang Yu, Genxiang Luo, Honghe Gao, Yu-Peng He
A series of phthalic acid derivatives (P) with a carbon-chain tail was designed and synthesized as single-component gelators. A combination of the single-component gelator P and a non-gelling additive n-alkylamine A through acid-base interaction brought about a series of novel phase-selective two-component gelators PA. The gelation capabilities of P and PA, and the structural, morphological, thermo-dynamic and rheological properties of the corresponding gels were investigated. A molecular dynamics simulation showed that the H-bonding network in PA formed between the NH of A and the carbonyl oxygen of P altered the assembly process of gelator P...
May 24, 2017: Soft Matter
Scott C Grindy, Niels Holten-Andersen
Control over the viscoelastic mechanical properties of hydrogels intended for use as biomedical materials has long been a goal of soft matter scientists. Recent research has shown that materials made from polymers with reversibly associating transient crosslinks are a promising strategy for controlling viscoelasticity in hydrogels, for example leading to systems with precisely tunable mechanical energy-dissipation. We and others have shown that bio-inspired histidine:transition metal ion complexes allow highly precise and tunable control over the viscoelastic properties of transient network hydrogels...
May 23, 2017: Soft Matter
Koki Imamura, Hiroyuki Yoshida, Masanori Ozaki
Liquid crystal (LC) micro-particles are functional materials possessing anisotropies of LCs originating from their inner molecular alignment, and are fabricated by polymerizing pre-aligned rod-like molecules in the LC state. Here we demonstrate field strength and frequency tunable two-way rotation control of LC micro-particles in a LC host, and unravel its mechanism by theoretically calculating the contributing free energies. Cuboid-shaped micro-particles with inner molecular alignment along the long axis are fabricated via two-photon excited direct laser writing, and dispersed in a dual-frequency (DF) LC to be electrically driven by a voltage applied in the in-plane direction of the cell...
May 22, 2017: Soft Matter
Mahati Chintapalli, Ksenia Timachova, Kevin R Olson, Michał Banaszak, Jacob L Thelen, Sue J Mecham, Joseph M DeSimone, Nitash P Balsara
Incipient microphase separation is observed by wide angle X-ray scattering (WAXS) in short chain multiblock copolymers consisting of perfluoropolyether (PFPE) and poly(ethylene oxide) (PEO) segments. Two PFPE-PEO block copolymers were studied; one with dihydroxyl end groups and one with dimethyl carbonate end groups. Despite having a low degree of polymerization (N ∼ 10), these materials exhibited significant scattering intensity, due to disordered concentration fluctuations between their PFPE-rich and PEO-rich domains...
May 18, 2017: Soft Matter
Timothy Ibru, Kyriaki Kalaitzidou, J Kevin Baldwin, Antonia Antoniou
Existing analyses predict that thin metal films deposited on compliant substrates are subject to a variety of surface instabilities, such as wrinkles, folds, creases, etc., that become more prominent with increased compressive residual stress. Under compressive stress, cracks have been assumed to form only when the interfacial strength is weak, allowing the film to detach from the substrate. In this work, we demonstrate that cracks also form on surfaces under compressive mismatch strain when the interface is strong...
May 18, 2017: Soft Matter
G Prabhudesai, I Bihi, F Zoueshtiagh, J Jose, M Baudoin
In this paper, we study the dynamics of cylindrical armoured bubbles excited by mechanical vibrations. A step by step transition from cylindrical to spherical shape is reported as the intensity of the vibration is increased, leading to a reduction of the bubble surface and a dissemination of the excess particles. We demonstrate through energy balance that nonspherical armoured bubbles constitute a metastable state. The vibration instills the activation energy necessary for the bubble to return to its least energetic stable state: a spherical armoured bubble...
May 18, 2017: Soft Matter
Kai Zhang, Chin-Chang Kuo, Nathaniel See, Corey O'Hern, Michael Dennin
Key features of the mechanical response of amorphous particulate materials, such as foams, emulsions, and granular media, to applied stress are determined by the frequency and size of particle rearrangements that occur as the system transitions from one mechanically stable state to another. This work describes coordinated experimental and computational studies of bubble rafts, which are quasi-two dimensional systems of bubbles confined to the air-water interface. We focus on small mechanically stable clusters of four, five, six, and seven bubbles with two different sizes with diameter ratio σL/σS ≃ 1...
May 17, 2017: Soft Matter
Lizeth Perez, Magi Mettry, Samuel S Hinman, Samantha R Byers, Kristy S McKeating, Bethany G Caulkins, Quan Cheng, Richard J Hooley
Self-folding deep cavitands with variably functionalized upper rims are able to selectively immobilize proteins at a biomimetic supported lipid bilayer surface. The immobilization process takes advantage of the dual-mode binding capabilities of the hosts, combining a defined binding pocket with upper rim charged/H-bonding groups. A variety of proteins can be selectively immobilized at the bilayer interface, either via complementary charge/H-bonding interactions, cavity-based molecular recognition, or a combination of both...
May 17, 2017: Soft Matter
Fabien Gerbal, Yuan Wang, Olivier Sandre, Fabien Montel, Jean-Claude Bacri
The usage of micro or nanorods is steadily increasing in various applications from fundamental research to industry. Therefore their geometrical, mechanical and eventually magnetic properties need to be well determined. Here, using an optical microscope equipped with magnetic tweezers, we report an experimental procedure to obtain all those information on a single magnetic rod. In particular, we measure magnetic susceptibility χ by analyzing the deformation of a rod subjected to a uniform magnetic field. To do so, we refine a theoretical model which takes into account the variation of χ with the internal field...
May 17, 2017: Soft Matter
Mehdi Habibi, Mokhtar Adda-Bedia, Daniel Bonn
While simple at first glance, the dense packing of sheets is a complex phenomenon that depends on material parameters and the packing protocol. We study the effect of plasticity on the crumpling of sheets of different materials by performing isotropic compaction experiments on sheets of different sizes and elasto-plastic properties. First, we quantify the material properties using a dimensionless foldability index. Then, the compaction force required to crumple a sheet into a ball as well as the average number of layers inside the ball are measured...
May 17, 2017: Soft Matter
Giulia Marafon, Ileana Menegazzo, Marta De Zotti, Marco Crisma, Claudio Toniolo, Alessandro Moretto
Two appropriately functionalized nucleobases, thymine and adenine, have been covalently linked at the N- and C-termini, respectively, of two α-aminoisobutyric acid-rich helical peptide foldamers, aiming at driving self-assembly through complementary recognition. A crystal-state analysis (by X-ray diffraction) on the shorter, achiral foldamer 1 unambiguously shows that adeninethymine base pairing, through Watson-Crick intermolecular H-bonding, does take place between either end of each peptide molecule. In the crystals, π-stacking between base pairs is also observed...
May 16, 2017: Soft Matter
K Nickmans, Ph Leclère, J Lub, D J Broer, A P H J Schenning
Oligo(dimethylsiloxane)-based reactive mesogens were prepared and shown to form room-temperature smectic phases which were 'frozen-in' by photopolymerization. Homeotropically aligned, nanostructured thin films were obtained by spincoating, and micropatterning was demonstrated. These hybrid reactive mesogens are suitable for the preparation of aligned nanostructured polymer thin films with potential applications ranging from stimuli responsive coatings to nanoporous membranes.
May 15, 2017: Soft Matter
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