Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Simon A. Rogers, M. Paul Lettinga; A sequence of physical processes determined quantified in large-amplitude oscillatory shear (LAOS): Application to theoretical nonlinear models. Journal Rheology 1 January 2012; 56 (1): 1–25. https://doi.org/10.1122/1.3662962 Download citation file: Ris (Zotero) Reference...

Abstract When a liquid crystal forming particles are confined to spatial volume with dimensions comparable that of their own size, they face complex trade-off between global tendency align and the local constraints imposed by boundary conditions. This interplay may lead non-trivial orientational patterns strongly depend on geometry confining volume. novel regime crystalline behavior can be probed colloidal macro-aggregates biomolecules. Here we study director fields filamentous fd -viruses...

We theoretically and experimentally study nematic liquid crystal equilibria within shallow rectangular wells. model the wells a two-dimensional Oseen-Frank framework, with strong tangent anchoring, obtain explicit analytical expressions for director fields energies of 'diagonal' 'rotated' solutions reported in literature. These separate leading-order defect from bulk distortion energy both families solutions. The continuum is complemented by microscopic mean-field approach. numerically...

We report the direct visualization at scale of single particles mass transport between smectic layers, also called permeation, in a suspension rodlike viruses. Self-diffusion takes place preferentially direction normal to and occurs by quasiquantized steps one rod length. The diffusion rate corresponds with calculated from nematic state lamellar periodic ordering potential that is obtained experimentally.

The effect of shear flow on the isotropic-nematic phase transition attractive colloidal rods is investigated by a combination simulations and experiments. isotropic aligns with flow, while nematic undergoes collective rotational motion which frustrates merging coexisting regions. location binodals, spinodals, tumbling-to-aligning line in shear-rate versus concentration plane are investigated. diagrams shear-concentration for various strengths attractions can be mapped onto master curve...

The interplay between shear band (SB) formation and boundary conditions (BC) is investigated in wormlike micellar systems (CPyCl-NaSal) using ultrasonic velocimetry coupled to standard rheology Couette geometry. Time-resolved velocity profiles are recorded during transient strain-controlled experiments smooth sandblasted geometries. For stick BC SB observed, although depending on the degree of entanglement temporal fluctuations reported highly sheared band. slip wall occurs only for rates...

When liquid crystals are confined to finite volumes, the competition between surface anchoring imposed by boundaries and intrinsic orientational symmetry-breaking of these materials gives rise a host intriguing phenomena involving topological defect structures. For synthetic molecular mesogens, like ones used in liquid-crystal displays, structures independent size molecules well described continuum theories. In contrast, colloidal systems such as carbon nanotubes biopolymers have...

We measure the self-diffusion of colloidal rod-like virus {\it fd} in an isotropic and nematic phase. A low volume fraction viruses are labelled with a fluorescent dye dissolved background unlabelled rods. The trajectories individual rods visualized using fluorescence microscopy from which diffusion constant is extracted. parallel ($D_{\parallel}$) perpendicular ($D_{\perp}$) to director measured. ratio ($D_{\parallel}/D_{\perp}$) increases monotonically increasing concentration. Crossing...

In this joint experimental-theoretical work we study hydrodynamic interaction effects in dense suspensions of charged colloidal spheres. Using x-ray photon correlation spectroscopy have determined the function $H(q)$, for a varying range electrosteric repulsion. We show that $H(q)$ can be quantitatively described by means novel Stokesian dynamics simulation method Brownian spheres, and modification many-body theory developed originally Beenakker Mazur. Very importantly, explain behavior...

The behavior of a colloidal suspension rodlike fd viruses in the nematic phase, subjected to steady state and transient shear flows, is studied. monodisperse nature these rods combined with relatively small textural contribution overall stress make this suitable model system investigate effects flow on nonequilibrium phase diagram. Transient rheological experiments are used determine critical rates at which director tumbling, wagging, flow-aligning occurs. present enables us study effect rod...

We present experimental evidence of an instability in the shear flow transient networks formed by telechelic associative polymers. Velocimetry experiments show formation bands, following a complex pattern upon increasing overall rate. The chaotic nature stress response is indicative spatiotemporal fluctuations banded structure. This supported time-resolved velocimetry measurements.

We combine large-amplitude oscillatory shear (LAOS) and time-resolved small angle neutron scattering (t-SANS) measurements on the dynamic response of a dispersion surfactant worm-like micelles. By viewing as being result sequence physical processes, we observe new features system response. identify three distinct frequency regimes including high Maxwell-like, yielding, settled flow regime. For each regime molecular origins, Kuhn segment scale, stress show ability material to 'over-orient'...

According to the Stokes-Einstein-Debye (SED) relation, rotational diffusion coefficient of a colloidal tracer sphere scales with inverse solvent viscosity. Here we investigate generalization SED relation in suspensions neutral and charged host spheres. Rotational coefficients are measured dynamic light scattering phosphorescence spectroscopy, calculated including two- three-particle hydrodynamic interactions. We find that is always faster than predicted by except for large tracer/host size...

We shall discuss the following phenomena found in various colloidal systems shear flow. recently observed shear-banding suspensions of fd-virus a cylindrical cell. Small angle light scattering experiments revealed that transition is preceded by relatively fast process (minutes) nematic-to-paranematic phase separation during which inhomogeneities on micrometer length scale are formed. After formation these inhomogeneities, slow (hours) appearence shear-bands observed, have height few mm. In...

We present the non-equilibrium phase diagram of rod-like colloids (fd-viruses) under shear flow. The shear-induced displacement isotropic–nematic binodal is obtained from time resolved rheology measurements. Vorticity banding observed within biphasic region, as bounded by binodal. Here, in stationary state, regular, millimetre sized bands with mutually differing orientational order are stacked along vorticity direction. For fully nematic we determine location transition lines tumbling to...

Translational tracer diffusion of spherical macromolecules in crowded suspensions rodlike colloids is investigated. Experiments are done using several kinds tracers fd-virus suspensions. A wide range size ratios L/2a the length L rods and diameter 2a sphere covered by combining experimental methods: fluorescence correlation spectroscopy for small spheres, dynamic light scattering intermediate sized video microscopy large spheres. Fluorescence shown to measure long-time only relatively...

Vorticity banding under steady shear flow is observed in a suspension of semiflexible colloidal rods (fd virus particles) within part the paranematic-nematic biphasic region. Banding occurs uniformly throughout cell gap shear-rate interval (.gamma-, .gamma+) , which depends on fd concentration. For rates below lower-border rate .gamma- only elongation inhomogeneities, are formed due to phase separation, observed. Within small region just above upper-border .gamma+ heterogeneously. An...

The instability of polysaccharide/protein mixtures occurs because either thermodynamic incompatibility or complexation. We studied which mechanism dominated given the external conditions. Therefore effect temperature, pH, and biopolymer concentration on phase separation pectin/caseinate was investigated. At pH > 6, with spinodal decomposition observed in resulting formation water-in-water emulsions intermediate stages process. demixing rate these appearance two macroscopic phases (lower...

The synthesis and selected macroscopic properties of a new model system consisting poly(N-isopropylacrylamide) (PNIPAM)-coated rod-like fd virus particles are presented. sticky colloids can be used to study effect particle shape on gelation transition, the structure viscoelasticity isotropic nematic gels, make both open as well ordered networks. This colloids, for which strength attraction between is tunable, obtained by chemically grafting highly monodisperse with thermoresponsive polymers,...

We study the nematic phase of rodlike f d-virus particles confined to channels with wedge-structured walls. Using laser scanning confocal microscopy we observe a splay-to-bend transition at single particle level as function wedge opening angle. Lattice Boltzmann simulations reveal underlying origin and its dependence on elasticity geometry. Our combined work provides simple method estimate ratios virus offers way control position defects through confining boundary conditions.

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Naveen Krishna Reddy, Zhenkun Zhang, M. Paul Lettinga, Jan K. G. Dhont, Vermant; Probing structure in colloidal gels of thermoreversible rodlike virus particles: Rheology scattering. J. Rheol. 1 September 2012; 56 (5): 1153–1174. https://doi.org/10.1122/1.4728335 Download citation file: Ris (Zotero) Reference...

Ultrasoft colloids typically do not spontaneously crystallize, but rather vitrify, at high concentrations. Combining in situ rheo-small-angle-neutron-scattering experiments and numerical simulations we show that shear facilitates crystallization of colloidal star polymers the vicinity their glass transition. With increasing rate well beyond rheological yielding, a transition is found from an initial bcc-dominated structure to fcc-dominated one. This crystal-to-crystal accompanied by...

Complex fluids containing low concentrations of slender colloidal rods can display a high viscosity, while little flow is needed to thin the fluid. This feature makes essential constituents in industrial applications and biology. Though this behavior strongly depends on rod-length, so far no direct relation could be identified. We employ library filamentous viruses study effect rod size flexibility zero-shear viscosity shear-thinning behavior. Rheology small-angle neutron scattering data are...

Polymers and rod-like colloids (PaRC) adopt a favorable orientation under sufficiently strong flows. However, how the flow kinematics affect alignment of such nanostructures according to their extensibility remains unclear. By analyzing shear- extension-induced chemically structurally different PaRC, we show that is key determinant structural response imposed kinematics. We propose unified description effectiveness extensional flow, compared shearing at aligning PaRC extensibility. Published...