Coarse-Grained Description of a Brush−Melt Interface in Equilibrium and under Flow

Pastorino, Claudio; Binder, Kurt; Müller, Marcus

doi:10.1021/ma8015757

Cited by 53 publications

(89 citation statements)

References 59 publications

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“…It has been a widespread practice to define the brush height, h , from the first moment of the total segment density profile [26,51,52] …”

Section: Resultsmentioning

confidence: 99%

“…Moreover, usually the height of the brush, as well as the surface density of tethered chains were scaled by the radius of gyration (or by some powers of the radius of gyration) of the chain molecules, cf. [26,32,48,51,52]. Unfortunately, the value of the radius of gyration cannot be self-consistently obtained within the framework of the considered approach.…”

Section: Resultsmentioning

confidence: 99%

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Changes in the structure of tethered chain molecules as predicted by density functional approach

Borówko¹,

Patrykiejew²,

Pizio³

et al. 2011

Condens. Matter Phys.

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We use a version of the density functional theory to study the changes in the height of the tethered layer of chains built of jointed spherical segments with the change of the length and surface density of chains. For the model in which the interactions between segments and solvent molecules are the same as between solvent molecules we have discovered two effects that have not been observed in previous studies. Under certain conditions and for low surface concentrations of the chains, the height of the pinned layer may attain a minimum. Moreover, for some systems we observe that when the temperature increases, the height of the layer of chains may decrease.

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“…It has been a widespread practice to define the brush height, h , from the first moment of the total segment density profile [26,51,52] …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Changes in the structure of tethered chain molecules as predicted by density functional approach

Borówko¹,

Patrykiejew²,

Pizio³

et al. 2011

Condens. Matter Phys.

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“…The extent of slip is dependent on the penetration length of the matrix chains into the flat brush region 48,55 (in our case the PGNP particles). In fact the WH model 49 suggests that slip becomes relevant in determining the intrinsic viscosity provided the width of the PGNPpolymer interface is smaller.…”

Section: 49mentioning

confidence: 99%

Anomalous Viscosity Reduction and Hydrodynamic Interactions of Polymeric Nanocolloids in Polymers

et al. 2015

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One of the central dogma of fluid physics is the no-slip boundary condition whose validity has come under scrutiny, especially in the fields of micro and nanofluidics.Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective viscosity experienced by polymeric nano colloids moving through a highly viscous and confined polymer, well above its glass transition temperature. The extent of reduction in effective interface viscosity increases with decreasing temperature and polymer film thickness. Concomitant with the reduction in effective viscosity we also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these colloids with an anomalous power law * To whom correspondence should be addressed † Indian Institute of Science ‡ Albert-Ludwig-University of Freiburg ¶ Deutsches Elektronen Synchrotron DESY 1 exponent of ∼ 2 at the lowest temperatures and film thickness studied. Such strong hydrodynamic interactions are not expected for polymeric colloidal motion in polymer melts. We suggest hydrodynamics, especially slip present at the colloid-polymer interface which determines the observed reduction in interface viscosity and presence of strong hydrodynamic interactions.

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“…The behaviour is similar for all bending rigidities: the chains elongate in the z direction upon increasing ρ g , due to excluded volume interactions, as reported in Refs. [18,19] for brushes composed of fully flexible chains. This effect is less pronounced for the more rigid chains (k b = 8ε) and barely noticeable for the stiffest case (k b = 80ε), due to the finite extension reachable by the chains.…”

Section: A Static Propertiesmentioning

confidence: 99%

“…However, the vast majority of work was devoted to fully flexible polymer chains. Computer simulation of coarse-grained systems studied friction of bearing brushes [14][15][16][17] and the flow of simple liquids or polymer melts confined in brush-coated polymer channels as function of grafting density, interface properties and flow intensity [18][19][20][21][22]. Milchev and Binder studied the structure of brushes formed by semiflexible chains by Monte Carlo and molecular dynamics simulations [23].…”

Section: Introductionmentioning

confidence: 99%

Brushes of semiflexible polymers in equilibrium and under flow in a super-hydrophobic regime

Speyer

Pastorino

2015

Soft Matter

Self Cite

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We performed molecular dynamics simulations to study equilibrium and flow properties of a liquid in a nano-channel with confining surfaces coated with a layer of grafted semiflexible polymers. The coverage spans a wide range of grafting densities from essentially isolated chains to dense brushes. The end-grafted polymers were described by a bead spring model with an harmonic potential to include the bond stiffness of the chains. We varied the rigidity of the chains, from fully flexible polymers to rigid rods, in which the configurational entropy of the chains is negligible. The brushliquid interaction was tuned to obtain a super-hydrophobic channel, in which the liquid did not penetrate the polymer brush, giving rise to a Cassie-Baxter state. Equilibrium properties such us brush height and bending energy were measured, varying the grafting density and the stiffness of the polymers. We studied also the characteristics of the brush-liquid interface and the morphology of the polymers chains supporting the liquid for different bending rigidities. Non-equilibrium simulations were performed, moving the walls of the channel in opposite directions at constant speed, obtaining a Couette velocity profile in the bulk liquid. The molecular degrees of freedom of the polymers were studied as a function of the Weissenberg number. Also, the violation of the no-slip boundary condition and the slip properties were analyzed as a function of the shear rate, grafting density and bending stiffness. At high grafting densities, a finite slip length independent of the shear rate or bending constant was found, while at low grafting densities a very interesting non-monotonic behaviour on the bending constant is observed.

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Coarse-Grained Description of a Brush−Melt Interface in Equilibrium and under Flow

Cited by 53 publications

References 59 publications

Changes in the structure of tethered chain molecules as predicted by density functional approach

Changes in the structure of tethered chain molecules as predicted by density functional approach

Anomalous Viscosity Reduction and Hydrodynamic Interactions of Polymeric Nanocolloids in Polymers

Brushes of semiflexible polymers in equilibrium and under flow in a super-hydrophobic regime

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