Flow-Induced Deformation and Desorption of Adsorbed Polymers

Soga, Iwao; Granick, Steve

doi:10.1021/la9800405

Cited by 22 publications

(32 citation statements)

References 28 publications

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“…It should be noted that shear-induced desorption has also been reported in prior experimental 17,[29][30][31][32][33][34][35] and theoretical [35][36][37][38][39][40][41][42][43][44][45][46][47][48] studies on neutral polymers. It is noteworthy that the experimental studies on the adsorption of both charged and neutral polymers involve multiple chains.…”

Section: Introductionsupporting

confidence: 68%

“…27,28 Furthermore, at a fixed ␥ , the desorbed chain fraction decreases with an increase in ⑀ w , which is in agreement with prior experimental observations that shear-induced desorption is less when polymer-surface attraction is strong. 31,34 Analogous to electrostatic bead-surface attraction, 27,28 non-electrostatic bead-surface attraction competes with HI-induced desorption. Above a critical shear rate ␥ c , the nonelectrostatic bead-surface attraction is overwhelmed and a chain desorbs.…”

Section: Effect Of Screeningmentioning

confidence: 99%

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Brownian dynamics simulations of polyelectrolyte adsorption in shear flow: Effects of solvent quality and charge patterning

Hoda

Kumar

2008

The Journal of Chemical Physics

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We probe the effects of solvent quality and charge patterning on polyelectrolyte adsorption in shear flow using Brownian dynamics simulations with hydrodynamic interaction (HI). The polyelectrolyte is modeled as a freely jointed bead-rod chain, and electrostatic and non-electrostatic interactions are accounted for by using screened Coulombic and Lennard-Jones potentials, respectively. In the absence of flow, the conformation of a polyelectrolyte molecule adsorbed onto a uniformly charged surface changes from flat to globular with an increase in bead-bead attraction (hydrophobicity), consistent with prior experimental observations. In the presence of flow, migration due to bead-wall HI and, as a consequence, desorption decrease with an increase in bead-bead attraction, implying that flow-induced desorption is more difficult under poor-solvent conditions. When bead-bead non-electrostatic attraction is strong, desorption can be enhanced by increasing bead-bead electrostatic repulsion. Analogous to the effect of bead-surface electrostatic attraction, an increase in the strength of bead-surface non-electrostatic attraction reduces desorption. We also study the effect of shear flow on the adsorption of a polyelectrolyte molecule onto surfaces decorated with periodic arrays of charged patches. An increase in patch periodicity increases desorption even when the effective surface charge density is kept the same. The results of this work suggest mechanisms for controlling the desorption of polyelectrolyte molecules in shear flows.

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Section: Introductionsupporting

confidence: 68%

Section: Effect Of Screeningmentioning

confidence: 99%

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow: Effects of solvent quality and charge patterning

Hoda

Kumar

2008

The Journal of Chemical Physics

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“…As a consequence, the resultant two chain architectures composed of the interfacial sublayer is analogous to those formed via polymer adsorption from a dilute solution. [33][34][35][36]43,44 In order to further understand the formation mechanism of the flattened layer, we studied the time evolution of the surface morphologies of the P2VP flattened layer by AFM. As shown in Figure 5c, we clarified that the transient P2VP flattened layer at t an = 65 h and subsequent DMF leaching also shows dimple structures with h f = 2.3 nm and ϕ p ∼75% that are nearly identical to those of the PS and PMMA quasiequilibrium flattened layers.…”

Section: Discussionmentioning

confidence: 99%

“…This overall behavior is similar to irreversible polymer adsorption from dilute solution. [33][34][35][36]43,44 However, the kinetics of the inner two-layer formation is still untouched. Here, we use three different homopolymers, polystyrene (PS), poly(2-vinylpyridine) (P2VP), and poly-(methyl methacrylate) (PMMA) as models since these polymers have similar inherent stiffness and bulk glass transition temperature (T g ), but different affinities with Si substrates.…”

Section: Introductionmentioning

confidence: 99%

Formation Mechanism of High-Density, Flattened Polymer Nanolayers Adsorbed on Planar Solids

et al. 2014

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Thermal annealing is one of the most indispensable polymer fabrication processes and plays essential roles in controlling morphologies and properties of polymeric materials. We here report that thermal annealing also facilitates polymer adsorption from the melt on planar silicon (Si) substrates, resulting in the formation of a high-density polymer nanolayer with flattened chain confirmations. Three different homopolymers (polystyrene, poly(2-vinylpyridine), and poly(methyl methacrylate)), which have similar inherent stiffness and bulk glass transition temperature (T g ), but have different affinities with Si substrates, were chosen as models. Spin-cast films (∼50 nm in thickness) with the three polymers were prepared on cleaned Si substrates and then placed in a vacuum oven set at a temperature far above the bulk T g . In order to monitor the polymer adsorption process at the solid-polymer melt interface during thermal annealing, we used the protocol that combines vitrification of the annealed films (via rapid quench to room temperature) and subsequent intensive solvent leaching (to remove nonadsorbed chains). The detailed structures of the residual films (i.e., flattened layers with 2−3 nm in thickness) were characterized by using X-ray reflectivity and atomic force microscopy. As a result, we found that the film thicknesses of the flattened layers for the three different polymers increase as a power-law of annealing time before reaching the "quasiequilibrium" state where the film growth is saturated. We have also revealed that the final thickness of the flattened layer at the quasiequilibrium state increases with increasing the solid-segment interaction, while the kinetics becomes more sluggish. The observed formation kinetics corresponds to a "zipping-down" process of the transient flattened chains on planar solids in order to further increase the number of solid/segment points, which is the driving force for flattening so as to overcome the conformational entropy loss in the total free energy.

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“…The dependence of film thickness and amount adsorbed on solvent quality and surface properties was also explored in several experiments. 11,[13][14][15] Detailed discussions of other experimental results pertaining to adsorption from flowing fluids can be found in the review by Kawaguchi and Takahashi. 16 A number of theoretical and computational studies 17-27 have attempted to develop an understanding of the experimental results discussed above.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of polymer adsorption from dilute solution in shear flow near a planar wall

Dutta

Dorfman

Kumar

2013

The Journal of Chemical Physics

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Adsorption of polymers from dilute solution subject to shear flow near a planar wall is studied using kinetic theory. A dumbbell model consisting of two beads connected by a nonlinear spring is used to describe the polymer molecules, and the beads interact with the wall via a short-range exponential potential. Bead-bead and bead-wall hydrodynamic interactions are also included in the theory. For an initially bare surface, it is found that the quantity of polymer adsorbed decreases with an increase in polymer molecular weight at a given shear rate and point in time. In addition, for a given molecular weight and point in time, the quantity adsorbed decreases with an increase in shear rate. When adsorbed polymer is initially present, similar trends are observed. Furthermore, complete desorption can be achieved at a sufficiently high shear rate. In all cases, the time required to approach a steady value of the adsorbed amount is many orders of magnitude larger than the dumbbell relaxation time. The above findings are in qualitative agreement with experimental measurements reported nearly three decades ago by Lee and Fuller [J. Colloid Interface Sci. 103, 569 (1985)]. Our findings also suggest that the physical mechanism underlying the long-standing observation that shear flow inhibits polymer adsorption and assists polymer desorption is hydrodynamic interaction between stretched polymer molecules and the adsorbing surface.

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Flow-Induced Deformation and Desorption of Adsorbed Polymers

Cited by 22 publications

References 28 publications

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow: Effects of solvent quality and charge patterning

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow: Effects of solvent quality and charge patterning

Formation Mechanism of High-Density, Flattened Polymer Nanolayers Adsorbed on Planar Solids

Dynamics of polymer adsorption from dilute solution in shear flow near a planar wall

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