Molecular Dynamics Simulations of the Force between a Polymer Brush and an AFM Tip

Murat, M.; Grest, Gary S.

doi:10.1021/ma961267e

Cited by 48 publications

(67 citation statements)

References 9 publications

(25 reference statements)

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“…Theory and simulations showed that the polymer chains partially avoid compression by escaping from underneath the AFM tip [838][839][840][841]. This escaping of chains is not only effective in the mushroom regime [842] but also in the brush regime [843].…”

Section: Steric Forcesmentioning

confidence: 98%

Force measurements with the atomic force microscope: Technique, interpretation and applications

Butt

Cappella

Kappl

2005

Surface Science Reports

3,187

2,949

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Section: Steric Forcesmentioning

confidence: 98%

Force measurements with the atomic force microscope: Technique, interpretation and applications

Butt

Cappella

Kappl

2005

Surface Science Reports

3,187

2,949

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“…This leads to A = η cp − η p , as opposed to A = η cp − η c for the case that the polymer is attached to the cone. There are a number of detailed studies of small surfaces (such as AFM tips) [35][36][37][38][39][40][41] compressing a single polymer (or few polymers) grafted to a surface. However, all these studies concern non-scale invariant geometries.…”

Section: Polymer-mediated Forcesmentioning

confidence: 99%

Polymer-mediated entropic forces between scale-free objects

2012

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The number of configurations of a polymer is reduced in the presence of a barrier or an obstacle. The resulting loss of entropy adds a repulsive component to other forces generated by interaction potentials. When the obstructions are scale invariant shapes (such as cones, wedges, lines or planes) the only relevant length scales are the polymer size R0 and characteristic separations, severely constraining the functional form of entropic forces. Specifically, we consider a polymer (single strand or star) attached to the tip of a cone, at a separation h from a surface (or another cone). At close proximity, such that h ≪ R0, separation is the only remaining relevant scale and the entropic force must take the form F = A kBT /h. The amplitude A is universal, and can be related to exponents η governing the anomalous scaling of polymer correlations in the presence of obstacles. We use analytical, numerical and ǫ-expansion techniques to compute the exponent η for a polymer attached to the tip of the cone (with or without an additional plate or cone) for ideal and selfavoiding polymers. The entropic force is of the order of 0.1pN at 0.1µm for a single polymer, and can be increased for a star polymer.

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“…The simulation 18 and theory 19 [20][21][22][23] There are only a few simulation studies of the force or free energy of interaction between grafted polymer layers. 24,25 These simulations were performed for athermal systems in vacuum under good ͑implicit͒ solvent conditions. We know of no force calculations for grafted chains under theta or poor solvent conditions, or in an explicit solvent, which are necessary to model colloids realistically in liquids and supercritical fluids.…”

Section: Introductionmentioning

confidence: 99%

“…Forces between surfaces are then calculated in vacuum, and compared to previous results. 24 These simulations provide a reference for the next section which addresses the effects of explicit solvent. For systems containing explicit solvent, forces are presented at a series of temperatures and densities spanning the good to poor solvent regimes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of structure and interaction forces for surfaces coated with grafted chains in a compressible solvent

Meredith

Sánchez

Johnston

et al. 1998

The Journal of Chemical Physics

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Lennard-Jones chains grafted to solid surfaces in a supercritical solvent are simulated with a continuum grand canonical Monte Carlo method. The force of interaction between two surfaces is calculated as a function of solvent density and temperature and analyzed as a function of the conformational properties of the grafted chains. At high, liquidlike bulk solvent densities, the chains are solvated and the interaction forces are repulsive. As the solvent density is lowered, the chains collapse, and the surfaces become attractive, indicating flocculation. The critical flocculation density coincides with the critical solution density for a bulk mixture of chains and solvent ͑corrected for local density enhancement͒. The bulk critical solution density, in turn, corresponds to the coil-to-globule transition of a single chain in bulk solution. The predicted correspondence between these properties agrees with results from lattice-fluid self-consistent field theory and colloid stability experiments. In good and poor solvents, the range of the interaction force between surfaces is much longer than the length of the grafted chains, due to expulsion of solvent from the interface as the surfaces are compressed. Very similar ranges were seen for forces measured with the surface forces apparatus in liquid solvent ͓G. Hadziioannou et al., J. Am. Chem. Soc. 108, 2869 ͑1986͔͒.

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Molecular Dynamics Simulations of the Force between a Polymer Brush and an AFM Tip

Cited by 48 publications

References 9 publications

Force measurements with the atomic force microscope: Technique, interpretation and applications

Force measurements with the atomic force microscope: Technique, interpretation and applications

Polymer-mediated entropic forces between scale-free objects

Simulation of structure and interaction forces for surfaces coated with grafted chains in a compressible solvent

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