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Mutable polyelectrolyte tube arrays: mesoscale modeling and lateral force microscopy
Journal article

Mutable polyelectrolyte tube arrays: mesoscale modeling and lateral force microscopy

Steven W. Cranford, Lin Han, Christine Ortiz and Markus J. Buehler
Soft matter, v 13(33), pp 5543-5557
04 Sep 2017
PMID: 28731083

Abstract

Chemistry Chemistry, Physical Materials Science Materials Science, Multidisciplinary Physical Sciences Physics Physics, Multidisciplinary Polymer Science Science & Technology Technology
In this study, the pH-dependent friction of layer-by-layer assemblies of poly(allylamine hydrochloride) and poly(acrylic acid) (PAH/PAA) are quantified for microtube array structures via experimental and simulated lateral force microscopy (LFM). A novel coarse-grain tube model is developed, utilizing a molecular dynamics (MD) framework with a Hertzian soft contact potential (such that F similar to delta(3/2)) to allow the efficient dynamic simulation of 3D arrays consisting of hundreds of tubes at micrometer length scales. By quantitatively comparing experimental LFM and computational results, the coupling between geometry (tube spacing and swelling) and material properties (intrinsic stiffness) results in a transition from bending dominated deformation to bending combined with inter-tube contact, independent of material adhesion assumptions. Variation of tube spacing (and thus control of contact) can be used to exploit the normal and lateral resistance of the tube arrays as a function of pH (2.0/5.5), beyond the effect of areal tube density, with increased resistances (potential mutability) up to a factor of similar to 60. This study provides a novel modeling platform to assess and design dynamic polyelectrolyte-based substrates/coatings with tailorable stimulus-responsive surface friction. Our results show that microgeometry can be used alongside stimulus-responsive material changes to amplify and systematically tune mutability.

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Web of Science research areas
Chemistry, Physical
Materials Science, Multidisciplinary
Physics, Multidisciplinary
Polymer Science
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