Polymer-mediated entropic forces between scale-free objects
Name
Maghrebi-2012-Polymer-mediated entropic forces between scale-free objects.pdf
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Author(s)
Faghfoor Maghrebi, Mohammad
Kantor, Yacov
Kardar, Mehran
Date Issued
December 2012
Journal
Physical Review E
Publisher
American Physical Society
Citation
Maghrebi, Mohammad F., Yacov Kantor, and Mehran Kardar. “Polymer-mediated Entropic Forces Between Scale-free Objects.” Physical Review E 86.6 (2012). ©2012 American Physical Society
Version
Final published version
Abstract
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 R[subscript 0] 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≪R[subscript 0], separation is the only remaining relevant scale and the entropic force must take the form F=Ak[subscript B]T/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 ε-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 self-avoiding polymers. The entropic force is of the order of 0.1 pN at 0.1 μm for a single polymer and can be increased for a star polymer.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1103/PhysRevE.86.061801
