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Elasticity of a Grafted Rod-like Filament with Fluctuating Bending Stiffness
Mohammadhosein Razbin1, Panayotis Benetatos2
1Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran 14588, Iran.
Polymers
|May 27, 2023
Summary
Polymers fluctuating between two states exhibit distinct elastic properties in different statistical ensembles. This study analyzes a semiflexible filament, revealing potential negative compressibility, a key finding for polymer elasticity research.
Area of Science:
- Polymer Physics
- Soft Matter Physics
- Statistical Mechanics
Background:
- Polymers often display varying elastic behavior based on statistical ensembles (Gibbs vs. Helmholtz) due to strong fluctuations.
- Two-state polymers, fluctuating between microstates, can show ensemble inequivalence and negative elastic moduli in the Helmholtz ensemble.
- Previous work predicted this for flexible polymers and reversible wormlike chains (rWLC); this study extends it to semiflexible filaments.
Purpose of the Study:
- To theoretically analyze the elasticity of a grafted rod-like semiflexible filament that fluctuates between two bending stiffness states.
- To investigate the response to a point force at the fluctuating tip in both Gibbs and Helmholtz ensembles.
- To calculate the entropic force on a confining wall and identify conditions for negative compressibility.
Main Methods:
- Theoretical analysis of a grafted semiflexible filament with two-state bending stiffness.
- Ensemble calculations (Gibbs and Helmholtz) for elastic response to a point force.
- Calculation of entropic forces in the Helmholtz ensemble.
Main Results:
- The study confirms ensemble inequivalence in the elasticity of two-state semiflexible filaments.
- Negative elastic moduli, including negative compressibility, are predicted under specific conditions.
- The theoretical framework applies to both two-state homopolymers and two-block copolymers.
Conclusions:
- Fluctuations between bending stiffness states significantly impact polymer elasticity and ensemble dependence.
- The findings offer insights into systems like grafted DNA, carbon nanorods, and F-actin bundles.
- Negative compressibility is a notable consequence of two-state fluctuations in semiflexible polymers.
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