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The entropic cost of polymer confinement
Mark R Smyda1, Stephen C Harvey
1School of Biology, Georgia Institute of Technology, Atlanta Georgia 30332, United States.
The Journal of Physical Chemistry. B
|August 22, 2012
Summary
Confinement of polymers to small spaces incurs an entropic penalty, increasing with reduced space. Finite chain diameter significantly alters this penalty, especially in narrow geometries and closed cavities.
Area of Science:
- Polymer physics
- Thermodynamics
- Statistical mechanics
Background:
- Polymer confinement in small spaces is thermodynamically unfavorable due to reduced conformational states.
- This entropic penalty impacts biological processes, polymer transport, and microfluidic devices.
Purpose of the Study:
- To determine the entropic penalty for confining elastic polymers in various geometries.
- To investigate the effects of chain diameter (volume exclusion) on confinement penalties.
Main Methods:
- Theoretical analysis of polymer confinement in slits, tubes, and spheres.
- Examination of ideal chains and chains with finite diameter.
- Analysis in both strong (d/P << 1) and weak (d/P >> 1) confinement regimes.
Main Results:
- Entropic penalty increases significantly as confinement space (d) decreases relative to polymer persistence length (P).
- Confinement in a tube shows a penalty twice that in a slit.
- Finite chain diameter increases entropic penalties, especially in narrow geometries and closed cavities.
Conclusions:
- The entropic penalty for polymer confinement is geometry-dependent and scales with confinement dimensions.
- Volume exclusion effects are crucial, leading to higher penalties than predicted for ideal chains.
- Entropic penalties can become infinitely large for finite chains in closed cavities exceeding chain volume.
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