How does a flexible chain of active particles swell?
Andreas Kaiser1, Sonja Babel1, Borge ten Hagen1
1Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
The Journal of Chemical Physics
|April 3, 2015
Summary
Active polymer chains swell differently depending on their environment. Self-propulsion affects chain extension but not the fundamental Flory exponent, acting like a higher effective temperature.
Area of Science:
- Polymer Physics
- Soft Matter Physics
- Statistical Mechanics
Background:
- Understanding polymer chain behavior is crucial in soft matter physics.
- Active matter systems, composed of self-propelled particles, exhibit unique properties distinct from equilibrium systems.
- The swelling of polymer chains is a fundamental characteristic influenced by internal forces and external constraints.
Purpose of the Study:
- To investigate the swelling behavior of flexible linear polymer chains composed of active particles.
- To analyze how self-propulsion influences chain extension in different environments: free, harmonically confined, and pulled.
- To compare analytical predictions with computer simulation results, considering both ideal chains and those with excluded volume interactions.
Main Methods:
- Generalized the Rouse model for polymers to include self-propelled monomers, solved analytically.
- Employed computer simulations to study the effect of self-avoidance (excluded volume) on active polymer swelling.
- Characterized swelling using the spatial extension of the chain and calculated the Flory exponent (ν).
Main Results:
- For ideal chains, activity did not alter the Flory exponent (ν=1/2, 0, 1 for the three cases) but affected the scaling prefactor, mimicking higher effective temperatures.
- With self-avoidance, the Flory exponent remained unchanged by self-propulsion (ν=3/4, 1/4, 1 for the three cases).
- Chain extension showed non-monotonic behavior with increasing self-propulsion strength when self-avoidance was considered.
Conclusions:
- Self-propulsion in flexible linear chains influences swelling primarily by modifying the effective temperature, not the fundamental scaling exponent.
- The presence of excluded volume interactions does not change the Flory exponent's dependence on self-propulsion.
- The non-monotonic dependence of chain extension on self-propulsion strength in simulations warrants further investigation into the underlying mechanisms.
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