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Spreading dynamics of chain-like monolayers: a molecular dynamics study
E Bertrand1, T D Blake, J De Coninck
1Centre for Research in Molecular Modelling, University of Mons-Hainaut, Parc Initialis, Av. Copernic, 1, 7000 Mons, Belgium. emilie.bertrand@crmm.umh.ac.be
Langmuir : the ACS Journal of Surfaces and Colloids
|June 29, 2005
Summary
We extended molecular-kinetic theory to model Langmuir-Blodgett monolayer spreading dynamics. Simulations show lateral pressure drives spreading, with rates dependent on pressure and molecular displacement frequency.
Area of Science:
- Surface science
- Materials science
- Physical chemistry
Background:
- Dynamic wetting of sessile drops is well-described by molecular-kinetic theory.
- Extending this theory to complex systems like monolayers is a significant challenge.
Purpose of the Study:
- To adapt and apply the molecular-kinetic theory of dynamic wetting to Langmuir-Blodgett monolayers.
- To investigate the fundamental mechanisms governing monolayer spreading dynamics.
Main Methods:
- Utilized large-scale molecular dynamics simulations.
- Employed a simplified version of the Karaborni and Toxvaerd monolayer model.
- Analyzed spreading rates under varying pressure conditions.
Main Results:
- Preliminary simulation results align with experimental observations.
- Identified lateral pressure as the primary driving force for monolayer spreading.
- Observed distinct spreading regimes: constant logarithmic dependence on pressure away from equilibrium and pseudo-diffusive, square-root-of-time behavior near equilibrium.
Conclusions:
- The molecular-kinetic theory provides a valid framework for understanding Langmuir-Blodgett monolayer spreading.
- Spreading dynamics are controlled by the equilibrium frequency of molecular displacements within the monolayer.
- This approach offers insights into the physical chemistry of thin films and interfacial phenomena.