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Computer simulations of amphiphilic worms and bi-layers.
Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts]. W.J. Briels W.K. den Otter
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Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
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Molecular dynamics simulations (N,V,U)
Classical mechanics ii) Periodic boundary conditions iii) N,V,U
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Molecular dynamics simulations (N,V,T)
system Thermostat i) Temperature ii) Thermostat Velocity scaling Langevin thermostat
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Molecular dynamics simulations
Measure: No Free energies, entropies, … Yes Energy, pressure Averages (e.g. structural properties) Free energy differences
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Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
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Simulation Models Bi-layer amphiphile Worm amphiphile Water
R.Goetz and R.Lipowsky, J.Chem.Phys. 108, 7397 (1998)
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Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
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Cylindrical micelle (worm)
W.K. den Otter, S.A. Shkulipa and W.J. Briels, J. Chem. Phys. 119, 2363 (2003)
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Free energy Tension Bending fluctuations
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Elastic modulus
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Bending fluctuations
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Simulating an entanglement
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Entangled worm 840 amphiphiles 45800 solvent
Twisted PBC: M.P. Allen and A.J. Masters, Mol. Phys. 79, 277 (1993)
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Entanglement under tension
WJB, P. Mulder and WKdO, J. Phys.: Condens. Matter. 16, S3965 (2004)
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Tension relaxation merging ‘chromosoming’
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Merging
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Relaxing
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Eating backbone 270 amphiphiles; tail 90 amphphiles
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Consequences Shear thickening near overlap concentration.
Shear thinning at large shear-rates by aligning of worms in flow direction.
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Shear thinning stress Shear rate
Shear thinning by merging and alignment
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Shear banding of micellar worms
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Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
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Amphiphilic bilayer (membrane)
1152 amphiphiles solvent
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Bi-layer free energy Helfrich
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Pore
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Punctured bi-layer free energy
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Stable states
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Radius versus stretch T.V. Tolpekina, WKdO and WJB, J. Chem. Phys. (Oct. 2004)
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Finite size scaling
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Radius versus stretch 1152 288
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Tension versus radius
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Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
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Polymer melt C120H242
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Equations of Motion Langevin equation
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Coarse model from atomistic simulation
Potential of mean force Friction
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Entanglements
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Results-diffusion coefficients
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Results-viscosities
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Thank you !! Brrrrrrr
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