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

Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts].

Molecular dynamics simulations (N,V,U) Classical mechanics ii) Periodic boundary conditions iii) N,V,U

Molecular dynamics simulations (N,V,T) system Thermostat i) Temperature ii) Thermostat Velocity scaling Langevin thermostat

Molecular dynamics simulations Measure: No Free energies, entropies, … Yes Energy, pressure Averages (e.g. structural properties) Free energy differences

Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts].

Simulation Models Bi-layer amphiphile Worm amphiphile Water R.Goetz and R.Lipowsky, J.Chem.Phys. 108, 7397 (1998)

Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts].

Cylindrical micelle (worm) W.K. den Otter, S.A. Shkulipa and W.J. Briels, J. Chem. Phys. 119, 2363 (2003)

Free energy Tension Bending fluctuations

Elastic modulus

Bending fluctuations

Simulating an entanglement

Entangled worm 840 amphiphiles 45800 solvent Twisted PBC: M.P. Allen and A.J. Masters, Mol. Phys. 79, 277 (1993)

Entanglement under tension WJB, P. Mulder and WKdO, J. Phys.: Condens. Matter. 16, S3965 (2004)

Tension relaxation merging ‘chromosoming’

Merging

Relaxing

Eating backbone 270 amphiphiles; tail 90 amphphiles

Consequences Shear thickening near overlap concentration. Shear thinning at large shear-rates by aligning of worms in flow direction.

Shear thinning stress Shear rate Shear thinning by merging and alignment

Shear banding of micellar worms

Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts].

Amphiphilic bilayer (membrane) 1152 amphiphiles 16740 solvent

Bi-layer free energy Helfrich

Pore

Punctured bi-layer free energy

Stable states

Radius versus stretch T.V. Tolpekina, WKdO and WJB, J. Chem. Phys. (Oct. 2004)

Finite size scaling

Radius versus stretch 1152 288

Tension versus radius

Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts].

Polymer melt C120H242

Equations of Motion Langevin equation

Coarse model from atomistic simulation Potential of mean force Friction

Entanglements

Results-diffusion coefficients

Results-viscosities

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