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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.

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Presentation on theme: "Computer simulations of amphiphilic worms and bi-layers. Molecular dynamics simulations Coarse amphiphiles Worms Bi-layers [polymer melts]. W.J. Briels."— Presentation transcript:

1 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

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

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

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

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

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

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

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

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

10 Free energy i)Tension ii)Bending fluctuations

11 Elastic modulus

12 Bending fluctuations

13 Simulating an entanglement

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

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

16 Tension relaxation merging ‘chromosoming’

17 Merging

18 Relaxing

19 backbone 270 amphiphiles; tail 90 amphphiles Eating

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

21 Shear thinning str ess Shear rate Shear thinning by merging and alignment

22 Shear banding of micellar worms

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

24 Amphiphilic bilayer (membrane) 1152 amphiphiles solvent

25 Bi-layer free energy Helfrich

26 Pore

27 Punctured bi-layer free energy

28 Stable states

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

30 Finite size scaling

31 Radius versus stretch

32 Tension versus radius

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

34 Polymer melt C 120 H 242

35 Equations of Motion Langevin equation

36 Coarse model from atomistic simulation Friction Potential of mean force

37 Entanglements

38 Results-diffusion coefficients

39 Results-viscosities

40 Thank you !! Brrrrrrr


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