Download presentation
Presentation is loading. Please wait.
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)
Classical mechanics ii) Periodic boundary conditions iii) N,V,U
4
Molecular dynamics simulations (N,V,T)
system Thermostat i) Temperature ii) Thermostat Velocity scaling Langevin thermostat
5
Molecular dynamics simulations
Measure: No Free energies, entropies, … Yes Energy, pressure Averages (e.g. structural properties) Free energy differences
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 Tension Bending fluctuations
11
Elastic modulus
12
Bending fluctuations
13
Simulating an entanglement
14
Entangled worm 840 amphiphiles 45800 solvent
Twisted PBC: M.P. Allen and A.J. Masters, Mol. Phys. 79, 277 (1993)
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
Eating backbone 270 amphiphiles; tail 90 amphphiles
20
Consequences Shear thickening near overlap concentration.
Shear thinning at large shear-rates by aligning of worms in flow direction.
21
Shear thinning stress 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 1152 288
32
Tension versus radius
33
Molecular dynamics simulations
Coarse amphiphiles Worms Bi-layers [polymer melts].
34
Polymer melt C120H242
35
Equations of Motion Langevin equation
36
Coarse model from atomistic simulation
Potential of mean force Friction
37
Entanglements
38
Results-diffusion coefficients
39
Results-viscosities
40
Thank you !! Brrrrrrr
Similar presentations
