Dr. Johan T. Padding

UPDATE: Since 1st June 2006 I work at the Computational Biophysics group of the University of Twente, supported by a VENI grant of the Netherlands Organisation for Scientific Research (NWO).

Dynamics of complex fluids

I study how the complex behaviour emerges from the underlying interactions between the constituent particles by means of computer simulations. Depending on the lengthscale of interest, I am applying different simulation techniques ranging from atomistically detailed Molecular Dynamics (MD) simulations to more "coarse grained" approaches, such as Langevin Dynamics (LD), Brownian Dynamics (BD), Dissipative Particle Dynamics (DPD), and Stochastic Rotation Dynamics (SRD).

In many cases I use statistical mechanical techniques to derive the interactions occurring on the "coarse grained" (or meso-) scale from detailed simulations of underlying microscopic models. The advantage of such a "bottom-up" approach is that no a priori assumptions about the interactions are needed. Another advantage is that direct comparison with experimental results is possible, which is a very important test of the validity of any simulation model.

Follow the hyperlinks below to get more information on specific topics.

• Dynamics and rheology of entangled viscoelastic polymer melts

• Dynamics and rheology of dilute and semi-dilute polymer solutions

• Coarse-graining the dynamics of suspensions, including both hydrodynamic and Brownian forces

• Computational modelling and design of responsive industrial fluids (wormlike micelles)

Sedimentation of 7800 colloidal spheres in a thermohydrodynamic solvent consisting of 9.000.000 SRD particles. Click on the picture to read more.

A schematic diagram of the two levels of coarse-graining of wormlike micelles. Click on the picture to read more.

Other interests

Recent publications

• (17) E.S. Boek, J.T. Padding, V.J. Anderson, W.J. Briels, and J.P. Crawshaw, Flow of entangled wormlike micellar fluids: mesoscopic simulations, rheology and micro-PIV experiments, submitted to J. Non-Newtonian Fluid Mech. (2006).
• (16) J.T. Padding and A.A. Louis Hydrodynamic interactions and Brownian forces in colloidal suspensions: Coarse-graining over time and length-scales, to be published in Phys. Rev. E (2006).
• (15) E.S. Boek, J.T. Padding, W.K. den Otter, and W.J. Briels, Mechanical properties of surfactant bilayer membranes from atomistic and coarse-grained molecular dynamics simulations, J. Phys. Chem. B 109, 19851 (2005).
• (14) J.T. Padding, A. Wysocki, H. Lowen, and A.A. Louis, Stick boundary conditions and rotational velocity auto-correlation functions for colloidal particles in a coarse-grained representation of the solvent, J. Phys.: Condens. Matter 17 S3393 (2005).
• (13) J.T. Padding, E.S. Boek, and W.J. Briels, Rheology of wormlike micellar fluids from Brownian and Molecular Dynamics simulations, J. Phys.: Condens. Matter 17 S3347 (2005).
• (12) Y. Tao, W.K. den Otter, J.T. Padding, J.K.G. Dhont, and W.J. Briels, Brownian dynamics simulations of the self and collective rotational diffusion coefficients of rigid long thin rods, J. Chem. Phys. 122, 244903 (2005).
• (11) E.S. Boek, J.T. Padding, et al., Constitutive equations for extensional flow of wormlike micelles: stability analysis of the Bautista-Manero model, J. Non-Newtonian Fluid Mech. 126, 39 (2005).
• (10) J.T. Padding and A.A. Louis, Hydrodynamic and Brownian Fluctuations in Sedimenting Suspensions, Phys. Rev. Lett. 93, 220601 (2004).
• (9) J.T. Padding and E.S. Boek, Influence of shear flow on the formation of rings in wormlike micelles: A nonequilibrium molecular dynamics study, Phys. Rev. E 70, 031502 (2004).
• (8) J.T. Padding and E.S. Boek, Evidence for diffusion-controlled recombination kinetics in model wormlike micelles, Europhys. Lett. 66, 756 (2004).
• (7) J.T. Padding and W.J. Briels, A time-integrated estimate of the entanglement mass in polymer melts in agreement with the one determined by time-resolved measurements, J. Chem. Phys. 120, 2996 (2004).
• (6) J.T. Padding and W.J. Briels, Coarse-grained molecular dynamics simulations of polymer melts in transient and steady shear flow, J. Chem. Phys. 118, 10276 (2003).
• (5) Johan T. Padding, Computer Simulation of Entanglements in Viscoelastic Polymer Melts, Ph.D. thesis, University of Twente (Twente University Press, Enschede, 2002).
• (4) J.T. Padding and W.J. Briels, Time and length scales of polymer melts studied by coarse-grained molecular dynamics simulations, J. Chem. Phys. 117, 925 (2002).
• (3) M.A.I. Schutyser, J.T. Padding et al., Discrete particle simulations predicting mixing behavior of solid substrate particles in a rotating drum fermenter, Biotechn. Bioeng. 75, 666 (2001).
• (2) J.T. Padding and W.J. Briels, Uncrossability constraints in mesoscopic polymer melt simulations: Non-Rouse behavior of C120H242, J. Chem. Phys. 115, 2846 (2001).
• (1) J.T. Padding and W.J. Briels, Zero-shear stress relaxation and long time dynamics of a linear polyethylene melt: A test of Rouse theory, J. Chem. Phys. 114, 8685 (2001).

Lecture notes

• J.T. Padding, Theory of Polymer Dynamics, lecture notes accompanying the Han-sur-Lesse 2005 Advanced Physical Chemistry course (PDF format, approx 800 kB).

Book chapters

• J.T. Padding and W.J. Briels, Ab-initio coarse-graining of entangled polymer systems, to appear in december 2006 in Nanostructured Soft Matter: Experiment, Theory, Simulation and Perspectives (Springer), edited by A.V. Zvelindovsky.
• J.T. Padding, W.K. den Otter, and W.J. Briels, Computer simulations of wormlike micelles, to appear in 2006 or 2007 in Giant Micelles: Properties and Applications (Surfactant Sciences Series, Taylor and Francis), edited by R. Zana and E.W. Kaler.

Contact information