Pulling polymers on energetically disordered surfaces: molecular dynamics tests of linear and non-linear response

• Main Authors: Raos, Guido (Author), Sluckin, Tim (Author)
• Format: Article
• Language: English
• Published: 2013-05.
• Subjects: Article
• Online Access: Get fulltext

 We present equilibrium and non-equilibrium molecular dynamics simulations of flexible polymer chains absorbed on heterogeneous surfaces. The surfaces are flat but energetically disordered, as they consist of a random mixture of weakly and more strongly absorbing sites (94% and 6%, respectively). For comparison, we have also simulated the two corresponding homogeneous surfaces. We find that this apparently weak energetic disorder can produce very significant changes of the chain statistics (expansion of the radii of gyration), equilibrium dynamics (reduction of the diffusion coefficients) and non equilibrium response to a horizontal pulling force. On the disordered surfaces, the polymer-surface effective friction coefficient (ratio of pulling force and drift velocity) becomes strongly force-dependent,as the dominant mode of motion changes from localized stick-slip events to smooth and continuous sliding. This is strongly reminiscent of the Schallamach model of rubber friction and the Maier-Goritz picture of the Payne effect in filled elastomers.