Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 5: Interfaces

CPP 5.5: Vortrag

Montag, 23. März 2009, 11:30–11:45, ZEU 160

Polymer Adsorption Transitions at Attractive Substrates: Analysis from Canonical and Microcanonical Perspectives — •Monika Möddel, Michael Bachmann, and Wolfhard Janke — Institut für Theoretische Physik, Universität Leipzig

Multicanonical simulations allow not only for a precise determination of canonical expectation values over a wide range of temperatures, they also provide a very precise estimation of the density of states. We used thermal fluctuations of energetic and structural quantities to identify the variety of pseudophases of a semiflexible off-lattice homopolymer near an attractive substrate [1]. Introducing a solvent parameter related to the strength of the surface attraction, the solubility-temperature phase diagram is constructed and discussed. Apart from the adsorption transition, several other structural transitions such as the freezing transition between energy-dominated crystalline low-temperature structures and globular entropy-dominated structures as well as the layering transition between single- and double-layered conformations are identified. With the density of states, we then performed a microcanonical analyses focused on the adsorption transition, where a convex intruder of the microcanonical entropy can be observed for short chains, which is a typical signal for a phase separation process. However, for longer chains, the latent heat decreases and seems to vanish in the thermodynamic limit. Thus, we interpret the adsorption process as a second-order phase transition.

[1] M. Möddel, M. Bachmann, and W. Janke, submitted to J. Phys. Chem. B (2008).