Coarse-grained modeling, solid surface polymer

In Section 1.3 we continue the discussion of Monte Carlo simulations of polymer blends and polymer solutions, but with the emphasis on interfaces that result in the context of phase separation interfaces between coexisting phases in the bulk (liquid-liquid interfaces in a blend, liquid-vapor-type interfaces in a solution) and at solid external walls. It will be shown how all the surface free energies entering Young s formula for the contact angle of droplets can be determined, and how one can estimate the location of wetting transitions. Coarse-grained models are the focus of this section. 

Systematic coarse-graining schemes have been applied to one-component polymer melts in contact with solid surfaces. In this framework, one starts with an atomistic modeling approach and systematically devises effective free energies of interaction between coarse-grained segments along the polymer. In this way, information on the atomistic scale may be transferred into coarse-grained models. 

The idea of a minimal coarse-grained model for polymer-solid contacts consists in not describing the structural details of the polymer-solid contact on the length scale of Angstroms because this length scale is not resolved. Instead, the aim is to tailor the interactions at the surface in order to match the difference in surface tension, Ay, of the coarse-grained model to the experimental data. In this way, the macroscopic interfacial thermodynamics is parameterized. 

To parameterize the coarse-grained model to a specific physical realization, one has to tune the interactions, Vwaii, between solid and polymer to reproduce the experimental value of the surface free energy difference. Ay. Once Ay has been obtained via the method described above for a particular strength, Ewaii, of Vwaii, the dependence on the attractive strength of the wall can be obtained via thermodynamic integration [120, 124] ... 

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