A refined flexible all-atom model for a room temperature ionic liquid, 1-n-butyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), is reported here. Extensive molecular dynamics simulations were performed to check the validity of this model. We found that the thermodynamic and dynamic properties such as density, isobaric expansivity, isothermal compressibility, and self-diffusion coefficient described by the present model are in good agreement with experimental observations. Based on the calculated results, there has been a considerable improvement in the force field with respect to the previous model by Lopes et al. [15,16].

Two different synthesis routes to prepare highly ordered and highly proton conductive sulfonic acid (SO3H) functionalized mesoporous silica materials are presented. The highest loading of Si-MCM-41 with SO3H groups was reached via a co-condensation route, which turned out to be advantageous compared to grafting, leading to hybrid materials exhibiting proton conductivities up to 0.2 S/cm at 100% relative humidity and 413 K. Especially at low humidities and under dry conditions, we show that the high group density of co-condensed materials is crucial for the proton transport. Experimental characterization, via impedance spectroscopy and water adsorption, and theoretical investigations of a simplified model system concordantly demonstrate the most important dependencies of the proton transport properties on the water content and on the density of SO3H groups. Computational studies were performed including classical molecular dynamic (MD) simulation and free energy calculation with a quantum mechanical method, which are showing comparable trends to the performed proton conductivity measurements of the material. Furthermore, the water uptake of the functionalized material was studied by MD simulation, which revealed the water density inside the porous system to be inhomogeneous in the case of low relative humidity.

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The reverse nonequilibrium molecular dynamics (RNEMD) method is implemented to predict the viscosity of a coarse-grained model of short-chain polystyrene. The coarse-grained model has been derived to reproduce the structure of polystyrene. It is therefore not a generic model, but polymer-specific. Here, its performance for dynamical quantities is tested. The zero-shear viscosity is compared with experimental data. The pronounced difference can be mainly attributed to the inherent dynamic properties of the coarse-grained model. The qualitative results are compared to previous results calculated via conventional nonequilibrium molecular dynamics (NEMD) and more generic polymer models, and the agreement is reasonable. The structural alterations under shear are investigated by characterizing the molecular deformation and birefringence extinction angle.