Thermoresponsive polymer architectures have become integral building blocks of 'smart' functional materials in modern applications. For a large range of developments, e.g., for drug delivery or nanocatalytic carrier systems, the selective adsorption and partitioning of molecules (ligands or reactants) inside the polymeric matrix are key processes that have to be controlled and tuned for the desired material function. In order to gain insights into the nanoscale structure and binding details in such systems, we here employ molecular dynamics simulations of the popular poly(Nisopropylacrylamide) (PNIPAM) polymer in explicit water in the presence of various representative solute types with focus on aromatic model reactants. We model a PNIPAM polymer chain and explore the influence of its elongation, stereochemistry, and temperature on the solute binding affinities. While we find that the excess adsorption generally raises with the size of the solute, the temperaturedependent affinity to the chains is highly solute specific and has a considerable dependence on the polymer elongation (i.e., polymer swelling state). We elucidate the molecular mechanisms of the selective binding in detail and eventually present how the results can be extrapolated to macroscopic partitioning of the solutes in swollen polymer architectures, such as hydrogels.

We present all-atom molecular dynamics computer simulations of molecular crystals of the conjugated organic molecule para-sexiphenyl (p-6P), which constitutes a popular basic molecule for optoelectronic applications. After validating single-molecule properties with ab initio calculations, we demonstrate that gradually performed simulated temperature annealing leads to the spontaneous self-assembly of p-6P molecules from the fully isotropic state into the correct roomtemperature solid crystal, with only a few percent deviation from the experimental unit-cell structure. A detailed investigation of the single crystal in anisotropic Gibbs ensemble simulations yields experimentally consistent structures and solid to liquid-crystal phase behavior over a wide temperature range, providing molecular insight into nanometer-scale structural and dynamic properties of self-assembled p-6P crystals. This study thus paves the way for future investigations of the computational description of nucleation and growth mechanisms of novel p-polyphenylene derivatives in the bulk as well as at functional interfaces or heterojunctions.

We study the long-time self-diffusion of a single conjugated organic para-sexiphenyl (p-6P) molecule physisorbed on an inorganic ZnO (101̅0) surface by means of all-atom molecular dynamics computer simulations. We find strongly anisotropic diffusion processes in which the diffusive motion along the polar [0001] direction of the surface is many orders of magnitude slower at relevant experimental temperatures than in the perpendicular direction. The observation can be rationalized by the underlying charge pattern of the electrostatically heterogeneous surface, which imposes direction-dependent energy barriers to the motion of the molecule. Furthermore, the diffusive behavior is found to be normal and Arrhenius-like, governed by thermally activated energy barrier crossings. The detailed analysis of the underlying potential energy landscape shows, however, that in general the activation barriers cannot be estimated from idealized zero-temperature trajectories but must include the conformational and positional excursion of the molecule along its pathway. Furthermore, the corresponding (Helmholtz) free energy barriers are significantly smaller than the pure energetic barriers with implications on absolute rate prediction. Our findings suggest that adequately engineered substrate charge patterns could be harvested to select desired growth modes of hybrid interfaces for optoelectronic device engineering.