Computer simulations of friction between polymer brushes are usually simplified compared to real systems in terms of solvents and geometry.In most simulations,the solvent is only implicit with infinite compressibility...Computer simulations of friction between polymer brushes are usually simplified compared to real systems in terms of solvents and geometry.In most simulations,the solvent is only implicit with infinite compressibility and zero inertia.In addition,the model geometries are parallel walls rather than curved or rough as in reality.In this work,we study the effects of these approximations and more generally the relevance of solvation on dissipation in polymer-brush systems by comparing simulations based on different solvation schemes.We find that the rate dependence of the energy loss during the collision of brush-bearing asperities can be different for explicit and implicit solvent.Moreover,the non-Newtonian rate dependences differ noticeably between normal and transverse motion,i.e.,between head-on and off-center asperity collisions.Lastly,when the two opposing brushes are made immiscible,the friction is dramatically reduced compared to an undersaturated miscible polymer-brush system,irrespective of the sliding direction.展开更多
We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-func...We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111)surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces.The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111)surface under ultra-high vacuum conditions;the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly,suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation.This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.展开更多
基金SdB acknowledges financial support by the Foundation for Fundamental research on Matter(FOM),which is financially supported by the Nether-lands Organization for Scientific Research(NWO)GDK thanks Twas-DFG Cooperation Visits Programme for financial support.
文摘Computer simulations of friction between polymer brushes are usually simplified compared to real systems in terms of solvents and geometry.In most simulations,the solvent is only implicit with infinite compressibility and zero inertia.In addition,the model geometries are parallel walls rather than curved or rough as in reality.In this work,we study the effects of these approximations and more generally the relevance of solvation on dissipation in polymer-brush systems by comparing simulations based on different solvation schemes.We find that the rate dependence of the energy loss during the collision of brush-bearing asperities can be different for explicit and implicit solvent.Moreover,the non-Newtonian rate dependences differ noticeably between normal and transverse motion,i.e.,between head-on and off-center asperity collisions.Lastly,when the two opposing brushes are made immiscible,the friction is dramatically reduced compared to an undersaturated miscible polymer-brush system,irrespective of the sliding direction.
基金the Danish Ministry for Science,Technology and Innovation through the iNANO Center,the Danish Research Councils,a Marie Curie-Intra-European Fellowship for H.G.(MEIF-CT-2004-010038)the SONS Eurocores program FUN-SMARTS,and the NMP Frontiers European project(NMP4-CT-2004-500328).
文摘We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111)surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces.The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111)surface under ultra-high vacuum conditions;the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly,suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation.This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.
