Scaling Theory And Molecular Dynamics Simulation Of Polymer Brushes On Solid-Liquid Interface

According to widely-existing literature,polymers play a key role in people's daily life and industrial production.Due to their unique physical and chemical propertles,polymer brushes,prepared from end-grafted polymer chains,have been studied in fields of polymer physics,surface material science,nanotechnology and biomimeties in recent decades.Some versatile theoretical models are used to predict their characteristic behaviors,such as scaling theory.However,when tihe architecture of these polymers becomes complicated,e.g.turning into a multi-branched dendritic structure or the substrate non-planar,then corresponding theoretical models have to be adapted.It is thus necessary to further develop more refined models to accurately describe these complex structures.In this thesis,starting from basic concepts of scaling theory,we,on one hand,present an effective method which allows us to generalize and unify the conditions which govern the properties of planar dendrimer brashes.Concerning the prediction of density profiles,there exist significant differences among models,and these deviations originate from their different approaches to the elastic properties of the spacers.On the other hand,for some special but important polymer brush systems,namely linear polymer brushes in nanochannels,we identify a possible mechanism to explain their morphologies and functions.Such nanopores serve as selective gates for nanoparticles in such a fashion that small-sized nanoparticles pass through the nanopores via a passive diffusion,whereas larger-sized nanoparticles can only penetrate when nanopores are open after a collapse transition of the decorating brushes.An effective triggering mechanism for such a collapse transition is based on concentration changes of co-nonsolvent,which effectively modify the property of solvent from good to poor status.These findings allow us to understand how similar systems in organisms,such as nuclear pore complexes,achieve the function of selective particle transport.The accuracy of these theoretical methods that are derived here is validated by coarse-grained molecular dynamics simulations,which explicitly yield the universal properties of polymeric systems without the need for chemical details.Our theoretical and simulation results may serve as a guide for subsequent experimental studies.