Aggregation And Dispersion Behavior For Nanoparticles/Polymer Melts Under Nonequilibrium

Polymer nanocomposites,because of the uniform distribution of highly ordered nanoparticles(NPs)can significantly enhance the mechanical,optical and electrical properties of materials,have been widely studied and applied in several research fields.It is well known that the aggregation and dispersion of NPs in polymer melts must be closely related to the interaction between polymer monomer(P-P),the interaction between NPs and polymer(N-P),and the interactions between NPs(N-N).We use molecular dynamics(MD)simulations to study the aggregation and dispersion behavior of NPs in NPs /linear polymer melts under three groups of different interactions.These three groups of interactions are: PP attractive/ N-P repulsive/ N-N repulsive,P-P attractive/ N-P attractive/ N-N repulsive,P-P repulsive / N-P attractive/ N-N repulsive.Under the action of P-P attractive/ N-P repulsive/ N-N repulsive,with the interaction intensity between NPs and polymer monomer increased,the structure of NPs in polymer melts changes from "spherical" aggregation to "linear" aggregation,but no good dispersion appeared.Under the action of P-P attractive/ N-P attractive/ N-N repulsive,an aggregation-dispersion transition occurs when the interaction intensity increased,and the bridge phase appears under the high interaction intensity.Under the action of P-P repulsive/N-P attractive/ N-N repulsive,the NPs shows good dispersion directly when the interaction intensity is low,and the NPs began to appear as bridging phase when the interaction intensity increased to moderate.This discussion has a reference value for us to further study on increasing the uniform distribution of nanoparticles in polymer melts.Nonequilibrium State(shear field)can affect the aggregation and dispersion of NPs in Polymer nanocomposites,and the different topological structures of ring polymers and linear polymers have differences in the effects of the dynamics of NPs.The study on the aggregation and dispersion of NPs in a linear/ring polymer melts in Nonequilibrium state may be a new discovery.The results show that the shear field can slow down the aggregation of NPs in the linear polymer melts,but the NPs aggregation-dispersion transition is still not achieved.In the ring polymer melt,the application of shear field can make the NPs that were originally aggregated tend to disperse,which proves that the shear field effectively enhances the dispersibility of NPs,and the shear field expands the adsorption energy interval needed for the dispersion of NPs.By comparing the configuration change of the two polymer chains in the shear field,we find that the ring polymers can surround the NPs by forming irregular rings in the shear field because of their special topological structure.The surrounding of many polymer monomer can prevent the proximity of other NPs,thus effectively promoting the transition of NPs from full aggregation to partial dispersion.The results of this study provide some ideas for obtain the uniform distribution and highly ordered Polymer nanocomposites.