The Selectivity Of Nanoparticles For Polydispersed Ligand Chains During The Grafting-to Process:A Computer Simulation Study

In polymer materials,the polymer nanocomposite(PNCs)filled with nanoparticles(NPs)has more excellent properties in optics,mechanics and so on.In recent years,there are many scientists carrying out a lot of corresponding works around the PNCs.As an important filler of PNCs,the dispersion of NPs is crucial to optimize the performance of such composites.To enhance the compatibility of inorganic NPs and the polymer matrix,a general design strategy is to covalently graft the polymer chains,which are similar to or the same as the polymer matrix,to the NP surface.The grafted ligand chain will stabilize the NPs.Will the dispersion of the ligand chain affect the dispersibility of the NPs in the matrix? Current work which reported grafting monodisperse ligand chains as well as bimodal polymer chains demonstrates that the system filled with NPs grafted bimodal polymer chains is more stable.In addition,some scientists calculated the potential of mean force between the NPs grafted polydispersed polymer chains.They found that the polydispersity of the grafted ligand chains not only alleviates the crowding of the polymer monomers near the surface of the nanoparticles,but also the presence of long chains introduces long-range spatial repulsion that alters the wettability of the grafted layer to the matrix.Thus,the systems filled with NPs grafted polydispersed polymer chain are more stable than those filled with grafted monodispersed polymer chains.However,what about the details of the grafting reaction of NPs in polydispersed polymer chain system? Is the NP selective to the ligand chain? Compared with grafting monodispersed polymer chains,what is the grafting density of polydispersed polymer chains? So far,this series of important scientific issues have not been reported.Using the method of molecular dynamics simulation and the grafting-to reaction model to simulate the process of polymer chains grafting onto NPs surface,we aim to explore the problem of the selectivity of nanoparticles in systems filled with polydispersed polymer chains.In this paper,by constructing a grafting-to reaction model of polydispersed polymer chains to bind onto NPs,we elucidate the changes of grafting density,polydispersity index and chain length distribution of grafted ligand chains as a dependence of the feeding polymer chains.Our study shows a linear dependence of the grafting density on the average chain length of the feeding polymers.We also clearly demonstrate the NP's selectivity of short chains in the later stage of the reaction.Our results also show that the polydispersity of the ligand chains on each individual NP is commonly higher than that of the feeding polymer chains.Furthermore,the simulations imply that polydispersed polymer chains are more easily bound during the grafting-to process compared to monodispersed chains.Thus,relatively higher polydispersity of feeding polymer chains are beneficial to promoting the grafting density of NPs.Our study helps to elucidate the cause of chain polydispersity and could act as a guide to finely regulate the polydispersity of ligand chains on nanoparticles.