Theoretical Simulation Of Self-assembly Of Polymer Decorated Nanoparticles In Solutions

Polymer grafted nanoparticles can self-assemble in selective solvents and form not only simple assemblies such as spherelike micelles,disklike micelles,vesicles and complex micelles,but also linear,plane or three-dimensional ordered meso-structures.Compared with the assemblies obtained from block copolymer,polymer grafted nanoparticles possess excellent physical and chemical properties,including structure stability,controllable size and photoelectric property.And all these property improvements are due to the combination of nanoparticles.In recent years,the self-assembly of nanoparticles grafted with polymer drew more and more attention and this field has already become one of the frontier of supramolecular chemistry and nanometer materials.These assemblies with simple or complex structures have great applications in drug delivery,biosensing,photoelectric material and nanometer devices.In this thesis,we use dissipative particle dynamics(DPD)method to investigate the self-assembly behavior of surfactant-like polymer grafted nanoparticle with two different self-assemble monomer types,one is nanoparticle grafted with a single polymer chain,the other is obtained from polymer surface patterning on nanoparticle which has certain grafted density.The main contents and results as follows:The self-assembly of surfactant-like amphiphiles in selective solvents.Our simulation model is based on the experimental investigations about giant surfactant PS-APOSS and PS-AC60,both are non-metallic nanoparticle grafted with polystyrene chain.In our model,APOSS and AC60,which are obtained after hydrophilization process on POSS and C60,represent hydrophilic head bead and connect with a long hydrophobic tail.In our investigation,the length of hydrophobic tail,the interaction parameter between tail and solvent,the interaction between head and solvent,monomer concentration and the radius of hydrophilic head are systematically taken into account.And by controlling these conditions,we found various self-assembled morphologies,including sphere-like micelles,disk-like micelles,vesicles,pomegranate-like micelles,pomegranate-like columnar structures,hierarchical colloidal polymeric(HCP)structures and branched hybrid structures.Our investigation results indicate that,sphere-like micelles,disk-like micelles,vesicles and other simple aggregates are mainly obtained when the radius of hydrophilic head is smaller than 2.5.These behaviors are comparable with the self-assembly behavior of amphiphilic block copolymers.Oppositely,with larger head radius,the aggregation results are basically pomegranate-like micelles,pomegranate-like columnar structures,hierarchical colloidal polymeric(HCP)structures and branched hybrid structures.And among them,the HCP structures,which have been found more and more in recent years.HCP structures have linear AB alternating structures which are similar with linear alternating copolymer in polymer science,however,they are linear alternating polymeride with mesoscopic size.In our simulation work,the monomers of HCP structure are simple two-component.The simulation results indicate that the formation of the HCP structure goes through three steps:aggregation,coalescence,and growth.The dimension of the HCP structure is largely controlled by the hydrophobic tail,the polymer concentration and the interaction parameter.Polymer patterning on nanoparticle's surface.We employed DPD method to investigate the self-assembly behavior of nanoparticles grafted with a certain number of polymer chains.By systematically changing the length and the number of polymer chains,the radius of nanoparticle and the interaction parameters,we obtain five different patterning types:core-shell type,single patch,double patch,triple patch and quadruple patch and we also explanation the formation of different patterning type in different conditions.Moreover,we investigate the self-assembly behavior of the pattering monomer and discover an interesting phenomenon that the coordination structure of self-assembled oligomers are basically same to hybridized orbital of atom.