Self-Assembly And Structural Manipulation Of Diblock-Copolymer Grafted Nanoparticles In A Homopolymer Matrix

Polymer nanocomposites are the focus of research in the field of materials science and engineering.They not only have better mechanical properties than traditional polymer materials,but also combine the excellent properties of filled nanoparticles,such as thermal conductivity,electrical conductivity and magnetic properties.However,how to control the good and uniform dispersion of nanoparticle fillers in the polymer matrix is the basis for achieving superior performance of polymer nanocomposites.Therefore,how to establish the relationship between its microstructure and macroscopic performance is the key to achieve controllable performance.Effective methods such as grafting diblock copolymers onto the surface of nanoparticles are available,thereby achieving controlled nanoparticle dispersion and specific self-assembly structure,which is attributed to the interaction enthalpy of nanoparticles and grafted block polymerization.The mutual competition between the conformational entropy of things.Considering that the polymer nanocomposite is a multi-scale and multi-interaction complex system,the characterization of microstructure is difficult to achieve by traditional experimental techniques,and it is difficult to construct an accurate quantitative relationship between microstructure and macroscopic performance.Therefore,computer simulation technology plays an increasingly important role in understanding and predicting the performance enhancement of polymer nanocomposites.Based on the above research background,this paper mainly conducted a preliminary exploration around the micro-mechanism of the effect of self-assembled structure on the dispersion and mechanical properties of polymer nanocomposites through coarse-grained molecular dynamics simulation.The research work is mainly carried out from the following two aspects:1.Micromechanism of the influence of nanoparticle grafted amphiphilic block polymer chain on the dispersion and mechanical properties of nanoparticles(NP)Using coarse-grained molecular dynamics simulations,we constructed a series of nanoparticle-grafted amphiphilic block polymers and blended them in a homopolymer matrix.By setting the interaction parameters between the components,part of the graft block chain is compatible with the nanoparticles and part of it is compatible with the matrix chain.Nanoparticles and their grafted chains form a core-shell self-assembled structure.The effects of different degrees of self-assembled structure on the dispersion of nanoparticles,chain dynamics,chain movement ability,and uniaxial tensile properties of macroscopic materials were studied and deepened.The relationship between the macroscopic mechanical properties of the material and the microstructure and microscopic interaction is explored.The simulation results show that the nanoparticles and their grafted chains form a core-shell self-assembly structure,and the existence of this structure effectively improves the dispersion of the nanoparticles.By regulating the graft density of the graft chain,the integrity of this core-shell self-assembled structure gradually improves as the graft density increases,so the dispersion of the nanoparticles also gradually improves.By adjusting the ratio of the two components of the graft chain,the core-shell self-assembly structure is further improved,which further improves the dispersion of the nanoparticles.And this self-assembled structure has little effect on mechanical properties.2.The mechanism of the influence of the rigidity and flexibility of the grafted polymer chain on the dispersion and mechanical properties of nanoparticles in the compositeIn polymer nanocomposites,the rigidity and flexibility of the polymer chain is an important means to improve the overall performance of the material.Therefore,we changed the block polymer grafted on the surface of nanoparticles from a pure flexible chain to a semi-flexible and semi-rigid polymer chain to explore the effect of this combination on the dispersion and mechanical properties of nanoparticles in composite materials.What microscopic mechanism dominates the performance enhancement?We found that:(1)after the introduction of the rigid chain,the core-shell self-assembled structure formed by the pure flexible grafted block chain disappeared,and the capsule structure was replaced;(2)the capsule structure was parallel in the system box Or cross arrangement;(3)The mechanical properties of the system were subsequently investigated.The arrangement of the capsule structure in space did not cause the anisotropy of the mechanical properties of the system,and compared with the pure grafted block chain system,Rigid semi-flexibility not only gives the composite material good nanoparticle dispersion,but also improves the macroscopic mechanical properties of the material.