The Design Of Highly Conductive Flexible Polymer Materials With Low-load Nanoparticles

Flexible conductive materials are usually fabricated by flexible polymers as matrix and conductive fillers,such as graphene,carbon nanotubes,metal nanowires,metal nanoparticles and conductive polymers,to form a conductive network for materials having excellent mechanical properties and high electrical conductivity.Flexible conductive materials have great application prospects in the fields of flexible robots,sensors,self-healing flexible electronic components,bio-integrated electronic skins,and wearable flexible electronic devices.Mechanical properties and electrical conductivity are the key performance parameters of flexible conductive materials.The common problem in flexible conductive materials is the tradeoff between the mechanical properties and the conductivity.For most conductive flexible materials,it needs to add a large quantity of conductive fillers to meet the demand for high electrical conductivity,which will significantly reduce their mechanical properties.Therefore,many scientific research efforts were devoted to optimizing the composition and structure of conductive nanocomposites in order to achieve excellent mechanical properties in combination with great electrical properties that meet the performance requirements of flexible wearable electronic devices.In this thesis,we proposed a new design idea of flexible conductive materials.High conductive gel or elastomer materials that are fabricated by polymers and low-loading nanoparticles can be achieved by changing the surface properties and interactions of conductive nanoparticles,and using their self-assembly in polymer substrates to form efficient conductive pathways.We employed Brownian dynamics simulation method to verify our design by investigating the self-assembly behaviors of nanoparticles in polymer matrix under equilibrium and tensile strain.The conductive network and percolation probability of the materials formed by conductive nanoparticles with different loading(volume fractions)in cases of various polymer contents were studied in the simulations.We find that,the conductive pathways with chain-like structure were induced by regulating the interaction between conductive nanoparticles.In equilibrium state,when the loading of conductive nanoparticles is as lower as 2 vol%,the materials still maintains the percolation(corresponding to a percolation probability ?100%).The chain-like conductive structure formed in the materials remains good with the continuous increase of tensile strain,and only a few fracture or reconnection are observed.When the tensile strain reaches 300%,the percolation probability in the system of 2 vol% nanoparticles loading is still greater than 35%.In addition,the nanoparticles and the conductive paths with the chain-like structures formed by the nanoparticles strongly can be oriented along the stretching direction under the strain.These computer simulation results provide a basis for the design of advanced flexible conductive materials.