Preparation Of Silica Janus Nanosheets And Their Applications In Polymer Materials

Janus particles,as a new functional nanomaterial,have attracted wide attention due to the irstrict asymmetric structures and unique physics-chemistry properties.Recently,a large number of Janus nanoparticles with different structures and properties have been developed and used in various fields,including surfactants,catalysts,biological carriers,optical probes,self-driving motors,and so on.The well-defined structures of Janus particles provide the most promise to break through the bottleneck of the above-mentioned materials.However,there are few researches to develop functional polymer composites by using these Janus materials.In this paper,an amphiphilic Janus nanosheet and an organic-inorganic hybrid Janus filler were designed and prepared by selective surface modification on silica based particles.The as-prepared Janus nanomaterials were then used as interfacital agents and thermally conductive fillers in polymer matrix to develop high-performance or functional polymer composite materials.The main contents are as follows:1.Using silica nanosheets with hydroxyl groups and amine groups on the opposite sides as templates,the amphiphilic Janus nanosheets PBd-silica-PI were synthesized with the attachment of reactive polyisoprene?PI?brushes and polybutadiene?PBd?brushes on the two sides.The coMPatibility between the attached polymer brushes and the rubber matrix accounted for reduced phase domains,revealing as a bicontinuous structure within the PBd-silica-PI Janus nanosheet filled solution styrene–butadiene rubber/natural rubber?SSBR/NR?blends.Thanks to the strength of silica template,the amphiphilic of polymer brusher and the co-vulcanization between polymer brushes and natural polymer matrix,PBd-silica-PI Janus Nanosheets not only greatly improved the coMPatibility of SSBR and NR,but also reinforced and toughened the rubber blend in which Janus nanosheets was distributed at the interface of two-phase.With only 3 phr Janus particles added in composites,the tensile strength of the polymer can be increased by more than 3 times.2.A special inorganic-organic hybrid Janus filler was fabricated,wherein high thermal conductivity silver nano-particles?AgNPs?and polystyrene?PS?brushes were anchored on opposite sides of a silica nanosheet by selective surface modification.To enable orientation of the Janus fillersin polymer matrix,the Janus fillers were dispersed in polymermatrix by layer-by-layer doctor blading.Consequently,there were several distinct advantages of using polymer composites with JPs,such as?1?the dense deposition of AgNPs on oneside of the Janus filler enabled the construction of a heat pathway within the Janus sheet,which contributed to low loading of thermally conducting particles;?2?the attachment of PS brushes on the other side of the Janus filler enabled good dispersion of the filler and reduced the interfacial thermal resistance between the thermally conducting particles;?3?the sheet-like structure and the deposition of AgNPs on oneside made the Janus filler tend to align in polymer matrix so as to construct the heat pathway.As a result,when the volume fraction of Janus filler is 10%,and the volume fraction of Ag nanoparticles is only 7.3%,the thermal conductivity of polystyrene composite can reach 4.57 W m^-1 K^-1,which is 30 times of the polystyrene matrix.