New progress has been made in the research of nano-centered graphene phase transitions. Recently, the Fangying research group of the National Nanoscience Center has developed a novel method that can directly and real-time observe the phase transition of graphene in polymers. They skillfully sandwiched Pristine graphene in a polymer matrix that is only a few hundred nanometers thick. When the system temperature is higher than the glass transition temperature of the polymer, graphene begins to curl, and this phase transition is irreversible. More interestingly, graphene can also be actively folded into a two-layer / three-layer structure, and the overlap between the layers expands to the order of micrometers along the surface. Raman spectroscopy further indicates that there is a strong electronic coupling between the layers. On the other hand, the oxidized graphene does not undergo a similar reaction even at higher temperatures, which indicates that the instability of Pristine graphene itself is the internal cause of the phase transition. According to reports, the new nanomaterial graphene has received extensive attention due to its superior electrical and mechanical properties. Graphene is a layer of monoatomic planar two-dimensional crystal, but the perfect two-dimensional structure cannot exist stably at a limited temperature. Recent theoretical simulations and transmission electron microscopy experimental results give a possible explanation, that is, there are nano-level microscopic distortions on the graphene plane. However, to what extent can these nano-level distortions stabilize graphene, or from another angle, under what conditions can the phase change of graphene be triggered, there has not been any relevant experimental reports, and the stability of graphene Application is essential. The research of Fangying's research group shows that in the future application of graphene-polymer composite materials, it can help to maintain a two-dimensional structure in the polymer matrix by introducing a certain degree of defects in the graphene, otherwise when the temperature is higher than the polymerization At the glass transition temperature of the material, the composite material will lose its ideal optical, mechanical, and electrical conductivity characteristics due to the curling and wrinkling of graphene.
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