Based polymer properties sub-nanometer material: Tsinghua University Professor Wang Xun
Traditional inorganic materials is usually hard and brittle, limiting its application in certain areas. People have been expected given inorganic material with highly flexible features, but so far there is not a very effective method. Because feature sizes in the sub-nanometer material is less than 1nm, so it is compared with larger-sized nanomaterials have some unique properties, a characteristic which is very important class of polymer. Therefore, the sub-nanometer material can be seen as an entry point to break the barriers between inorganic materials and polymer materials, functional sub-nanometer material reasonable assembly and processing will bring huge building and application of inorganic nanomaterials micro-nano devices opportunity. In view of this, Wang Xun professor at Tsinghua University research group carried out on the sub-nanometer-based polymer material properties and further assembly processing depth and systematic research, and made a series of progress.
1. Conformations and rheological properties of the sub-nanometer line
Wang Xun TF was first discovered in the sub-nanometer line system gadolinium oxyhydroxide and the system shows the polymer characteristics of the class. linear polymer with sub-nanometer line close in size, diameter of less than 1 nm, a length of up to several micrometers. As shown in FIG. 1, the sub-nanometer line has high flexibility, showing a variety of conformations in the dispersion. As the concentration increases, the sub-nanometer line also can be assembled into a number of nano-undulated wire harness or a porous structure. When standing for some time, the dispersion can form a gel, which has been tested and found to characteristic shear thinning, non-Newtonian fluid which is described. In addition to sub-nanometer line system gadolinium hydroxide, the other sub-nanometer material was also observed in polymer-like properties, such as tungsten oxide nanoribbons, like tungsten bronze nanowires. See related work has been published an article ( J Am.Chem Soc 2013, 135, 11115-11124;… Small 2015, 11, 1144-1149;. Chem Mater . 2018, 30, 8727-8731).
2. The assembly and processing of sub-nanometer line
As shown in FIG 2A-D, with sub-nanometer indium sulfide in the dispersion exhibit multiple conformations, assembling properties more similar to biological macromolecules, concentration under suitable conditions, solvents, etc., by adjusting their conformation, the formation of highly ordered superlattice. Further assembly, it can also be obtained as crystals macroscopic assembly. This first study conformational nanocrystalline self-adjusting and self-assembly properties of the class of biological macromolecules. The method of addition, based on the characteristics of the sub-nanometer-based polymer material, and wet spinning, electrospinning method or the like method generally used for processing polymers can also be used to process the sub-nanometer material. As shown in FIG. 2E-H, in successfully prepared without adding any electrical spinning the polymer by a smooth surface, the diameter of the controllable sub-nanometer line fiber. using a roller receiving fiber, a nonwoven fabric can be obtained a large area. Under the action of an electric field, highly ordered arrangement of the fibers in the sub-nanometer line, so that fiber having high strength and low modulus, high tensile strength uniaxially 712.5MPa, modulus is 10.3GPa , and polymer materials fairly. FIG 2I-L, in another operation, prepared by wet spinning to obtain a sub-nanometer line highly flexible fibers, These fibers are made of a spring-like sub-nanometer line composed of an ordered arrangement of the elastic tension set up to 10%. Polymer based on the sub-nanometer material properties, processing methods for assembling study constructing micro-nano device of inorganic nanomaterials and the development of functional materials bring new opportunities. See related work has been published an article ( J Am.Chem Soc 2013, 135, 6834-6837;….. J Am Chem.Soc 2017, 139,. 8579-8585;.. Adv Funct Mater 2019, 29, 1903477)..
3. Study of optical properties of film and sub-nanometer line
In this work, we are showing the flexible application prospect in the field of optics sub-nanometer film. As shown, prepared by wet-spinning a 3 sub-nanometer line of the flexible transparent film which has a highly anisotropic, without any additives and the base polymer. Since the sub-nanometer line arranged in a highly oriented film, which film has a significant birefringence, and has an effect of anisotropic scattering of visible light. Further, when adding a fluorescent film line sub-nanometer quantum dots or quantum rods, the composite film is capable of emitting fluorescence polarization. This work provides a new way by using sub-nanometer line optical waveplate and a polarizing plate was prepared. See related work has been published an article ( Angew.Chem. Int. Ed. 2019, 58, 8730-8735).
4. Study spiral sub-nanometer line macroscopic assembly (MHAs) and chiral optical properties
In another work, shown in Figure 4, in the absence of any additives and chiral ligand, by evaporation-induced self-assembly was prepared by sub-nano wire spiral the macroscopic assembly. Since the sub-nanometer line highly flexible van der Waals interactions and multiple sites, they can effectively recognize each other, effect, and thus to adjust the conformation of 100% self-assembly. Prior reports have been predicted by theoretical simulation through chiral sub-nanometer lines, but there has never been proved that. This work demonstrated the sub-nanometer line is gadolinium hydroxide having a chiral structure, which is a racemic dispersion system. In addition, the non-handDACT fluorescent organic dye precursor and the assembly is introduced TMD can be obtained DACT-MHAs and TMD-MHAs chiral fluorescence signal, demonstrated the chiral inorganic material transfer to non-chiral organic molecules. the experimental results, molecular dynamics simulation further revealed the formation mechanism of chiral sub-nanometer line, and a sub-nanometer line of the chiral MHAs evolution. The delivery work to achieve a chiral material to a chiral inorganic nano achiral organic molecules revealed a molecular scale to macro-scale evolution chirality, chiral inorganic nanomaterials and study novel chiral structure build provides a new way of thinking. See related work has been published an article ( J. Am.Chem. Soc. 2020, 142, 1375-1381.).
is just beginning, there is a huge research space, by further precise regulation of its component structure, ligand exchange surface, controlled studies assembly processing, structure-activity relationships can be more feature-rich sub-nanometer to obtain wire material has a broad application prospect in the field of energy, optics, magnetism and the like.
