\”German Applied Chemistry\” eutectic supramolecular polymer: novel supramolecular bulk materials

Compared to polymer, the supramolecular polymer has many unique chemical, physical and mechanical properties, mainly due to the hydrogen contained in the system, a coordinate bond and a main object recognition non-covalent interactions. In recent years, the supramolecular polymer materials design and function much widespread attention. As an important part supramolecular polymer system, based on macrocyclic supramolecular polymers it is considered to have broad prospects in the preparation of advanced functional materials. Currently, the development of macrocyclic supramolecular polymer-based, most studies have focused on the supramolecular polymer solution or gel, but less in the bulk phase study. In addition to the preparation and use of a solvent process supramolecular polymer greatly reduces the stability and processability of the material, thus limiting the practical applicability of the supramolecular polymer. For this reason, the development of solvent-free supramolecular polymer has an important significance to the development of supramolecular chemistry. Recently, the School of Chemistry and Chemical Engineering Professor Dong Sheng Yi, Chinese Academy of Agricultural Science Institute of Bast and Tan Zhijian Research Associate Department of Chemistry, Central South University, Professor Li Fenfang inspired by eutectic solvent interactions and macro mode state, proposed a new strategy, prepared solvent-free macrocyclic supramolecular polymer. The outcome with \”Deep Eutectic Supramolecular Polymers: New Type of Bulk Supramolecular Materials\” was published in the \”German Applied Chemistry\” (Angew Chem Int Ed.doi:… 10.1002 / anie.202004104). OF selected cyclodextrin (α-, β-, γ- cyclodextrin) as a hydrogen bond acceptor, small molecule natural organic acids (citric acid, malic acid and tartaric acid) as a hydrogen bond donor, mixed at a certain proportion, by It was heated briefly to obtain solvent-free transparent state supramolecular polymer (eutectic supramolecular polymer). In order to study the internal low supramolecular polymer interactions eutectic manner, methylated cyclodextrin selected as a model compound, found methylated cyclodextrin and organic acids can not form a supramolecular polymer under the same conditions, the main the reason is that the hydroxyl groups on the cyclodextrin are substituted methyl group, with an organic acid can not form hydrogen bonds. In contrast, α-, β-, γ- cyclodextrin rich in hydroxyl groups, can form hydrogen bond networks with organic acids having a carboxyl group described supramolecular polymerComposed mainly formed by hydrogen bonding interactions.

《德国应用化学》低共熔超分子聚合物:新型本体超分子材料
FIG. 1, (a) preparing a eutectic chemical structural formula of the supramolecular polymer material; (b) preparation of supramolecular polymer flow eutectic; (c) eutectic supramolecular drawing and fabrication process of a polymer film.

Since the eutectic supramolecular polymer prepared rich network of hydrogen bonds, having high fluidity and viscosity, which makes eutectic supramolecular polymers have some workability. At room temperature, eutectic supramolecular polymer can be drawn micrometers to millimeters in diameter filaments. Further, the eutectic supramolecular polymer under heat uniformly coated on a substrate rheometer, after being hot-pressed for 30 seconds, with the increase of the rotor, the supramolecular polymer eutectic layer can be pulled film.

《德国应用化学》低共熔超分子聚合物:新型本体超分子材料
FIG. 2, (a) a cyclodextrin, organic acids, and small molecules eutectic supramolecular polymer melt SEM image; (b) a dye adsorption Protocol; (c) reversible temperature rheological tests; (d) nano-scratch test.

In order to understand the eutectic morphology supramolecular polymer, characterized by scanning electron microscopy of the method, the surface of the supramolecular polymer found eutectic it is very dense and smooth. At the same time, the dye adsorption experiments also done; the first eutectic supramolecular polymer coated glass plate, and then, applied with the coated glass was placed in an organic solvent containing a dye, after soaking for 24 hours, found that low eutectic supramolecular polymer coating not only does not fall off, and there is no discoloration, further explanation eutectic supramolecular polymer has a very dense surface, which also shows the internal phase separation has good stability in organic solvents.

《德国应用化学》低共熔超分子聚合物:新型本体超分子材料
FIG 3, (a) the eutectic supramolecular polymer adhesion macro image; (b) a supramolecular polymer in an organic solvent eutectic adhesion macro image; (c) eutectic adhesion schematic supramolecular polymer melt; (d) a eutectic shear bond strength of the supramolecular polymer to the glass surface; (d) a eutectic of the supramolecular polymer the shear viscosity of the glass surface in dichloromethane knot strength.

In the dye adsorption experiments, it was found eutectic supramolecular polymer has strong adhesion to glass, then the system assessment of its glass, iron, glass, polytetrafluoroethylene, and biological tissues like effect of the surface of the adhesion, eutectic found supramolecular polymer to the fiveSpecies have good substrate adhesion properties such as adhesion strength of iron up to 6.57 MPa. At the same time, to explore the effect of environmental influences on adhesion, such as low temperature, high temperature, low humidity and an organic solvent and other factors, not easily found in the adhesion of outside influences, which is in the supramolecular polymer system relatively rare. In addition, theoretical calculation method of use, further elaborated adhesion mechanism. In short, the combination of two different concepts OF i.e. \”eutectic solvent\” and \”supramolecular aggregation\”, a new strategy designed supramolecular polymer without solvent. Reversible hydrogen bonding network eutectic imparting excellent supramolecular polymer processability, but also gives very good adhesion of the surface of various substrates. For the design of novel supramolecular polymers has opened up a new way, but also to provide ideas for design research and low resistance to organic solvents supramolecular adhesive.

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