Nature: new optical polymer materials can be hard and soft conversion

Nature: new optical polymer material can convert, hard and soft Nature: new optical polymer material can convert, hard and soft

the Massachusetts institute of technology ( MIT) The researchers designed a in response to the light by changing the structure of polymer materials, from hard material into flexible material can heal when damaged.
associate professor of chemistry at the Massachusetts institute of technology Jeremiah Johnson, is cork comprehensive cancer research institute at the Massachusetts institute of technology ( 麻省理工学院的科赫研究所综合癌症研究) A member of the polymer and soft matter project team leader. He said: 'you can switch back and forth material status, and in each state, even made up of the same composition as completely different materials. '
Johnson is put forward, this kind of material attached to the light-sensitive molecules by polymer composition, formed within the molecule can be used to change the material of chemical bonds. Although this kind of material can be used to coat a car or satellite and other objects, to make them after damage can heal, but the application is still a long way in the future.
this paper published in the journal Nature, is the first author of the Massachusetts institute of technology graduate Yuwei Gu. Other authors and the Massachusetts institute of technology graduate student Eric Alt, Adam Willard, assistant professor of chemistry at the Massachusetts institute of technology, of the university of south Florida Heng Wang and Xiaopeng Li.
many properties of polymers, such as the hardness and expansion ability, are usually controlled by its topology structure, and material composition is how to arrange the relevant things. Usually, the material once formed, its topology structure cannot be reversibly change. Rubber ball, for example, flexibility and without changing the chemical composition of the cases, not brittle.
in this thesis, Johnson and his colleagues wanted to create a kind of never had the material, it can be reversible to switch between two different topologies states. They realize that they designed a few years ago a polymer metal organic polyMOCs cage material, the material is made of the implementation of promising candidates. PolyMOCs are connected by a flexible polymer through the metal, forming the cage structure.
researchers are attached to the called ligands groups by mixing the polymer to make these materials, these groups can be combined with metal atoms. Each metal atoms ( In this case is usually metal palladium) With four ligand molecular bonding, forming with different palladium and ligand molecular ratio of rigid cage cluster. These ratios to the size of the cage clusters.
in the new study, the researchers plan to design a can be in two different sizes of reversible switching between cage clusters materials: one who has a 24 palladium atoms and ligands, 48 a has three palladium atoms and six ligand molecules.
in order to achieve this goal, they will be a light-sensitive molecules called DTE into the ligand. The size of the cage by ligands on nitrogen molecules and palladium form the Angle of the key decisions. When DTE is exposed to uv light, it formed in the ligand ring, this increases the nitrogen from the perspective of palladium bonding. This makes the cluster rupture and form bigger clusters.
when the researchers on the material green ring was damaged, the bond Angle smaller, to form smaller clusters. This process takes about five hours to complete, the researchers found that they can carry out seven times. Every time reversal, there is always a small part of the polymer cannot be reversed, eventually leading to separation materials.
when the material is in a state of small clusters, it was 10 times higher than the flexible material under normal condition and much more dynamic. Johnson said: 'they can flow during heating, this means that you can cut them and under the condition of moderate heat self-healing. '
this method overcome the problem of self-healing materials often occur, namely, they tend to be relatively weak in the structure. In this case, the material can be self-healing of soft switch between state and more rigid.
in this study, the researchers used polymer polyethylene glycol ( PEG） Manufacturing materials, they think that this method can be used for any type of polymer. Potential applications include self-healing materials, although this method to get extensive application, palladium this rare and expensive metal must be replaced by a cheaper substitute.
Johnson said, 'if anything made of plastic or rubber, it can repair when damaged, so you don't have to throw it away. Maybe this method can make material with longer life. '
the another possible application of these materials is drug delivery. Johnson thinks that drug encapsulation in a bigger cage structure, then make them exposed to the green light to open and release is possible. Application of the green light is also can make the drug to capture, for reversible provide a new method of drug delivery.
the researchers are also committed to creating can reversibly from solid to liquid material, and use the light in the same material to produce the design of flexible and rigid. Conversion table packaging printing knowledge