Dear XFNANO customers:

Nature Communications (IF12.353), published in July 2018, reported a rigid and healable materials prepared by Li Cheng Hui and Zuo Jing Lin research team from Nanjing University with the title A rigid and healable polymer cross-linked by weak but abundant Zn(II)-carboxylate interactions.

They describe a design concept that utilizes weak but abundant coordination bonds to achieve rigid and healable materials. The coordination bonds used in their study are weak but still significantly stronger than hydrogen bonds. Therefore, the resulting polymer is very strong (with flexural Young’s modulus as high as 480MPa) and rigid (with an elongation at break smaller than 4%) at room temperature. The coordination equilibrium is sensitive to temperature; thus, the mechanical strength of their polymer exhibits distinct(as high as almost 4 orders of magnitude in a narrow temperature range (ΔT<100°C)), fast (within tens of seconds) and reversible change upon heating or cooling. Such features make their polymer applicable in various situations. For example, due to its rapid softening and hardening property, their polymer can be used in orthopedic immobilization to replace traditional plaster casting, and it also has the advantages of being lightweight, removable and recyclable.Their polymer can also be used for 3D printing since it turns into a viscous liquid upon heating to 120℃ and quickly forms a rigid solid upon cooling. With its thermal healing properties, objects made of our polymer using 3D printing can be healed when damaged.They can also obtain large or complex objects with only a small 3D printer by taking advantage of the healing processes of this material. Thus they can combine the advantages of modern 3D-printing processes and traditional brickand-mortar operation using our materials. Moreover, our polymer can be used to prepare conductive composites/adhesives that are reshapable, healable, and 3D printable.

Three-dimensional (3D) printing, also known as additive manufacturing, has advanced rapidly in recent years, as it can proceed quickly, save time and money, increase design freedom, and enhance design innovation. However, common 3D printing techniques face some challenges. One such challenge is that-the whole 3D object will have to be discarded if it is broken or locally cracked by an external force. This is in contrast to traditional brickwork construction methods in which objects are assembled from independent bricks and therefore can be repaired through brick replacement when damaged. Moreover, the dimensions of 3D-printed objects are restricted by the size of the printer, since a 3D printer cannot print anything bigger than itself. Their polymer is well suited to 3D printing because it turns into a viscous liquid when it is heated to 120°C, and it quickly forms a rigid solid upon cooling.

Figure 3e shows that upon gentle heating, a fusilli can be made by twisting a dumbbellshaped sample. After cooling, the fusilli can keep its shape and sustain a heavy load (100g) (no apparent deformation was observed within 1h). Such a reshaping process can be accomplished by a common household blow drier within tens of seconds. Notably, compared to other malleable polymers that are based on dynamic covalent bonds, our polymer has advantages including requiring no additives (such as catalysts or solvents) and having a significantly lower reshaping temperature. The rapid softening and hardening properties of the PDMS-COO-Zn polymer make it applicable in medical fields such as in orthopedic immobilization and external fixation systems. It is known that plaster-casting is needed to ensure bone healing when people suffer from bone fractures. However, plaster casting is cumbersome, inconvenient and the materials cannot be recycled after use. Figure 3f shows that a flaky sample can be reshaped and adapted into an orthosis upon heating with a blow drier. The orthosis is rigid enough to restrict body movements to facilitate bone healing, yet it is lightweight, removable and recyclable.

The raw material graphene (with a diameter of 5-10μm and thickness of 3-10nm) was provided by XFNANO.It is a great honor for XFNANO to provide high quality graphene material for researchers.