Highly stretchable elastomeric self-healing, self-healing may be implemented in a variety of extreme conditions
Skin and muscles will automatically repair itself when damaged, and this ability has been the dream of scientists want to give a special performance of the material. However, most of the current design of repair materials require external energy to heal or mechanical strength of these materials is weak. Dynamic supramolecular materials can solve this problem to a certain extent, it will repair itself without external conditions can occur at room temperature. However, with a dynamic supramolecular self-repairing material properties are often not suitable for extreme conditions, because: (i) when the underwater repair material injury or rupture, water molecules can interfere with the dynamic key to reconnect, causing the material can not be repaired . (Ii) In freezing conditions, the dynamic characteristics of the keys in the recoverable material encountered a lot of obstacles, which greatly limits the self-healing process. (Iii) the interaction of a number of self-repair susceptible to pH change.
the results of
Based on the above issue, Professor Zhang Lei and young teachers from the School of Chemical Engineering and Technology Yang Jing cooperation, collaboration in the exchange polydimethylsiloxane polymers combined with multi-strength hydrogen bonds and disulfide bonds, design a universal and high stretchability healing supramolecular elastomer . It can achieve rapid autonomous self-healing under extreme conditions, including at room temperature, ultra-low temperature (-40 ° C), water, a high concentration of cold brine (30% NaCl solution at -10 ° C), and acid / base environment (pH = 0 or 14). These dynamic properties due to the synergistic interaction and weak hydrogen bonds with strong hydrogen bonds strong disulfide bonds. Related outcomes to \”Universally autonomous self-healing elastomer with high stretchability\” in the title, published in \” Nature Communications \” on. 
Analytical graphic
1. Design Strategies
First look supramolecular elastomer design, the design combines high tensile properties and a unique universal autonomous self-repair. The key to the design is a synergistic interaction of a plurality of dynamic keys, including a disulfide bond (the SS), strong crosslinking hydrogen bond (BNB-BNB) and weakly crosslinking hydrogen bond (IP-IP, IP-BNB or IP-SS etc.), as shown in FIG. These dynamic linkages into polydimethylsiloxane (PDMS) polymer backbone (PDMS-SS-IP-BNB), the dynamic spontaneously form supramolecular polymer network (Fig. 1a and b). Supramolecular polymer in a dynamic network, the strong hydrogen bonds predominantly crosslinked elastomeric imparting firmness and elasticity, and weak hydrogen bonds and effective reforming reversible bond breakage to dissipate strain energy. Disulfide bonds mainly contributes to self-repair. These binding sites impart synergy high tensile elastomer (14,000%) , and rapid spontaneous healing ability (FIG. 1c) under conventional conditions and extreme ambient conditions.
2. The rheological and mechanical properties
rheological measurements can reveal the viscosity and elasticity of the material, its mechanical properties can be explained. Rheological measurements indicate PDMS-SS-IP-BNB elastic material predominantly at room temperature, at elevated temperatures and may become more viscous liquids like (FIG S8). Then look mechanical testing, Figure 2 shows the resulting PDMS-SS-IP-BNB film having a high stretchability and excellent mechanical strength. Researchers believe that high stretchability due to the synergistic interaction of a plurality of dynamic characteristic bonded supramolecular polymer network. Mechanical properties of materials depend on the ratio of PDMS, SS, BNB and IP unit, in particular, high crosslinking BNB-BNB (strong hydrogen bonds) will have a density higher mechanical strength. Supramolecular polymer network, in between the RA BNB
is formed as the strong hydrogen bonds (quadruple hydrogen bonding), thereby allowing greater BNB-BNB crosslinked elasticTogether to obtain the elastic holding member (FIG. 1b). Synergy of three dynamic bonding sites in the polymer backbone provided a strong cross-linking interactions and energy dissipation mechanism, a bond rupture, and a variety of switching modes reforming. It may be advantageous for the mechanical strength of the PDMS-IP-SS-BNB resulting material.
3. The universal self-repair capacity
The results show that, PDMS-IP-SS-BNB enable rapid autonomous self-healing under extreme conditions, including (10min healing) in the room temperature, cryogenic (-40 ° C), underwater (93% efficiency healing), subcooled high concentration physiological saline (- 30% NaCl solution at 10 ° C in the healing efficiency of 89% at room temperature ) and acid / alkaline environment (pH = 0 or 14, the healing efficiency of 88% or 84%) (FIG. 3). These dynamic properties due to the synergistic interaction and weak hydrogen bonds with strong hydrogen bonds strong disulfide bonds. This greatly expanded its field of application.
Application of 4 – A self-healing scalable conducting means
PDMS-SS-IP-BNB elastomer having excellent mechanical properties, stretchability and general healing properties It is very suitable for electrically conductive device conductive. Thus, the use of liquid metal as EGaIn wire, and P3 used as encapsulating elastomer layer and the support, producing an self-repairing stretch conductor (FIG. 4a). When the wire cut in half, the circuit is opened, causes the LED off. When the two parts are connected together again, resume immediately conductivity, excellent mechanical properties to recover 10 minutes (Figure 4b). Furthermore, the healing wire remains conductive when stretched to 150%.
