Functional Self-healing Materials Based On Hyperbranched Poly(Aimdo Amine)

It is inevitable that some damage may happen to the polymer materials during their lifespan. Small cracks can be induced inside the materials. If the materials were not repaired instantly, the cracks will grow, resulting in failure of the whole material. Therefore, a lot of problems arise, for example, environmental pollution, wastes of raw materials, or even some fatal accidents. It is well known that the animals or plants can heal their wounds and restore functions spontaneously. Inspired by the nature, researchers design and produce a lot of polymer materials and their composites with self-healing ability. Among them, the multi-functional self-healing materials are more attractive. Nowadays, although great progress has been made in the field of self-healing conductive materials, there are still some problems to be solved, such as, how to construct a high-efficient self-healing conductive composite without external stimuli,etc.Hyperbranched poly(amido amine) (HPAMAM-1) synthesized from cysteinbiacrylamide and N-ethylpiperazine by Michael addition is a kind of polymer with highly branched structure. The other structural features include:lots of amine, amide groups and a great many disulfide bonds on their molecular backbone. It enables the HPAMAM-1 not only strong molecular mobility, but also strong inter-molecular hydrogen bonds. It is because the hydrogen bonds and disulfide bonds are all dynamic interactions that the HPAMAM-1 will be of excellent self-healing ability. This kind of polymer is good candidate in fabricating stimuli-free self-healing conductive composites. Here in this work, we constructed a self-healing conductive composite with Sushi-like structure by employing HPAMAM-1 and carbon nanotubes. The results showed that the excellent self-healing ability of HPAMAM-1 and the unique assembly structure were essential to the stimuli-free property, alignment-free property and high efficiency of the obtained self-healing conductive composite.Different from the HPAMAM with disulfide bonds, the HPAMAM (being named as HPAMAM-2) synthesized from methylenebiacrylamide and N-ethylpiperazine are more popular due to the abundant raw materials. We fabricated a novel composite hydrogel with HPAMAM-2 and metal ions (Ca2+ and M2+) according to the strong binding ability of HPAMAM to the metal ions. The results showed that the composite hydrogel was of good self-healing ability. The fluorescent intensity of HPAMAM-2 was increased greatly after binding with Ca2+ and Mg2+. Moreover, a unique responsiveness of fluorescet intensity to the power-on time was observed. It could even be reversible. This kind of composite hydrogel is of high potential to be applied in flexible electricity-fluorescence appliances as a smart soft matter.