A facile method to prepare UV light-triggered self-healing polyphosphazenes

It is of importance to prepare self-healing materials using reversible covalent bonding within polymers. In this work, we introduced ethyl 4-aminocinnamate (EA) to polyphosphazenes to prepare a novel self-healing elastomer via the reversible photochemical [2+2] cycloaddition. Linear polymer, poly[(n-butylamino) (x) (ethyl 4-aminocinnamate) (y) ] phosphazene, was synthesized firstly via the ring-opening polymerization, and then substitution reaction was conducted to introduce EA as side groups. Consequently, the damaged polyphosphazenes were re-healed by being exposed to UV light. Their structures were characterized by H-1-NMR, P-31-NMR, FTIR, and GPC; thermal properties were tested by TGA and DMA. The [2+2] cycloaddition reaction and retro-[2+2] cycloaddition were investigated by UV-vis. The results showed that the broken polyphosphazenes could be self-healed by the UV light irradiation at 365 nm. The damaged polyphasphozene could be re-healed almost completely within about half an hour.