Self-healing of poly(propylene oxide)-polybenzoxazine thermosets by photoinduced coumarine dimerization

In this work, a self-healing strategy for poly(propylene oxide)s bearing coumarine-benzoxazine units (PPO-CouBenz)s based on light induced coumarine dimerization reactions is described. Four different types of poly(propylene oxide) amines with molecular weights ranging from 440 to 5000 Da were reacted with formaldehyde and 4-methyl-7-hydroxycoumarin to yield desired (PPO-CouBenz)s. The crosslinked polymer films were prepared by solvent casting of various compositions of PPO-CouBenzs in chloroform followed by thermal ring opening reaction of benzoxazine groups at 210-240 C. Thermal curing and thermal stability of the initial PPOs and final products were investigated. Using allyl benzoxazine in the formulation, it was demonstrated that the toughness of the films was improved. Photoinduced healing of coumarin-based cured PPO-CouBenz polymer films was investigated.