Photoinduced mendable network polymer from poly(butylene adipate) end-functionalized with cinnamoyl groups

Abstract

A network polymer with photoinduced mending abilities was prepared from cinnamoyl-telechelic prepolymer of poly(butylene adipate), PBAC 2 , and a tetra-cinnamoyl linker, C 4 , by photodimerization. The photodimerization reaction of the cinnamoyl groups was analyzed using both ultraviolet (UV)/visible (vis) and infrared (IR) spectroscopy. In the reaction, the isomerization of the cinnamate group from the trans to the cis conformation competes with the dimerization reaction of cinnamates. The fractions of dimer and isomer populations estimated from the UV/vis spectra revealed that dimerization was the more preferred reaction at temperatures higher than the melting point of PBAC 2 . When a film of the network polymer was damaged by tapping, the cinnamate dimers dissociated to form cinnamate monomers due to the reversibility of the dimerization. To recover the network structure, these monomers could be dimerized once again through a photoirradiation process. These results show that cracks in the network polymer can be recovered through photoirradiation.

How to Design a Self‐Healing Polymer: General Concepts of Dynamic Covalent Bonds and Their Application for Intrinsic Healable Materials

“…Ling et al demonstrated a self‐healing polyurethane network with coumarin sidechains, which can be cleaved upon irradiation with UV light at 254 nm and reform the crosslinks at 350 nm . The characteristic of cinnamate groups, as described by Yoshie and co‐workers is the mechanism of photoisomerization, which occurs alongside the dimerization . In order to overcome the isomerization, since this can be problematic for some polymers if only one of the isomers is reactive toward addition, examples of [4 + 4] cycloaddition in reversible covalent polymer networks have been described.…”

Self-repair of structural and functional composites with intrinsically self-healing polymer matrices: A review

“…In their study, healing was conducted by photoirradiation (λ > 280 nm) for 10 minutes. More recently, Ling et al and Oya et al continued this line of research by synthesizing novel self-healing polymers based on [2+2] photocycloaddition [49,50].…”

Early damage detection in epoxy matrix using cyclobutane-based polymers

“…Figure 1(a) displays the UV absorbance variation of TCE dilute solution as a function of UV exposure time. It had strong UV absorbance between 250 and 350 nm with a peak centered at approximately 280 nm; this likely corresponds to the abundance of π-π* transitions of the C=C double bond from cinnamoyl groups before photoirradiation, as reported elsewhere 26,[32][33] . The change in the absorbance value was monitored for continual irradiation, and it is obvious to notice that the absorbance band decreases rapidly with exposure time and disappears almost completely within 30 minutes of photoirradiation.…”