Green, Removable Adhesive Based on Graft Copolymers of Aliphatic Polyesters for Multiple Types of Substrates

Aremovable, green adhesive based on graft copolymers ofaliphatic polyesters has been developed, which has strong adhesionto various substrate surfaces by forming noncovalent interactionswith the adherends. When out of service, the adhesive could be debondedunder mild conditions to achieve intact recovery of the adherends.Moreover, the residue of debonded adhesive could be depolymerizedto corresponding monomers with high purity. Adhesive is a widely used material. However, most oftraditionalsynthetic adhesives are difficult to be peeled and removed withoutdamaging the adherends due to their excellent chemical stability andstrong interaction (covalent bonds, physical interactions, or theircombinations) with the substrate surfaces. Therefore, complete andefficient recovery of the substrates has become a huge challenge.In this work, a green, removable adhesive based on graft copolymersof aliphatic polyesters, i.e., PPDO (poly(1,4-dioxan-2-one)) and PCL(poly(epsilon-caprolactone)) was prepared through one-pot ring-openingpolymerization using polyvinyl alcohol (PVA) as the macro-initiator.The graft copolymers have abundant graft chains and hydroxyl end groupsowing to their comb-like molecular topology, which therefore act asactive sites for bonding with the substrate surfaces. The graft copolymersshowed considerable adhesive strength to various substrates, includingstainless steel plates (lap shear strength >1 MPa), woods (>1MPa),glasses with a very low surface roughness (<10 nm) (0.62 & PLUSMN;0.04 MPa), and plastics with low surface energy such as PE (T-peelstrength: 427.0 g(f)/25 mm). Furthermore, the adhesives basedon aliphatic polyesters could be easily debonded under a relativelymild condition through degradation when they were taken out of service,thus realizing the intact recovery of the substrates. The debondedadhesive and its degradation products could be further depolymerizedto monomers with a very high purity (>99.5%) by acidification-dehydrativecyclization or simple pyrolysis (150 & DEG;C) under vacuum. In thewhole life cycle, almost no versatile organic compounds were used.In addition, CCK8 experiments proved that the graft copolymer adhesivehad no toxicity to HEK 293T human cells, indicating that it is a greenadhesive with great potential.