A research group led by Graduate Student Takuma Wada (at the time of research), Assistant Professor Kenji Yamaoka, and Professor Yoshinori Takashima of the Graduate School of Science at the University of Osaka have developed a novel polymer adhesion material that enables easy dismantling and re-adhesion through external stimuli by controlling the formation of host-guest complexes at polymer interfaces. Additionally, by visualizing the adhesion interface at the nanoscale, they revealed for the first time in the world the seemingly contradictory phenomenon that adhesion strength increases even though complex formation suppresses polymer chain diffusion. The adhesion technology developed by the group is an adhesive that is dismantlable and repeatedly reusable on demand, and in this capacity enables improved yield through reduction of defects during assembly and separation, recovery, and recycling of composite material products after use, contributing to the realization of a resource-recycling society. Their findings were published in Advanced Materials.
(b) Changes in adhesion strength during repeated adhesion-detachment cycles.
(c) Regulation of adhesion strength through the addition and removal of a competitive inhibitor molecule (toluene).
Provided by the University of Osaka
Adhesion is a fundamental technology supporting all industries and has become indispensable in daily life. As we work toward a recycling-based society, there is strong demand for recyclable adhesion and reusable bonding technologies, but conventional adhesives often "adhere strongly but cannot be removed," making recycling, repair, and component replacement difficult.
There were expectations of applying host-guest complexes to easily dismantlable adhesion (adhering strongly but removable when desired) due to their molecular selectivity and stimuli responsiveness, but the mechanism of why they can be repeatedly attached and removed has not been sufficiently clarified. Notably, while molecular recombination and polymer chain diffusion (interdiffusion) have been considered as adhesion mechanisms, it was unclear which one contributes to adhesion strength.
The research group developed a novel polymer adhesion material that enables easy dismantling and re-adhesion through external stimuli by controlling the formation of host-guest complexes at polymer interfaces. Furthermore, by observing the adhesion interface at the nanoscale using neutron reflectivity, they elucidated for the first time in the world the seemingly contradictory phenomenon that adhesion strength increases even though complex formation suppresses diffusion.
In this study, control of host-guest complex formation at the adhesion interface was made possible by optimizing the chemical composition and adjusting the mobility of polymers. The host polymer and guest polymer maintained 90% adhesion strength even after repeating adhesion and peeling five times. Furthermore, control of adhesion strength was achieved by using a competitive inhibitor molecule (toluene) that dissociates the host-guest complex. When the competitive inhibitor molecule is added, adhesion strength reduces to 15% of the original, allowing for easy removal. Additionally, when the competitive inhibitor molecule is removed, adhesion strength recovers to 76%, enabling re-adhesion.
The adhesive material developed not only enables the separation and recovery of bonded components but also allows the adhesive itself to be repeatedly used and recycled. As an on-demand dismantlable and repeatedly reusable adhesive, it enables a resource-recycling society and economic value creation through improved yield in manufacturing processes, enhancement of recycling efficiency, waste reduction, and other benefits.
Takashima commented: "We have succeeded in adhesion via host-guest complex formation at the interface between polymers, which was not possible for many years. This research outcome is filled with the excitement of materials research, which controls invisible molecules to manifest functions. I hope this achievement will lead to the creation of next-generation materials based on molecular-level design."
Journal Information
Publication: Advanced Materials
Title: Supramolecular Interface Engineering via Interdiffusion for Reusable and Dismantlable Polymer Adhesion
DOI: 10.1002/adma.202507939
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