Novel linear ionic PU adhesives could play conservation role

Researchers at Shaanxi Normal University in Xi’an, China have created a new family of polyurethane‑based adhesives that remain strong even in water, organic solvents and liquid nitrogen: a discovery that could reshape both industrial bonding and cultural heritage conservation.

The team – led by Wenhe Jiang, Zhongwen Sun and Ruitong Wan – engineered what they call linear ionic polyurethanes (LIPUs)—a redesigned form of polyurethane that incorporates ionic liquid segments directly into the polymer backbone. This structural twist dramatically improves how well the adhesive wets and grips different surfaces, a long‑standing weakness of traditional PU systems.

But the real leap came from pairing these new polymers with a supramolecular “combinatorial” strategy. By blending the LIPUs with carefully chosen additives that interact through non‑covalent forces – such as hydrogen bonding, electrostatic attraction and π‑π stacking – the researchers were able to fine‑tune the internal structure of the adhesive at the molecular level.

The result is a material the researchers claim is not only stronger but far more resilient than existing PU adhesives. Pure LIPUs already reached an adhesion strength of 12 MPa, but the supramolecular composites more than doubled that performance, achieving 26 MPa. Even under extreme conditions – including full immersion in solvents or exposure to liquid nitrogen – the adhesives maintained 11–23 MPa of strength. Traditional LIPUs, by comparison, often fall to 0–5 MPa in similar tests.

Beyond industrial applications, the researchers demonstrated the technology’s potential in cultural heritage restoration, an area where adhesives must be strong yet gentle, durable yet reversible, and stable under unpredictable environmental conditions. The new system successfully repaired paper, ceramics, jade and mud‑based sculptures using only mild heating, offering conservators a promising new tool for delicate restoration work.

Photo: a graphical abstract of the research (© Elsevier)

The study has been published in the journal Materials Today.