We have developed a transparent organic polymeric material that can repeatedly mend or "re-mend" itself under mild conditions. The material is a tough solid at room temperature and below with mechanical properties equaling those of commercial epoxy resins. At temperatures above 120 degrees C, approximately 30% (as determined by solid-state nuclear magnetic resonance spectroscopy) of "intermonomer" linkages disconnect but then reconnect upon cooling, This process is fully reversible and can be used to restore a fractured part of the polymer multiple times, and it does not require additional ingredients such as a catalyst, additional monomer, or special surface treatment of the fractured interface.

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Two new remendable highly cross-linked polymers, 2ME4F and 2MEP4F, were prepared without solvent. Solid-state NMR (nuclear magnetic resonance) was used to study the thermal reversibility of Diels−Alder (DA) cross-linking, and it was found that DA connections and disconnections of both polymers are thermally reversible. Differential scanning calorimeter and dynamical mechanical analysis were applied to study thermal and mechanical properties of these materials, and it is found that the glass transition temperature (T g) of 2ME4F is about 30−40 °C and that of 2MEP4F is about 80 °C. A qualitative study of the healing efficiency of 2MEP4F showed that cracks can be healed effectively with a simple thermal healing procedure. This process can be repeated to heal cracks multiple times.

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