Supramolecular polymers offer a range of useful stimuli-responsive properties if binding motifs with dynamic characteristics are used. For example, nanocomposites based on a telechelic poly(ethylene-co-butylene) (PEB) terminated with hydrogen-bonding ureidopyrimidone (UPy) groups (UPy-PEB-UPy) and UPy-decorated cellulose nanocrystals are light-healable and show much better mechanical properties than the supramolecular polymer alone. Upon exposure to ultraviolet radiation, the UPy motifs convert the absorbed energy into heat, which causes disengagement of the hydrogen-bonding motifs and a decrease of the material's molecular weight and viscosity. As a result, defects can be healed quickly and efficiently, even at a filler content of 20% w/w. UPy-PEB-UPy is also useful as reversible adhesive, which permits bonding and debonding on demand. Lap joints bonded with the material (which contains an auxiliary light-heat converter) display appreciable shear strength, but can be rapidly debonded upon exposure to heat or UV light. With the objective to identify a simpler and modifyable H-bonding motif that supports the formation of supramolecular polymers, we investigated the isophthalic acid-pyridine (IPA-Py) pair, which appears to have been forgotten in the context of supramolecular materials. Gratifyingly, materials assembled from IPA-terminated PEB (IPA-PEB-IPA) and bis-pyridines display a higher storage modulus (12-21 MPa) than the corresponding UPy-PEB-UPy. Finally, we report a new supramolecular glass that is formed by a low-molecular weight monomer with three UPy moieties. The material displays an intriguing combination of optical and mechanical properties.

Stimuli-responsive hydrogen-bonded supramolecular polymers

248th National Meeting (2014)

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