Tunable supramolecular gel properties by varying thermal history

Debnath, Sisir and Roy, Sangita and Abul‐Haija, Yousef M. and Frederix, Pim W. J. M. and Ramalhete, Susana M. and Hirst, Andrew R. and Javid, Nadeem and Hunt, Neil T. and Kelly, Sharon M. and Angulo, Jesús and Khimyak, Yaroslav Z. and Ulijn, Rein V. (2019) Tunable supramolecular gel properties by varying thermal history. Chemistry - A European Journal, 25 (33). pp. 7881-7887. ISSN 0947-6539 (https://doi.org/10.1002/chem.201806281)

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The possibility of using differential pre-heating prior to supramolecular gelation to control the balance between hydrogen-bonding and aromatic stacking interactions in supramolecular gels and obtain consequent systematic regulation of structure and properties is demonstrated. Using a model aromatic peptide amphiphile, Fmoc-tyrosyl-leucine (Fmoc-YL) and a combination of fluorescence, infrared, circular dichroism and NMR spectroscopy, it is shown that the balance of these interactions can be adjusted by temporary exposure to elevated temperatures in the range 313–365 K, followed by supramolecular locking in the gel state by cooling to room temperature. Distinct regimes can be identified regarding the balance between H-bonding and aromatic stacking interactions, with a transition point at 333 K. Consequently, gels can be obtained with customizable properties, including supramolecular chirality and gel stiffness. The differential supramolecular structures also result in changes in proteolytic stability, highlighting the possibility of obtaining a range of supramolecular architectures from a single molecular structure by simply controlling the pre-assembly temperature.