In the field of intelligent materials, the rise of out-of-equilibrium molecular machines capable of converting light into mechanical work represents a new opportunity to develop increasingly complex reactive systems. The development of artificial muscle-like materials, where nanoscopic motor units can work simultaneously to induce macroscopic motion, is one of the main challenges that remain to be addressed. To this end, our team has developed a contractive chemical gel incorporating Feringa’s light fuelled unidirectional rotary molecular motors as reticulating points. Until now, exposure to UV has been necessary to induce movement in these systems. However, the destructive nature of an irradiation at these wavelengths on organic and biologic materials led us developing an alternative strategy using visible light instead. The addition of a porphyrin-based photosensitizer in solution allowed intermolecular triplet energy transfer to the molecular motor inducing its rotation at 530 nm. NMR and phosphorescence quenching were successfully used to quantify the excitation and rotation kinetics. The measurement of the evolution of gel surface showed a maximum contraction of 45% with no sign of degradation over long period of irradiation, paving the way for new applications with softer and/or more sensitive systems.

Macroscopic contraction of chemical gel incorporating unidirectional rotary molecular motors with visible light

ACS Spring Meeting 2021

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