INTEGRAted moTIONS from molecular machines and motors – INTEGRATIONS

The first chemical syntheses have been performed to access rotaxane-based contractile systems. In particular, those have been linked to diaminopyridine end groups. In parallel, we have synthesized connecting groups as soluble rigid rods with bis-uracile end groups. We have demonstrated that the association between the rotaxanes and the rods leads to hydrogen bonds supramolecular polymers (with a recognition motif diaminopyridine / bis-uracile), and that very long fibers can be obtained. Because of the cooperative action of the connectors, these polymers can be bundled in larger fibers with an aspect that resembles muscular tissues. Then, we have succeeded in connecting molecular machines using ureidipyrimidinone H-bond stickers, but also by using covalent bonds to form permanently cross-linked polymer networks and gel-like materials. We have also developed a generic synthesis of rotary molecular motors to insert them within polymer chains in order to access another kind of chemical gels.

The contraction and extension of the rotaxanes within the micrometric fibers have shown concomitant changes of their mesoscale morphologies. In the case of gels of rotaxanes, we have shown that a mechanic actuation of the machine can lead to sol-gel transitions, or to the contraction / expansion of the entire material. Finally, we have shown that the rotation of the motors under light irradiation generates twisting and braiding of the polymer chains up to the entire contraction of the material. These examples are the first ones in the literature that couple the motions of artificial molecular machines up to the macroscopic scale.

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On rotaxanes : 2 J. Am. Chem. Soc. (including 1 highlight by the editor); 1 Angew. Chem. Int. Ed. (hot paper and press release by the editor) ; 1 Nanoscale ; and an invited mini-review on that new topic in CCS Chemistry (for its 1st issue).
On motors : 2 Nature Nanotech. (including 1 highlight by the editor, and 1 selected as « Research of the Year 2017» by the C&EN magazine, december 18th 2017) ; 1 Nanoscale (submitted); 1 Tetrahedron (invited by Ben Feringa, Nobel Prize Laureate 2016) ; 1 invited concept article in Adv. Mat. (special issue on responsive materials) ; 1 invited review article in Chem. Rev. (submitted).

One of the most intriguing functional properties of living systems is their capacity to generate collective molecular motions which produce macroscopic responses. For instance, in muscular tissues, the coordinate movements of thousands of myosin heads lead to the gliding of thick myosin filaments along thin actin filaments which result in a cooperative contraction of the entire sarcomere. In that particular case, the individual shifts of the proteins take place in the 10 nm range whereas their integrated translation produces a 1 µm contraction of the sarcomeres, these latter being in turn coupled together, up to producing macroscopic motions. The synthesis of artificial molecular machines and motors is thus of central interest for chemists and physicists in order to mimic their biological counterparts with the long-term aim of engineering dynamic functional materials by bottom-up approaches. However, one of the most fundamental and challenging objectives associated to nano-machines remains their coupling (in space and time) in order to transfer controlled motions from the molecular arena to the macroscopic scale. Recently, we have published an important scientific breakthrough showing the four orders of magnitude amplification of the mechanical output of thousands of molecular machines linked within a single-strand supramolecular chain, and transferring reversible contractile motions from the low nanometer scale to the ten of micrometers. Based on these seminal results, we now propose to integrate linear and circular motions of molecular machines with polymer chemistry and supramolecular chemistry, in order to produce macroscopic contractile gels and films at macroscopic scale. In particular, two series of machines will be developed, one being considered as a nano-switch and functioning at thermodynamic equilibrium; the other being considered as a real nano-motor and functioning out of equilibrium when fuelled by light energy. This work will be developed thanks to a close-knit collaboration between synthetic chemists, experimental physicists, and theoretical physicists. By using state-of-the-art knowledge and techniques, such a synergy will allow a full characterization and understanding of our chemical systems, from molecular to macroscopic scales. It will result in the first implementation of nano-machines in responsive polymer-based materials and devices with production of a useful work at our scale.