Bistable, rotaxane-based “molecular muscles”, whose switchable motions are enabled by mechanical bonds, have become one of the most important members in the family of mechanically interlocked molecules (MIMs) during the last two decades. Polyrotaxane and daisy chains (mostly double-threaded dimer) are critical components for molecular actuators, rendering unique mechanical properties to these stimuli-responsive materials.<br/>Most importantly, their motions are based on specific recognition sites within molecules and can be modulated by applying external stimuli, such as changes in ions, pH, redox chemistry and light. However, macroscopic molecular actuators have remained a major challenge in this field, in part because of the synthetic difficulty of obtaining multidimensional daisy-chain molecules. Rational design of daisy-chain monomers by fine tuning their rigidity and exploring alternative synthetic routes should improve the current situation and result in a variety of interesting molecular actuators.<br/>In this project, we propose synthesizing redox switchable daisy-chain based polymers that can either contract or expand through radical-pairing interactions using a pumping followed by polymerization approach. A rotaxane-like monomer has been assembled firstly through a molecular pumping process and will be further polymerized using Click reactions. We anticipate the resultant responsive polymer network formed by crosslinking with multi-arm poly(ethylene glycol)s will exhibit macroscopic motions under reducing conditions and fully reversible when oxidized.

Redox controlled molecular muscles: A daisy-chain polymer using pumping followed by polymerization

256th National Meeting (2018)

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