Abstract
The use of light to actuate materials is advantageous because it represents a cost-effective and operationally straightforward way to introduce energy into a stimuli-responsive system. Common strategies for photoinduced actuation of materials typically rely on light irradiation to isomerize azobenzene or spiropyran derivatives, or to induce unidirectional rotation of molecular motors incorporated into a 3D polymer network. Although interest in photoredox catalysis has risen exponentially in the past decade, there are far fewer examples where photoinduced electron transfer (PET) processes are employed to actuate materials. Here, a novel mode of actuation in a series of redox-responsive hydrogels doped with a visible-light-absorbing ruthenium-based photocatalyst is reported. The hydrogels are composed primarily of polyethylene glycol and low molar concentrations of a unimolecular electroactive polyviologen that is activated through a PET mechanism. The rate and degree of contraction of the hydrogels are measured over several hours while irradiating with blue light. Likewise, the change in mechanical properties—determined through oscillatory shear rheology experiments—is assessed as a function of polyviologen concentration. Finally, an artificial molecular muscle is fabricated using the best-performing hydrogel composition, and its ability to perform work, while irradiated, is demonstrated by lifting a small weight.
Original language | English |
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Article number | 1700781 |
Journal | Macromolecular Rapid Communications |
Volume | 39 |
Issue number | 17 |
DOIs | |
State | Published - Sep 2018 |
Externally published | Yes |
Funding
K.P.L. and A.F.G. contributed equally to this work. The authors thank Washington University in St. Louis (WUSTL) for supporting this research. The rheological characterization data were obtained through the Department of Mechanical Engineering and Materials Science at WUSTL, and the authors thank Dr. Ruth J. Okamoto for her help with setup and training to assess the mechanical properties of the hydrogel samples.
Keywords
- actuation
- artificial molecular muscles
- hydrogels
- polyviologen
- visible light photoredox catalysis