Abstract

Interest in the development of soft-material artificial molecular muscles has inspired scientists to pursue novel stimuli-responsive systems capable of undergoing change in the physical and mechanical properties of a material in response to external stimuli. This interest has been driven primarily by advances, or the desire for advances, in fields such as soft robotics, microfluidics, and bio-compatible drug-delivery systems. In this work, redox-responsive viologens and their ability to form stable radical-cation complexes were evaluated as a method of actuation in stimuli-responsive materials, specifically hydrogels. First, a brief overview of hydrogel actuators is covered, with some examples given of the broad varieties of stimuli-responsive hydrogels. Then, viologens and their behavior and characteristics are discussed, with special attention paid to the effect of the tether between viologens on their ability to pimerize and the previous work on incorporating viologens into hydrogel actuators. A study was performed to allow viologen-containing hydrogels to respond to a different stimuli than was implemented previously, namely the use of light to actuate the viologen-containing hydrogel using a blue light sensitive photo-redox catalyst that allowed the material to lose 50% of its total volume over five hours. In the same study, it was also shown that the integration of oligoviologen above 5 mol % was detrimental to the physical properties of the material with no noticeable benefit in actuation speed or amount. Viologen-containing hydrogels were then incorporated into a hydrogel network using a different method of polymerization, namely uncontrolled free radical polymerization where the previous studies had utilized copper-mediated azide-alkyne “click” chemistry. These hydrogels were shown to actuate in a similar manner and change color to those shown in previous studies. These viologen-containing hydrogels were then photopatterned using a mask and a ruthenium-based photocatalyst. There is a lot of potential for these viologens to be utilized in hydrogel actuators due to their responsiveness to differing stimuli, such as those described here.

Committee Chair

Jonathan C. Barnes

Committee Members

John-Stephen Taylor Julio D'Arcy

Comments

Permanent URL: https://doi.org/10.7936/htxb-9q38

Degree

Master of Arts (AM/MA)

Author's Department

Chemistry

Author's School

Graduate School of Arts and Sciences

Document Type

Thesis

Date of Award

Winter 12-5-2018

Language

English (en)

Author's ORCID

https://orcid.org/0000-0001-9213-4708

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