UC Merced

Stimuli responsive polymers change shape or properties in response to external stimuli such as light, heat, electric or ionic current, or solvents to name a few. These materials have gained a lot of attention in recent years due to their promising application as artificial muscles, smart clothes and wearable devices, drug delivery systems, and more. This dissertation introduces a new class of stimuli responsive polymers, dibenzocyclooctadiene (DBCOD) based materials. DBCODs are molecules capable of negative thermal expansion through a low energy activated conformational change. Similar actuators are compared and a history of DBCOD polymers and their unique properties is provided. Herein, contribution to the field is made by taking advantage of DBCOD as a new mechanism for actuation. A highly sensitive thermal and light actuating bilayer capable of reversible deformation at as low as a few degrees of temperature rise is presented. Coordinated conformational changes of DBCODs result in macroscopic thermal contraction that is inherently fast, repeatable, and low-energy driven. High precision actuation and excellent cycle stability of the bilayer is demonstrated. A platform consisting of poly(vinylidene fluoride) in tandem with the bilayer can harvest low-grade thermal energy and convert it into electricity. Furthermore, the DBCOD active material is shown to be sensitive to moisture and solvents, adding additional stimuli for actuation. The outlook of DBCOD-based materials is promising with actuation adding the potential to be used as energy harvesters, sensors, soft robots, biomedical devices, etc. The main focus of this dissertation is to take advantage of DBCOD’s unique properties to offer new stimuli-responsive behavior which expands the application potential of polymeric DBCOD.