Synthesis and Characterization of Conducting Polymer Actuators

Conducting polymers are known to mechanically respond to electrochemical stimuli and have been utilized as linear actuators. To date, the most successful mechanism for actuation is ionic ingress and egress, though mechanisms based on conformational changes and molecular interactions have also been proposed. In the pursuit of new conducting polymer actuators it is necessary to design, synthesize, and characterize new materials, spanning scientific disciplines from synthetic chemistry to materials and mechanical engineering. As such, the topics of synthesis and characterization of new conducting polymers are discussed, highlighting developments in techniques and instrumentation. Actuation in poly(3,4-ethylenedioxythiophene), or PEDOT, and composites of PEDOT and carbon nanotubes is presented, demonstrating strains of 4.5% and strain rates of 0.2% per second with faster responses generated in carbon nanotube composites. Actuation in poly(3-hexylthiophene) is presented, demonstrating the observation of a novel actuation mechanism relating the potential of the polymer to the mechanical response. Further study of the actuation of polypyrrole at temperatures above 25°C is also discussed, in which response times decrease and magnitudes increase with temperature. Discrete time models of equivalent circuits and diffusion are utilized to predict conducting polymer actuator performance. Thesis Supervisor: Timothy M. Swager Title: John D. MacArthur Professor of Chemistry Thesis Supervisor: Ian W. Hunter Title: Hatsopoulos Professor of Mechanical Engineering