Artificial muscle morphology : structure/property relationships in polypyrrole actuators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (leaves 183-204).We seek to improve polypyrrole and other conducting polymer actuators by discovering and exploiting the connection between nanoscale transport events and macroscale active strain. To this end we have used diffraction and electron microscopy to investigate the microstructure of polypyrrole. and propose a new description consisting of disordered polypyrrole chains held together by small crystalline bundles, around which solvent and counterions are randomly distributed. We utilize different modes of deformation to impart orientational texture to polypyrrole films, and show that by controlling polymer chain conformation and packing at a sub-micron level a conducting polymer actuator can be engineered that shows a significantly larger macroscopic electroactive response. We also alter the synthesis and doping conditions to produce films with widely varying surface morphologies, allowing us to control the rate of electroactive response. Our detailed understanding of polypyrrole morphology at different lengthscales provides valuable insight to the mechanisms of polypyrrole actuation, and has helped us process polypyrrole more intelligently for improved electroactive devices.by Rachel Zimet Pytel.Ph.D