(187d) Mechanical and Electrical Properties of Nanostructured Polymer Systems

Considerable efforts are currently underway in the field of electroactive polymeric (EAP) materials as actuators. This attention stems from the broadly attractive properties of polymers: they are lightweight, easily fabricated into various shapes and relatively inexpensive, and their properties can be tailored by both chemical and physical means. The key attributes of actuator materials include energy density, specific energy density, actuation strain, hysteresis under cyclic loading/unloading, actuation pressure, efficiency, and response time. One of the most widely used EAP materials presently available is VHB acrylic foam manufactured by 3M. The present work describes and investigates the mechanical and electrical response of multifunctional nanostructured polymer systems. The systems of interest consist of incompatible block copolymers that microphase-separate into well-defined nanostructural elements, thereby providing a tunable avenue to material properties. Copolymer systems varying in molecular weight and composition have been fabricated, and their mechanical and electrical properties have been tested for actuator and sensory technologies. The hysteresis behavior of these EAP materials has been measured under cyclic loading/unloading at constant strain and compared with the VHB acrylic foam, which constitutes the leading commercial EAP material presently available. All the copolymer systems investigated here reveal less nonrecoverable strain upon cyclic loading/unloading relative to the acrylic foam. In fact, nonrecoverable strain is entirely absent in some of the systems developed during the course of this study, indicating that nanostructured polymer design could yield new and competitive materials for soft, reliable and robust actuators.