The electromechanical response of ionic polymers to an applied electric field is of significant interest to a variety of fields including flexible electronics, biomimetic devices, and nano-fluidics. While the use of Nafion and similar polymers as actuators has been thoroughly studied, a full understanding of the complex interplay between electromechanical response and the chemical structure, morphology, and ion mobility of these ionomeric systems is still lacking. The actuating behavior of ionic polymer systems results from deformation due to electric/Maxwell stress (electrostatics of ion distribution) as well as viscous/hydrodynamic stress (properties of the polymer structure and chemical identity). To address this fundamental question we used Reversible addition fragmentation chain transfer (RAFT) to synthesize di- and triblock copolymers with a novel imidazole monomer as the soft block while the hard blocks were comprised of styrene or deuterated styrene. We utilized neutron reflectometry to investigate how the composition of ionic block copolymers affects the electrostatic interactions and morphology under an applied electric field in polymer thin films. The sensitivity of neutron reflectometry to scattering length density as well as sub nanometer changes in thickness make it an ideal tool for investigating polymer and counter-ion mobility under an applied electric fields. To this end, we have designed a sample environment for the Liquids Reflectometer (BL-4B) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) that is capable of applying an electric field to a sample during neutron reflectometry measurements. The results of molecular dynamic and self-consistent field theory (SCFT) simulations along with the neutron reflectivity data will be presented and used to gain a better understanding of the mesoscale changes that contribute to the macroscopic electromechanical response and aid in the rationale design of new soft materials.

Determining the electromechanical response mechanism of nanostructured ionic block copolymers under an applied electric field

253rd National Meeting (2017)

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