Evaluating the Electrical Response of Polyaniline to Mechanical Strain

Abstract

This thesis focuses on the electrical output of polyaniline films subjected to uniaxial strain in hydrochloric acid solutions. Polyaniline belongs to novel class of materials known as conducting polymers. Alternating single and double bonds in the backbone of conducting polymers allow them to transmit electric charge when they are doped with negatively charged ions. Modifying the degree of doping and other electrical/chemical treatments allow conducting polymers to exhibit conducting, semiconducting, or insulating electrical properties. Resilient mechanical properties, good processability, and low cost make conducting polymers good candidates for applications traditionally held by metals and semi-conductors.When tensile strain is applied to polyaniline in an electrolyte solution, the material selectively absorbs negatively charged ions. This charge imbalance produces a measurable electrical output. Theoretical models based on Fick's second law of diffusion were compared against experimental results to determine fundamental material properties such as diffusivity and ion solubility in polyaniline. These properties were used to quantify polyaniline as a sensor material based on characteristics including sensitivity, accuracy, precision, range, linearity, and error. Films were cast from solutions of polyaniline powder (M n = 65,000) in N-methyl-2-pyrrolidinone solvent, with thicknesses ranging from 2.72 to 158 µm.