A new method for stabilising conducting polymer latices using short chain alcohol ethoxylate surfactants

Abstract

This study involves the investigation of a new method for the preparation of colloidally stable poly(3,4-ethylenedioxythiophene) (PEDT) dispersions. Our experimental data show for the first time that a relatively short-chain alcohol ethoxylate surfactant (C₁₆E₁₆, where C and E represent the methylene and ethylene oxide groups, respectively) can be used to stabilise a conducting polymer dispersion. The principle techniques used to study the PEDT dispersions are photon correlation spectroscopy, transmission electron microscopy and electrical conductivity measurements (of pelletised samples). Microanalytical data are also presented. The oxidant (ammonium persulfate, APS) oxidises the surfactant and monomer simultaneously during dispersion synthesis causing production of surfactant aggregates and conducting polymer particles, respectively. The oxidation results in control samples of surfactant solution becoming turbid. The anionic surfactant aggregates adsorb onto the growing PEDT particles and provide electrosteric stabilisation for the PEDT dispersions. The effect of several key parameters on the hydrodynamic diameter for the PEDT particles are investigated, e.g., APS and surfactant concentration. Stable dispersions result only when critical concentrations of the APS and surfactant are exceeded. The electrical conductivity for PEDT samples increases with decreasing amount of surfactant used during preparation. A maximum conductivity of 0.016 S cm⁻¹ was measured.