Electric field induced cloudy–clear transitions in micellar solutions of a block copolymeric amphiphile

Abstract

We report observations of cloudy–clear transitions, triggered by electric fields, in micellar solutions of a poly(oxy ethylene/propylene)–poly(dimethylsiloxane) based triblock amphiphile dissolved in silicone oil (DC245). Initial studies showed complete clarification of a cloudy 2% solution at ambient temperature when subjected to a uniform electric field of ∼5 kV cm⁻¹. Static Light Scattering measurements showed that the clarification was associated with a significant reduction in the size of the micellar aggregate from ca. 200 nm to 50 nm. Field strength studies at varying temperatures established the potency of the effect at 1 kV cm⁻¹ field equivalent to a 1 K decrease in temperature. The observed effect was qualitatively different from the electric field induced macroscopic pattern formations, or self assembled domain rotations or mesogen alignment phenomena; and quantitatively far more impactful than the minor shifts in phase boundaries reported earlier. Although the mechanistic underpinning of the observed field effect has yet to be established, the optical switchability of the solutions could be exploited for various electro-optical applications such as displays, and optical filters. The work also opens up the possibilities of using electric fields for manipulating micellar solubilization or creating tunable templates for nano-material synthesis.