Disassembly of an Interconjugated Polyelectrolyte Complex Using Ionic Surfactants

Abstract

The ability to manipulate the state of assembly of light-harvesting molecular materials can be important to control light-induced damage at high illumination intensities. Disassembly of such materials is thus an important consideration from a photoprotection perspective. Here, we show that an artificial light-harvesting antenna based on an interconjugated polyelectrolyte complex can be disassembled using ionic surfactants in aqueous solution. We demonstrate that both anionic and cationic surfactants can do so with comparable efficiency, thereby shutting electronic energy transfer between the exciton donor and acceptor conjugated polyelectrolytes. However, the structural evolution of the aqueous complexes both above and below the critical micelle concentration differed significantly depending on the sign of the ionic surfactant and the relative polyion charge ratio.

Ionic Tunability of Conjugated Polyelectrolyte Solutions

“…Conjugated polyelectrolytes (CPEs) enable the same opportunities for aqueous solubility and mixed conduction as PEDOT:PSS, but in a single-component material that can be molecularly engineered for enhanced properties of interest. − CPEs have a π-conjugated backbone modulating the optoelectronic properties appended with ionic side chains that confer electrostatic interactions and solubility in polar solvents. − The strong coupling between ionic and electronic degrees of freedom results in material properties that depend sensitively on the chain microstructure in solution and solid-state. The structure and electronic properties of the same polymer chain can be tuned by the choice of polar solvent, concentration, and charge-compensating counterion, and the presence of salt, surfactant, and other polymers. − Rational control of these design parameters can be leveraged for sensing and actuation. ,− Yet, a more comprehensive understanding of the tunability of the electrostatic interactions present in solutions of conjugated polyelectrolytes is required to improve the use and design of this class of polymers.…”

“…Electrostatic screening can be achieved through manipulation of the ionic content, namely the concentration and chemical nature of the charged species. Variation of the ionic strength and charge compensating counterion are extensively used to control the properties of conjugated polyelectrolytes in the solid state and in solution. ,,,− More recently, it has been shown that the solution structure and properties of a CPE can be dramatically controlled by complexation with an oppositely charged polyelectrolyte. ,,− Polyelectrolyte complexation upon mixing two oppositely charged polyelectrolytes can result in a liquid–liquid phase separation with a dense fluid coacervate coexisting with a dilute supernatant. The dense fluid phase promotes the accessibility of viscous, concentrated solutions of electroactive materials and have been proposed to be a route toward environmentally friendly, high-throughput, low-cost processing. , Furthermore, the ionic complexation modulates the nature of the excitonic wave function permitting control of radiative relaxation and exciton-diffusion dynamics. , CPE–CPE complexes in dilute solutions and in the solid state have been shown to undergo ultrafast interpolyelectrolyte electronic energy transfer suggesting the potential for light harvesting antennas. ,,, …”

Functional Nano-Objects by Electrostatic Self-Assembly: Structure, Switching, and Photocatalysis

“…Ayzner et al presented polyelectrolyte-surfactant complexes in the solution formed by interconjugated polyelectrolyte complexes which can be separated by ionic surfactants. The assemblies act as light-harvesting antennae and enable the electronic energy transfer above and below the critical micelle concentration ( Segura et al, 2019 ). In some cases, the association of small ionic dendrimers with surfactants can lead to amphiphile assemblies in aqueous solution rather than the macroscopic materials outlined in Section 4.3 .…”

Semiconducting Eggs and Ladders: Understanding Exciton Landscape Formation in Aqueous π-Conjugated Inter-Polyelectrolyte Complexes

“…Neither requires excess thermal energy to drive the process. 15 A CPE differs qualitatively from a conventional polyelectrolyte due to the presence of delocalized, highly polarizable π- electrons. 16 To rationally manipulate the landscape that underpins exciton transport in the inter-CPE complex (CPEC), the following fundamental questions must be answered.…”

“…This was a surprising finding given (i) the current understanding of nonconjugated polyelectrolyte complexes and (ii) that this finding stood in stark contrast to complexation of CPEs with oppositely charged surfactants. Neither requires excess thermal energy to drive the process …”