Aqueous Formulation of Concentrated Semiconductive Fluid Using Polyelectrolyte Coacervation

Abstract

Conjugated polyelectrolytes (CPEs), which combine πconjugated backbones with ionic side chains, are intrinsically soluble in polar solvents and have demonstrated tunability with respect to solution processability and optoelectronic performance. However, this class of polymers often suffers from limited solubility in water. Here, we demonstrate how polyelectrolyte coacervation can be utilized for aqueous processing of conjugated polymers at extremely high polymer loading. Sampling various mixing conditions, we identify compositions that enable the formation of complex coacervates of an alkoxysulfonatesubstituted PEDOT (PEDOT-S) with poly(3-methyl-1-propylimidazolylacrylamide) (PA-MPI). The resulting coacervate is a viscous fluid containing 50% w/v polymer and can be readily blade-coated into films of 4 ± 0.5 μm thick. Subsequent acid doping of the film increased the electrical conductivity of the coacervate to twice that of a doped film of neat PEDOT-S. This higher conductivity of the doped coacervate film suggests an enhancement in charge carrier transport along PEDOT-S backbone, in agreement with spectroscopic data, which shows an enhancement in the conjugation length of PEDOT-S upon coacervation. This study illustrates the utilization of electrostatic interactions in aqueous processing of conjugated polymers, which will be useful in large-scale industrial processing of semiconductive materials using limited solvent and with added enhancements to optoelectronic properties.

Conjugated Polyelectrolyte‐Based Complex Fluids as Aqueous Exciton Transport Networks

“…By probing the CPE photophysics, we can directly elucidate how the delocalized electronic wavefunction of the CPE evolves across the transition from the two‐phase to the one‐phase region of the phase diagram. To the best of our knowledge, our work is the first to demonstrate the formation of an aqueous complex fluid composed of an exciton donor/acceptor network capable of efficient EET [27–29] …”

“…To the best of our knowledge, our work is the first to demonstrate the formation of an aqueous complex fluid composed of an exciton donor/ acceptor network capable of efficient EET. [27][28][29]…”

“…The photophysics within the polymer‐rich phase were found to be strongly coupled to the ionic atmosphere. The Segalman and Chabinyc groups have also shown that oppositely charged systems with one conjugated and one non‐conjugated polyelectrolyte can be used to form semiconducting and conducting fluids [27, 28] …”

Ionic Compatibilization of Polymers

“…The melt intractability and limited solubility of conjugated polymers have restricted the processing of these materials, hindering the fabrication of bulk/shaped structures that are required in various applications such as actuators, bioelectronic scaffolds, or thermoelectric modules. Recently, solvated mixtures of a conjugated polyelectrolyte (CPE) and an oppositely charged insulating polymer have been demonstrated to form fluid- or gel-like complex coacervates that can be processed at very high polymer loading. − Electrostatic interactions have previously been utilized to improve the processability of conjugated polymers in water, such as the widely investigated interpolymer complexes poly­(3,4-ethylenedioxythiophene)/poly­(styrenesulfonate) (PEDOT:PSS) and polyaniline/poly­(2-acryl amido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA). In these systems, the conjugated monomers are polymerized on the polymer acid templates, where the hydrophilic nature of the template forms a shell that stabilizes the hydrophobic conjugated core in water.…”

Conjugated Polyelectrolyte‐Based Complex Fluids as Aqueous Exciton Transport Networks

“…The Segalman and Chabinyc groups have also shown that oppositely charged systems with one conjugated and one non-conjugated polyelectrolyte can be used to form semiconducting and conducting fluids. [27,28] In this work, we have used aqueous associative phase separation to form complex fluids composed of two oppositely charged CPEs which function as an exciton donor/acceptor pair. We find spectrally broad light absorption and highly efficient exciton transfer from the donor to the acceptor CPE.…”