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

Abstract

Conjugated polymers display remarkable optoelectronic properties that emerge from the strong coupling between delocalized π-electrons, leading to highly mobile excited states. This is a very useful property from a light-harvesting perspective. We showed previously that a promising and environmentally attractive approach to formation of an ultrafast light-harvesting antenna is to use aqueous ionic assembly of oppositely charged conjugated polyelectrolytes (CPEs). However, to rationally design the excited-state transfer efficiency, the basic physical chemistry of inter-CPE assembly must be elucidated. We demonstrate that the delocalization of π-electrons and the orientation of ionic sidechains relative to the conjugation plane together dictate the complexation kinetics and thermodynamics, and thus the resulting structure. We find that the enthalpy of complexation is substantially larger than previously observed with nonconjugated polyelectrolytes. We further show that the reaction enthalpy changes sign with increasing temperature. We argue that the interaction between the water solvation shell and the polarizable aromatic backbone is key to understanding both the activation energy and the reaction enthalpy.

Aqueous Formulation of Concentrated Semiconductive Fluid Using Polyelectrolyte Coacervation

“…CPE–polyelectrolyte coacervation was also reported to occur in aqueous high-salt media, with the mixture’s phase behavior and photophysical properties showing a strong dependence on the identity of the cation salt . Studies on CPE–CPE complexation in salt-free water, , focusing on dilute regimes and the solid-state complexes, have further elucidated how the inclusion of the conjugated moieties fundamentally affects complexation thermodynamics. Similar to the CPE–polyelectrolyte coacervate, complexation of two CPEs in the dilute regime was shown to induce extension and planarization of the CPE backbone.…”

Conjugated Polyelectrolyte‐Based Complex Fluids as Aqueous Exciton Transport Networks

“…The color coding indicated by the circles will be used to distinguish between the salts in subsequent figures. Our choice of the CPEs was based on the following: 1) The photophysical properties of these CPEs allow them to function as an exciton donor/acceptor pair shown by their spectral overlap in Figure 1 [30] . We show in the Supporting Information that these optical properties change relatively little in different environments (Figures S14, S19, and S20).…”

Conjugated polyelectrolyte-based ternary exciton funnels via liposome scaffolds

“…Our prior work had shown that inter-CPE binding may be characterized by a significant thermal activation barrier. 32 Thus, we first aimed to determine whether raPTAK binding to the liposome surface was similarly temperature-dependent. We first prepared raPTAK/liposome complexes at 70% raPTAK by mole relative to DOTAP based on the total anionic raPTAK charge concentration (1 charge per monomer).…”

“…S5 † that we find excellent colocalization of raPTAK and PFPI, which was determined by separately measuring PL intensity in the polymers' distinct emission windows. 32 Two questions immediately arise: (A) do dissolved CPE chains coexist with adsorbed CPEs states? (B) Does the introduction of PFPI lead to desorption of raPTAK from the liposome surface, thereby forming dissolved PFPI/raPTAK complexes?…”