Conjugated
polyelectrolytes (CPEs) combine ionic, electronic, and
optical functionality with the mechanical and thermodynamic properties
of semiflexible, amphiphilic polyelectrolytes. Critical to CPE design
is the coupling between macromolecular conformations, ionic interactions,
and electronic transport, the combination of which spans electronic
to mesoscopic length scales, rendering coherent theoretical analysis
challenging. Here, we utilize a recently developed anisotropic coarse-grained
model in combination with a phenomenological tight-binding Hamiltonian
to explore the interplay of single-chain conformational and electronic
structure in CPEs. Accessible single-chain conformations are explored
as a function of solvent conditions and chain stiffness, reproducing
a rich landscape of rod-like, racquet, pearl necklace, and helical
conformations observed in previous works. The electronic structure
of each conformational archetype is further analyzed, incorporating
through-bond coupling, through-space coupling, and electrostatic contributions
to the Hamiltonian. Electrostatics is observed to influence electronic
structure primarily by modifying the accessible conformational space
and only minimally by direct modulation of on-site energies. Electron
transport in CPEs is most efficient in helical and racquet conformations,
which is attributed to the flattening of dihedrals and through-space
coupling within collapsed conformations. Relatedly, kink formation
within racquets does not significantly deteriorate electronic conjugation
within CPEsan insight critical to understanding transport
within locally ordered aggregates. These conclusions provide unprecedented
computational insight into structure function relationships defining
emerging classes of CPEs.
Known since antiquity, ball lightning is a natural, long-lived plasma-like phenomenon associated with thunderstorms and is not well understood due to its rarity and unpredictability. A recently discovered laboratory phenomenon with striking similarity to ball lightning is observed when a high-power spark is discharged from a cathode protruding from a grounded electrolyte solution. Whereas several investigations of these long-lived plasmas have been reported over the past decade, the underlying chemical and physical processes are still unknown. The present work attempts to gain further insight into this phenomenon by examining the effect of electrolyte pH on the plasmoid and observing the chemical and physical structure of the plasmoid using high-speed schlieren videography and FTIR absorption spectroscopy. The results indicate that the lifetime and size of the plasmoid slightly increase as the pH of isoohmic electrolyte solutions deviate from neutrality. The observed absorption spectra of the plasmoids exhibit absorption cross sections in the 620-700, 1500-1560, 2280-2390, and 3650-4000 cm(-1) ranges, the last attributed to the presence of water clusters. Finally, schlieren images revealed a single, sharp density gradient at the boundary layer of the top and sides of the expanding ball-shaped plasmoid, and turbulent mixing below the ball.
Conjugated polyelectrolytes (CPEs) are a rising class of organic mixed ionic-electronic conductors, with applications in bio-interfacing electronics and energy harvesting and storage devices. Here, we employ a quantum mechanically informed...
Conjugated polyelectrolytes (CPEs) are a rising class of organic mixed ionic-electronic conductors, with applications in bio-interfacing electronics and energy harvesting and storage devices. Here, we employ a quantum mechanically informed coarse-grained model coupled with semiclassical rate theory to generate a first view of semidilute CPE morphologies and their corresponding ionic and electronic transport properties. We observe that the poor solvent quality of CPE backbones drives the formation of electrostatically repulsive fibers capable of forming percolating networks at semi- dilute concentrations. The thickness of the fibers and the degree of network connectivity are found to strongly influence the electronic mobilities of the morphologies. Calculated structure factors reveal that fiber formation alters the position and scaling of the inter-chain PE peak relative to good solvent predictions and induces a narrower distribution of interchain spacings. We also observe that electrostatic interactions play a significant role in determining CPE morphology, but have only a small impact on the local site energetics. This work presents a significant step forward in the ability to predict CPE morphology and ion-electron transport properties, and provides insights into how morphology influences electronic and ionic transport in conjugated materials.
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