Advancements in π-conjugated polymers: harnessing cycloalkyl straps for high-performance π-conjugated materials.

Pendant alkyl chains are widely used to successfully obtain a wide variety of soluble linear 1D π-conjugated polymers. Over the past several decades, a wide variety of π-conjugated polymers have been synthesized to realize the desired properties and improve the performance of organic electronic devices. However, this strategy is not suitable for generating soluble 2D-π-conjugated materials, including ladder polymers, nanoribbons, and 2D-π-conjugated polymers, due to strong van der Waals interactions between the ribbons and sheets.

Controlling π-Conjugated Polymer-Acceptor Interactions by Designing Polymers with a Mixture of π-Face Strapped and Nonstrapped Monomers.

Controlling π-conjugated polymer-acceptor complex interaction, including the interaction strength and location along the polymer backbone, is central to organic electronics and energy applications. Straps in the strapped π-conjugated polymers mask the π-face of the polymer backbone and hence are useful to control the interactions of the π-face of the polymer backbone with other polymer chains and small molecules compared to the conventional pendant solubilizing chains. Herein, we have synthesized a series of strapped π-conjugated copolymers containing a mixture of strapped and nonstrapped comonomers to control the polymer-acceptor interactions.

Pyrazinacene conjugated polymers: a breakthrough in synthesis and unraveling the conjugation continuum.

Pyrazinacenes are next generation N-heteroacenes and represent a novel class of stable n-type materials capable of accepting more than one electron and displaying intriguing features, including prototropism, halochromism, and redox chromism. Astonishingly, despite a century since their discovery, there have been no reports on the conjugated polymers of pyrazinacenes due to unknown substrate scope and lack of pyrazinacene monomers that are conducive to condensation polymerization. Breaking through these challenges, in this work, we report the synthesis of previously undiscovered and highly coveted conjugated polymers of pyrazinacenes.

Using molecular straps to engineer conjugated porous polymer growth, chemical doping, and conductivity.

Controlling network growth and architecture of 3D-conjugated porous polymers (CPPs) is challenging and therefore has limited the ability to systematically tune the network architecture and study its impact on doping efficiency and conductivity. We have proposed that π-face masking straps mask the π-face of the polymer backbone and therefore help to control π-π interchain interactions in higher dimensional π-conjugated materials unlike the conventional linear alkyl pendant solubilizing chains that are incapable of masking the π-face. Herein, we used cycloaraliphane-based π-face masking strapped monomers and show that the strapped repeat units, unlike the conventional monomers, help to overcome the strong interchain π-π interactions, extend network residence time, tune network growth, and increase chemical doping and conductivity in 3D-conjugated porous polymers.

Molecular tetrominoes: selective masking of the donor π-face to control the configuration of donor-acceptor complexes.

Understanding the doping mechanism in organic semiconductors and generating molecular design rules to control the doping process are crucial for improving the performance of organic electronics. Even though controlling the location and orientation of the dopant along the semiconductor backbone is an important step in the doping mechanism, studies in this direction are scarce as it is a challenging task. To address this, herein, we incorporated π-face masked (strapped) units in 1,4-bis(phenylethynylene)benzene (donor) to control the acceptor (dopant) location along the trimer, donor-acceptor binding strength, and acceptor ionization.

Role of Aryl Amphiphile Hydrophobe Size on the Concentration and Stability of Graphene Nanoplatelet Dispersions.

Graphene nanoplatelets (GNPs) are stable and relatively inexpensive compared to single-layer graphene sheets and carbon nanotubes and are useful in diverse electronic, optoelectronic, and mechanical applications. Solution-state processing of the active material is desired in most of the applications mentioned above, and thus, there is great interest in increasing the concentration and stability of GNP suspension. Herein, to elucidate the role of the stabilizer structural parameters on the concentration and stability of GNP dispersions, we synthesized and used a series of aryl amphiphiles (ArAs) of varying aryl hydrophobe sizes and geometries.

Waveguiding properties of perylene microcrystals synthesized by retarding the growth along the π-stack direction.

Selective, hard to realize growth retardation of the π-stacking direction over the edge-packing direction has been achieved in perylene microcrystals using an aryl amphiphile. The perylene microcrystals grow predominantly along the edge-packing direction resulting in novel and hitherto unknown perylene square rods. The rods show exciton-polariton waveguiding along the rod axis even though it corresponds to pure edge-packing of the molecules, which is unprecedented in organic microcrystals.

β-Strand inspired bifacial π-conjugated polymers.

Access to diverse, relatively high molecular weight soluble linear polymers without pendant solubilizing chains is the key to solution state synthesis of structurally diverse nanoribbons of conjugated materials. However, realizing soluble 1D-π-conjugated polymers without pendant solubilizing chains is a daunting task. Herein, inspired from the polypeptide β-strand architecture, we have designed and developed novel bifacial π-conjugated polymers ( : 24 kDa) that are soluble ( 70 to >250 mM) despite the absence of pendant solubilizing chains.

Aryl amphiphile shape-directors for shape-controlled synthesis of organic semiconductor particles.

Currently, shape- and size-controlled synthesis of organic micro- and nano-particles mostly relies on aliphatic amphiphiles, which lack the structural diversity to provide tunable amphiphile-particle facet interaction energies and result in a limited range of particle shapes. Herein we report the design, synthesis, and utilization of two novel aryl amphiphiles as shape-directors (ShaDs) to obtain particles of different shape. By changing the ShaDs aryl hydrophobe structure, 9,10-diphenylanthracene microcrystals of different shape were obtained with greater than 90% shape yield.

Macromolecular Design Strategies for Preventing Active-Material Crossover in Non-Aqueous All-Organic Redox-Flow Batteries.

Intermittent energy sources, including solar and wind, require scalable, low-cost, multi-hour energy storage solutions in order to be effectively incorporated into the grid. All-Organic non-aqueous redox-flow batteries offer a solution, but suffer from rapid capacity fade and low Coulombic efficiency due to the high permeability of redox-active species across the battery's membrane. Here we show that active-species crossover is arrested by scaling the membrane's pore size to molecular dimensions and in turn increasing the size of the active material above the membrane's pore-size exclusion limit.

Redox Active Colloids as Discrete Energy Storage Carriers.

Versatile and readily available battery materials compatible with a range of electrode configurations and cell designs are desirable for renewable energy storage. Here we report a promising class of materials based on redox active colloids (RACs) that are inherently modular in their design and overcome challenges faced by small-molecule organic materials for battery applications, such as crossover and chemical/morphological stability. RACs are cross-linked polymer spheres, synthesized with uniform diameters between 80 and 800 nm, and exhibit reversible redox activity as single particles, as monolayer films, and in the form of flowable dispersions.

Efficient charge transport in assemblies of surfactant-stabilized semiconducting nanoparticles.

Charge transport through a semiconducting nanoparticle assembly is demonstrated. The hole mobility of low and high molecular weight and regioreglular poly(3-hexylthiophene) (P3HT) nanoparticles is on the order of 2 × 10(-4) to 5 × 10(-4) cm(2) V(-1) s(-1) , which is comparable to drop-cast thin films of pristine P3HT. Various methods are employed to understand the nature and importance of the nanoparticle packing.

Tuning aggregation of poly(3-hexylthiophene) within nanoparticles.

Nanoparticles derived from π-conjugated polymers have gained widespread attention as active layer materials in various organic electronics applications. The optoelectronic, charge transfer, and charge transport properties of π-conjugated polymers are intimately connected to the polymer aggregate structure. Herein we show that the internal aggregate structure of regioregular poly(3-hexylthiophene) (P3HT) within polymer nanoparticles can be tuned by solvent composition during nanoparticle fabrication through the miniemulsion process.