Interplay between Long-Range Crystal Order and Short-Range Molecular Interactions Tunes Carrier Mobility in Liquid Crystal Dyes

Structural-Functional Properties of Asymmetric Fluoro-Alkoxy Substituted Benzothiadiazole Homopolymers with Flanked Chalcogen-Based Heterocycles

The synthesis and characterization of asymmetric alkoxy- are reported, fluoro-benzothiadiazole (BT) acceptor core derivatized with a series of six different heterocycles (selenophene, thiophene, furan, 5-thiazole, 2-thiazole and 2-oxazole). The effect of the flanked-heterocycles containing different chalcogen atoms of the six homopolymers (HPX) is studied using optical, thermal, electrochemical, and computational analysis. Computational calculations indicate a strong relationship between the most stable conformation for each homopolymer and their bearing heterocycle, thus homopolymers HPSe', HPTp', HPFu', and HPTzC5, adopted the syn-syn and syn-anti conformations due to their noncovalent interactions with shorter distances, while HPTzC2' and HPOx' demonstrate preference for the anti-anti conformation. Optical property studies of the homopolymers reveal a strong red-shift in solution and film upon exchanging the chalcogen atom from Oxygen < Sulfur < Selenium in HPFu, HPTp, and HPSe, respectively. In addition, deeper highest occupied molecular orbital (HOMO) energy levels are observed when the donor-acceptor moieties (HPSe, HPTp, and HPFu) are substituted for the acceptor-acceptor systems such as HPTzC5, HPTzC2, and HPOx. Improved packing and morphology are exhibited for the donor-acceptor homopolymers. Thus, having a flanked heterocycle containing different chalcogen-atoms in polymeric systems is one way of tuning the physicochemical properties of conjugated materials for optoelectronic applications.

Confinement-Induced Fabrication of Liquid Crystalline Polymeric Fibers

In aqueous media, liquid crystalline droplets typically form spherical shapes in order to minimize surface energy. Recently, non-spherical geometry has been reported using molecular self-assembly of surfactant-stabilized liquid crystalline oligomers, resulting in branched and randomly oriented filamentous networks. In this study, we report a polymerization of liquid crystalline polymeric fibers within a micro-mold. When liquid crystal oligomers are polymerized in freely suspended aqueous media, curvilinear and randomly networked filaments are obtained. When reactive liquid crystalline monomers are oligomerized in a micro-channel, however, highly aligned linear fibers are polymerized. Within a top-down microfabricated mold, a bottom-up molecular assembly was successfully achieved in a controlled manner by micro-confinement, suggesting a unique opportunity for the programming architecture of materials via a hybrid approach.