Side-Chain Labeling Strategy for Forming Self-Sorted Columnar Liquid Crystals from Binary Discotic Systems

Abstract

The spontaneous formation of self-sorted columnar structures of electron-donating and accepting π-conjugated molecules is attractive for photoconducting and photovoltaic properties. However, the simple mixing of donor–acceptor discotic molecules usually results in the formation of mixed-stacked or alternating-stacked columns. As a new strategy for overcoming this problem, here, we report the “side-chain labeling” approach using binary discotic systems and realize the preferential formation of such self-sorted columnar structures in a thermodynamically stable phase. The demonstrated key strategy involves the use of hydrophobic and hydrophilic side chains. The prepared blend is composed of liquid crystalline phthalocyanine with branched alkyl chains (H2Pc) and perylenediimide (PDI) carrying alkyl chains at one side and triethyleneglycol (TEG) chains at the other side (PDIC12/TEG). To avoid the thermodynamically unfavorable contact among hydrophobic and hydrophilic chains, PDIC12/TEG self-assembles to stack up on top of each other and H2Pc as well, forming a homo-stacked pair of columns (self-sort). Importantly, H2Pc and PDIC12/TEG in the blend are macroscopically miscible and uniform, and mesoscopically segregated. The columnar liquid crystalline microdomains of H2Pc and PDIC12/TEG are homeotropically aligned in a glass sandwiched cell. The “labeling” strategy demonstrated here is potentially applicable to any binary discotic system and enables the preferential formation of self-sorted columnar structures.