Synthesis and Hole Transport Properties of Highly Soluble Pyrene-Based Discotic Liquid Crystals with Trialkylsilylethynyl Groups

Abstract

Abstract Four pyrene-based discotic compounds with trialkylsilylethynyl groups in the side chains were prepared and characterized by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction measurements. All of the compounds were highly soluble in organic solvents, and two of the compounds exhibited a columnar phase, Colr, and the others were crystalline. The hole transport ability in the liquid-crystalline phases was determined by the time-of-flight (TOF) method to be on the order of 10−2 cm2 V−1 s−1, the highest hole mobilities for pyrene derivatives yet observed. Keywords: Discotic liquid crystalhole transportpyrene derivativessynthesistrialkylsilylethynyl group Notes Transition temperatures were determined by DSC. Scan rate was 5°C/min. Abbreviations: Cr = crystalline phase; I = isotropic phase; Colr = rectangular columnar phase. a Not crystallized during the DSC measurement. Z = (ρ·a·b·h·NA)/M. Z = Molecular numbers per unit cell, NA = Avogadro's number, a and b = lattice constant, h = stacking distance, ρ = density (assumed to be 1.0 g cm−3), M = molecular weight of the compound.