Transforming a <i>C</i>₃-Symmetrical Liquid Crystal to a π-Gelator by Alkoxy Chain Variation

Abstract

Rational understanding of the structural features involving different noncovalent interactions is necessary to design a liquid crystal (LC) or an organogelator. Herein, we report the effect of the number and positions of alkoxy chains on the self-assembly induced physical properties of a few π-conjugated molecules. For this purpose, we designed and synthesized three <i>C</i> ₃-symmetrical molecules based on oligo(<i>p</i>-phenylenevinylene), <i><b>C</b></i> _<b>3</b> <b>OPV1</b>-<b>3</b>. The self-assembly properties of these molecules are studied in the solid and solution states. All of the three molecules follow the isodesmic self-assembly pathway. Upon cooling from isotropic melt, <i><b>C</b></i> _<b>3</b> <b>OPV1</b> having nine alkoxy chains (-OC₁₂H₂₅) formed a columnar phase with two-dimensional rectangular lattice and retained the LC phase even at room temperature. Interestingly, when one of the -OC₁₂H₂₅ groups from each of the end benzene rings is knocked out, the resultant molecule, <i><b>C</b></i> _<b>3</b> <b>OPV2</b> lost the LC property, however, transformed as a gelator in toluene and <i>n</i>-decane. Surprisingly, when the -OC₁₂H₂₅ group from the middle position is removed, the resultant molecule <i><b>C</b></i> _<b>3</b> <b>OPV3</b> failed to form either the LC or the gel phases.