Transforming a C3-Symmetrical Liquid Crystal to a π-Gelator by Alkoxy Chain Variation

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 pi-conjugated molecules. For this purpose, we designed and synthesized three C-3-symmetrical molecules based on oligo(p-phenylenevinylene), C(3)OPV1-3. 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, C(3)OPV1 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, C(3)OPV2 lost the LC property, however, transformed as a gelator in toluene and n-decane. Surprisingly, when the -OC12H25 group from the middle position is removed, the resultant molecule C3OPV3 failed to form either the LC or the gel phases.