Cyclotriguaiacyclene-functionalized trans-cinnamic acid with alkyl arms: an efficient supramolecular system for solar cell and liquid crystalline applications†

Four novel tri-substituted supramolecular materials (CTGC₁–CTGC₄) have been synthesized by converting cyclotriveratrylene to cyclotriguaiacyclene followed by esterification using 4-n-alkoxy derivatives of trans cinnamic acid (B₁–B₄). The synthesized materials were characterized by IR, ¹H-NMR, ¹³C-NMR, and MALDI-TOF analysis. The liquid crystalline properties of these cinnamate-based trimers were confirmed by polarized optical microscopy, differential scanning calorimetry, thermogravimetry and small and wide-angle X-ray scattering analysis. These compounds displayed an enantiotropic type columnar hexagonal (Col_h) phase with broad thermal stability. The higher alkoxy tail substituted mesogens (CTGC₃ and CTGC₄) with decyloxy and tetradecyloxy groups stabilized the mesophase at 32.0 °C and 26.0 °C, respectively. The synthesized CTG-linked trans-cinnamic acid trimers with alkoxy side groups exhibited self-assembly, which makes them good candidates for device applications. The current–voltage relationship indicates the ohmic-type behavior for the pristine and 100 °C annealed films while 200 °C films showed deviation. The optical properties indicate the high transmittance of 200 °C annealed films in visible and near IR regions. As wide optical energy band gaps of 2.93 eV, 2.87 eV and 3.45 eV were observed for CTGC₃ thin films, they could be utilized as optical window in second and transport layers in third generation solar cells.