Hexa-peri-hexabenzocoronene derivatives carrying dovetailed alkyl and diacetylenic side chains: a synthesis, characterization, and polymerization study

Novel discotic liquid crystalline (DLC) monomers with a mesogenic 2,8,14-triphenylhexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) core bearing alternating dovetailed alkyl and linear alkyl chains with a diacetylenic unit at different positions along the chain were successfully synthesized in this study. These monomers exhibited a discotic hexagonal columnar mesophase at room temperature. Depending on the location of the diacetylene unit in the linear alkyl chain (closer to or farther away from the HBC core), different aggregation patterns and reactivities toward photo-induced polymerization were observed. Thus polymerization along the discotic liquid crystalline column yielding a fiber-like polymer was achieved for the compound with the diacetylene unit closer to the HBC core, whereas cross-linking between neighboring molecules was suggested for the compound with the diacetylene unit farther away from the HBC core. Powder X-ray diffraction, differential scanning calorimetry, polarized optical microscopy, UV spectroscopy, and dynamic light scattering were used to characterize these systems.