Polymerization of Columnar Mesogens Tethered with Diacetylenic Side Chains

Hexa-peri-hexabenzocoronene (HBC) derivatives tend to form discotic columnar liquid crystalline (DCLC) phases capable of charge transport and anisotropic photoresponses. However, their noncovalently bonded molecular assemblies are prone to decompose upon heat or organic solvent treatment. Here we designed a series of cross-linkable HBC derivatives in which the HBC core was tethered with three diacetylene-containing side chains and three alkyl chains in alternating positions. Both film and solution states of these derivatives were found to aggregate into columns and undergo polymerization/ cross-linking reaction by either UV-irradiation or thermal treatment, presumably due to reaction between the diacetylenic units. The DCLC characteristics and polymerization/cross-linking reactions have been investigated by differential scanning calorimetry, powder X-ray diffraction, Raman spectroscopy, and UV-vis spectroscopy. The optoelectronic measurements of the films were performed using the time-resolved microwave conductivity technique, which gave the largest signal for one of the derivatives, HBC-1,3,5-C-8,C-9-DA-C-4, indicating its potential use as an optoelectronic material.