Intra-and Intermolecular Photodimerization of Mesogenic Triphenylene Derivative having Cinnamate Groups: Effects of Orientation and Mobility of the Mesogenic Molecules on the Photoreaction Behavior

Abstract

The photoreactivity of cinnamate groups attached to a triphenylene ring was investigated in terms of formation of oligomers by photodimerization between cinnamate groups. It was found that the triphenylene derivative, 2,3,6,7,10,11-hexa(4′-octadecyloxycinnamate)triphenylene, showed discotic mesophases: a hexagonal disordered columnar phase (D _hd) and a nematic columnar phase (N _D) as discotic mesophases and a solid biphase which consisted of a glassy phase and a D _hd, phase. The photooligomerization was strongly depressed both in the solid biphase and isotropic phase. The less mobility of mesogenic molecules in the solid biphase led to a low conversion of photooligomerization. On the other hand, the intramolecular photodimerization due to less ordering of the mesogenic molecules in the isotropic phase resulted in a low conversion to photooligomers.

Key Words:

• discotic liquid crystal
• cinnamate
• photodimerization
• photooligomerization