화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals, Vol.691, No.1, 35-41, 2019
Supramolecular liquid crystals displaying competitive hydrogen bonding: Mesogenic associative chain structures using rigid and flexible pyridyl groups
A series of liquid-crystalline supramolecular copolymers formed through hydrogen bonding has been created. These polymers are composed of a bis-benzoic acid and two different pyridyl species - a small rigid bispyridyl capable of forming a mesophase when assembled and one of a pair of flexible bis pyridyl non-mesogenic "disruptor" species. The latter set of molecules consist of the pyridyl functionality separated by six or ten methylene units (6BPD and 10BPD, respectively). It was found that the associative chain polymers display monotropic characteristics depending upon the length of the methylene spacer group. The hexamethylene chain produced smectic phases up to 15% composition and cleared nematic characteristics at 70% loading. The decamethylene species eliminated smectic phases at 5% loading and displayed nematic phases up to 40% inclusion. It is believed that the increased length and flexibility of the alkyl chain allows for too much conformational mobility and freedom to efficiently form liquid-crystalline phases at high concentrations.