Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding: a study of flexible bis-acids and a mixture of rigid and flexible polypyridyls

Abstract

A series of novel liquid crystalline supramolecular networks formed through hydrogen bonds have been synthesised. These networks are based on flexible bi-benzoic acid and two types of pyridyl species – a small rigid bipyridyl capable of forming liquid crystalline phases and polyfunctional non-mesogenic pyridyl species that can compete for available hydrogen bond donor molecules. It was found that the networks display monotropic nematic character at high concentrations of disrupting net points – up to 50% for tetrapyridyls, 40% for tripyridyls and 35% for bipyridyls. Weak smectic phases were observed in all systems in loadings up to 10% of each disrupting unit. It is believed that the reversibility of the hydrogen bond allows for the formation of the ordered mesophases in the presence of the non-liquid crystalline groups.