Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding

Abstract

A series of supramolecular polymers and networks with variable liquid crystalline characteristics have been created. These species are formed though the benzoic acid/pyridine associations of a flexible bisacid and a mixture of a rigid bispyridyl and a non-mesogenic tetrapyridyl. The networked systems displayed liquid crystalline characteristics up to and including 22.5% netpoint inclusion. Above this concentration, only crystalline and melting behaviours were observed. This observed phenomenon would seem to be linked to the statistical correlation of hydrogen bond acceptors and donors. There was also no observed phase segregation of the species after multiple heat/cool cycles and extended periods of time in the isotropic state. This would indicate that the thermodynamically more stable mesogenic phase cannot out-compete the non-liquid crystalline network. Computational analysis indicates no significant difference in hydrogen bond strength between the two different hydrogen bond acceptors.

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

“…In each, the smectic phase was observable only in the optical analysis -it was too weak of a transition to be observed in thermograms. The overall loadings of the nPD agent were markedly higher in these systems as compared to pre viously reported analogous networked and polymeric systems (37)(38). Such networks, when created utilis ing a smaller bisbenzoic acid hydrogen bond accep tor (tetraethyleneglycoxy bis-4-benzoic acid) utilising loadings of 4PD, 3PD and 2PD agents eliminated liq uid crystallinity at 25%, 31% and 22.5%, respectively.…”

“…The synthesis of 4PD, 3PD and 2PD have been previously described. (37,38) The synthesis of 5EOBBA is described later in this report. All compounds used in this study can be found in Scheme 1.…”

“…Previous work (36)(37)(38)(39) in our laboratory involved a flexible bis-acid and mixtures of a rigid bi-pyridyl and a non-mesogenic tetrapyridyl species. These produced supramolecular networks with variable liquid crys talline characteristics.…”

Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding: a study of rigid networking agents in supramolecular systems

“…Previous work [36][37][38][39][40] in our laboratory involved a flexible bisacid and mixtures of a rigid bi-pyridyl and a non-mesogenic tetrapyridyl species. These produced supramolecular networks with variable liquid crystalline characteristics.…”

Synthesis and Properties of Mesogens Containing Chiral Terminal Substituent with Hydroxy Group

“…В связи с этим Н-связанные жидкокристаллические системы следует рассматривать как типичные объекты супрамоле-кулярной химии, поскольку говорить о мезомор-физме можно только по отношению к достаточно населенному супрамолекулярному ансамблю [4,5].…”