Memory effects in supramolecular networks of diacids and polyfunctional pyridine derivatives

Abstract

Highly crosslinked networks were produced through a series of diacids and tetrakis pyridyls. These materials displayed complex crystallization behaviors over multiple heat/cool cycles. The shifting of crystallization behaviors with time in the melt phase seems to indicate that the materials move toward thermodynamically ideal structures. This behavior is suggestive of a type of memory in which the networks remember the morphological structure previous to the melt and improve upon that structure in the next cooling cycle. The network/memory phenomena observed in small molecule diacid/tetrapyridyl systems also appeared to exist when poly(ethylene terephthalate) (PET) polymer was used as the source of carboxylic acid functionalities. The same time-dependent behaviors, suggestive of sequential steps toward thermodynamically optimum states, were observed when the PET/tetrapyridyl systems were thermally cycled. It was also observed that complexation of tetrapyridyl with PET brought about a significant change in oxygen gas barrier properties; these changes were opposite to those obtained when covalent crosslinks were introduced into PET.

Supramolecular main chain liquid crystalline polymers utilizing azopyridine derivatives

“…Spectrographic grade solvents were used for all measurements. The synthesis of AzP [18], 3, 4 and 5 BA [22], and 4 BPA [23] have been previously described. …”

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

“…The synthesis of the nSBZ series is described later in this report. The synthesis of 4EOBBA has been previously described [36]. All compounds used in this study can be found in Scheme 1.…”

“…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.…”

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

“…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.…”