6-acylamino nicotinic acid-based hydrogelators applicable in phase selective gelation, reproducible mat formation and toxic dye removal

Abstract

Formation of nanofibers and nanovesicles in the self-assembled state of small amphiphilic molecules has applications in versatile fields such as tissue engineering, controlled delivery of drug molecules, etc. This paper demonstrated the self-aggregation behavior of three synthesized 6-acylamino nicotinic acid amphiphiles named 6-octanoylamino-nicotinic acid (OANA), 6-decanoylamino-nicotinic acid (DANA) and 6-dodecanoylamino-nicotinic acid (DDANA) in water and basic aqueous solution. The result showed that the amphiphiles successfully self-organize into vesicles and twisted ribbons in water. FT-IR study revealed existence of mixtures of handedness in the fibrous structures. CD spectroscopy and TEM study elucidated formation of chiral structures through aggregation. Results showed that DDANA forms thermoreversible hydrogel in aqueous solutions of NaOH and Na2CO3, whereas other two amphiphiles form hydrogel only in the presence of NaOH. Morphological investigation revealed that the hydrogel is formed due to self-assembly of fibrils of micron length. The elastic fibrillar networks are quite stable to external forces. Existence of bilayer columnar square packing arrangement in the self-assembled state was recognized by XRD measurement. Spectroscopy and theoretical studies established that hydrogen bonding interactions are responsible to self-assemble the amphiphilic molecules. The amphiphiles are efficient phase selective gelators of mineral oils in water–mineral oil mixtures and excellent remover of rhodamine 6G, eosin Y and rose bengal from water. The amphiphiles successfully create reproducible fiber mat applicable in tissue engineering field.