Remarkable shape-sustaining, load-bearing, and self-healing properties displayed by a supramolecular gel derived from a bis-pyridyl-bis-amide of L-phenyl alanine

Abstract

A series of bis-amides decorated with pyridyl and phenyl moieties derived from L-amino acids having an innocent side chain (L-alanine and L-phenyl alanine) were synthesized as potential low-molecular-weight gelators (LMWGs). Both protic and aprotic solvents were found to be gelled by most of the bis-amides with moderate to excellent gelation efficiency (minimum gelator concentration=0.32–4.0 wt. % and gel–sol dissociation temperature T_gel=52–110 °C). The gels were characterized by rheology, DSC, SEM, TEM, and temperature-variable ¹H NMR measurements. pH-dependent gelation studies revealed that the pyridyl moieties took part in gelation. Structure–property correlation was attempted using single-crystal X-ray and powder X-ray diffraction data. Remarkably, one of the bis-pyridyl bis-amide gelators, namely 3,3-Phe (3-pyridyl bis-amide of L-phenylalanine) displayed outstanding shape-sustaining, load-bearing, and self-healing properties.