Formation of gel and fibrous microstructures by 1-alkyne amphiphiles bearing L-serine headgroup in organic solvents

Abstract

The study of amphiphiles that form non-spheroidal, and other assemblies, upon solvation is the key to understanding the :relationship between molecular structure and supramolecular morphology. With this aim in mind, we have employed L -serine and L -histidine derivatives that are linked via amide bond to hydrophobic chain. L-Serine amphiphiles form gels in CHCl₃, CH₂Cl₂ and CCI, Microscopic examinations of these gels reveal the coexistence of tubules, helical ribbons, and spheres. On the other hand, they produce only spherical structures and rods when dispersed in aqueous media (phosphate buffer). In contrast, amphiphiles based on the L-histidine group, neither formed any gel nor produced any microstructures in non-aqueous solvents like CHCl₃, but produced spherical structures and helical rods in water. We also examined the effect of introducing 1-yne or 1-ene moieties into the hydrocarbon chain of such amphiphiles. These moieties, when present in the hydrophobic segment, do not perturb the supramolecular assembly features of the respective serine amphiphiles. Actually, 1-yne moiety, when present in the hydrophobic portion of the amphiphiles, gives characteristic UV-fine structures upon aggregation in water and might be used as a non-invasive marker for probing critical aggregate concentration.