The Effect of Branched Alkyl Chain Length on the Properties of Supramolecular Organogels from Mono-N-Alkylated Primary Oxalamides

Abstract

Mono-N-alkylated primary oxalamide derivatives with different sized branched alkyl tail-groups were excellent low molecular weight gelators for a variety of different organic solvents with different polarities and hydrogen-bonding abilities. Solvent-gelator interactions were analyzed using Hansen solubility parameters, while 1H NMR and FTIR spectroscopy were used to probe the driving forces for the supramolecular gelation. The molecular structures of the twin tail-groups did not significantly affect the supramolecular gelation behavior in different solvents. However, for select solvents, the molecular structures of the tail-groups did have a significant effect on gel properties such as the critical gelator concentration, thermal stability, gel stiffness, gel strength, network morphology, and molecular packing. Finally, metabolic activity studies showed that the primary alkyl oxalamide gelators had no effect on the metabolic activity of mouse immune cells, which suggests that the compounds are not cytotoxic and are suitable for use in biomedical applications.

Development of Gelled-Oil Nanoparticles for the Encapsulation and Release of Berberine

“…Although individual fibers are difficult to discern within bundles and in densely entangled regions at the magnifications shown in Figure , the fibers are estimated to have widths in the 0.1–1 μm range and lengths in the 100–1000 μm range. These results indicate that the compound AOx24 undergoes hierarchical self-assembly to form fibrous structures that entangle to form 3D SAFINs, which leads to the formation of stable organogels (Figure ) through the entrapment of the SO, Cin, and Tw80 solvent molecules as well as BCl and trace water molecules, which is also consistent with the self-assembly of AOx24 and other N -alkylated primary oxalamides in other organic solvents. , Note that the corresponding xerogels were not examined at higher magnification by SEM because SO, Cin, and Tw80 are all nonvolatile and hindered sample preparations. These results confirm that AOx24 should be able to form networks of submicron-scale fibers within the dispersed oil droplets, which should provide surfaces for BCl to adsorb to via weak, noncovalent interactions and/or provide a tortuous path to hinder diffusion within and egress from the oil phase.…”

“…Especially Tw80, CA, and water, which possess both hydrogen bond accepting and donating groups, could disrupt the intermolecular hydrogen bonding of AOx24 molecules. Interestingly, AOx24 formed a gel with Tw80 (Figure f) at 2 wt %, which is not all that surprising since the structure of Tw80 has three oxyethylene groups and considering that AOx24 is also a good gelator for the oxyethylene solvents ethylene and propylene glycol . Gelation tests carried out in the presence of BCl in both SO and Cin confirmed that BCl does not significantly disrupt the gel networks formed by AOx24 (Figure b,e).…”

“…Among these were organogels from AOx24 with the water immiscible and GRAS liquids SO and Cin (Figure ). For this work, the CGC or the minimum concentration was determined to be slightly lower for the organogels with SO (0.4 wt %) than Cin (1.6 wt %) for relatively short gel times (i.e., 30 min). Gels from AOx24 with Cin did form at lower concentrations; however, longer gel times were required, i.e., 3 h at 1.2 wt % and 1 h at 1.4 wt %.…”

“…Among a variety of supramolecular organogelators available in our laboratories, the compound 2-decyltetradecanoxalamide ( AOx24 , Figure S1) was selected for the formation of aqueous dispersions of GNPs for this work. The compound AOx24 is a versatile and efficient organogelator that forms gels with a large number of protic and aprotic organic liquids with different polarities at low gelator concentrations . Among these were organogels from AOx24 with the water immiscible and GRAS liquids SO and Cin (Figure ).…”

“…Recently, we reported a family of versatile and efficient LMWGs based on N-alkylated primary oxalamides (i.e., AOx24 , Figure S1) for a variety of different organic solvents, which were also biocompatible with mouse mast cells . Coupled with the known health benefits and low aqueous solubility of BCl, the objective of the current study was to develop formulations of BCl-loaded GNPs from Tw80-stabilized nanoemulsions and a LMWG, in order to achieve a high BCl loading.…”