Investigations on Chain Length‐Dependent Gelation in PEG ‐Based Amphiphilic Organogelators

ABSTRACT Amphiphilic organogelators have diverse applications in drug delivery, cosmetics, and food science due to their thermoreversible and self‐assembling properties. Tuning of the gelator's molecular structure facilitates the desirable properties. The present study reports the synthesis and characterization of amphiphilic organogelators derived from polyethene glycol (PEG) of two different molecular weights, approximately 400 and 600, which exhibit thermoreversible gelation. PEG‐amphiphilic organogelators were made by treating PEG‐dihydrazide with fatty acid chlorides with different alkyl chain lengths, such as myristoyl (C 14 ), palmitoyl (C 16 ), and stearoyl chloride (C 18 ). The molecular solutions of the amphiphiles formed stable three‐dimensional gel networks upon cooling in polar aprotic solvents, namely, DMSO, DMF, DMAC, and NMP. The minimum gelation concentration was found to decrease drastically with an increase in alkyl chain length for a fixed molecular weight of PEG unit. Depending on the mass of the PEG core, xerogels of these compounds exhibited flake‐like and fiber‐like morphologies at the microscopic level, as inferred from FE‐SEM. The rheological study confirmed the gel's viscoelastic nature, showing that their mechanical strength increased with concentration. x‐ray diffraction studies confirmed the molecular layered packing arrangement and orientation of gelator molecules during self‐assembly. It was observed that PEG 600 ‐C 18 was the most efficient organogelator, with a minimum gelation concentration of approximately 7 mg/mL.