Novel sorbitan monostearate organogels

Area of Science:

• Materials Science
• Colloid and Surface Chemistry

Background:

• Sorbitan monostearate is a hydrophobic nonionic surfactant capable of gelling organic solvents.
• Organogel formation involves dissolving the gelator in hot solvent, followed by cooling to induce self-assembly.
• The self-assembly process leads to the formation of a three-dimensional network that immobilizes the solvent.

Purpose of the Study:

• To investigate the gelation properties of sorbitan monostearate and sorbitan monopalmitate in organic solvents.
• To characterize the microstructure of the resulting organogels.
• To explore the effects of additives on gel properties and microstructure.

Main Methods:

• Dissolving sorbitan esters in hot organic solvents (e.g., hexadecane, isopropyl myristate, vegetable oils).
• Cooling the solutions to induce gelation and observing the self-assembly into vesicles and tubules.
• Analyzing the microstructure of the organogels using microscopy.
• Investigating the impact of additives like polysorbate 20 on gel stability and microstructure.

Main Results:

• Sorbitan monostearate forms opaque, thermoreversible organogels by self-assembling into toroidal inverse vesicles and then rod-shaped tubules.
• Sorbitan monopalmitate also forms similar opaque, thermoreversible organogels with a microstructure of interconnected rodlike tubules.
• Additives like polysorbate 20 alter the microstructure; in sorbitan monostearate gels, it causes clustering, while in sorbitan monopalmitate gels, it increases tubular length.

Conclusions:

• Sorbitan monostearate and sorbitan monopalmitate are effective organogelators for various organic solvents.
• The resulting organogels are thermoreversible semisolids with potential applications in drug and antigen delivery.
• Gel microstructure and stability can be modulated by the addition of specific surfactants.