Charge-free reverse wormlike micelles in nonaqueous media

Area of Science:

• Colloid and Surface Science
• Materials Chemistry
• Rheology

Background:

• Traditionally, reverse wormlike micelles required ionic surfactants, water, and/or salts for formation and growth.
• Nonionic surfactant systems typically do not form such structures under ambient conditions without water.

Purpose of the Study:

• To report a facile method for forming charge-free reverse wormlike micelles in a nonionic surfactant/oil system.
• To investigate the role of sucrose dioleate (SDO) in promoting micellar growth and network formation with sucrose trioleate (STO).

Main Methods:

• Utilizing nonionic surfactants sucrose trioleate (STO) and sucrose dioleate (SDO) in hexadecane.
• Employing small-angle X-ray scattering (SAXS) to characterize micelle structure.
• Conducting rheometry measurements to determine viscoelastic properties and viscosity changes.

Main Results:

• Successfully formed charge-free reverse wormlike micelles without water addition.
• Observed a significant increase in zero-shear viscosity by approximately four orders of magnitude.
• Demonstrated that the mixing fraction of SDO to STO dictates the viscosity growth and formation of transient networks.

Conclusions:

• A novel route to create viscoelastic reverse wormlike micelle networks using nonionic surfactants has been established.
• The addition of a less lipophilic nonionic surfactant (SDO) effectively promotes one-dimensional growth of STO reverse micelles.
• This method offers a new pathway for designing and controlling rheological properties in surfactant-oil systems.