Micellar spheres in a high frequency oscillatory field

Area of Science:

• Polymer Science
• Physical Chemistry
• Rheology

Background:

• Aqueous micellar solutions of oxyethylene/oxybutylene block copolymers are utilized in various applications.
• Understanding their viscoelastic properties is crucial for optimizing their performance.

Purpose of the Study:

• To investigate the viscoelasticity of two specific block copolymers (E(92)B(18) and B(20)E(510)) in aqueous micellar solutions.
• To analyze the impact of high-frequency fields on micellar structure and interactions.

Main Methods:

• Dynamic viscoelasticity measurements using a torsional resonator at 26 kHz.
• Analysis of dynamic viscosity (eta'(infinity)) and elastic modulus (G'(infinity)).

Main Results:

• Dynamic viscosity indicates partial draining of the micellar corona under high-frequency oscillatory fields.
• Repulsive intermicellar interactions at low concentrations follow a power law (u(r) ~ 1/r^nu).
• Exponents (nu) for E(92)B(18) and B(20)E(510) were approximately 13 and 6, respectively.
• Deviation from power-law behavior at critical concentrations (c*) suggests ergodic/non-ergodic transitions.

Conclusions:

• High-frequency fields induce structural changes (partial corona draining) in these block copolymer micelles.
• Interactions between micelles are concentration-dependent and transition towards non-ergodic behavior at higher concentrations.