Micellar Solutions of Associative Triblock Copolymers:  The Relationship between Structure and Rheology

• Published in: Macromolecules Vol. 32; no. 15; pp. 5139 - 5146
• Main Authors: Pham, Q. T, Russel, W. B, Thibeault, J. C, Lau, W
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 27-07-1999
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Ethylene oxide polymer; Monodispersed polymer; Shear viscosity; End group; Shear modulus; Solution structure; Concentration effect; Hydrophobic group; Property structure relationship; Aqueous solution; Experimental study; Micellar solution
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma990215x

We report the rheology of the micellar solutions formed from narrow-molecular-weight poly(ethylene oxide) chains fully endcapped with C16 or C18 alkanes and correlate the viscoelasticity, characterized by the high-frequency modulus G ∞‘ and a single relaxation time λ, with the measured characteristics of the micellar solutions. Scaling G ∞‘ by p 3/2 kT/τ R H 3 (p = aggregation number, R H = hydrodynamic radius, 1/τ = attractive virial coefficient, k = Boltzmann's constant, and T = temperature) and plotting against the hydrodynamic volume fraction of micelles collapses the two sets of data. The relaxation time scales as the diffusion time, μ R c 3/kT, for a free hydrophobe escaping from a micellar core of radius R c times a Boltzmann factor accounting for an association energy that increases linearly with hydrophobe length. The low shear viscosity follows as η o = λ G ∞‘.