Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association

Journal Article · Mon Apr 25 00:00:00 EDT 1994 · Macromolecules; (United States)

DOI:https://doi.org/10.1021/ma00087a009· OSTI ID:7185227

Alexandridis, P; Hatton, T A ^[1]; Holzwarth, J F ^[2]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering
2. Fritz-Haber-Inst. der Max-Planck-Gesellschaft, Dahlem (Germany)

The critical micellization temperature (cmt) and critical micellization concentration (cmc) values of 12 Pluronic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, covering a wide range of molecular weights (2,900--14,600) and PPO/PEO ratios (0.19--1.79), were determined employing a dye solubilization method. A closed association model was found to describe adequately the copolymer micellization process for the majority of the Pluronics and used to obtain the standard free energies ([Delta]G[degree]), enthalpies ([Delta]H[degree]), and entropies ([Delta]S[degree]) of micellization. It was determined that the micellization process is entropy-driven and has an endothermic micellization enthalpy. The hydrophobic part of the Pluronics, PPO, was responsible for the micellization, apparently due to diminishing hydrogen bonding between water and PPO with increasing temperature. The cmc dependence on temperature and size of headgroup (PEO) of Pluronics follows a similar trend with lower molecular weight C[sub i]E[sub j] nonionic surfactants, the effect of temperature being more pronounced with the Pluronics. The PEO-PPO-PEO block copolymers were compared to PPO-PEO-PPO block and PEO-PPO random copolymers, in an attempt to probe the effect of molecular architecture in the formation of micelles. No micelles were observed in aqueous PPO-PEO-PPO block copolymer solutions with increasing temperature, up to the cloud point.

• DOE Contract Number: FG02-92ER14262
• OSTI ID: 7185227
• Journal Information: Macromolecules; (United States), Journal Name: Macromolecules; (United States) Vol. 27:9; ISSN MAMOBX; ISSN 0024-9297
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606 -- Other Materials-- Physical Properties-- (1992-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALCOHOLS
CHEMICAL PREPARATION
CONCENTRATION RATIO
COPOLYMERS
GLYCOLS
HYDROXY COMPOUNDS
MICELLAR SYSTEMS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHYSICAL PROPERTIES
POLYETHYLENE GLYCOLS
POLYMERS
SURFACTANTS
SYNTHESIS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES