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

Abstract

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.

Authors:
;  [1];  [2]
  1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering
  2. Fritz-Haber-Inst. der Max-Planck-Gesellschaft, Dahlem (Germany)
Publication Date:
OSTI Identifier:
7185227
DOE Contract Number:  
FG02-92ER14262
Resource Type:
Journal Article
Journal Name:
Macromolecules; (United States)
Additional Journal Information:
Journal Volume: 27:9; Journal ID: ISSN 0024-9297
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; COPOLYMERS; CHEMICAL PREPARATION; THERMODYNAMIC PROPERTIES; CONCENTRATION RATIO; MICELLAR SYSTEMS; POLYETHYLENE GLYCOLS; SURFACTANTS; TEMPERATURE DEPENDENCE; ALCOHOLS; GLYCOLS; HYDROXY COMPOUNDS; ORGANIC COMPOUNDS; ORGANIC POLYMERS; PHYSICAL PROPERTIES; POLYMERS; SYNTHESIS; 400201* - Chemical & Physicochemical Properties; 360606 - Other Materials- Physical Properties- (1992-)

Citation Formats

Alexandridis, P, Hatton, T A, and Holzwarth, J F. Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association. United States: N. p., 1994. Web. doi:10.1021/ma00087a009.
Alexandridis, P, Hatton, T A, & Holzwarth, J F. Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association. United States. doi:10.1021/ma00087a009.
Alexandridis, P, Hatton, T A, and Holzwarth, J F. Mon . "Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association". United States. doi:10.1021/ma00087a009.
@article{osti_7185227,
title = {Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association},
author = {Alexandridis, P and Hatton, T A and Holzwarth, J F},
abstractNote = {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.},
doi = {10.1021/ma00087a009},
journal = {Macromolecules; (United States)},
issn = {0024-9297},
number = ,
volume = 27:9,
place = {United States},
year = {1994},
month = {4}
}