Microviscosity in Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer micelles
- Massachusetts Inst. of Technology, Cambridge, MA (United States)
The micellar microviscosity afforded by Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer aqueous solutions has been investigated by fluorescence and NMR spectroscopy. Comparison is made with bulk poly(propylene oxide) (PPO) samples of different molecular weights. The microviscosity in Pluronic PEO-PPO-PEO copolymer micelles is much larger than that observed in conventional surfactant micelles and depends strongly on the size of the hydrophobic PPO block: the larger this block, the higher the viscosity. Above the critical micellar temperature (CMT), as temperature increases, the microviscosity decreases. However, this decrease is not as important as that observed in bulk PPO. Hence, the relative microviscosity, defined as the ratio of the two observed phenomena, increases. This suggests structural transformation of the micelles resulting in a core becoming more and more compact as temperature increases. Such results have been confirmed by NMR studies that showed broadening of the PPO peak and relatively constant spin-lattice relaxation time, T[sub i], with increasing temperature while the PEO signal remained relatively sharp with an exponential increase in T[sub 1]. 30 refs., 9 figs., 1 tab.
- DOE Contract Number:
- FG02-92ER14262
- OSTI ID:
- 6539154
- Journal Information:
- Langmuir; (United States), Vol. 11:1; ISSN 0743-7463
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
74 ATOMIC AND MOLECULAR PHYSICS
COPOLYMERS
FLUORESCENCE SPECTROSCOPY
NMR SPECTRA
SPIN-LATTICE RELAXATION
VISCOSITY
MICELLAR SYSTEMS
POLYETHYLENE GLYCOLS
TEMPERATURE DEPENDENCE
ALCOHOLS
EMISSION SPECTROSCOPY
GLYCOLS
HYDROXY COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
POLYMERS
RELAXATION
SPECTRA
SPECTROSCOPY
400201* - Chemical & Physicochemical Properties
360600 - Other Materials
360602 - Other Materials- Structure & Phase Studies
664200 - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)