Fluorescence probe studies of pluronic copolymer solutions as a function of temperature
- Massachusetts Inst. of Technology, Cambridge, MA (United States)
- Univ. of Toronto, Ontario (Canada)
The temperature variation of the I{sub 1}/I{sub 3} ratio of pyrene vibrational fine structure has been studied in aqueous poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer solutions, in bulk PEO, PPO, and various organic solvents. Linear decreases were observed in organic solvents and in mixtures of bulk PEO and PPO. The data in aqueous PEO-PPO-PEO copolymer solutions reveal three distinct solution conditions: at low temperatures, the linear decrease with temperature parallels that for water; over a small intermediate temperature range there is a sharp decrease in the ratio, attributed to the formation of micelles; and at higher temperatures, a linear decrease is again observed. Values in this region are strongly dependent on the PPO block and are consistent with the representation of micelles with a core dominated by PPO. The composition of the micelle core was estimated using these data and indicated an increase of poly(ethylene oxide) as the polymer becomes more hydrophilic. In addition, the size of the micelles and their aggregation numbers were determined using light scattering and pyrene luminescence decay studies, respectively. These data showed an increase of the aggregation number with temperature while the hydrodynamic radius remained constant and were interpreted in terms of dehydration of the PEO block. 38 refs., 11 figs., 3 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-92ER14262
- OSTI ID:
- 41631
- Journal Information:
- Langmuir, Vol. 11, Issue 3; Other Information: PBD: Mar 1995
- Country of Publication:
- United States
- Language:
- English
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