Pluronic-P105 PEO-PPO-PEO block copolymer in aqueous urea solutions. Micelle formation, structure, and microenvironment
- Massachusetts Inst. of Technology, Cambridge, MA (United States)
The effects of urea on the micellization properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer (commercially available as Pluronic P105) and on the structure and microenvironment of the micelles are reported. Urea increased the critical micelle concentration (cmc) and critical micelle temperature (cmt) of the PEO-PPO-PEO copolymer; the effect of urea on the cmt was more pronounced at low copolymer concentrations and diminished at concentrations of nearly 2.5%. The surface activity and the partial specific volume of the block copolymer decreased with an increase in the urea concentration, whereas the hydrodynamic radii of the copolymer micelles, determined using dynamic light scattering, remained unaffected by the presence of 4 M urea in the solution. The micropolarity in copolymer solutions in urea/water was probed as a function of temperature using the I{sub 1}/I{sub 3} intensity ratio of the pyrene vibrational fine structure recorded in fluorescence emission spectra; a small decrease in the micropolarity of the micelle core was observed in the presence of urea. The microviscosity in the micelle interior, estimated from the intramolecular excimer fluorescence of the hydrophobic probe bis(1-pyrenylmethyl) ether (dipyme), also exhibited a small decrease with an increase in the urea concentration. 80 refs., 8 figs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-92ER14262
- OSTI ID:
- 91256
- Journal Information:
- Langmuir, Vol. 11, Issue 7; Other Information: PBD: Jul 1995
- Country of Publication:
- United States
- Language:
- English
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