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A Calorimetry and Light Scattering Study of the Formation and Shape Transition of Mixed Micelles of EO20PO68EO20 Triblock Copolymer (P123) and Nonionic Surfactant (C12EO6)

Löf, David LU ; Niemiec, Anna; Schillén, Karin LU ; Loh, Watson and Olofsson, Gerd LU (2007) In The Journal of Physical Chemistry Part B 111(21). p.5911-5920
Abstract
The interaction between the nonionic surfactant C12EO6 and the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer EO20PO68EO20 (P123) has been investigated by means of isothermal titration and differential scanning calorimetry (DSC) as well as static and dynamic light scattering (SLS and DLS). P123 self-assembles in water into spherical micelles at ambient temperatures. At raised temperatures, the DSC data revealed a sphere-to-rod transition of the P123 micelles around 60 degrees C. C12EO6 interacts strongly with P123 micelles in aqueous solution to give mixed micelles with a critical micelle concentration (cmc) well below the cmc for pure C12EO6. The presence of C12EO6 also lowers the critical micelle... (More)
The interaction between the nonionic surfactant C12EO6 and the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer EO20PO68EO20 (P123) has been investigated by means of isothermal titration and differential scanning calorimetry (DSC) as well as static and dynamic light scattering (SLS and DLS). P123 self-assembles in water into spherical micelles at ambient temperatures. At raised temperatures, the DSC data revealed a sphere-to-rod transition of the P123 micelles around 60 degrees C. C12EO6 interacts strongly with P123 micelles in aqueous solution to give mixed micelles with a critical micelle concentration (cmc) well below the cmc for pure C12EO6. The presence of C12EO6 also lowers the critical micelle temperature of P123 so aggregation starts at significantly lower temperatures. A new phenomenon was observed in the P123-C12EO6 system, namely, a well-defined sphere-to-rod transition of the mixed micelles. A visual phase study of mixtures containing 1.00 wt % P123 showed that in a narrow concentration range of C12EO6 both the sphere-to-rod transition and the liquid-liquid phase separation temperature are strongly depressed compared to the pure P123-water system. The hydrodynamic radius of spherical mixed micelles at a C12EO6/P123 molar ratio of 2.2 was estimated from DLS to be 9.1 nm, whereas it is 24.1 nm for the rodlike micelles. Furthermore, the hydrodynamic length of the rods at a molar ratio of 2.2 is in the range of 100 nm. The retarded kinetics of the shape transition was detected in titration calorimetric experiments at 40 degrees C and further studied by using time-resolved DLS and SLS. The rate of growth, which was slow (> 2000 s), was found to increase with the total concentration. (Less)
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published
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keywords
OXIDE) BLOCK-COPOLYMERS, ANGLE NEUTRON-SCATTERING, ISOTHERMAL TITRATION CALORIMETRY, TO-ROD TRANSITION, N-DODECYL ETHER, PHASE-BEHAVIOR, AQUEOUS-SOLUTION, IONIC SURFACTANTS, WATER, MICELLIZATION
in
The Journal of Physical Chemistry Part B
volume
111
issue
21
pages
5911 - 5920
publisher
The American Chemical Society
external identifiers
  • wos:000246695100016
  • scopus:34250327965
ISSN
1520-5207
DOI
10.1021/jp071101n
language
English
LU publication?
yes
id
09396c80-9e23-4c98-8159-3eb904c66c28 (old id 697122)
date added to LUP
2007-12-12 13:49:19
date last changed
2017-08-27 05:19:27
@article{09396c80-9e23-4c98-8159-3eb904c66c28,
  abstract     = {The interaction between the nonionic surfactant C12EO6 and the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer EO20PO68EO20 (P123) has been investigated by means of isothermal titration and differential scanning calorimetry (DSC) as well as static and dynamic light scattering (SLS and DLS). P123 self-assembles in water into spherical micelles at ambient temperatures. At raised temperatures, the DSC data revealed a sphere-to-rod transition of the P123 micelles around 60 degrees C. C12EO6 interacts strongly with P123 micelles in aqueous solution to give mixed micelles with a critical micelle concentration (cmc) well below the cmc for pure C12EO6. The presence of C12EO6 also lowers the critical micelle temperature of P123 so aggregation starts at significantly lower temperatures. A new phenomenon was observed in the P123-C12EO6 system, namely, a well-defined sphere-to-rod transition of the mixed micelles. A visual phase study of mixtures containing 1.00 wt % P123 showed that in a narrow concentration range of C12EO6 both the sphere-to-rod transition and the liquid-liquid phase separation temperature are strongly depressed compared to the pure P123-water system. The hydrodynamic radius of spherical mixed micelles at a C12EO6/P123 molar ratio of 2.2 was estimated from DLS to be 9.1 nm, whereas it is 24.1 nm for the rodlike micelles. Furthermore, the hydrodynamic length of the rods at a molar ratio of 2.2 is in the range of 100 nm. The retarded kinetics of the shape transition was detected in titration calorimetric experiments at 40 degrees C and further studied by using time-resolved DLS and SLS. The rate of growth, which was slow (> 2000 s), was found to increase with the total concentration.},
  author       = {Löf, David and Niemiec, Anna and Schillén, Karin and Loh, Watson and Olofsson, Gerd},
  issn         = {1520-5207},
  keyword      = {OXIDE) BLOCK-COPOLYMERS,ANGLE NEUTRON-SCATTERING,ISOTHERMAL TITRATION CALORIMETRY,TO-ROD TRANSITION,N-DODECYL ETHER,PHASE-BEHAVIOR,AQUEOUS-SOLUTION,IONIC SURFACTANTS,WATER,MICELLIZATION},
  language     = {eng},
  number       = {21},
  pages        = {5911--5920},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {A Calorimetry and Light Scattering Study of the Formation and Shape Transition of Mixed Micelles of EO20PO68EO20 Triblock Copolymer (P123) and Nonionic Surfactant (C12EO6)},
  url          = {http://dx.doi.org/10.1021/jp071101n},
  volume       = {111},
  year         = {2007},
}