### Abstract

The surface conformational states of the Gibbs monolayer of ethylene glycol mono-n-dodecyl ether (C_{12}E_{1}) at the air/water interface was studied using dynamic surface tension, external reflection-absorption FT-IR spectroscopy (ERA FT-IR), and two-dimensional infrared (2D IR) correlation methods at constant temperature. The dynamic surface tensions were measured at different bulk concentrations of C_{12}E_{1}, and it was observed that a constant surface tension region appears at ∼38.5 mN m ^{-1} in a dynamic surface tension profile at concentrations higher than 11 μmol kg^{-1}. This constant surface tension region corresponds to the surface phase transition from liquid expanded (LE) to liquid condensed (LC). Two sets of ERA FT-IR spectra were collected, one at different bulk concentrations but after equilibrium time (equilibrium measurements) and another at constant bulk concentration (m = 16 μmol kg^{-1}) but at different times (dynamic measurements). The first set of these measurements show that the peak area increases in the range of 11 < m ≤ 16 μmol kg ^{-1}, which means the increase in the number of surfactant molecules at the air/water interface. Also, the wavenumber of antisymmetric CH_{2} stretching decreases gradually from ∼2923 cm^{-1} (for 10 and 11 μmol kg^{-1}) to ∼2918 cm^{-1} (for m ≥ 16 μmol kg^{-1}) with increasing concentration. The wavenumbers of 2923 and 2918 cm^{-1} were assigned to LE and LC phases, respectively, and the decrease of wavenumber in the concentration range of 11 < m ≤ 16 μmol kg^{-1} were correlated to the surface phase transition (LE → LC), or in other words, in the mentioned concentration range, two phases coexist. The dynamic ERA FT-IR measurements at 16 μmol kg^{-1} also confirm the surface phase transition from LE to LC. The 2D IR correlation method was applied to the both equilibrium and dynamic IR spectra of the C_{12}E _{1} monolayer. The synchronous correlation maps show two strong autopeaks at ∼2922 and ∼2851 cm^{-1} and also show a strong correlation (cross-peaks) between antisymmetric CH_{2} stretching (v_{a}) and symmetric CEk stretching (vs). The asynchronous correlation maps show that both observed bands of v_{a} and v_{s} in one-dimensional IR split into two components with the characteristic of overlapped bands, which reveals the coexistence of two phases (LE and LC) at the interface at 11 < m ≤ 16 μmol kg^{-1}. The synchronous and asynchronous maps that were obtained from dynamic IR spectra closely resembled the equilibrium map.

Original language | English |
---|---|

Pages (from-to) | 17034-17042 |

Number of pages | 9 |

Journal | Journal of Physical Chemistry B |

Volume | 110 |

Issue number | 34 |

DOIs | |

Publication status | Published - Aug 31 2006 |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry

### Cite this

_{12}E

_{1}at the air/water interface: A study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods.

*Journal of Physical Chemistry B*,

*110*(34), 17034-17042. https://doi.org/10.1021/jp063301p

**Surface phase transition of C _{12}E_{1} at the air/water interface : A study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods.** / Azizian, S.; Shibata, K.; Matsuda, T.; Takiue, Takanori; Matsubara, Hiroki; Aratono, Makoto.

Research output: Contribution to journal › Article

_{12}E

_{1}at the air/water interface: A study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods',

*Journal of Physical Chemistry B*, vol. 110, no. 34, pp. 17034-17042. https://doi.org/10.1021/jp063301p

_{12}E

_{1}at the air/water interface: A study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods. Journal of Physical Chemistry B. 2006 Aug 31;110(34):17034-17042. https://doi.org/10.1021/jp063301p

}

TY - JOUR

T1 - Surface phase transition of C12E1 at the air/water interface

T2 - A study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods

AU - Azizian, S.

AU - Shibata, K.

AU - Matsuda, T.

AU - Takiue, Takanori

AU - Matsubara, Hiroki

AU - Aratono, Makoto

PY - 2006/8/31

Y1 - 2006/8/31

N2 - The surface conformational states of the Gibbs monolayer of ethylene glycol mono-n-dodecyl ether (C12E1) at the air/water interface was studied using dynamic surface tension, external reflection-absorption FT-IR spectroscopy (ERA FT-IR), and two-dimensional infrared (2D IR) correlation methods at constant temperature. The dynamic surface tensions were measured at different bulk concentrations of C12E1, and it was observed that a constant surface tension region appears at ∼38.5 mN m -1 in a dynamic surface tension profile at concentrations higher than 11 μmol kg-1. This constant surface tension region corresponds to the surface phase transition from liquid expanded (LE) to liquid condensed (LC). Two sets of ERA FT-IR spectra were collected, one at different bulk concentrations but after equilibrium time (equilibrium measurements) and another at constant bulk concentration (m = 16 μmol kg-1) but at different times (dynamic measurements). The first set of these measurements show that the peak area increases in the range of 11 < m ≤ 16 μmol kg -1, which means the increase in the number of surfactant molecules at the air/water interface. Also, the wavenumber of antisymmetric CH2 stretching decreases gradually from ∼2923 cm-1 (for 10 and 11 μmol kg-1) to ∼2918 cm-1 (for m ≥ 16 μmol kg-1) with increasing concentration. The wavenumbers of 2923 and 2918 cm-1 were assigned to LE and LC phases, respectively, and the decrease of wavenumber in the concentration range of 11 < m ≤ 16 μmol kg-1 were correlated to the surface phase transition (LE → LC), or in other words, in the mentioned concentration range, two phases coexist. The dynamic ERA FT-IR measurements at 16 μmol kg-1 also confirm the surface phase transition from LE to LC. The 2D IR correlation method was applied to the both equilibrium and dynamic IR spectra of the C12E 1 monolayer. The synchronous correlation maps show two strong autopeaks at ∼2922 and ∼2851 cm-1 and also show a strong correlation (cross-peaks) between antisymmetric CH2 stretching (va) and symmetric CEk stretching (vs). The asynchronous correlation maps show that both observed bands of va and vs in one-dimensional IR split into two components with the characteristic of overlapped bands, which reveals the coexistence of two phases (LE and LC) at the interface at 11 < m ≤ 16 μmol kg-1. The synchronous and asynchronous maps that were obtained from dynamic IR spectra closely resembled the equilibrium map.

AB - The surface conformational states of the Gibbs monolayer of ethylene glycol mono-n-dodecyl ether (C12E1) at the air/water interface was studied using dynamic surface tension, external reflection-absorption FT-IR spectroscopy (ERA FT-IR), and two-dimensional infrared (2D IR) correlation methods at constant temperature. The dynamic surface tensions were measured at different bulk concentrations of C12E1, and it was observed that a constant surface tension region appears at ∼38.5 mN m -1 in a dynamic surface tension profile at concentrations higher than 11 μmol kg-1. This constant surface tension region corresponds to the surface phase transition from liquid expanded (LE) to liquid condensed (LC). Two sets of ERA FT-IR spectra were collected, one at different bulk concentrations but after equilibrium time (equilibrium measurements) and another at constant bulk concentration (m = 16 μmol kg-1) but at different times (dynamic measurements). The first set of these measurements show that the peak area increases in the range of 11 < m ≤ 16 μmol kg -1, which means the increase in the number of surfactant molecules at the air/water interface. Also, the wavenumber of antisymmetric CH2 stretching decreases gradually from ∼2923 cm-1 (for 10 and 11 μmol kg-1) to ∼2918 cm-1 (for m ≥ 16 μmol kg-1) with increasing concentration. The wavenumbers of 2923 and 2918 cm-1 were assigned to LE and LC phases, respectively, and the decrease of wavenumber in the concentration range of 11 < m ≤ 16 μmol kg-1 were correlated to the surface phase transition (LE → LC), or in other words, in the mentioned concentration range, two phases coexist. The dynamic ERA FT-IR measurements at 16 μmol kg-1 also confirm the surface phase transition from LE to LC. The 2D IR correlation method was applied to the both equilibrium and dynamic IR spectra of the C12E 1 monolayer. The synchronous correlation maps show two strong autopeaks at ∼2922 and ∼2851 cm-1 and also show a strong correlation (cross-peaks) between antisymmetric CH2 stretching (va) and symmetric CEk stretching (vs). The asynchronous correlation maps show that both observed bands of va and vs in one-dimensional IR split into two components with the characteristic of overlapped bands, which reveals the coexistence of two phases (LE and LC) at the interface at 11 < m ≤ 16 μmol kg-1. The synchronous and asynchronous maps that were obtained from dynamic IR spectra closely resembled the equilibrium map.

UR - http://www.scopus.com/inward/record.url?scp=33748779800&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33748779800&partnerID=8YFLogxK

U2 - 10.1021/jp063301p

DO - 10.1021/jp063301p

M3 - Article

VL - 110

SP - 17034

EP - 17042

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 34

ER -