FTIR study of lamellar and reversed micellar phases in the mono-oleoylglycerol/water system.
The lamellar liquid crystalline (L alpha) and the reversed micellar (L2) phases of mono-oleoylglycerol (MO) in water were investigated by Fourier transform infrared (FTIR) spectroscopy. From polarized infrared spectra of aligned bilayers of MO/water, order parameters (S) were determined for vibrational modes in the hydrocarbon chain region (symmetric CH2 stretch and olefinic CH=CH stretch) and the aggregate surface region (C=O stretch and asymmetric CO-O-C stretch). The phase transition between L alpha and L2 (10 wt% water) occurs in the temperature range 43-46 degrees C. Already at about 32 degrees C the LD value for the C-OH stretching vibration has decreased to 50% of its value at 25 degrees C. A similar relative decrease in LD is obtained for the C=O stretch and the asymmetric CO-O-C stretch at about 38 degrees C and for the CH=CH stretch at about 43 degrees C. It is concluded that the molecular ordering in the region of the aggregate surface starts to decrease at a lower temperature than for the acyl chain region. Infrared spectra show a significant decrease in the conformational order of the hydrocarbon chains at the L alpha/L2 phase transition.
Nilsson
A
A
Department of Physical Chemistry, Umeå University, Sweden.
Holmgren
A
A
Lindblom
G
G
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005989:Glycerides / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D008823:Micelles; D008968:Molecular Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry
D005989:Glycerides; D008051:Lipid Bilayers; D008823:Micelles; D014867:Water; C005953:monoolein