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Ellipsometric studies of behenic acid at the air‐water interface
Author(s) -
Paudler Michaela,
Ruths Jens,
Alberti Bernhard,
Riegler Hans
Publication year - 1991
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19910460158
Subject(s) - ellipsometry , behenic acid , anisotropy , monolayer , phase transition , isobaric process , refractive index , intensity (physics) , phase (matter) , analytical chemistry (journal) , materials science , chemistry , optics , condensed matter physics , thermodynamics , thin film , physics , chromatography , nanotechnology , organic chemistry , fatty acid , palmitic acid
The rich phase behaviour of monolayers of behenic acid (=docosanoic acid) has been analyzed by null ellipsometry in isothermic and isobaric measurements. By using structural data known from x‐ray measurements the anisotropy and refractive indices in the vicinity of the S‐CS phase transition have been calculated with a minimum of model assumptions. The calculated values are: n s x =1.47. n cs x =1.48. n s z =1.54. n cs z =1.55. and anisotropy γ=n x /n z ≈0.95. It is also shown that ellipsometry is a very sensitive and convenient method of detecting phase transitions. Its value for quantifying the roughness of the monolayer in the close vicinity of phase transitions due to thickness and density fluctuations is shown by the measurement of the parabolic intensity variations of the ellipsometric angle δΔ. The intensity minimum at the phase transition is much wider than in the adjacent homogeneous phases.