Quantitative Brewster angle microscopy measurements of chiral symmetry breaking and chiral boundaries in fatty acid Langmuir monolayers
Institute of Experimental Physics I, University of Leipzig, 04103 Leipzig, Germany
Revised: 3 August 1998
Accepted: 7 August 1998
Published online: 15 January 1999
Brewster angle microscopy (BAM) measurements of the low temperature region of the phase diagram of eicosanoic acid monolayers at an acidic subphase are performed. The existence of a new chiral I phase intervening between the L2 and phase recently discovered by Durbin et al. [M.K. Durbin, A. Malik, A.G. Richter, R. Ghastkadvi, T. Gog, P. Dutta, J. Chem. Phys. 106, 8216 (1997)] using grazing incidence X-ray diffraction (GIXD) is confirmed. Chiral symmetry breaking within the monolayers creates characteristic boundaries separating domains of opposite handedness. These disclination lines are associated with a jump in the tilt azimuth of the director, while the underlying hexatic orientation is continuous across the boundary. The disclination lines are observed with the Brewster angle microscope and analyzed as a function of surface pressure. The jump in tilt azimuth is determined. Agreement with an extended Landau theory proposed by Durbin is achieved.
PACS: 68.10.-m – Fluid surfaces and fluid-fluid interfaces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999