Quantitative Brewster angle microscopy measurements of chiral symmetry breaking and chiral boundaries in fatty acid Langmuir monolayers

Brewster angle microscopy (BAM) measurements of the low temperature region of the phase diagram of eicosanoic acid monolayers at an acidic subphase ar e performed. The existence of a new chiral I phase intervening between the L-2 and L-2' phase recently discovered by Durbin et al. [M.K. Durbin, A. Ma lik, A.G. Richter, R. Ghastkadvi, T. Gog, P. Dutta, J. Chem. Phys. 106, 821 6 (1997)] using grazing incidence X-ray diffraction (GIXD) is confirmed. Ch iral symmetry breaking within the monolayers creates characteristic boundar ies separating domains of opposite handedness. These disclination lines are associated with a jump in the tilt azimuth of the director, while the unde rlying hexatic orientation is continuous across the boundary. The disclinat ion lines are observed with the Brewster angle microscope and analyzed as a function of surface pressure. The jump in tilt azimuth is determined. Agre ement with an extended Landau theory proposed by Durbin is achieved.