Orientation phase transitions of undissociated n-decanoic acid at the air/solution interface revealed by surface pressure and electric potential

Change of the effective dipole moment, μ⊥/εs, versus the bulk concentraqtion, c, of undissociated n-decanoic acid at the air/solution interface, at 25oC, indicates three 2D phase transitions between the monophases reflected in the local maxima of μ⊥/εs vs. c, namely: liquid expanded → liquid condensed tilted → liquid condensed untilted.Within the higher concn. region, the liquid condensed untilted coexists with 2D aggregates.125