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. Author manuscript; available in PMC: 2011 Mar 11.
Published in final edited form as: J Phys Chem B. 2010 Mar 11;114(9):3276–3284. doi: 10.1021/jp908730t

Figure 2.

Figure 2

Compression isotherms of EPC (A) and TO (B) monolayers spread on a Langmuir trough. EPC showed a collapse point at an area per molecule of 58 ± 3 Å2/molecule and a Π of 38.9 ± 0.8 mN/m (mean and standard deviation; N=9). Π deviates from 0 at an approximate area per molecule of 140 Å2 and the extrapolated deviation from Π=0 is 90 Å2/molecule. The surface was compressed at a rate of 3.75 cm2/min. The isotherm was reversible when reexpanded from 37 mN/m but when it was reexpanded beyond Π=40 mN/m it was irreversible. Compression isotherm of TO spread on a Langmuir trough showed a break in the curve at a pressure of 12.1 mN/m (at 23°C and a compression rate of 3.75 cm2/minute). At an area smaller than 90 Å2/molecule and Π greater than 12.1 mN/m some of the TO is expelled from the monolayer and forms a new bulk phase which is in equilibrium with the TO monolayer at its minimum area (~90 Å2/molecule).