ISSN:
1435-1536
Keywords:
Monolayers
;
penetration
;
sodium cetylsulfate
;
phosphatidylethanolamine
;
thermodynamics
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The penetration of sodium cetylsulfate into monolayers of dipalmitoyl- and dimyristoyl-phosphatidylethanolamine was studied by the measurement of surface and penetration pressures using the vertical plate method of Wilhelmy. The penetration isotherms in two systems were investigated at different initial molecular areasA M : System I: Sodium cetylsulfate/1,2-dipalmitoyl-phosphatidylethanolamine atA M = 0.85; 0.75; 0.65; 0.55; 0.50; 0.46 and 0.44 nm2 · molecule−1. System II: Sodium cetylsulfate/1,2-dimyristoyl-phosphatidylethanolamine atA M = 0.85; 0.75; 0.60 and 0.55 nm2 · molecule−1. (T=295 K; substrate 0.1 M NaCl) The penetration isotherms (F t vs. logc s ) increase linearly atF t 〉 10 mN · m−1 in system I and atF t 〉25 mN · m−1 in system II. The isotherms of both systems are shifted to lower surfactant concentrations with decreasing molecular area of spread monolayer. A maximum of the slopes (dFt/d logc s )occurs at AM=0.50 nm2 · molecule−1. This behavior is also reflected in the dependenceΔG p 0 (free standard penetration enthalpy) andΓ s (relative surface excess concentration of surfactant) onA M . These changes are related to a different packing of the compounds in the binary penetrated monolayers. In the high pressure region both system are nearly identical. Differences in the low pressure region arise from the penetration into different monolayer states.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01421889
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