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Mixing of Partially Fluorinated Carboxylic Acids and Their Hydrocarbon Analogues with Dipalmitoylphosphatidylcholine at the Air−Water Interface
Journal article   Peer reviewed

Mixing of Partially Fluorinated Carboxylic Acids and Their Hydrocarbon Analogues with Dipalmitoylphosphatidylcholine at the Air−Water Interface

Hans-Joachim Lehmler, Michael Jay and Paul M Bummer
Langmuir, Vol.16(26), pp.10161-10166
12/26/2000
DOI: 10.1021/la991598v

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Abstract

The interaction of partially fluorinated carboxylic acids with a biologically relevant surfactant, dipalmitoylphosphatidylcholine (DPPC), was investigated at the air−water interface. The compression isotherms of mixtures of three partially fluorinated carboxylic acids (1−3) and their hydrocarbon analogues (4 − 6) with DPPC were recorded at various compositions on hydrochloric acid (pH = 1.9, 32 ± 2 °C) as a subphase. The mixing behavior was assessed by analyzing the concentration dependence of the average molecular area at constant film pressure (area/mole fraction or A − X diagram). All six carboxylic acids (1 − 6) show a negative deviation from ideal behavior at surface pressures between 3 and 25 mN/m, which is indicative of an attractive interaction with DPPC in the mixed monolayer at the air−water interface. With the exception of nonafluorpentadecanoic acid (1), all carboxylic acids investigated show a concentration dependence of the breakpoint of the phase transition from the liquid-expanded to the liquid-condensed state, which supports the interpretation of the A − X diagrams.

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