Short Communication

Colloid and Polymer Science

, Volume 274, Issue 10, pp 995-999

Isotherms of phospholipid monolayers measured by a pendant drop technique

  • J. B. LiAffiliated withMax-Planck-Institut für Kolloid- und Grenzflächenforschung
  • , R. MillerAffiliated withMax-Planck-Institut für Kolloid- und Grenzflächenforschung
  • , D. VollhardtAffiliated withMax-Planck-Institut für Kolloid- und Grenzflächenforschung
  • , G. WeidemannAffiliated withMax-Planck-Institut für Kolloid- und Grenzflächenforschung
  • , H. MöhwaldAffiliated withMax-Planck-Institut für Kolloid- und Grenzflächenforschung

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Abstract

The Axisymmetric Drop Shape Analysis (ADSA) has been used to study the surface pressure/area isotherms of insoluble surfactant monolayers. The continuous measurement of surface tension as a function of surface area by increasing and decreasing the drop volume allows to investigate the phase transitions in monolayers. The isotherms of two phospholipids, dipalmitoyl phosphatidyl choline (DPPC) and dimyristoyl phosphatidyl ethanolamine (DMPE), show good agreement with those measured by using a conventional Langmuir-Blodgett film balance, except in the coexistence region. The observed disagreements are discussed in terms of differences in compression rate, curvature of the surface and effect of impurities. Evidence of possible geometric effects on monolayer domain formation and growth is given on the basis of BAM images.

Due to the small total surface area, the ADSA technique provides advantages as regards homogeneity of temperature, surface pressure, surface concentration and the symmetry of area changes.

Key words

ADSA phospholipids LB film balance monolayer isotherms BAM