Surface characterization of octadecylamine films prepared by langmuir-blodgett and vacuum deposition methods by dynamic contact angle measurements

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Abstract

The behavior of octadecylamine (ODA) monolayers on various subphases is investigated. The monolayer is then transferred to a hydrophilic glass surface to prepare a LB film of one monolayer. The uniformity, stability, and molecular orientation of the LB films were studied by the measurement of dynamic contact angle and compared with characteristics of vacuum-deposited films. The results show that the ODA monolayer is especially stable on alkaline solution. The LB film transferred from the alkaline solution is stable and uniform in wettability. The advancing and receding contact angles of water on one layer of ODA film are about 113° and 62°, respectively. These values are the same as those on a vacuum-deposited ODA film of equivalent thickness. The growth of ODA on a glass surface in a vacuum deposition is thus found to follow a mode of layer growth. The orientation and arrangement of molecules on the LB films are affected by the surface pressure and transferring rate during the transferring procedure. When the transfer is proceeded at low surface pressure and high transferring rate, the ODA molecules are irregularly packed without uniform orientation. However, during the analysis of dynamic contact angle (DCA), the movement of the three-phase contact line has an effect to rearrange the irregularly packed molecules of ODA on the LB films and the surface becomes more and more uniform with the analytic cycles of the DCA. By comparing between the LB films of ODA and stearic acid, the advancing contact angles are identical for both, but the very small value of receding contact angle on stearic acid reflects the exposure of the hydrophilic glass on the stearic acid film. The existence of holes in the stearic acid monolayer is thus proved by the measurement of wettability.

Original languageEnglish
Pages (from-to)1796-1801
Number of pages6
JournalLangmuir
Volume15
Issue number5
Publication statusPublished - 1999 Dec 1

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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