Relaxation Behaviors of Monolayers of Octadecylamine and Stearic Acid at the Air/Water Interface

Yuh-Lang Lee, Kou Liang Liu

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

This study investigated the relaxation behaviors of octadecylamine (ODA), stearic acid (SA), and SA/ODA mixed monolayers at the air/water interface. Area relaxations of monolayers at constant surface pressure were studied by a nucleation and growth mechanism and by direct observation using a Brewster angle microscope (BAM). The results showed that ODA and SA monolayers exhibit different characteristics in the area loss and in the BAM morphology. In the initial relaxation stage, SA monolayer illustrates a more stable characteristic than ODA. But at the later stage, the area loss of SA monolayer increases more quickly than that for ODA due to significant nucleation and growth of 3D aggregates. The BAM results demonstrated that 3D aggregates of large scale domains are likely to form on a SA monolayer even when the area loss is insignificant. On the contrary, only dotlike aggregates of low density were found on the ODA monolayer when relaxation is carried out at higher surface pressure. The relaxation behavior of SA monolayer can be described by the Vollhardt model. However, the relaxation of ODA monolayer does not follow the nucleation model described by Vollhard but can reasonably be attributed to the effect of dissolution. For the SA/ODA mixed monolayers, the relaxation behaviors in the initial and final stages follow different mechanisms, which is attributed to the formation of distinct phases as observed from the BAM. This result also implied that SA and ODA are not completely miscible to be a homogeneous phase. Phases of various compositions were formed in the mixed monolayers, and thus, the relaxation mechanism was shifted during the relaxation process as dominated by different relaxation behaviors of various phases.

Original languageEnglish
Pages (from-to)3180-3187
Number of pages8
JournalLangmuir
Volume20
Issue number8
Publication statusPublished - 2004 Apr 13

Fingerprint

Stearic acid
Monolayers
acids
Water
air
Air
Brewster angle
water
microscopes
Microscopes
Nucleation
nucleation
stearylamine
stearic acid
Relaxation processes
dissolving
Dissolution

All Science Journal Classification (ASJC) codes

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

Cite this

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abstract = "This study investigated the relaxation behaviors of octadecylamine (ODA), stearic acid (SA), and SA/ODA mixed monolayers at the air/water interface. Area relaxations of monolayers at constant surface pressure were studied by a nucleation and growth mechanism and by direct observation using a Brewster angle microscope (BAM). The results showed that ODA and SA monolayers exhibit different characteristics in the area loss and in the BAM morphology. In the initial relaxation stage, SA monolayer illustrates a more stable characteristic than ODA. But at the later stage, the area loss of SA monolayer increases more quickly than that for ODA due to significant nucleation and growth of 3D aggregates. The BAM results demonstrated that 3D aggregates of large scale domains are likely to form on a SA monolayer even when the area loss is insignificant. On the contrary, only dotlike aggregates of low density were found on the ODA monolayer when relaxation is carried out at higher surface pressure. The relaxation behavior of SA monolayer can be described by the Vollhardt model. However, the relaxation of ODA monolayer does not follow the nucleation model described by Vollhard but can reasonably be attributed to the effect of dissolution. For the SA/ODA mixed monolayers, the relaxation behaviors in the initial and final stages follow different mechanisms, which is attributed to the formation of distinct phases as observed from the BAM. This result also implied that SA and ODA are not completely miscible to be a homogeneous phase. Phases of various compositions were formed in the mixed monolayers, and thus, the relaxation mechanism was shifted during the relaxation process as dominated by different relaxation behaviors of various phases.",
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Relaxation Behaviors of Monolayers of Octadecylamine and Stearic Acid at the Air/Water Interface. / Lee, Yuh-Lang; Liu, Kou Liang.

In: Langmuir, Vol. 20, No. 8, 13.04.2004, p. 3180-3187.

Research output: Contribution to journalArticle

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