Structure and lateral interaction in mixed monolayers of dioctadecyldimethylammonium chloride (DOAC) and stearyl alcohol

Aimin Ge, Hengliang Wu, Tamim A. Darwish, Michael James, Masatoshi Osawa, Shen Ye

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

π-A isotherms, atomic force microscopy (AFM), and sum frequency generation (SFG) vibrational spectroscopy are employed to investigate the molecular structure and lateral interactions in mixed monolayers of dioctadecyldimethylammonium chloride (DOAC) and stearyl alcohol (SA) at air/water and air/solid interfaces. To avoid possible interference between the two molecules in the SFG spectroscopic measurements, perprotonated DOAC and perdeuterated SA (dSA) were used. The thermodynamic analyses for the π-A isotherms show that DOAC is miscible with dSA. SFG observations reveal that DOAC molecules become conformationally ordered as dSA molecules are introduced into the monolayer. AFM observations demonstrate coexistence of DOAC-rich and dSA-rich domains in the mixed monolayer with ratios different from their initial composition in the subphase. The present study suggests that DOAC molecules in the mixed monolayer are condensed by mixing with dSA in which the repulsive interactions between positively charged head groups of the DOAC molecules are largely reduced along with an increase of van der Waals interactions with dSA.

Original languageEnglish
Pages (from-to)5407-5417
Number of pages11
JournalLangmuir
Volume29
Issue number18
DOIs
Publication statusPublished - 2013 May 7
Externally publishedYes

ASJC Scopus subject areas

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

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