TITLE:
Surface Properties of Novel Surfactant, Dihexadecyl Gemini Phosphate, Monolayers on Water Surface by Dropping Method
AUTHORS:
Yusuke Kobayashi, Takahiko Amano, Keijiro Taga, Yasushi Yamamoto, Zameer Shervani, Masato Yamamoto
KEYWORDS:
Dihexadecyl Gemini Phosphates, Monolayers, Surface Tension Measurement, Brewster Angle Microscopy, Density Functional Theory Calculation
JOURNAL NAME:
Journal of Biophysical Chemistry,
Vol.8 No.4,
November
3,
2017
ABSTRACT: We have synthesized first novel dihexadecyl
phosphate (DHGP-n) gemini surfactants
containing alkyl chain ((CnH2n); n = 3, 4, 5, and 6) spacers. Surfactants were used to form monolayers
on water surface. Surface tension measurement (STm), Brewster angle microscopy
(BAM), and density functional theory (DFT) calculation were used to investigate
these monolayers. Surface pressure (π) and molecular area (A); π-A isotherm curves of all DHGP-n gemini surfactants showed a gradual
increase in surface pressure without any break points in the curves, confirmed
the formation of liquid-expand (LE) type monolayers. BAM observations also
supported the STm results. Limited molecular area (A0) of these monolayers depended on the spacer of gemini
surfactants without spacer n = 4. Longer alkyl chain spacer in the
series had higher value of A0 in π-A isotherm plots. In the
series, A0 of spacer n = 4 was smallest among A0 values of other spacers.
Density functional theory (DFT) method calculation also confirmed π-A isotherm curves pattern of these surfactants.
Calculation showed that both odd and even numbers and length of the alkyl chain
spacer influenced the structure of DHGP-n monolayer formation on the water surface.