The crystal lattice of an arachidic acid/Cd2+ (CdA) monolayer on the surface of aqueous CdCl2 subphase in a Langmuir trough was investigated in situ by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). The spectra reveal a hexagonal packing of the hydrocarbon chains on the subphase of pH=6.2 and 293–283 K. Cooling from 283 to 280 K induces the hexagonal unit cell to transform to an orthorhombic one, as evidenced by the splitting of the CH2 scissoring mode. This transition is observed to be reversible with temperature variation within 293–274 K. On the subphase of pH=8.4, the crystal lattice of CdA is orthorhombic even at 293 K. The temperature-dependent crystal lattice transition of CdA is compared with the monotonic hexagonal subcell of a cadmium stearate monolayer within 293–274 K and the orthorhombic subcell of a cadmium behenate monolayer within 293–274 K.

1.
P.
Dutta
,
J. B.
Peng
,
B.
Lin
et al.,
Phys. Rev. Lett.
58
,
2228
(
1987
).
2.
M. J.
Bedzyk
,
G. M.
Bommarito
,
M.
Caffrey
, and
T. L.
Penner
,
Science
248
,
52
(
1990
).
3.
F.
Leveiller
,
D.
Jacquemain
,
M.
Lahav
et al.,
Science
252
,
1532
(
1991
).
4.
K.
Kjaer
,
J.
Als-Nielsen
,
C. A.
Helm
et al.,
J. Phys. Chem.
93
,
3200
(
1989
).
5.
P.
Tippmann-Krayer
,
R. M.
Kenn
, and
H.
Möhwald
,
Thin Solid Films
210
,
577
(
1992
).
6.
F.
Leveiller
,
C.
Böhm
,
D.
Jacquemain
et al.,
Langmuir
10
,
819
(
1994
).
7.
D.
Blaudez
,
J.-M.
Turlet
,
J.
Dufourcq
et al.,
J. Chem. Soc., Faraday Trans.
92
,
525
(
1996
).
8.
J.
Simon-Kutscher
,
A.
Gericke
, and
H.
Hühnerfuss
,
Langmuir
12
,
1027
(
1996
).
9.
J. G. Weers and D. R. Scheuing, in Fourier Transform Infrared Spectroscopy in Colloid and Interface Science, edited by D. R. Scheuing (American Chemical Society, Boston, 1991). Page 91 is about the δ(CH2) mode of hexagonal (a singlet band around 1468 cm−1) and orthorhombic packing (splitting to two bands) of hydrocarbon chains.
10.
R. G.
Snyder
,
J. Mol. Spectrosc.
7
,
116
(
1961
).
11.
D. K.
Schwartz
,
J.
Garnaes
,
R.
Viswanathan
, and
J. A. N.
Zasadzinski
,
Science
257
,
508
(
1992
).
12.
We have reported the orthorhombic unit cell of a cadmium behenate monolayer at 293 K, identified by PM-IRRAS.
Y. Z.
Ren
,
M.
Hossain
,
K.
Iimura
, and
T.
Kato
,
Chem. Phys. Lett.
325
,
503
(
2000
).
13.
A.
Gericke
and
H.
Hühnerfuss
,
Thin Solid Films
245
,
74
(
1994
).
This content is only available via PDF.
You do not currently have access to this content.