Spread Lipid Films on Liquid Surfaces (Langmuir–Blodgett Films) - Surface and Colloid Chemistry: Principles and Applications - page 95

In a recent study, LB films of iron stearate was deposited from aqueous solution
into a substrate only on the down journey. On the up journey, the substrate was with-
drawn through a clean area. The condition of the aqueous surface was the same as
that for the preparation of the Y-type layer. The Fe55 tracer techniques was used for
the examination of the direction of molecules. The unidirectional surface conduc-
tance of monolayers of stearic acid deposited on a glass support was investigated.
The influence of two-dimensional pressure on the tangential permeability of the
layers for various cations was examined. The current in the channel formed by the
monomolecular film and the substrate is carried by hydrated cations. The permeabil-
ity of the channel to various cations diminishes in the order
Ca ++ , Zn ++ , Ba ++ , Mg ++ , H + , Cs + , K + , Na + , Li +
The contact angles and adhesional energy changes during the transfer of monolayers
from the air-water interface to solid (hydrophobic glass) supports have been ana-
lyzed (Gaines, 1966; Birdi, 1989).
4.6.3.1 molecular orientation in mixed-dye
monolayers on Polymer Surfaces
In the past few years, there has been an increasing interest in the use of surface-active
dyes to study the properties of biological and artificial membranes and to construct
monomolecular systems by self-organization. When these dyes are incorporated in
lamellar systems, it is found that the paraffin chains stand perpendicularly on the
plane of the layer, while the chromophores lie flat near the hydrophilic interface. In
order to develop new molecules as functional components of monolayer assemblies,
a series of nine surface-active azo and stilbine compounds were synthesized. Their
monolayer properties at the air-water interface were investigated by Π and spec-
troscopic techniques. The adsorption on stretched polyvinyl alcohol (PVA) films of
mixed monolayers of n -octadecyltrichlorosilane [OTS-C 18 H 37 SiC l3 ] plus long-chain-
substituted cyanine dyes were investigated. These systems were selected because of
i. The solid support possesses a simple organization with uniaxial symmetry,
which allows a straightforward correlation with the molecular orientation
induced in the monolayer.
ii. The solid substrate (PVA) is transparent, and the adsorbed molecules con-
tain elongated dye chromophores, so that the molecular orientation within
the monolayer can be readily determined by means of polarized absorption
spectroscopy (linear dichroism [LD]).
iii. It is easy to produce the support in large quantities, and adsorption is easy
for oleophobic octadecyltricholorosilane (OTS) monolayers.
Furthermore, PVA is not soluble, and does not swell in the organic solvents used in
monolayer studies. The orientational effects were estimated from LD.
An application of neutron activation analysis for the determination of inor-
ganic ions in LB multilayers was reported. A special technique for the removal of