2 research outputs found
Morphology and Composition of Structured, Phase-Separated Behenic Acid–Perfluorotetradecanoic Acid Monolayer Films
The phase separation
of immiscible surfactants in mixed monolayer
films provides an approach to physically manipulate important properties
of thin films, including surface morphology, microscale composition,
and mechanical properties. In this work, we predict, based upon existing
miscibility studies and their thermodynamic underpinnings described
in the literature, the miscibility and film morphology of mixed monolayers
comprised of behenic acid (C<sub>21</sub>H<sub>43</sub>COOH) and perfluorotetradecanoic
acid (C<sub>13</sub>F<sub>27</sub>COOH) in various molar ratios. Predictions
are tested using a combination of experimental surface characterization
methods for probing miscibility and film morphology at the solid/air
and air/water interfaces. Film components were immiscible and phase-separated
into chemically well-defined domains under a variety of experimental
conditions, with monolayer morphology consistent with initial predictions.
The extensibility of these basic predictions to other systems is discussed
in the context of using these works for different perfluorinated surfactant
molecules
Spectroscopic and Structural Studies of a Surface Active Porphyrin in Solution and in Langmuir–Blodgett Films
Controlling aggregation of the dual
sensitizer–emitter (S-E)
zinc tetraphenylporphyrin (ZnTPP) is an important consideration in
solid state noncoherent photon upconversion (NCPU) applications. The
Langmuir–Blodgett (LB) technique is a facile means of preparing
ordered assemblies in thin films to study distance-dependent energy
transfer processes in S-E systems and was used in this report to control
the aggregation of a functionalized ZnTPP on solid substrates. This
was achieved by synthetic addition of a short polar tail to one of
the pendant phenyl rings in ZnTPP in order to make it surface active.
The surface active ZnTPP derivative formed rigid films at the air–water
interface and exhibited mean molecular areas consistent with approximately
vertically oriented molecules under appropriate film compression.
A red shift in the UV–vis spectra as well as unquenched fluorescence
emission of the LB films indicated formation of well-ordered aggregates.
However, NCPU, present in the solution phase, was not observed in
the LB films, suggesting that NCPU from ZnTPP as a dual S-E required
not just a controlled aggregation but a specific orientation of the
molecules with respect to each other