la703022s_si_001.pdf (615.72 kB)
Synthesis of Novel Amphiphilic Azobenzenes and X-ray Scattering Studies of Their Langmuir Monolayers
journal contribution
posted on 2020-04-02, 17:06 authored by Thomas J. Sørensen, Kristan Kjaer, Dag W. Breiby, Bo W. LaursenWe report a simple synthetic route to novel symmetrical alkylated and acylated amphiphilic 4,4‘-diaminoazobenzene
dyes, with their optical axis perpendicular to the amphiphilic direction of the molecule. Three different substitution
patterns are reported, two of which are highly amphiphilic. At the air−water interface, the amphiphilic azobenzenes
form noncrystalline but stable Langmuir films that display an unusual reversible monolayer collapse close to 35 mN/m.
The structures and phase transitions were studied by X-ray reflectivity (XR) and grazing-incidence X-ray diffraction,
both utilizing synchrotron radiation. Compression beyond the collapse point does not change the XR data, showing
that the film is unchanged at the molecular level, even at areas less than half of that of the collapse. This leads to
the conclusion that few macroscopic collapse sites are responsible for reversibly removing large amounts of material
from the interface.
History
Usage metrics
Categories
Keywords
Langmuir filmsNovel Amphiphilic AzobenzenesX-ray Scattering StudiesinterfaceLangmuir Monolayersgrazing-incidence X-ray diffractionsubstitution patternsX-ray reflectivityXR dataamphiphilic directionphase transitionsmonolayer collapseamphiphilic azobenzenes form noncrystallinecollapse pointsynchrotron radiationmacroscopic collapse sites