Gero Dr. Decher

Optical second harmonic generation in Langmuir-Blodgett films of novel donor-acceptor substituted pyridine and benzene derivatives

Abstract A series of sixteen novel amphiphiles has been prepared containing substituted nitropyridine and nitroaniline units as polar headgroups. The film forming properties of the amphiphiles at the air-water interface are described. Langmuir-Blodgett-films are characterized by spectroscopic methods and by xray diffraction. A comprehensive study of measurements of optical second harmonic generation in the films is reported. Among the compounds investigated 2-alkylamino-5-nitropyridines with C18 to C26 alkyl chains are best suited for second harmonic generation. Our studies show for the first time that LB-films of a single material not forming an asymmetric head-to-tail (X- or Z-type) structure can produce significant second harmonic signals. Structure models are presented, which explain the observation of nonlinear optical properties in terms of formation of either a non-centrosymmetric herringbonetype structure or an intercalated structure of the molecules with preferential orientation of the polar head...

Optical second-harmonic generation in Langmuir–Blodgett films of 2-docosylamino-5-nitropyridine

The first preparation of non-centrosymmetric Langmuir–Blodgett multilayer films of 2-docosylamino-5-nitropyridine, and the first measurements of optical second-harmonic generation from these films are reported.

Thermochromic Langmuir-Blodgett films of a novel amphiphilic azo dye with homogeneous chromophore orientation☆

Abstract Langmuir-Blodgett (LB) multilayers have been prepared from a novel amphiphilic azobenzene derivative. These films were transparent and showed homogeneous polarization of visible light over the whole film area. They exhibit reversible thermochromism with a red shift of 60 nm over a temperature range of less than 10°C. This thermochromism can be explained by a “J-like” aggregation of the azo chromophores that is slightly effected by temperature.