Langmuir–Blodgett films of non-linear optical dyes with chiral centers in matrices of amylose esters

The structure and second harmonic generation of a dye belonging to a new class of NLO dyes have been investigated. The pure dye did not form a stable monolayer at the air-water interface. The dye was mixed with amylose acetate which resulted in a stable monolayer when the amount of dye did not exceed the 50 base mol%. The mixture of the dye and amylose acetate consisted of domains. The domains of the dye are crystalline and can be considered as H-aggregates. The mixed monolayer can be transferred on to solid substrates. FT-IR and UV-vis spectroscopy were used to determine the molecular orientation in the multilayers. Second harmonic generation signals were detected in the reflection mode. The multilayers as deposited showed SHG signals when the primary beam is p-polarized resulting in an s-polarized SHG signal. When the monolayer was heated above the melt temperature of the dye and cooled down again, the signal was strongly enhanced and a p-polarized fundamental beam resulted in s and p polarized SHG