SYNTHESIS AND 2ND-HARMONIC GENERATION STUDIES OF LANGMUIR-BLODGETT MONOLAYERS OF 4-(N-DOCOSYL-N-METHYLAMINO)-BETA-NITROSTYRENE

The nonlinear optical chromophore 4-amino-beta-nitrostyrene was deriva tized to yield a Langmuir-Blodgett (LB) film forming amphiphillic mole cule 4-(N-docosyl-N-methylamino)-beta-nitrostyrene (DMANST). The Z-typ e LB monolayers of DMANST was transferred onto hydrophilic silica subs trates and characterized by optical second harmonic generation (SHG) m easurements. The SHG results reveal that the LB film of pure DMANST de posited onto a silica substrate consists of molecular inhomogeneities on a scale larger than a wavelength. The presence of a strong SHG sign al for both the p- and s-polarized fundamental beams, at the normal in cidence, suggests the lack of in-plane symmetry in the monolayer of pu re DMANST on the silica surface. The LB film of DMANST mixed with doco sanoic acid shows a SHG behavior that is pertaining to the C-infinity upsilon symmetry. This indicates that the symmetry in the film plane i s restored in monolayers of DMANST mixed with docosanoic acid. The chr omophore tilt angle of DMANST mixed with docosanoic acid is calculated to be 42 degrees with respect to the film normal.