Second harmonic generation in Langmuir-Blodgett multilayers of stilbazolium chloride polyethers

Abstract Multilayer Langmuir-Blodgett (LB) films of a new dye-substitutted polymer, dialkylaminostilbazolium poly(epichlorohydrin) are studied with second harmonic generation (SHG) and UV-visible absorption techniques. The synthesis resulted in a nearly quantitatively substituted stilbazolium chloride polyether (stilbazolium-PECH) with a “comb” structure. The dye can be compressed up to 47 mNm −1 to form a stable monolayer that is easily transferred to glass supports, and can be interleaved with behenic acid to form non-centrosymmetric structures. The second-order susceptibility of the stilbazolium-PECH is comparable in magnitude with that of a well-known hemicyanine dye and is thus potentially a useful material for fabricating films for non-linear optics. Multilayers of stilbazolium-PECH interleaved with behenic acid display enhancement of the SHG efficiency, although not quadratic. Unlike the hemicyanine dye, stilbazolium-PECH does not appear to form H aggregates in LB films. We have also investigated the effect of varying the number of behenic acid spacer layers between each pair of dye layers on SHG intensity and absorbance.