Second harmonic generation from Langmuir–Blodgett multilayers assembled from ‘active’ non-polymeric amphiphiles and ‘inactive’ polymeric amphiphiles

Abstract

Alternating Langmuir–Blodgett (LB) multilayers have been prepared from a non-polymeric hemicyanine and a poly(4-vinylpyridine) 66% quaternised with docosyl bromide, and from a non-polymeric azobenzene and the same pyridinium polymer. With both types of multilayer the intensity of the SHG signal increased as the square of the number of layers up to a thickness ofca. 60 bilayers. The slopes of the plots correspond to second order susceptibilities of 17.5 and 9 pm V^–1 respectively. Although these properties and the stabilities of the films over time compare favourably with many other LB films described in the literature, these films prepared from ‘active’ non-polymeric amphiphiles and a ssive’ polymeric amphiphile are not as satisfactory as the closely related all-polymeric films described previously.