NLO properties of polymeric Langmuir-Blodgett films of sulfonamide-substituted azobenzenes

Abstract

The behaviour at the air/water interface of polymeric materials containing sulfonamide-substituted azobenzene chromophores has been investigated using surface pressure versus area measurements. Langmuir-Blodgett (LB) films of the polymers have been built up and then studied using X-ray diffraction. The polymer which gave the best organised LB film has been used to prepare an alternating Y-type multilayer structure with a polymer inactive in non-linear optics. The obtained film has a well-ordered polymeric LB structure giving three Bragg peaks. A series of films with various numbers of bilayers within the range from 2 to 80 has been prepared and the second harmonic generating properties of the films investigated. The measured intensity of the SH signal produced from incident light of wavelength 1064 nm was proportional to the square of the number of bilayers. The alternating LB films exhibited a non-linear susceptibility of up to 24 pm V ^–1 corresponding to a chromophore non-linear vector susceptibility of magnitude χ _zzz ⁽²⁾ =170 pm V ^–1 .