An azobenzene functionalised DMA-copolymer was prepared and monolayers at the air-water interface characterised by pi-A isotherms. Z-type deposition was observed in LB film formation. The LB films were characterised by dichroic UV spectroscopy and second harmonic generation. The hyperpolarisability and the tilt angle of the chromophore side groups were determined. The strong decrease in hyperpolarisability, compared to solution values, was explained by orientation and interaction effects.