Third harmonic generation from a monolayer film of a polydiacetylene, poly-4-BCMU

Third harmonic generation has been observed for the first time from a monolayer film on water subphase. This study, conducted for a polydiacetylene, poly-4-BCMU, reveals a conformational transition in the monolayer film whereby the effective π-electron conjugation is reduced. From the study, the orientation of the polymer at the water subphase and the value of the second hyperpolarizability γ along the polymer chain is also determined. The corresponding bulk susceptibility χ(3) is found to be in agreement with those reported by earlier studies.