Electrical and nonlinear optical properties of polydiacetylene Langmuir-Blodgett film

The electrical and optical properties of polydiacetylene (10, 12-pentacosa-diynoic acid) films deposited by using the Langmuir-Blodgett technique and then polymerized were studied. A change in electrical conduction with polymerization suggested the contribution of the conjugated system as hopping centers. Third harmonic generation was observed, and a change in third order susceptibility χ⁽³⁾ is discussed in connection with structural change associated with polymerization, annealing, and so on. The third-harmonic generation is mainly due to the blue form and the structure responsible for the optical absorption around 700 nm did not contribute much to the third-harmonic generation. Steric constraints due to this structure may suppress the polymerization and extension of a conjugate system. Deposition of multilayers seems to increase structural defects and hinder the progress of polymerization. The conjugated system due to polymerization may act as additional hopping centers