DIACETYLENE AND POLYDIACETYLENE DERIVATIVES OF 2-METHYL-4-NITROANILINE OR 2ND-HARMONIC GENERATION

A novel diacetylene derivative of 2-methyl-4-nitroaniline (MNA), a well-known material for second-harmonic generation (SHG), is synthesized. This monomer (diacetylene methylnitroaniline, DAMNA) is characterized by means of the Kurtz technique at 1064 nm and is found to have an SHG powder efficiency 62.5 % that of MNA itself. Thin crystalline films of DAMNA are grown onto quartz, Teflon, and Kapton substrates by means of vapor deposition in vacuum. These films are then polymerized in the solid state by exposure to long-wavelength UV radiation to give crystalline polydiacetylene thin films (PDAMNA). The films are next characterized for SHG, using an unpolymerized DAMNA film as a reference. Interestingly, films grown onto Teflon exhibit greater orientation and significantly greater SHG than those grown onto quartz and Kapton. This result is promising in that it demonstrates the potential of PDAMNA as both a crystalline and polymeric material for SHG applications, in which highly oriented thin films are desired. Computational modeling (using AM1) is also carried out on DAMNA and is compared to the experimental results.