NOVEL UNSYMMETRICAL POLYDIACETYLENES AS MATERIALS FOR 2ND-ORDER AND 3RD-ORDER NONLINEAR OPTICS

The objective of this investigation was to develop stable nonlinear op tical (NLO) materials which possess both second- and third-order NLO p roperties. These materials were envisioned as having a polydiacetylene (PDA) backbone with a second-order active NLO chromophoric substituen t. The choice of a PDA backbone in this investigation was 2-fold. In t erms of third-order NLO properties, the extensive pi-conjugation of th e PDA backbone leads to large ultrafast third-order effects. In terms of second-order NLO properties, the high thermal stability and rigidit y of the PDA matrix in a ''perfect'' polymeric single crystal are expe cted to prevent the randomization of the NLO chromophores in the nonce ntrosymmetric environment. This paper focuses on the synthesis, struct ural analysis, and NLO properties of the unsymmetrical diacetylene mon omers 9-((butoxycarbonyl)methylurethanyl)-1-(-4- urethanyl-4'-nitrobip henyl)nona-2,4-diyne and -1-(4-urethanyl-4'-nitroazobenzene)nona-2,4-d iyne.