The objective of this investigation was to develop stable nonlinear optical (NLO) materials which possess both second and third order NLO properties. These materials were envisioned as having a polydiacetylene (PDA) backbone with a second order active NLO chromophoric substituent. The choice of a PDA backbone in this investigation was twofold. In terms of third order NLO properties, the extensive pi-conjugation of the PDA backbone leads to large ultrafast third order effects. In terms of second order NLO properties, the high thermal stability and rigidity of the PDA matrix in a perfect polymeric single crystal is expected to prevent the randomization of the NLO chromophores in the noncentrosymmetric environment. This paper focuses on the synthesis, FT-Raman structural analysis, and NLO properties of the unsymmetrical diacetylene monomers, ((9-Butoxy carbonyl) methyl urethanyl)-1-(4-urethanyl-4’-nitrobiphenyl)-nona-2,4-diyne, and ((9-Butoxy carbonyl)methyl urethanyl)-1-(4-urethanyl-4’-nitroazobenzene)-nona-2,4-diyne.