New processable, functionalizable polydiacetylenes

A new series of diacetylenes, 9-(arylamino)-5,7-nonadiynyl-N-(alkoxycarbonylmethyl)-urethanes was synthesized based on three design paradigms: (1) the polydiacetylene (PDA) conjugated backbone, (2) one side group as a chromophore, and (3) the remaining side group with components to promote solubility and processability. After exposure to 60 Co γ-radiation, the resulting polydiacetylenes were highly soluble in many common organic solvents. These diacetylene monomers can be functionalized with ease not only before but after polymerization as well. Tricyanovinylation of diacetylene monomers followed by polymerization gave insoluble polymers, possibly due to strong interactions involving tricyanovinyl groups. However, tricyanovinylation after polymerization gave polymers soluble in common organic solvents with 45-55% degree of functionalization. The diazonium coupling reaction could also be carried out at the phenyl ring of the diacetylene monomer both before and after polymerization. In contrast to the intractable product from the direct polymerization of the azodiacetylene, postpolymerization diazonium coupling reaction yielded azobenzene-substituted polydiacetylene with good solubility in polar organic solvents. The degree of functionalization was in the same range as that of tricyanovinylated PDA. The second-order NLO coefficient (d 33 ) of the poled tricyanovinylated PDA (via postpolymerization functionalization) was found to be 33 pm/V at 1.136 μm. The photorefractive response of the tricyanovinylated PDA was demonstrated by two-beam-coupling measurements. The PDA-containing 4-[4-(carboxylic acid)phenylazolaniline chromophores can directly be photomanipulated to form surface relief gratings.