Solid state polymerization of diacetylenes with pi-conjugating substituents for third-order nonlinear optical properties

Topochemical reactivity of some conjugated diacetylenes with pi-conjugating substituents upon exposure to gamma-radiation, UV-visible radiation and up on thermal annealing is described. Few of the diacetylenes undergo solid st ate polymerization to provide corresponding polydiacetylenes. The reflectan ce spectra of the resultant polydiacetylenes showed significant backbone-si de-group electron coupling. The third-order nonlinear susceptibility of two of the polydiacetylenes obtained were evaluated using Maker's fringe techn ique. The third-order nonlinear susceptibility, chi((3)) value obtained for the two samples were in the order of 10(-11) esu for the fully polymerized polydiacetylene films. These values are comparable to the values reported previously for PDAs with aromatic sidegroups.