In order to improve third-order nonlinear optical properties of polydiacetylenes (PDAs), we have been investigating modification of PDA structures. From the point of view of PDA molecular design, three series of monomers for ladder-type PDAs were prepared. Oligoyne monomers having more than five conjugated acetylenes gave polymers which showed broad bands at longer wavelength than their excitonic absorption bands. This implies production of π-conjugated ladder polymer having two PDA backbones linked by acetylenic groups in each repeating unit. From monomers with two butadiynes connected by an alkylene group, ladder-type PDAs were obtained when the carbon number of the alkylene group is more than four. However, monomers with two butadiynes connected by an arylene group gave only single-chain PDAs. From the point of view of PDA morphological engineering, PDA microcrystal water dispersions were applied to evaluate nonlinear optical susceptibilities (χ(3)) by z-scan method together with PDA thin films. High-density microcrystal deposited film prepared by layer-by-layer deposition technique showed more than three orders of magnitude enhanced χ(3) than the dispersion state. Polycrystalline thin films compose of ladder-type PDAs were also found to have large χ(3). The quite large nonlinear refractive index of -41 cm2/GW was attained just near excitonic absorption maximum for one of the polymers.
|Number of pages
|Proceedings of SPIE - The International Society for Optical Engineering
|Published - 1999
|Proceedings of the 1999 Organic Nonlinear Optical Materials - Denver, CO, USA
Duration: 1999 Jul 19 → 1999 Jul 22