STRUCTURE AND NONLINEAR-OPTICAL PROPERTIES OF DIACETYLENE THIN-FILMS VAPOR-DEPOSITED ON HIGHLY ORIENTED POLYTETRAFLUOROETHYLENE THIN-FILMS

Five diacetylene compounds were vapor-deposited on a highly oriented thin film of polytetrafluoroethylene (PTFE) prepared by mechanical deposition. 1,6-Di-(N-carbazolyl)-2,4-hexadiyne (DCHD) film was composed of needlelike crystallites along the chain axis of the PTFE macromolecules. The DCHD crystal was oriented with respect to the PTFE crystal substrate in the relation of (100)*[010](DCHD)//(100)[001](PTFE). Other diacetylenes also formed uniaxially oriented thin layers. Upon photoirradiation, diacetylene films changed to polymer films having extremely high crystallinity and considerable in-plane dichroism. The third-order susceptibility chi((3)) of the uniaxially oriented polydiacetylene films were several times larger than those of the randomly oriented films. Crystal growth observed by electron microscopy on local and microscopic scales was confirmed by THG measurement on a macroscopic scale.