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Polydiacetylenes are a very promising class of polymers for both photonic and electronic applications because of their highly conjugated structures. For these applications, high-quality thin polydiacetylene films are required. We have discovered a novel technique for obtaining such films of a polydiacetylene derivative of 2-methyl-4-nitroaniline using photodeposition from monomer solutions onto UV transparent substrates. This heretofore unreported process yields amorphous polydiacetylene films with thicknesses on the order of I micron that have optical quality superior to that of films grown by standard crystal growth techniques. Furthermore, these films exhibit good third-order nonlinear optical susceptibilities; degenerate four-wave mixing experiments give x(3) values on the order of 10(exp -8) - 10(exp -7) esu. We have conducted masking experiments which demonstrate that photodeposition occurs only where the substrate is directly irradiated, clearly indicating that the reaction occurs at the surface. Additionally, we have also been able to carry out photodeposition using lasers to form thin polymer circuits. In this work, we discuss the photodeposition of polydiacetylene thin films from solution, perform chemical characterization of these films, investigate the role of the substrate, speculate on the mechanism of the reaction, and make a preliminary determination of the third-order optical nonlinearity of the films. This simple, straightforward technique may ultimately make feasible the production of polydiacetylene thin films for technological applications.

A novel diacetylene derivative of 2-Methyl-4-NitroAniline (MNA), a well-known material for Second-Harmonic Generation (SHG), is synthesized. This monomer DiAcetylene MethylNitroAniline, (DAMNA) is characterized by means of the Kurtz technique at 1064 nm and is found to have an SHG powder efficiency 62.5 % that of MNA itself. Thin crystalline films of DAMNA are grown onto quartz, Teflon, and Kapton substrates by means of vapor deposition in vacuum. These films are then polymerized in the solid state by exposure to long-wavelength UV radiation to give crystalline polydiacetylene thin films (PDAMNA). The films are next characterized for SHG, using an unpolymerized DAMNA film as a reference. Interestingly, films grown onto Teflon exhibit greater orientation and significantly greater SHG than those grown onto quartz and Kapton. This result is promising in that it demonstrates the potential of PDAMNA as both a crystalline and polymeric material for SHG applications, in which highly oriented thin films are desired. Computational modeling (usingAM1) is also carried out on DAMNA and is compared to the experimental results.

In the present work two diacetylene derivatives of pyrrole which are predicted by semiempirical AM1 calculations to have very different properties, are synthesized; the polymerizability of these diacetylenes in the solid state is determined, and the results are compared to the computer predictions. Diacetylene 1 is novel in that the monomer is a liquid at room temperature; this may allow for the possibility of polymerization in the liquid state as well as the solid state. Thin poly(diacetylene) films are obtained from compound 1 by growing films of the monomer using vapor deposition and polymerizing with UV light; these films are then characterized. Interestingly, while the poly(diacetylene) from 1 does not possess good nonlinear optical properties, the monomer exhibits very good third-order effects (phase conjugation) in solution. Dilute acetone solutions of the monomer 1 give intensity-dependent refractive indices on the order of 10 exp -6 esu; these are 10 exp 6 times better than for CS2.

A novel diacetylene derivative of 2-Methyl-4-NitroAniline (MNA), a well-known material for Second-Harmonic Generation (SHG), is synthesized. This monomer DiAcetylene MethylNitroAniline, (DAMNA) is characterized by means of the Kurtz technique at 1064 nm and is found to have an SHG powder efficiency 62.5 % that of MNA itself. Thin crystalline films of DAMNA are grown onto quartz, Teflon, and Kapton substrates by means of vapor deposition in vacuum. These films are then polymerized in the solid state by exposure to long-wavelength UV radiation to give crystalline polydiacetylene thin films (PDAMNA). The films are next characterized for SHG, using an unpolymerized DAMNA film as a reference. Interestingly, films grown onto Teflon exhibit greater orientation and significantly greater SHG than those grown onto quartz and Kapton. This result is promising in that it demonstrates the potential of PDAMNA as both a crystalline and polymeric material for SHG applications, in which highly oriented thin films are desired. Computational modeling (usingAM1) is also carried out on DAMNA and is compared to the experimental results.

In the present work two diacetylene derivatives of pyrrole which are predicted by semiempirical AM1 calculations to have very different properties, are synthesized; the polymerizability of these diacetylenes in the solid state is determined, and the results are compared to the computer predictions. Diacetylene 1 is novel in that the monomer is a liquid at room temperature; this may allow for the possibility of polymerization in the liquid state as well as the solid state. Thin poly(diacetylene) films are obtained from compound 1 by growing films of the monomer using vapor deposition and polymerizing with UV light; these films are then characterized. Interestingly, while the poly(diacetylene) from 1 does not possess good nonlinear optical properties, the monomer exhibits very good third-order effects (phase conjugation) in solution. Dilute acetone solutions of the monomer 1 give intensity-dependent refractive indices on the order of 10 exp -6 esu; these are 10 exp 6 times better than for CS2.

Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

A modified Bridgman-Stockbarger crystal growth system has been designed and fabricated by relatively low-temperature (up to 250 degrees C) nonlinear optical organic materials. The novel feature is that the crystal melt surface can be viewed from any direction and the temperature gradient between the hot and cold zone can be adjusted at any time. The ampoule can be lowered at a rate as slow as 0.1 mm h-1. The temperature can be maintained to a precision of +or-0.01 degrees C. High-quality single crystals of benzil have been successfully grown using this system.

SHG and THG signals were observed by reflection from the Langmuir-Blodgett monolayer of a Sec-butyl derivative of 4-methyl-6-nitro-2-quinolinamine. A floating monolayer was obtained by spreading chloroform solutions on ultrapure water and the subsequent evaporation of chloroform. The monolayer was deposited on a suitably treated glass slide at a compression rate of 100 cm2/min and a pressure of 12 mN/m. The 1064 nm fundamental wave emanating from a Nd:YAG laser was incident at a 45° angle on the monolayer surface, with the length of the substrate in a vertical plane. Signals were observed at 532 nm (SHG) and 355 nm (THG). When the sample was rotated by 90° in a vertical plane, the SHG signal vanished and the THG signal became much smaller. SHG and THG signals were also observed by reflection from a L-B film of 20 monolayers. When this sample was rotated by 90°, there was no significant difference in the intensity of the signals. The values of χ2 and χ3 were determined to be 10−6 and 5 × 10−4 esu, respectively, by using standard relations.

A real time observation of the growth of agglomerates of pyramidal crystallites of mercuric iodide on a porous glass surface using tapping mode atomic force microscopy is reported. Crystallites are observed to grow from the pores (5.0 nm diameter) onto the surface of the porous glass impregnated with mercuric iodide. Immediately after fracturing the impregnated porous glasses, topographical images reveal a surface with a root mean square roughness of 75–130 nm over a 5 μm×5 μm area, which is typical for surfaces of fractured porous glass. After 3 h, 60–90 nm pyramidal structures with a high aspect ratio (pyramid base to height) begin to appear on the surface. Some of the pyramidal structures agglometrate and form structures much larger and higher than the surrounding ones. The bottom of some of these agglomerated pyramids form equilateral triangles with dimensions of 300–500 nm, exhibiting a preferred orientation on the surface. 6 h after fracturing, micrometer‐size crystallites are observed. Most of the pyramidal structures are no longer observed and mostly needlelike features are covering the surface. Step heights consistent with multiples of the c axis of α‐mercuric ioide are observed on the micrometer‐sized crystallites. Some pyramidal structures are observed between the large crystallites, with sizes comparable to the early stage pyramidal structures. Raman and electronic spectra are also reported for mercuric iodide confined in porous glasses. The Raman spectra have peaks located at 39 and 141 cm−1, indicating that the confined mercuric iodide is stabilized in the yellow, orthorhombic (β phase) at room temperature. Confinement of mercuric iodide in pores with radii smaller than 3.75 nm results in the appearance of a new band at 145 cm−1 in the Raman spectra, suggesting the presence of a new or modified β phase of mercuric iodide. Further evidence supporting the presence of a new phase of mercuric iodide is found in the electronic spectra where an energy gap of 2.7 eV is observed, and lies between the energy gaps of the red, tetragonal, α phase (2.2 eV) and the yellow, orthorhombic β phase (3.1 eV) of mercuric iodide. The atomic force microscopy measurements provide a unique method for real time monitoring of the crystal growth and morphology changes of nanocrystalline mercuric iodide, while the spectroscopy provides insight to the phonon structure and energy gaps of the confined material.

Surface-enhanced Raman spectroscopy has been used to study the molecular interactions of malononitrile with copper electrode surfaces. The doubly degenerate CN stretching frequency at 2263/cm is removed when malononitrile adsorbs on copper. Two nu(CN) bands are observed at 2096 and 2204/cm at -0.6 V(SCE). The result shows that only one CN group is pi-coordinated with Cu, which contributes to the observed large shift (-167/cm) in nu(CN). The other CN group is not coordinated to the metal surface.

Etudes de l'adsorption d'isomeres cis- et trans- du succinonitrile sur le cuivre. Mise en evidence d'une chimisorption

Use of a two-wavelength holographic technique results in a simultaneous determination of temperature and composition profiles during directional solidification in a system with a miscibility gap. The relationships among fluid flow, phase separation, and mass transport during the solidification of the monotectic alloy are discussed. The primary sources of fluid motion in this system are buoyancy and thermocapillary forces. These forces act together when phase separation results in the formation of droplets (this occurs at the solid-liquid interface and in the bulk melt). In the absence of phase separation, buoyancy results from density gradients related to temperature and compositional gradients in the single-phase bulk melt. The effects of buoyancy are especially evident in association with water- or ethanol-rich volumes created at the solid-liquid growth interface.

The infrared spectrum of solid chlorotrifluoromethane (CF3Cl) has been studied and compared with that of matrix-isolated CF3Cl. Crystal field splitting patterns of the strongest modes nu1 and nu4 suggest the crystal structure to be orthorhombic with a C(2v) factor group and two molecules per unit cell located on C(s) sites.

Surfaced-enhanced Raman spectroscopy has been used to study rotational isomers of succinonitrile and N-methyl-thioacetamide on Cu and Ag surfaces. Both the gauche and trans conformers of succinonitrile are found to chemisorb on the metal surface. The doubly degenerate nu(C-triple bond-N) in the free molecules is removed when succinonitrile adsorbs on copper, which indicates that the two (C-triple bond-N) groups are no longer chemically equivalent. Both conformers are found to coordinate to the copper surface through the pi system of one of the two (C-triple bond-N) groups. In the case of N-methyl-thioacetamide, the population of the cis isomer is greatly increased on Cu and Ag surfaces. This is probably due to surface-induced cis-trans isomerization, in which the predominant trans isomer is converted to the cis isomer.