This report describes change in the characteristics of vapor deposition films for bis-styrylbenzene derivatives (BSDs) after thermal treatment. The compounds employed in the present study were trifluoromethyl-group substituted BSDs: E,E-1,4- bis(2-trifluoromethylstyryl)benzene, (2-CF3), E,E-1,4-bis(3-trifluoromethylstyryl)benzene, (3-CF3), and E,E-1,4-bis(4- trifluoromethylstyryl)benzene, (4-CF3). The fluorescence spectra and the morphologies of the evaporated films of 2-CF3 changed depending on the thermal treatment temperature. As-evaporated film was aggregation of micron size crystalline domains. After thermal treatment at 100°C for 30 min, these changed into a long rectangular parallelepiped crystals suggesting that structural order has increased. Meanwhile, the optical properties and crystalline structures of the evaporated 3-CF3 films did not change even after thermal treatment at 110°C for 30 min. In the case of 4-CF3, the fluorescence spectrum of the evaporated film shifted to the shorter wavelength side after the thermal treatment. From the results of X-ray diffraction, the evaporated film showing crystallinity decreased in the structure orderliness by thermal treatment at 170°C for 30 min.
We examined the thermal crystallization of deposited films made of 2,5-bis(4-biphenylyl)thiophene (BP1T) and
1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), which are thiophene/phenylene co-oligomers (TPCOs). The deposited films
of both BP1T and AC5 showed a microcrystalline phase, and initial microcrystals got larger 10 - 100 times with thermal
treatment. Furthermore, we measured the optical properties of microcrystals of BP1T and AC5. At the energy density
below the spontaneous amplified emission threshold, it was found that there was a big fluorescent difference between
femtosecond laser irradiation and continuous lamp irradiation.
Femtosecond laser micromachining by filamentation is used to fabricate volumetric optical elements in polymer
materials. In this paper, we review the induction of filamentary refractive index modifications and its application to the
fabrication of diffractive optical elements in various polymer materials.
A polymer optical amplifier with a large core was prepared by a vacuum process. The laser dye as an active compound
was dispersed into the large core by a vacuum process, which can disperse organic dyes in polymers at high density
preventing dye aggregation. Amplification of signal beam at 650 nm was observed by lateral pumping with a pulsed
laser at 488 nm. Gain of the amplifier increased with pump energy and reached 3.74 dB/cm by pumping of 80 μJ.
We have explored a new doping method, which could disperse densely dyes into polymers, and have developed the present method into preparation of polymeric devices, such as storage media, luminescent media, switching devices, and waveguides. Preparation of the waveguide was based on dispersal of organofluorine (OF) compounds with a low refractive index in a polymer plate functioning as a cladding layer. The layer dispersed with the OF compound showed uniform concentration of the OF compound independent of the dispersal depth indicating that dispersion behavior was not governed by Fick's law. This means that the waveguide in the present study is step index. As a further development, we expanded the present method to preparation of a polymeric optical amplifier (POA) because reduction in intensity of a signal beam is clear due to driving of splitters in a short distance network using polymer optical fibers with large cores. A laser dye was dispersed densely within the core by the present method, followed by the dispersal of the OF compound to form the cladding layer resulting in the fabrication of POA with the large core. Amplification of the signal beam at 650 nm was confirmed in the waveguide upon irradiation of a pulsed laser.
We have developed a dye-doping process into a polymer, termed the "vapor transportation method." This method enables us to prepare a favorable doped layer in the polymer, possessing both a uniform dye concentration and a smooth surface. As one of developments of the vapor transportation method, we expanded to preparation of the optical waveguide. In preparation of the waveguide, low-molecular weight compound (phenyl benzoate; PB) showing the higher refractive index was dispersed in a matrix polymer (poly (methyl methacrylate), PMMA) through a mask by the developed method. After dispersion, the mask was removed, and another PMMA plate was put on doped PMMA by
vacuum press. A double-layered structure of the doped and non-doped regions was observed in the cross section, further, two regions described were transparent. It was confirmed that a beam incident on the edge of the doped region of the prepared sample emerged from the other edge, indicating that the doped regions acted as a core. The core radius (depth of the doped region) increased with treatment time and treatment temperature. Furthermore, refractive index of the core was controlled by treatment temperature. The fabricated waveguide showed the propagation loss of 0.47 dB/cm at 650 nm.
We have developed a simple process method, "vapor transportation method", for surface treatments and functionalization of polymeric materials. The method is addition of versatile functions to the solid polymeric materials with treatment of vapors under vacuum. Polymeric waveguides can be easily fabricated using the method. Exposing rods of transparent polymer, poly(methylmethacrylate) (PMMA), by vapor of organofluorine compounds, fluorinated esters, with lower refractive indices made the organofluorines dispersed into the PMMA from the surface. The refractive index of the organofluorine-doped PMMA surface was decreased and a cladding layer was formed. The core was the central part of the rod, which was the PMMA without dispersion of organofluorines. The properties of the waveguides made by the method were characterized. The refractive index and thickness of the cladding layer can be controlled by conditions of vapor transportation, such as treatment time and temperature.
The "vapor transportation method" with vacuum technique, developed previsouly in our laboratory, was used to form polymer thin layers with densely dispersed photochromic dyes on polystyrene (PS), poly(methyl methacrylate) (PMMA), and polymcarbonate (PC) substrates. The organic photochrmoic dye cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethane (CMTE) was used, and the rate of formation of the CMTE-conatining layer was as follows: PS > PC > PMMA. These observations are important for application of the present method to the formation of organic memory media for optical recording etc. These results also indicate that the formation rate is dependent on not only the chemical composition and the structure of the polymer substrate, but also on the treatment temperature. Optical density measurements of the CMTE-dispersed thin polymer films showed maximum values near the glass transition temperature (g) with increases in temperature of film formation. The Tg values of CMTE-dispersed polymers decreased rapidly after CMTE-dispersal into the polymer matrices, indicating that Tg values of the polymers are important parameters for investigation of the mechanism of formation of CMTE-dispersed layers on polymer substrates using the present method.
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