Short-wavelength-absorbing polysilane

Abstract: The present invention relates to a novel polysilane composition and, more specifically, to a polysilane composition that is soluble in organic solvents, that has a number average molecular weight in the range of 2,000 to 1,000,000, and that has a short-wavelength (≦ 285 nm) absorption maximum at room temperature.

Description: The present invention relates to a polysilane composition that is soluble in organic solvents, that has a number average molecular weight in the range of 2,000 to 1,000,000, and that has a short-wavelength (≤ 285 nm) absorption maximum at room temperature. Polysilanes are currently under investigation as conductive materials, photoconductive materials, nonlinear optical materials, and photoresists. However, since these materials generally absorb in the 300 to 400 nm region, the exploitation of their nonlinear optical properties requires polysilanes that absorb at shorter wavelengths. Moreover, utilization as a deep UV patterning material also requires polysilanes that absorb at shorter wavelengths. To date, the soluble high-molecular-weight polysilane with the shortest absorption wavelength is (3,3,3- trifluoropropyl)methylpolysilane - [CF 3 CH 2 CH 2 (CH 3 )Si] n - , as described by Masaie Fujino, et al., Macromolecules, Volume 25, p. 1079, (1992). EP-A-0 189 991 discloses polysilanes carrying optionally halo-substituted organic pendants. In particular it describes homopolymers of cyclopolymethylenesilylene units and copolymers of diorganosilylene units. The present invention takes as its object the introduction of a high-molecular-weight polysilane that absorbs at shorter wavelengths and is also soluble in organic solvents. The present invention comprises a random polysilane composition having a number average molecular weight within a range of 2,000 to 1,000,000 and described by formula where R 1 is described by formula -(CH 2 ) x CF 3 in which x = 2, 3, or 4; each R 2 is independently selected from a group consisting of alkyls comprising one to five carbon atoms; R 3 is selected from a group consisting of -C 5 H 10 - and -C 4 H 8 -; 0.25 ≤ n/m ≤ 100 when R 3 is -C 5 H 10 - , and 0.01 ≤ n/m ≤ 100 when R 3 is -C 4 H 8 -. Values of n/m below 0.25 for when R 3 is - C 5 H 10 - result in poor solubility in ordinary organic solvents, while values of n/m above 100 for when R 3 is -C 5 H 10 - make the occurrence of an absorption maximum at > 285 nm increasingly likely. When n/m does not fall within the interval defined by 0.01 < n/m < 100 for when R 3 is -C 4 H 8 -, the occurrence of an absorption maximum at > 285 nm is again increasingly likely. The number average molecular weight of the polysilane of the present invention must fall in the range of 2,000 to 1,000,000, but the range of 4,000 to 100,000 is generally preferred. The method for synthesizing polysilane according to the present invention is not specifically restricted, but this polysilane is typically synthesized by a Wurtz-type Na reduction. The reaction solvent again is not specifically restricted; however, solvents generally used for this reaction, e.g., toluene or (toluene/diglyme) mixed solvent, can be used in the present case. While the reaction temperature is also not specifically restricted, the general trend is for higher temperatures (for example, ≥ 120°C) to provide better polymer synthesis yields. In some cases the yield can be increased by irradiating the mixture with ultrasound. In addition, suitable additives such as, for example, crown ether, may be added to the reaction solution. Operative reaction techniques include the standard method of adding monomer to the reaction solution as well as reverse addition in which Na is added to the reaction solution. The standard method is specifically exemplified by the addition while heating at reflux of R 1 R 2 SiCl 2 and where R 1 , R 2 , and R 3 are as defined above, to solvent containing the appropriate quantity of Na; reaction for an additional several hours while heating under reflux and stirring vigorously; and finally addition of an alcohol such as isopropyl alcohol after completion of the reaction in order to precipitate the polysilane. In the reverse addition method, R 1 R 2 SiCl 2 and where R 1 , R 2 , and R 3 are defined as above, are both added to the solvent; Na is added while heating under reflux; and the reaction is subsequently run as in the standard method to obtain the compound of the present invention. The present invention is explained below using illustrative examples. Example 1. 70 mL dry toluene and then 1.15 g sodium were introduced into a 200 mL four-neck flask equipped with a condenser, addition funnel, and stirrer. While heating this liquid mixture at reflux with vigorous stirring, a liquid mixture of 3.744 g 3,3,3-trifluoropropylmethyldichlorosilane, 1.02 g cyclopentamethylenedichlorosilane, and 1.5 g dry toluene was carefully added dropwise from the addition funnel. The reaction was run for another 8 hours by vigorously stirring under reflux. After completion of the reaction, isopropyl alcohol was added to the reaction solution in order to precipitate the polysilane. This was then washed with water, filtered, and dried to afford a colorless solid polysilane (8.5% yield). The number average molecular weight of this material was measured by gel permeation chromotography (GPC calibration, polystyrene standard) at 54,000. The positions of the principal peaks in the infrared absorption spectrum of the bulk polymer were as follows (cm -1 ): 2924.4 1444.8 1361.9 1313.6 1263.5 1211.4 1126.5 1066.7 1024.3 893.1 837.2 752.3 677.1 625.0 549.8 515.0 484.2 Example 2. Following the procedure of Example 1, 100 mL dry toluene and then 3.07 g sodium were introduced into a 300 mL four-neck flask equipped with a condenser, addition funnel, and stirrer. While heating this liquid mixture at reflux with vigorous stirring, a liquid mixture of 6.33 g 3,3,3-trifluoropropylmethyldichlorosilane, 5.0 g cyclopentamethylenedichlorosilane, and 3.2 dry toluene was carefully added dropwise from the addition funnel. The reaction was run for another 12 hours by vigorously stirring under reflux. After completion of the reaction, isopropyl alcohol was added to the reaction solution in order to precipitate the polysilane. This was then washed with water, filtered and dried to afford a colorless solid polysilane (8.5% yield). The number average molecular weight of this material was measured by GPC (calibration, polystyrene standard) at 32,000. The positions of the principal peaks in the infrared absorption spectrum of the bulk polymer were as follows (cm -1 ): 2910.9 1446.7 1359.9 1197.9 1130.4 1070.6 983.8 895.1 837.2 750.4 682.9 628.9 549.8 509.3 432.1. Example 3. Following the procedure of Example 1, 60 mL dry toluene and then 1.166 g sodium were introduced into a 200 mL four-neck flask equipped with a condenser, addition funnel, and stirrer. While heating this liquid mixture at reflux with vigorous stirring, a liquid mixture of 1.605 g 3,3,3-trifluoropropylmethyldichlorosilane, 3.0 g cyclopentamethylenedichlorosilane, and 2.0 g dry toluene was carefully added dropwise from the addition funnel. The reaction was run for another 10 hours by vigorously stirring under reflux. After completion of the reaction, isopropyl alcohol was added to the reaction solution in order to precipitate the polysilane. This was then washed with water, filtered, and dried to afford a colorless solid polysilane (9.0% yield). The number average molecular weight of this material was measured by GPC (calibration, polystyrene standard) at 45,000. The positions of the principal peaks in the infrared absorption spectrum of the bulk polymer were as follows (cm -1 ): 2918.6 2851.1 1444.8 1359.9 1311.7 1261.6 1211.4 1124.6 1064.8 981.9 910.5 837.2 754.2 613.4 484.2 424.4. Example 4. Following the procedure of Example 1, 80 mL dry toluene and then 0.95 g sodium were introduced into a 200 mL four-neck flask equipped with a condenser, addition funnel, and stirrer. While heating this liquid mixture at reflux with vigorous stirring, a liquid mixture of 2.11 g 3,3,3-trifluoropropylmethyldichlorosilane, 1.55 g cyclotetramethylenedichlorosilane, and 2.0 g dry toluene was carefully added dropwise from the addition funnel. The reaction was run for another 8 hours by vigorously stirring under reflux. After completion of the reaction, isopropyl alcohol was added to the reaction solution in order to precipitate the polysilane. This was then washed with water, filtered, and dried to afford a colorless solid polysilane (9.5% yield). The number average molecular weight of this material was measured by GPC (calibration, polystyrene standard) at 9,000. The positions of the principal peaks in the infrared absorption spectrum of the bulk polymer were as follows (cm -1 ): 4338.3 3682.4 2928.2 2851.1 2598.4 2542.4 2476.8 2091.0 1446.7 1408.2 1361.9 1311.7 1263.5 1209.5 1124.6 1068.7 1020.4 943.3 895.1 835.3 767.7 652.0 549.8 491.9 The UV absorption maximum for this product in organic solvent occurred at 272 nm. The properties of the compounds synthesized in Examples 1 to 4 are reported in Table 1. Example R 3 Molecular Weight n/m Yield (%) Absorption Maximum (nm) 1 -C 5 H 10 - 54,000 3 8.5 285 2 -C 5 H 10 - 32,000 1 8.5 280 3 -C 5 H 10 - 45,000 0.33 9.0 275 4 -C 4 H 8 - 9,000 1 9.5 282

Claims: A random polysilane composition having a number average molecular weight (measured by GPC calibrated with polystyrene standard) within a range of 2,000 to 1,000,000 and described by formula where R 1 is described by formula -(CH 2 ) x CF 3 in which x = 2, 3, or 4; each R 2 is independently selected from a group consisting of alkyls comprising one to five carbon atoms; R 3 is selected from a group consisting of -C 5 H 10 - and -C 4 H 8 -; 0.25 ≤ n/m ≤ 100 when R 3 is -C 5 H 10 - , and 0.01 ≤ n/m ≤ 100 when R 3 is -C 4 H 8 -. A random polysilane composition according to Claim 1, where the number average molecular weight is within a range of 4,000 to 100,000.

Inventors: TAKAO ITOH, TAKAO, ITOH, TAKAO, ITOH, DOW CORNING JAPAN, LTD., SUMITOMO
Applicants: DOW CORNING KK, DOW CORNING JAPAN, LTD.
Application year: 1993
Main classification: C08G77
IPC codes: C08G77, G03F7