Photoluminescent silacyclobutene monomers and polymers

Abstract: Silacyclobutene monomers and polymers based on silacyclobutene building blocks surprisingly exhibit photoluminescence in the blue region of the visible spectrum when excited by ultraviolet light. Such materials and methods for their preparation are disclosed herein.

Description: This invention is directed to silacyclobutene monomers and polymers that exhibit photoluminescence in the blue region of the visible spectrum when excited by ultraviolet light. While articles relative to silacyclobutenes have been published, none of those articles describe monomers or polymers which replicate the monomers or polymers described and claimed herein. Reference may be had, for example, to Angew. Chem. Int. Ed. Engl., Volume 30, No. 9, Pages 1151-1152, (1991); Organometallics, Volume 12, Pages 4135-4140, (1993): Bull. Soc. Chim. Fr., Volume 132, Pages 599-603, (1995); and J. Prakt. Chem., Volume 337, Pages 79-92, (1995). This invention provides photoluminescent silacyclobutene monomers and polymers and methods of making such monomers and polymers. Our photoluminescent silacyclobutene polymers and monomers have structures which are represented by the following repeating units and formulas: where a is an integer having a value of 3 to 20; b is an integer having a value of 1 to 15; c is an integer having a value of 2 to 20; R3 and R4 are the same or diffferent and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; R5 and R6 are the same or different and reprsent aryl groups; R7 and R8 are the same or different and represent an alkyl group containing 1 to 10 carbon atoms or an aryl group; and R9 and R10 are the same or different and represent hydroxyl, an alkyl, aryl, alkenyl or alkynyl group. This invention introduces photoluminescent silacyclobutene monomers and photoluminescent silacyclobutene polymers having low to medium degrees of polymerization based on silacyclobutene building blocks. Unexpectedly, we found that these silacyclobutene monomers and silacyclobutene polymers exhibit strong photoluminescence in the blue region of the visible spectrum, when excited by ultraviolet (UV) light with a wavelength of 337 nanometers (nm). One type of polymer representative of our invention is a polysilacyclobutene which has repeating units shown generically as: where a R3, R4, R5 and R6 are as defined hereinabove. These polysilacyclobutenes are linear polymers which are terminated by suitable alkyl, alkoxy, aryl or silyl groups. One species (I) of the genus is shown below: A compositional analysis of this polymer was carried out. Gel Permeation Chromatography (GPC) revealed that the molecular weight of the polymer was 1,950 dalton (number average) with a dispersity of 1.64 (weight average 3,200 dalton). Thus, the average number a of repeat units for this polymer was seven. Ultraviolet Spectroscopy showed UV absorption maxima at 210 nanometers, 234 nanometers and 284 nanometers. Particles of the above polymer were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 millijoule (mJ) per pulse. The photoluminescence was very bright whitish, barely blue, and well visible in ambient room illumination. The process for making these polymers is illustrated schematically as shown below: Other types of monomers can be used in this process such as monomers conforming to the formula where R1 and R2 are the same or diffferent and represent halogen atom or an alkoxy group; R3, R4, R5 and R6 are as defined hereinabove. Isolation or recovery of these photoluminescent polysilacyclobutenes is carried out by extraction, crystallization or precipitation by addition of alcohol. An example representing this process is set forth below to further illustrate our invention in more detail. EXAMPLE I A silacyclobutene monomer of the structure represented below i.e., 1,1-dichloro-4-neopentyl-2,3-diphenyl-1-silacyclo-2-butene, was polymerized in toluene by refluxing it in the presence of sodium metal for ten hours. Ninety grams of polymer of the structure represented below were recovered after removing the solvent. This polymer was identified as species (I) and a had an average value of seven. Another type of silacyclobutene representative of our invention is a co-polymer which has repeating units which are shown generically as: where b,c, R3, R4, R5, R6, R7 and R8 are as defined hereabove These polysilacyclobutenes are linear copolymers which are terminated by suitable alkyl, aryl or silyl groups. One species (II) of this genus is shown below: A compositional analysis of this co-polymer where b = 9 was carried out. GPC revealed that the molecular weight of the co-polymer was 3,620 dalton (number average) with a dispersity of 1.45 (weight average 5,240 dalton). Thus, the average number c of repeat units for this co-polymer was three. Particles of the above copolymer were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 millijoule (mJ) per pulse. The photoluminescence was very bright whitish, barely blue, and well visible in ambient room illumination. The process for making this type of co-polymer is illustrated schematically as: Isolation or recovery of these photoluminescent polysilacyclobutenes was carried out by extraction, crystallization or precipitation by addition of alcohol. An example representing this process is set forth below to illustrate our invention in more detail. EXAMPLE II Example I was repeated, and a stoichiometric amount of phenylmethyldichlorosilane was added as another component of the polymerization mixture. Ten grams of co-polymer of the structure were recovered after removing the solvent. This co-polymer was identified as species (II) where b = 9 and c = 3. The process was performed by drying the silacyclobutene monomer used in Example I and storing it under nitrogen. The same procedure was conducted with the solvent. The silacyclobutene monomer and the phenylmethyldichlorosilane were transferred into a toluene solution containing 0.7 to 1.3 mole/l toluene. Sodium metal was added in an exact stoichiometric quantity as granules. The reaction was run for 10 to 15 hours at 110°C. while refluxing the boiling toluene. The reaction solution was then reduced to half its volume and poured hot into methanol at 0°C. The product was isolated and dried. There was obtained a white to yellowish powder in a yield between 48% to 63% (species II). By changing the amount of phenylmethyldichlorosilane relative to the amount of silacyclobutene monomer in Example I, different values of b are obtained, before polymerization is initiated. This modification also causes changes in the molecular weight of the resulting copolymer. One silacyclobutene monomer representative of our invention is shown generically as: where R3, R4, R5, R6, R9 and R10 are as defined hereinabove. Some representative unsaturated groups are, for example, vinyl, allyl, H-C≡C-, CH 3 -C≡C- and aromatically substituted unsaturated groups such as C 6 H 5 -C≡C-. One species (III) of this monomer genus is shown below: Particles of the above monomer III were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 mJ per pulse. The photoluminescence was very bright, deep blue. Isolation or recovery of this photoluminescent silacyclobutene monomer was done by extraction, crystallization or precipitation by addition of alcohol. An example representing a process for making 1,1-diphenyl-4-neopentyl-2,3-diphenyl-1-silacyclobut-2-ene, i.e., monomer species III, is set forth below to illustrate our invention in more detail. In this example, photoluminescent silacyclobutene monomers are made by heating and stirring a reaction mixture containing a halosilacyclobutene, an organolithium reagent and a solvent. EXAMPLE III To a solution of 10.0 grams (0.027 mole) 1,1-dichloro-4-neopentyl-2,3-diphenyl-1-silacyclobut-2-ene in 150 ml tetrahydrofuran (THF), was added a solution of 0.055 mole phenyllithium, freshly prepared from phenyl bromide and lithium in THF at -50°C. The reaction mixture was stirred and heated under reflux for three hours. The volatiles were removed under reduced pressure, and the residue was extracted twice with 75 ml pentane. After filtration, pentane was stripped off in vacuum, and an oily liquid product was transferred to a chromatographic column packed with silica gel. The product was eluted with ethyl ether. Further purification was conducted by high vacuum distillation, (boiling range 185-190°C. and 10 -5 mbar pressure), providing 8.4 grams (0.019 mole, 70%) of a white solid. The white solid (species III) was crystallized from a saturated CH 3 OH/C 2 H 5 OH/CHCl 3 (10:2:1) solution at room temperature as white needles. Elemental Analysis for C 32 H 32 Si (M r , 444.70): Calculated: C, 86.43%; H, 7.25%; Si, 6.32%. Found: C, 87.53%; H, 7.36%. While phenyllithium is shown in Example III as the organolithium reagent, other lithium alkyls or lithium aryls can be used to make other different monomer species, such as methyllithium, tert-butyllithium or hexyllithium. A second species (III-A) of this monomer genus is a silanol functional monomer shown below: Particles of the above monomer III-A were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 mJ per pulse. The photoluminescence was bright deep blue. Isolation or recovery of this photoluminescent silacyclobutene monomer was performed by extraction, crystallization or precipitation by addition of alcohol. An example representing a process for making 2,3-diphenyl-4-neopentyl-1-silacyclo-2-butene-1,1-diol, i.e., monomer species III-A, is set forth below to illustrate our invention in more detail. In this example, photoluminescent silacyclobutene monomers are made by the hydrolysis of a halosilacyclobutene. EXAMPLE III-A A 250 milliliter three-necked flask equipped with a 100 ml dropping funnel and magnetic stirrer was charged with 100 ml of a saturated aqueous solution of sodium bicarbonate. Using an ice bath at 0°C., a solution of 10.0 grams of the silacyclobutene shown below (27.67 mmole) dissolved in 100 ml of diethylether, was added dropwise over a period of 20 minutes. The mixture was stirred for 15 minutes and 50 ml of diethylether was added to the cold mixture. Two layers separated and the organic layer was washed twice by water and the organic layer was dried over magnesium sulfate. The solvent was removed by evaporation and a white, fine, light powder was obtained. The powder was purified by recrystallization from hot toluene. The resulting product was a fine, white powder with a melting point of 171.14°C. Elemental Analysis for C 20 H 24 O 2 Si (M r , 342.50): Calculated: C, 74.03%; H, 7.45%; O, 9.86%; Si, 8.66%. Found: C, 74.11%; H, 7.36%. A third species (III-B) of this monomer genus is a phenylethynyl functional monomer shown below: Particles of the above monomer III-B were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 mJ per pulse. The photoluminescence was bright deep blue. Other monomers representative of our invention are spiro-type cyclosiloxy-silacyclobutenes which can be shown generically as: where R3, R4, R5, R6, R7 and R8 are as defined hereinabove. One species (IV) of this monomer genus is shown below: Particles of the above monomer were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 mJ per pulse. The photoluminescence was very bright, deep blue. Isolation or recovery of this photoluminescent spiro-type cyclosiloxy-silacyclobutene monomer was accomplished by extraction, crystallization or precipitation by addition of alcohol. An example representing a process for making monomer species IV is set forth below to illustrate our invention in more detail. The process involves the condensation of the silacyclobutene with the 1,1,3,3-tetramethyldisiloxane-1,3-diol yielding monomer species IV, i.e., 1-(2',3'-diphenyl-4'-neopentyl-1-silacyclo-2'-butene)-3,3,5,5-tetramethylcyclotrisiloxane. EXAMPLE IV A 500 ml two-necked flask equipped with a 100 ml dropping funnel and magnetic stirrer was charged with a solution of 2 grams of 1,1,3,3-tetramethyldisiloxane-1,3-diol (12 mmole), and 2.6 ml of ethyldimethylamine in 200 ml of diethylether. To the flask was added dropwise at room temperature (20-25°C./68-77°F.), 4.35 grams of the silacyclobutene above, dissolved in 100 ml of diethylether. The mixture was stirred for 30 minutes. The solution was washed several times with water, and the organic phase was separated and dried over sodium sulfate. The solvent was removed by evaporation and a white powder was obtained. The white powder was purified by recrystallization in cold refrigerated pentane. The product was a white, hard solid with a melting point of 136°C. Elemental Analysis for C 24 H 34 O 3 Si 3 (M r , 454.79): Calculated: C, 63.38%; H, 7.54%; O, 10.55%; Si, 18.53%. Found: C, 63.37%; H, 7.37%. Another species (V) of this monomer genus is shown below: Particles of the above monomer were irradiated with UV light at a wavelength of 337 nm generated by a pulsed nitrogen laser with 0.1 mJ per pulse. The photoluminescence was very bright, deep blue. Isolation or recovery of this photoluminescent spiro-type cyclosiloxy-silacyclobutene monomer was conducted by extraction, crystallization or precipitation by addition of alcohol. Monomer species V was made in the same way as shown above in Example IV, except that the process involved the condensation of the silacyclobutene with the 1,1,3,3-tetraphenyldisiloxane-1,3-diol yielding monomer species V, i.e., 1-(2',3'-diphenyl-4'-neopentyl-1-silacyclo-2'-butene)-3,3,5,5-tetraphenylcyclotrisiloxane. Recrystallization of the product from warm pentane afforded colorless crystals with a melting point of 156°C. Although the photoluminescence of species (IV) and (V) was similar, the photoluminescence of species (IV) was 1.5-2 times brighter than the photoluminescence of species (V). The following example represents the process for making silacyclobutene monomer 1,1-dichloro-4-neopentyl-2,3-diphenyl-l-silacyclo-2-butene, i.e., used in the above examples. EXAMPLE V A 200 ml three-necked flask equipped with a 250 ml dropping funnel, magnetic stirrer, inert gas inlet and pressure release valve, was charged with 50 grams (280.5 mmole) of diphenylacetylene, and 35.7 ml of trichlorovinylsilane (1 equ.) dissolved in 500 ml of pentane. Under an inert gas atmosphere, 167 ml of a 1.7 molar solution of tert-butyllithium in pentane (1 equ.), was added dropwise at room temperature until first fogging by precipitation of lithium chloride was observed. The remaining tert-butyllithium was added gently to prevent heating of the sample to the boiling point of the solvent. The mixture was stirred for ten hours to complete lithium chloride elimination. Precipitate was separated by filtration using a glass frit, and the solvent was removed by evaporation. The remaining yellow oil was fractionated by distillation to separate unreacted diphenylacetylene (boiling point 86°C. at 0.7 x 10 -6 mbar pressure) from the product. Silacyclobutene monomer 1,1-dichloro-4-neopentyl-2,3-diphenyl-1-silacyclo-2-butene was yielded as 54.7 grams of a colorless, highly viscous oil (53.9% theor.) with a boiling point of 122°C. at 2 x 10 -6 mbar pressure. Elemental Analysis for C 20 H 22 Cl 2 Si (M r , 361.39): Calculated: C, 66.47%; H, 6.13%; Cl, 19.62%; Si, 7.78%. Found: C, 65.01%; H, 6.25%; Si, 7.72%. Silacyclobutene monomers and silacyclobutene polymers, according to our invention, are useful as passive or active display materials and also in electroluminescent devices. In such utility, they are incorporated into road signs and lane markers. The monomers and polymers also find application in various types of displays as luminescent coatings for improving visibility.

Claims: Photoluminescent silacyclobutene monomers and silacyclobutene polymers having a repeating unit or formula selected from the group consisting of where a is an integer having a value of 3 to 20; b is an integer having a value of 1 to 15; c is an integer having a value of 2 to 20; R3 and R4 are the same or diffferent and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; R5 and R6 are the same or different and reprsent aryl groups; R7 and R8 are the same or different and represent an alkyl group containing 1 to 10 carbon atoms or an aryl group; and R9 and R10 are the same or different and represent hydroxyl, an alkyl, aryl, alkenyl or alkynyl group. Photoluminescent silacyclobutene monomers and silacyclobutene polymers according to claim 1 exhibiting photoluminescence in the blue region of the visible spectrum when excited by ultraviolet light. A method of making photoluminescent polysilacyclobutenes comprising polymerizing in a solvent containing sodium metal, a monomer having the formula where R1 and R2 are the same or different and represent halogen atom or an alkoxy group; R3 and R4 are the same or different and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; and R5 and R6 are the same or different and represent aryl groups. The method of claim 3 further comprising the presence of an arylalkyldihalosilane. A method of making photoluminescent silacyclobutene monomers comprising heating and stirring a reaction mixture comprising a halosilacyclobutene, an organolithium reagent and a solvent; the halosilacyclobutene being a monomer having the formula where R1 and R2 are the same or different and represent halogen atom or an alkoxy group; R3 and R4 are the same or different and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; and R5 and R6 are the same or different and represent aryl groups. A method of making photoluminescent silacyclobutene monomers comprising hydrolyzing a halosilacyclobutene in the presence of a solvent at a temperature of 0-25°C.; the halosilacyclobutene being a monomer having the formula where R1 and R2 are the same or different and represent halogen atom or an alkoxy group; R3 and R4 are the same or different and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; and R5 and R6 are the same or different and represent aryl groups. A method of making photoluminescent spiro-type cyclosiloxy-silacyclobutenes comprising condensing a halosilacyclobutene with a siloxane diol at room temperature; the halosilacyclobutene being a monomer having the formula where R1 and R2 are the same or different and represent halogen atom or an alkoxy group; R3 and R4 are the same or different and represent hydrogen atom or an alkyl group containing 2 to 10 carbon atoms; and R5 and R6 are the same or different and represent aryl groups.

Inventors: AUNER NORBERT, PERNISZ UDO C, AUNER, NORBERT, PERNISZ, UDO C.
Applicants: DOW CORNING, DOW CORNING CORPORATION
Application year: 1998
Main classification: C09K11
IPC codes: C07F7, C08G77, C09K11