Phenylsilane Research Articles

Photoinitiation of cationic polymerization by using poly(methyl phenyl silane) in combination with addition–fragmentation agents

Poly(methyl phenyl silane) (PhMeSi) n was used in combination with the addition–fragmentation agents (AFA), namely 2-ethoxycarbonyl-2-propenylpyridinium hexafluoroantimonate (EPP +), ethyl- α-tetrahydrothiophenium methyl acrylate hexafluoroantimonate (ETM +) and 2-ethoxycarbonyl-propenyl triphenyl phosphonium hexafluroantimonate (ethoxy carbonly allyl phosphonium salt) (ECAP +) to photoinitiate the cationic polymerization of cyclic ethers such as cyclohexane oxide (CHO), alkyl ethers like n-buthyl vinyl ether (BVE) and vinyl monomers such as methoxy styrene (MOS). By using poly(methyl phenyl silane), the spectral response was extended to 330 nm at which the allyl onium salts are transparent. The feasible mechanism involves radical addition to the allylic bond and subsequent fragmentation to yield reactive species capable of initiating cationic polymerization of related monomers. An alternative mechanism which involves the oxidation of electron donor radicals is also discussed. The initiation efficiency of the salts was studied by determination of the conversion of CHO and BVE.

Synthesis, characterization, thermal and flame-retardant properties of silicon-based epoxy resins

A new silicon-containing oxirane triglycidyl phenyl silane oxide (TGPSO) and its corresponding silicon-containing epoxy resins are synthesized and characterized. The activation energies of TGPSO curing reaction with various curing agents, including 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylsulfone, and dicyanodiaminde, are found to be 180, 196.5, and 154 kJ/mol. The curing reaction of TGPSO with diamines is determined to be a first-order reaction through means of Arrhenius plots. The introduction of the silicon-containing group results in higher curing reactivity. This silicon-containing resin possesses higher char yield as well as higher limiting oxygen index (LOI = 35) than the commercial epoxy resins, confirming the usefulness of these silicon-containing epoxy resins as flame retardants. Char yields and LOI measurements demonstrate that incorporating silicon into epoxy resins is able to improve their flame retardancy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1231–1238, 1999

Crosslinking of polysilanes by ion beam irradiation

Poly(methyl phenyl silane), PMPSi, poly(biphenyl methyl silane), PBMSi, poly(c-hexyl methyl silane), PcHexMSi, and poly(methyl n-hexyl silane), PMnHexSi, were irradiated in the absence of air with 300 MeV 86Kr14+, 200 MeV 129Xe14+ and 120 MeV 20Ne5+ ions. PMPSi was also irradiated with 65 MeV 15N3+ and 95 MeV 40Ar5+ ions. In all cases, the ion beam irradiation induced insolubilization of the polysilanes indicating that intermolecular crosslinking dominates over main-chain scission. By contrast, irradiation with 60Co-γ-rays (dE/dx=0.02–0.03 eV/Å) led to a decrease in the average molar mass indicating that main-chain scission is the dominating effect when the polysilanes are subjected to radiation of low linear energy transfer (LET, dE/dx). In the case of ion beam irradiation the dose to gelation, Dgel, was determined by solubility tests. Dgel is inversely proportional to G(X), the number of crosslinks per 100 eV absorbed by the polymer. On this basis G(X) was estimated and it turned out that G(X) increases with increasing dE/dx, e.g. in the case of PMPSi G(X) increases from 0.024 to 0.42 by increasing dE/dx from 42 to 565 eV/Å.

Cobalt catalysed hydro-sulfenylation of Michael acceptors

The reaction of certain types of Michael acceptors, limited to those having methylene groups, with a mixture of diphenyl disulfide and phenyl silane, under the influence of 10% of the cobalt catalyst, Co(eobe) 3, results in the formation of hydro-sulfenylated products, such as α-phenylthio carbonyl compounds, in moderate to good yields. The process involves intermediates having radical character, judging by the 5- exo-trig cyclisation product 21 observed in the reaction of α,β-unsaturated ester 20 having a suitable unsaturated side-chain.

AN ALTERNATE SYNTHESIS OF THE POTENT ANTIMUSCARINIC AGENT SILA-BIPERIDEN

Sila-biperiden, 9x(RS,SR ), i. e. racemic (SiRS, C2SR)-(exo-bicyclo[2.2.1]hept-5-en-2-yl)phenyl(2-piperidinoethyl)silanol, the silicon analogue of the antimuscarinic agent biperiden, is prepared by a seven-step synthesis. The first step consists in the hydrosilylation of 5-exo-bromobicyclo[2.2.1]-hept-2-ene (2) with dichloro(phenyl)silane (1) in the presence of H2PtCl6. The product of the last synthetic step is a mixture of four endo- (9n) and four exo-diastereomers (9x) of (bicyclo[2.2.1]hept-5-en-2-yl)phenyl(2-piperidinoethyl)silanol and of the (tricyclo[2.2.1.02,6]hept-1−yl)silanol derivative 9t. Eight-fold crystallization of the 9n/9x/9t-mixture gave pure sila-biperiden (racemate) in an overall yield of 5.3%, which represents a more than 30-fold improvement over the earlier synthesis.

Polymerization of n-Butyl Vinyl Ether Photoinitiated by the Initiator System Poly(methyl phenyl silane)/N-Ethoxy-2-methylpyridinium Iodide/ZnI2/Benzaldehyde

Polymerization of n -Butyl Vinyl Ether Photoinitiated by the Initiator System Poly(methyl phenyl silane)/ N -Ethoxy-2-methylpyridinium Iodide/ZnI 2 /Benzaldehyde

Improvement of Photosensitivity in Fluorenone Bisazo Pigment/Poly(Methyl Phenyl Silane) Layered Device

The low photocarrier generation efficiency of a layered device consisting of an azo-pigment-based carrier generation layer (CGL) and a poly(methyl phenyl silane) (PMPS) layer was investigated. We found that the electron transfer efficiency to generate geminate hole-electron pairs, which are the precursor of free carriers, was quite low, whereas electron transfer efficiently occurs in a layered system using a small carrier transport molecule instead of the large PMPS. These results were explained in terms of the number of electron transfer sites created by the molecular penetration during the overcoating operation. A high electron transfer efficiency was observed in a single layer of mixed PMPS and azo pigment. According to these results, a high carrier generation efficiency has been demonstrated for the layered device using the azo pigment with PMPS in the CGL and only PMPS in the overlayer.

Study on the Mechanism of the Cationic Polymerization of Cyclohexene Oxide Initiated by the Photosystem of Poly(methyl phenyl silane) and Pyridinium Salts

The initiation process of photoinduced polymerization of cyclohexene oxide (CHO) in the presence of pyridinium salts and poly(methyl phenyl silane) (PMPS) was investigated by CW-ESR, time-resolved ESR, 19 F NMR, and by the polymerization behavior with three kinds of pyridinium salts. The results of CW-ESR measurements suggest that photolysis of PMPS under UV irradiation at wavelength longer than 310 nm mainly through main-chain scission. The facts that the life time of the transient radicals of PM PS under irradiation decreased significantly when N-ethoxy-2-methyl pyridinium hexafluorophosphate (EMP + PF 6 - ) was added suggest that single electron transfer from the silyl radicals to EMP + ions took place. The polymerization of CHO could be easily initiated by irradiation (λ inc =345nm) on dichloromethane solutions of CHO containing EMP + PF 6 - and PMPS. However, no polymerization of CHO took place when ClO 4 - or I - was the counter ion of EMP + ions. This effect of the counter ion on the polymerization of CHO indicates that the silylenium ion, obtained by the electron transfer reaction from silyl radical, hardly initiates the polymerization of CHO. When the counter ion of EMP + ion is PF 6 - , PF 5 , produced by the reaction of silylenium ion with PF 6 - , is considered to be an initiator for the polymerization of CHO, because Si-F bond, which is obtained by the F - abstraction of silylenium ion from PF 6 - , was found in residual hexane-insoluble polysilanes by 19 F NMR spectroscopy.

Ultrasonic production of block copolymers as in situ compatibilizers for polymer mixtures

The use of high-intensity ultrasound for forming copolymers by sonication of mixtures of homopolymers is discussed. It is shown that the block copolymers formed in situ by this method can be used to compatibilize blends of immiscible polymers. The mixtures used in this preliminary study were polystyrene with either poly( cis-butadiene) or poly(methyl phenyl silane). The sonochemical method was found to be convenient and easy to use compared with the usual procedure of adding preformed block copolymers as compatibilizing agents.

AlCl3-Catalyzed transformations of organo(trichloromethyl) silanes

Reactions of organo(trichloromcthyl)silanes RMc2SiCCl3 (R = Me, Ph, Mc3Si) with aluminum chloride have been studied. The interaction of trimetltyl(tricltlorometltyl)silane with AlCl3 carried out in cyclohexane or in benzene leads to Me3SiCHCI2 (in 75 % yield) or ClMe2SiCPh2Me (in 70 % yield), respectively; whereas no conversions are observed inn-hexane and methylene chloride. Treatment of dimetltyl(phenyl)(ricltloromethyl)silane with aluminum chloride in an-C5H12/CH2CI2 mixture gives an aromatic cross-linked insoluble polymer. The reaction of pentamethyl(trichloromcthyl)disilane (R = Mc3Si) with AICl3 in pentane affords the rearrangement product, Me3SiCCl2SiMc2Cl, in 65 % yield. In methylene chloride the further cleavage of the disilane occurs to yield Me2SiCl2 and CH2=CHMe2SiCl.

Ansa-Metallocenes: Catalysts for the dehydrocoupling of hydrosilanes

The dehydrocoupling of PhMeSiH 2 to form oligomers and of PhSiH 3 to form polysilanes has been performed with the precatalyst combination of [Me 2El(C 5H 4) 2MCl 2 (El = Si, C; M = Ti, Zr, Hf) and nBuLi. The results are compared to those produced from (η 5- C 5H 5) 2MCl 2 BuLi .

Preparation of enantiomerically pure ( R )-(1-hydroxyethyl)dimethyl(phenyl)silane using resting cells of Saccharomyces cerevisiae (DHW S-3) as biocatalyst

Preparation of enantiomerically pure ( R )-(1-hydroxyethyl)dimethyl(phenyl)silane using resting cells of Saccharomyces cerevisiae (DHW S-3) as biocatalyst

A Novel Synthesis and Extremely High Thermal Stability of Poly[(phenylsilylene)ethynylene-1,3-phenyleneethynylene

The polymer [SiH(Ph)-C≡C-Ph-C≡C] n was obtained by dehydrogenative coupling polymerization between phenyl silane and m-diethynylbenzene in the presence of alkaline earth metal oxides. After thermal curing the resulting polymer was found to have a 5% mass loss temperature of 860°c and a residue of 94% at 1000°C under argon

Synthesis of block copolymers by using polysilanes

AbstractPoly(methyl phenyl silane) was used to photoinitiate the polymerization of methyl methacrylate. Poly(methyl methacrylate) (PMMA), obtained this way, contains remaining polysilane chains. Photolysis of this PMMA in the presence of vinyl monomers such as styrene makes it possible to prepare block copolymers. Such PMMA prepolymers were also used to induce the polymerization of cyclohexene oxide through formation of PMMA‐attached silyl radicals and subsequent oxidation to the corresponding ions in the presence of N‐ethoxy‐2‐methylpyridinium hexafluorophosphate resulting in the formation of a block copolymer.

Diode laser spectroscopy of SiH 3 in the 4.5 μm region

The SiH 3 radical, which plays an important role in plasma processes as well as in photo-excited processes, was investigated by high resolution infrared diode laser absorption spectroscopy. The radical was generated by the discharge of phenyl silane diluted with argon in a multi-pass absorption cell. The spectrum was recorded by the discharge modulation technique. About seventy spectral lines in the 4.5 μm region were unambiguously identified as belonging to the v 3 (Si-H degenerated stretch) vibrational band of SiH 3, and are available for application to monitoring by the infrared diode laser absorption spectroscopy (IRLAS) method.

Reactions of Phenylsilanes with O(3P)-Atoms

Reactions of Phenylsilanes with O(³P)-Atoms

フェニル基を有するシランで化学修飾した多孔質シリカ膜におけるＣＯ２選択透過性

Porous silica membrane was modified with phenyltriethoxysilane and was used to separate N2-CO2 and N2-CO2-H2O mixtures. The experiment of the separation for N2-CO2 mixture, the separation factor for CO2 (α CO2/N2) was 0.9 in the case of using porous silica membrane (S membrane), however, when the silica membrane modified with phenyl silane coupling reagents (SC membrane) was used, the highest separation factor for CO2 (α CO2/N2) reached 1.19. This was due to the fact that the phenyl group modified the surface of porous, and increased affinity of CO2. So, CO2 was easy to condense on the surface of porous, and N2 become difficult to permeate. For this reason, the separation factor for CO2 can be improved. Further, the experiment of SC membrane in the separation for N2-CO2-H2O mixture, the highest separation factor for CO2 (α CO2/N2) was 1.66, which is higher than that for N2-CO2 mixture.

Strukturuntersuchungen an Verbindungen mit höher koordiniertem Silicium: Modelle zum Studium der nucleophilen Substitution an Silicium-Zentren

Silicon compounds substituted by 2-(dimethylaminomethyl)phenyl groups [C 6H 4CH 2N(CH 3) 2] n SiX 4- n (X  Cl, H, organo group, n = 1–4) are available by the reaction of the appropriate chlorosilanes with 2-(dimethylaminomethyl)phenyllithium. A comparison of the 29Si NMR spectroscopic shifts δ with the values obtained for corresponding phenyl silanes shows that there is higher coordination of the silicon atom by N → Si contacts, except for the silanes 11 (X  Cl; n = 3) and 12 ( n = 4). X-ray crystal structure analysis confirms pentacoordination of the silicon atom in the dichlorosilanes 4 (X  Cl; n = 2) and 5. For [C 6H 4CH 2N(CH 3) 2] 3SiH ( 10) heptacoordination of the silicon atom is found in the crystalline state [ d(N → Si) ≈ 301 pm]. The tetrasubstituted derivative [C 6H 4CH 2N(CH 3) 2] 4Si ( 12) has no N → Si contacts in solution and in the solid state: st eric congestion does not allow higher coordination. 10: colourless prisms, monoclinic, space group P 2 1/ n; lattice constants: a = 889.0(3), b = 1677.5(8), c = 3471(1) pm; β = 90.35(3)°. 12: colourless prisms, pseudo tetragonal, space group I4 1/ a; lattice constants: a = b = 1699.7(4), c = 3398.9(17) pm.

Silicon-carbon unsaturated compounds: XLVI. Nickel-catalyzed reaction of 2-tolyl- and 2-phenyl-2-(phenylethynyl)hexamethyltrisilanes in the presence of 2,3-dimethylbutadiene and dicyclopentadiene

The reaction of 2-phenyl-2-(phenylethynyl)-hexamethyltrisilane ( 1a) with 2,3-dimethylbutadiene in the presence of Ni(cod) 2 at 200°C for 20 h gave 1-[2,3-dimethyl-4-(trimethylsilyl)-2-butenyl]-1-phenyl-1-(phenylethynyl)trimethyldisilane and bis[2,3-dimethyl-4- (trimethylsilyl)-2-butenyl]phenyl (phenylethynyl)silane, while treatment of 1a with dicyclopentadiene in the presence of Ni(cod) 2 gave an isomerization product, 1-phenyl-1,2-bis(trimethylsilyl)-1-silaindene. Similar reactions of 2-phenylethynyl-2- o-tolyl-hexamethyltrisilane, 2-phenylethynyl-2- m-tolylhexamethyltrisilane, and 2-phenylethynyl-2- p-tolylhexamethyltrisilane are also described.

Observations concerning the inactivity of dimethylhafnocene as a catalyst for the dehydrocoupling of phenylsilane

Observations concerning the inactivity of dimethylhafnocene as a catalyst for the dehydrocoupling of phenylsilane