Organosilicon Monomers Research Articles

Shaped ceramics with tunable magnetic properties from metal-containing polymers

A shaped, magnetic ceramic was obtained from a metal-containing polymer network, which was synthesized by thermal polymerization of a metal-containing organosilicon monomer. Pyrolysis of a cylinder, shape, or film of the metal-containing polymer precursor produced a low-density magnetic ceramic replica in high yield. The magnetic properties of the shaped ceramic could be tuned between a superparamagnetic and ferromagnetic state by controlling the pyrolysis conditions, with the particular state dependent on the size of iron nanoclusters homogeneously dispersed throughout the carbosilane-graphitic-silicon nitride matrix. These results indicate that cross-linked metal-containing polymers may be useful precursors to ceramic monoliths with tailorable magnetic properties.

Overall kinetics of SiOx remote-PECVD using different organosilicon monomers

An experimental study was performed using nine different organosilicon monomers for the deposition of silicon oxide films by remote plasma-enhanced CVD. The measured deposition rates are interpreted with a previously developed semi-empirical model. The model enables the estimation of the critical flow rates of oxygen atoms necessary to achieve a complete monomer conversion. The critical flow rates can be correlated to the monomer structure. Starting from tetramethoxysilane and tetraethoxysilane, the critical flow rates of oxygen atoms increase when alkoxy groups are replaced by alkyl groups. A comparison between the methoxy/methyl and the ethoxy/ethyl series shows that monomers containing ethoxy groups are easier to deposit than those containing methoxy groups. These observations are discussed with respect to the possible reaction mechanism.

XPS and XPS valence band characterizations of amorphous or polymeric silicon based thin films prepared by PACVD from organosilicon monomers

XPS core levels and XPS valence band spectra were recorded on air-exposed or Ar + sputtered surfaces of a-SiC x :H and a-SiO x C y :H PECVD thin films prepared from various organosilicon precursors with changing the preparation conditions. Their compositions and their XPS valence band spectra were compared with those obtained for SiC, SiO 2 and PDMS conventional polymer. From the calculated compositions and the valence band spectra obtained on air-exposed surfaces, we were able to show the evolutions of the polymeric nature of the films with changing the monomer precursor or the preparation conditions. Futhermore, variations in chemical compositions and valence band spectra induced by Ar sputtering have been shown and also used to reveal differences between siloxane-like plasma polymers and more inorganic amorphous materials. Informations provided by these investigations were well consistent with other characterization results obtained from XPS core level peak fittings as well as from FTIR and NMR analyses.

Organically modified silicate films for stable pH sensors

Organically modified silicate films prepared from tetraethoxysilane (TEOS) and either methyltrimethoxysilane, phenyltrimethoxysilane or isobutyltrimethoxysilane have been investigated as pH sensors. The hybrid sol, prepared by hydrolyzing and co-condensing TEOS with the organosilicon monomer, was doped with the pH indicator dyes, bromocresol green or cresol red, and spin cast on a glass cover slip to form a thin film. The pH sensing range, rate of response, stability, and long-term leaching was evaluated as a function of the amount and type of organosilicon precursor introduced into the sol. Films prepared with a 1:1 or 2:1 TEOS:organosilane mole ratio were found to be the best in terms of transparency, uniformity, stability, and response. Response times to solutions of varying pH were less than 60 s. The pH vs. absorbance response curve for both gel-immobilized bromocresol green or cresol red were broad and the mid-point shifted by approximately 2–3 pH units more basic than their reported p K a's in water. When the dye-doped hybrid films were soaked in pH 7.0, 0.1 M phosphate buffer for extended periods of time (1–2 weeks), no significant leaching of the dye was observed. The improved stability of the immobilized dye can be attributed to the organosilicon functional group incorporated into the film.

Infrared absorption analysis of organosilicon/oxygen plasmas in a microwave multipolar plasma excited by distributed electron cyclotron resonance

The dissociation of four groups of organosilicon monomers (hexamethyldisiloxane, tetraethoxysilane, tetramethylsilane or tetramethoxysilane) in a multipolar microwave plasma reactor is analyzed by infrared absorption spectroscopy (IRAS). The parent molecules are totally dissociated above 100 W. The resulting stable molecules, such as C 2H 2, CH 4, CO 2, CO, C 2H 4, and OCH 2 have been detected at low power but are dissociated at higher power. Each group exhibits its own characteristics of dissociation as well as production of new species depending on its chemical composition. The IR measurements confirm the extreme effectiveness of the distributed electron cyclotron resonance (DECR) plasma excitation mode in molecular dissociation. It seems that the DECR plasma at high energy dissociates the monomer molecule into its constituent atoms.

Silicon nitride film growth by remote plasma CVD using Tris(dimethylamino)silane

Silicon nitride (SiN x) films were prepared using an organosilicon monomer, Trisdimethyl-aminosilane ((Me 2N) 3SiH: TDMAS) by a remote plasma CVD. Plasma was generated by a mixture of hydrogen and nitrogen gases while the monomer was introduced into the downstream. Deposition of SiN x films were initiated by hydrogen radicals since no film deposition was observed in the absence of hydrogen radicals. The deposited films were contaminated with a small amount of carbon atoms for the substrate temperature over 400°C. It is proposed that at the initial step, Si–N or N–C bonds of the monomer are broken by hydrogen radicals. Furthermore, N atoms in the films are assumed to be originated from the plasma.

On the Correlation Between Deposition Rate and Process Parameters in Remote Plasma-Enhanced Chemical Vapor Deposition

Plasma-enhanced chemical vapor deposition has become one of the most important thin film deposition technologies. To avoid direct plasma exposure the substrates may be placed in the remote region. A carrier gas conveys the plasma energy to the deposition area where the reactions with the monomer molecules take place. For the engineering of such a process the modeling of the achievable deposition rate is of great interest. Among different possibilities semiempirical models provide a fast and easily utilizable tool without intensive computer simulations or the necessity of detailed knowledge about the chemistry involved. From deposition experiments with oxygen and an organosilicon monomer (hexamethyldisiloxane, HMDSO) the remote composite parameter is suggested. It combines microwave power, monomer and carrier gas flow rate, and the distance of the substrate from the plasma source. This parameter was derived from the ratio between atomic oxygen and monomer flow rate. In the parameter range considered the deposition rate is described as well ordered and the energy- and monomer-deficient regions are clearly separated.

Plasma surface modification of polyethylene with organosilicon and organotin monomers

Plasmochemical modification of a polyethylene (PE) film surface by several selected silicon and tin containing monomers, such as vinyltriethoxysilane (VTES), hexamethyldisiloxane (HMDS), 3-aminopropyltriethoxysilane (APTS), tetraethylstannane (TES) and hexabutyldistannoxane (HBDS) were all examined. The structure and properties of plasma polymers obtained and plasma modified PE film surfaces were studied by FTIR, photoacoustic FTIR spectroscopies and by using surface energy and swelling measurements. It is shown that the structure of plasma polymers formed either on the inorganic non-active or on the organic active (PE films) surfaces do not differ much from each other. In the structure of the organosilicon surface plasma polymers, mainly polysiloxane type fragments emerge; while for the organotin analogs primarily carboxylate fragments predominate. The plasma of organosilicon and organotin compounds were used to modify PE film surfaces to produce thin hydrophobic, biologically active and inactive surfaces. The results of surface energy studies as followed by the interaction with methylene iodide (non-polar) and ethylene glycol (polar components), and degree of swelling studies for both unmodified as well as plasma modified PE films, in xylene showed decrease in the latter and an increase of hydrophobic components as expected.

Some applications of the diels–alder reaction in organosilicon chemistry

AbstractA review of advances in the applications of the Diels–Alder reaction in organosilicon chemistry in our laboratory is presented. Using this reaction, we have synthesized a series of organosilicon monomers and polymers with polyphenyl groups and condensed rings and established a novel vulcanization system for silicone rubber. In addition, we discuss the influences of the large aromatic groups on the properties of the polymers.

Siloxane and Organosilicon Dimers, Monomers, and Polymers with Amide-Linked Ferrocenyl Moieties. Synthesis, Characterization, and Redox Properties

Polymers [ -S~(CH~)~(CHZ)~N HC(O)(~~-C~~)F~( ~;~~-C~H)~O-~~ (4), and [-C&C(O)NHCH2CH2(q5-C5&)Fe($-Cg&)CH2CH2NHC(O)C6I-L+Si(CH3)2-]n (S), in which the amide-linked ferrocenyl moieties are part of the main polymer chain, have been prepared via solution and interfacial polycondensations. As an aid to the spectroscopic and electrochemical characterization, the corresponding dimeric model compounds [ { $CsHs}Fe{115-Cs&C(0)NH(CH~)3Si(CH3)2}l~-0 (I), and [{T~-C~H~}F~{~~~-C~&CHZCH~NHC(O)(C&)}IZS~M~Z (2) were synthesized. Electrochemical measurements show that in 1 and 2 the oxidation wave represents a twoelectron process, as expected for independent reversible one-electron transfer, at the same potential, of the two ferrocenyl moieties. The cationic dimetallic species [ 12+][PF6-]2 and [22+][PF6-]2 have been generated and characterized via infrared spectroelectrochemistry. A redox-active monomer, { T,W~HS}F~{ vs-C$I&(0)NH(CH2)3SiCH3(0CH2CH3)2} (3), has been successfully attached to Pt electrodes and to silica surfaces, via siloxane bond formation. In addition, a series of poly(methylsi1oxanes) 6-11, containing pendant ferrocenyl moieties attached to the polymer backbone through amide linkages, with varying degrees of ferrocene substitution, were prepared and characterized. Solution electrochemical studies showed that all the ferrocenyl redox centers present in the polymers are electrochemically independent, and that neutral 6,7, and 10 undergo oxidative precipitation, yielding polymer films on the platinum electrode surfaces. The electrochemistry of electrodes modified with electroactive films of ferrocene-containing polysiloxanes was studied by cyclic voltammetry. Amperometric glucose sensing electrodes based on a ferrocene-containing poly(methylsi1oxane) have been prepared.

Hydrosilylation Catalyzed by Polysiloxane-Bound Platinum Complexes

Abstract A series of polysiloxane-bound platinum complexes was prepared by the reaction of chloroplatinic acid with silica-supported polysiloxane ligands containing S and -COOH (D) groups. These were tested as catalysts for the hydrosilylation of acetylene and olefins with functional groups, with the aim of synthesizing organosilicon monomers and silane coupling agents. It was found that supported platinum Catalyst A was an active catalyst for the hydrosilylation of acetylene and allyl chloride by dichloromethylsilane or trichlorosilane. By these catalytic reactions, several useful organosilicon monomers, such as dichloromethylvinylsilane and 3-chloropropyl-trichlorosilane, were obtained in good yield. Supported platinum Catalysts B, C, and D proved to be effective for the hydrosilylation of allyl glycidyl ether by trimethoxysilane to yield an important silane coupling agent, 3-glycidoxypropyltrimethoxysilane. The stability of supported Catalyst A is reported.

A cobaltoorganosiloxane with an unusual structure

The metal organosiioxanes which have been obtained from trifnnctional organosilicon monomers and polyvaient metals have had polymer structure. We are the first to report that the consecutive reaction of a mixture of [PhSi(ONa)O]3'3H20 and [PhSiOi.5] 8 with NaOH and then with CoC12 (6.6:7.5:20:10 mole ratio) gives a low-molecular-weight crystalline compound (I) having an intense blue color in addition to polycobaltophenylsiloxane. The crystal and molecular structure of (I) were established by x-ray structural analysis~ The unit cell parameters for monoclinic crystals of (I) at -120~ are as follows: a = 18.714(4)~ b = 18.797(4), c = 24~735 (6) ~, ~ = 99.98(2) ~ , V + 8569(3) ~, z = 2, space group P2 I. The crystals consist of {[(PhSi)7013Co]3SiPh} ~anions having normal contacts with each other and Na + cations coordinated by oxygen atoms of the anions and of the molecules of water of crystallization. The unusual, architecturally attractive, cobaltosiloxane framework of the anion (Fig. I) has approximate C 3 symmetry which holds well for the heavy atoms. The bond lengths in the anion are close to normal. The bond angles at the oxygen atoms range from 121 to 157 ~ in the eight-membered cobaltosiloxane rings, from 133 to 158 ~ in the tetrasiloxane rings~ and from 147 to 150 ~ in the atoms bound to the central siliconatom.

(Polyfluoroorganoxyalkyl)trialkoxysilanes

Fluorine-containing organosilicon monomers and polymers are of great importance for manufacturing anti-adhesive hydrophobic coatings, heat resistant lubricants, etc. We have worked out a process for manufacturing a new class of polyfluoroorganosilicon compounds, (polyfluoroorganoxy- alkyl)trialkoxysilanes. (Polyfluorophenoxyalkyl)trialkoxysilanes are synthesized by the reaction of (haloalkyl)trialkoxysilanes with alkali polyfluorophenoxides in a medium of aromatic hydrocarbons and dimethylsulfoxide at 80–90°C: ▪ M = Na, K; Ar F = C 6F 5, C 6F 4OMe, C 6F 4Cl, C 6F 3Cl 2, C 6F 4H; n = 1, 3; R = Me, Et The reaction of (haloalkyl)trialkoxysilanes with polyfluorinated alkoxides is carried out in a similar way. This reaction, however, is accompanied by some side-processes due to which the yield of (polyfluoroalkoxyalkyl)trialkoxysilanes does not exceed 20%. Besides, the products of transetherificcation and SiC bond cleavage are formed. The reaction of (polyfluoroorganoxyalkyl)trialkoxysilanes with triethanolamine leads to the corresponding 1-substituted silatranes, R FO(CH 2) n Si(OCH 2CH 2) 3N (I) with R F = C 6F 5, C 6F 4Cl, C 6F 3Cl 2, CH 2CF 2CF 2H, CH 2(CF 2CF 2) 2H, CH 2(CF 2) 3CF 3. The toxicity of (I) ranges within LD 50 = 16–9OO mg/kg. Some of these compounds display a bacteriostatic activity with respect to Staphylococcus aureus .

A conformational analysis of eight-membered cyclosiloxanes

UDC 541.636 The method of atom--atom potential functions has been used to study the conformational possibilities of the tetrasiloxane ring, present in various organosilicon monomers and polymers. In the first part, the regions of conformational space satisfying the condition for ring closure are determined, and, in the second part, the relative energies of the canonical symmetrical forms are calculated, and the range of existence of the low-energy conformation established. It has been shown that the tetrasiloxane ring is much more flexible than cyclooctane: The typical energy difference between its conformations is 0.1-0.2 kcal/mole. The small difference in the conformational energies is related to the large variety of unsymmetrical structures of the tetrasiloxane ring observed in crystals, which can be represented approximately as the superposition of the symmetrical canonical forms.

Organosilicon monomers for plasma-developed x-ray resists

A variety of silicon-containing monomers for plasma-developed resists formulated with chlorine-containing host polymers have been prepared and evaluated for use with x-ray lithography. The major design problems encountered were monomer incompatibility, high volatility, and low reactivity. One class of monomers, the bis-acryloxy- and and methacryloxyalkyltetramethyldisiloxanes, satisfies all requirements. A formulation with optimum properties contains 90 parts poly(2,3-dichloro-1-propyl acrylate) (DCPA) and 10 parts bis-acryloxybutyltetramethyldisiloxane (BABTDS). It is very sensitive (30–60 s exposure time), has high resolution (better than 0.5 μm), and can be developed by reactive ion etching which provides extremely uniform developed patterns.

Properties of ethylene-vinylsilane copolymers and their variation after irradiation

Using statistical copolymers of ethylene with 0·2–7 mol.% tris-(trimethylsiloxy) vinylsilane, vinyltrinonoxysilane, vinyltriethylsilane and vinyltrimethylsilane a study was made of the possibility of improving properties of PE by combining two methods of modification: copolymerization of ethylene with organosilicon monomers and radiation. A correlation was established between the composition, chemical structure and properties of these copolymers and it was found that properties change after irradiation. Some special features of radiation-chemical crosslingking of PE were detected in the presence of silicon-containing units. It was found that the heat stability of non-irradiated ethylene-vinylsilane copolymers is higher in the presence of atmospheric oxygen than in nitrogen or than that of PE in air.

Bromine- and iodine-containing (Haloalkyl)trichlorosilanes and methyl(Haloalkyl)chlorosilanes and their conversions

1. The organosilicon monomers XCH2(CH3)33−nSiCln with X=Cl (n=2, 3) are smoothly converted when reacted with aluminum iodide or aluminum bromide into the corresponding C-iodo and C-bromo derivatives (X=I, Br). Compounds with the general formula X(CH2)m(CH3)3−n,SiCln with X=Cl are converted upon reaction with NaI into the corresponding C-iodo derivatives (X=I). 2. When reacted with SbF3 or KHF2, (iodoalkyl)- and (bromoalkyl)trichlorosilanes are converted into the corresponding (haloalkyl)trifluorosilanes. 3. The corresponding (iodoalkyl)- and (bromoalkyl)silatranes and their exo-D-methyl derivatives have been synthesized on the basis of the (haloalkyl)trichlorosilanes obtained.

Compounds of [btilde]-Cyclodextrin and Organosilicon Oligomers

Abstract Products of hydrolysis and condensation of organosilicon monomers in the presence of [btilde]-cyclodextrin (cycloheptaamylose [btilde]-CD) were studied by IR, NMR, MS, and x-ray methods. It was established that when an aqueous solution of [btilde]-CD is treated with dimethyldichlorosilane (DMDCS), diphenyldichlorosilane (DFDCS), methylphenyldichlorosilane (MFDCS), or with a mixture of the DMDCS and DFDCS, crystalline compounds of cyclodextrin with appropriate siloxane oligomers, are formed: /3-CD-MSO (69% yield by weight), [btilde] -CD-FSO (6.0% yield by weight), [btilde]-CD-MFSO (16%) yield by weight), [btilde]-CD-(MSO + FSO) (22–63% yield by weight). The content of the obtained products showed: [btilde]-CD:MSO = 1 mole of [btilde]-CD:2 (CH3)2SiO elements; [btilde]-CD:FSO = 1 mole of [btilde]-CD:0.57 mole of (C6H5)2SiO; [btilde]-CD:MFSO = 1 mole of [btilde]-CD:0.87 mole of (CH3) (C6H5)SiO. Contents of [btilde]-CD′ (MSO + FSO) depend on the starting monomer mixture. It is suggested that nonchemic...

Gas—liquid chromatography on micro-packed columns with chemically bonded stationary phases

Column packings with chemically bonded stationary phases of the “brush” type on controlled-porosity glass beads were prepared. The following organosilicon monomers with different functional groups were used: octadecyltrichlorosilane, phenyltrichlorosilane, 2-cyanoethylmethyldichlorosilane and 3-aminopropyltriethoxysilane. Micro-packed columns of length 5 m and I.D. 0.8 mm were prepared. The efficiency and selectivity of micro-packed and packed columns of I.D. 4 mm were compared. The mean efficiency of micro-packed columsn was 2500 theoretical plates per metre for a partition ration K′ ⩾ 3.

A radiation-chemical installation with an EU-0.4 electron accelerator for obtaining organosilicon monomers

A radiation-chemical installation with an EU-0.4 electron accelerator for obtaining organosilicon monomers