Vinyltrimethylsilane Research Articles

Role of unsaturated groups in glow discharge polymerization

The role of unsaturated groups of the starting compounds in glow discharge polymerization was investigated by elemental analysis, infrared spectroscopy, and ESCA. Tetramethylsilane (TMS), trimethylvinylsilane (TMVS), and ethyltrimethylsilane (ETMS) were used as starting materials. Glow discharge conditions (W/FM value meaning the rf power input per mass of the monomers) as well as a degree of the unsaturation of the starting materials had strong influences upon the polymer deposition rate and the elemental composition of the formed polymers. The C1s and the Si2p spectra showed that the chemical composition of these polymers was distinguished by either presence or absence of the unsaturated groups in the starting compounds rather than kind of the unsaturated groups. The polymer formation, when the monomers containing double and triple bonds were served, is proceeded not only through these unsaturated bonds but also through the cleavage between Si and C atoms.

Glow discharge polymerization of trimethylvinylsilane and tetramethylsilane

AbstractGlow discharge polymerizations of trimethylvinylsilane (TMVS) and tetramethylsilane (TMS) were compared. Vinyl groups in TMVS slightly contribute the polymer‐formation process only when glow discharge polymerization was performed at the W/FM parameter less than 500 MJ/kg. Elemental compositions of the polymers prepared from TMVS, which are rich in carbon content, shows strong dependence on operational conditions, the W/FM parameter; but the polymers from TMVS consist of the almost same chemical structures as those from TMS. Slight differences between the starting materials in chemical structure does not reflect on bulk properties of the formed polymers but on surface properties such as surface energy and adhesion.

Plasma-polymerized organosilanes as protective coatings for solar front-surface mirrors

A plasma-polymerization technique has been investigated as a method to apply uniform, thin (micrometers) protective coatings to front surface mirrors employed in various solar applications. These coatings were also found to offer anti-static qualities and weather resistance. Specifically, the coatings were organosilicone polymers based on precursors such as vinyltrimethylsilane (VTMS), methyltrimethoxysilane (MTMOS), and vinyltrimethoxysilane (VTMOS). We found negligible changes in hemispherical and specular reflectance when these coatings were applied. Both silver and aluminum front surface mirrors were evaluated. Surface electrostatic charge decay measured following corona charging mirror surfaces suggest that coatings containing oxygen (MTMOS, VTMOS) had improved anti-static behavior compared to the nonoxygen containing polymer (VTMS). The initial charge decay on the oxygenated materials occurred in less than 1 min versus greater than half an hour for the VTMS coating. Weatherability tests conducted in a temperature-humidity cycling environmental chamber showed that the plasma-polymerized coatings provided excellent protection for aluminized mirrors (6 month test). Silvered mirrors were observed to degrade after 2 months, however, unprotected silver mirrors degrade in a matter of hours in this environment. Improved abrasion resistance was achieved for MTMOS coatings synthesized in an oxygen rich plasma when compared to the uncoated glass in a falling sand abrasion test (ASTM D968-51).

Regularities of copolymerization of vinyltrimethyl(phenyl)silanes with butadiene initiated with n-butyllithium

A study was made of kinetics of anionic copolymerization of vinyltrimethylsilane and vinyldimethylphenylsilane with butadiene, the process being initiated with n-butyllithium in a hydrocarbon medium; it was shown that the rate of copolymerization increases on transition from vinyltrimethylsilane to vinyldimethylphenylsilane. The rate of copolymerization of the vinyltrimethylsilane-butadiene pair increases with an increase in butadiene content and of the vinyldimethylphenylsilane-butadiene pair, with an increase in the content of vinyldimethylphenylsilane.

Thermodynamics of polymerization of vinyltrimethylsilane

The thermodynamic parameters of the process vinyltrimethylsilane (VTMS)→→polyvinyltrimethylsilane (PVTMS) have been determined in the temperature region of 50–300°K. It was found that at 300°K ΔH 0 = − 47·8 kcal/mole, ΔS 0 = − 22·9 kcal/mole/deg and Δ 0 = − 10·9 kcal/mole (VTMS-liquid, PVTMS-glassy state). The polymerization-depolymerization equilibrium constant K = 8·8 × 10 6 at the same temperature. The thermodynamic characteristics of VTMS and PVTMS were determined, namely C p in the 60–300°K region, p (torr) = f( T) and the enthalpy of combustion of PVTMS (−1038·2±1·8 kcal/mole). H T 0 H 0 0 S T 0 and G T 0 H 0 0 in the region of 0–300°K have been calculated for the monomer and polymer.

The block copolymerization of acrylonitrile and vinyltrialkyl(aryl)silanes

The copolymerization of acrylonitrile with vinyl derivatives of silicon by an anionic mechanism was studied in the presence of n-butyl lithium. The lithium-initiated copolymerization of the monomers used was found not to yield random copolymers. Type A-B block copolymers of vinyltrimethyl(phenyl)silanes and acrylonitrile with various block lengths were produced by the “living” chain mechanism. The first stage in the synthesis consisted of vinyltrimethyl-(phenyl)silane polymerization over n-butyl lithium and was carried out in heptane at 20°C; the second stage—the acrylonitrile polymerization—took place at 0°C on the “living” polyvinyltri-organo-silane anions.

Mass-spectrometric ion sampling from reactive plasmas: III. Mixtures of vinyltrimethysilane and argon or helium

In an extension of earlier studies on vinyltrimethylsilane (VTMS) containing reactive plasma [1, 3], the reactor was modified so as to allow less elapsed reaction time before sampling. This resulted in only a modest increase in the detection of primary electron impact produced species. The relative amounts of ionic and neutral species were mapped as a function of axial distance between the electrodes, and this showed that the discharge has a definite structure. The concentration of VTMS is somewhat greater near the driving electrode, making it appear as if the electrode behaves as a getter. The mass spectra of VTMS—helium and VTMS—argon discharges differ: low pressure VTMS—helium discharges resemble the 26 eV electron impact spectrum of VTMS while VTMS—argon discharges are relatively more abundant in mass 43 and 45 fragment ions. In both cases, the mass 73 fragment ion is overabundant relative to the electron impact results. From the present studies, argon ion and metastable energy exchange processes are believed to be less important than previously suggested [1], while low energy successive electron impact is believed to be responsible for the results obtained. Only those processes have been observed which involve species that are not incorporated into polymer at the electrode surfaces, although polymer formation is an extremely efficient pathway for utilizing VTMS molecules.

Mass-spectrometric ion sampling from reactive plasmas II. Mixtures of vinyltrimethylsilane and argon

A study was made of the ionic and neutral species formed in 1, 5, 8, and 13 % vinyltrimethylsilane (VTMS)—argon discharges over the pressure range 0.1 to 1.0 torr. The total ion signal for each composition was found to fall off rapidly with increasing number density of VTMS molecules. For the 13 % mixture, the major ions in the discharge below 0.15 torr were ArH +, Ar +, C 2H 2 +, CH 3 +, and H 3 +; at about 0.3 torr the major ions were H 2SiMe + and SiMe +; above 0.5 torr they were SiMe 3 + and HSiMe 2 +. The neutral species produced in this discharge were also pressure dependent, being mainly C 2H 4, C 2H 2, and H 2 below 0.3 torr and SiMe 3, HSiMe 2, C 2H 4, C 2H 2, and H 2 above 0.5 torr. VTMS was found to be rapidly and efficiently consumed in the discharge. It is postulated that argon actively participates in the chemistry of the discharge by dissociative charge transfer from the argon ion to VTMS at low pressures, and transfer of excitation energy from argon metastables to VTMS at high pressures.

Mass-spectrometric ion sampling from reactive plasmas I. Apparatus for argon and reactive discharges

An apparatus has been constructed to sample the ionic and neutral species that emerge from r.f. discharges in which chemical reactions are taking place. The results for pure argon show that the sheath potential (∼ 50 V) between the sampling orifice and the plasma is too large to be supported by the plasma electron temperature (1.9eV ≤ T e ≤ 2.3 eV, as determined by a floating double probe experiment). Most ions are sampled after at least one collision in the sheat. A 1 % mixture of vinyltrimethylsilane (VTMS) in argon yielded ions (ArH +, H 3 +, CH 3 +, C 2H 2 + and C 2H 3 +) characteristic of elementary ion—molecule reactions or dissociative charge exchange rather than primary electron impact. The most probable sources of ArH + are Ar + + H 2 → ArH + + H H 2 + + Ar → ArH + + H Ar + + VTMS → ArH + + (VTMS—H). Reactions of VTMS in the r.f. discharge appear to be very efficient.

Radical copolymerization of vinyltrimethyl(phenyl)silanes with acrylonitrile

Radical copolymerization of vinyltrimethyl(phenyl)silanes with acrylonitrile

Light scattering by and viscometry of polyvinyltrimethylsilane solutions

EARLIER we had shown the possibility of producing new silicon-hydrocarbon polymers by polymerizing vinyltrialkyl(phenyl)silanes, this process taking place in the presence of metallic lithium and organolithium compounds [1, 2]. Vinyltrimethylsilane (VMS)~ a simpler representative of this type of compound, was polymerized in the presence of butylli thium using a large molar ratio of monomer to catalyst. This gave polymers with a large intrinsic viscosity.