Poly Vinyltrimethylsilane Research Articles

Modification of the gas-separating properties of ion-implantation polymer membranes

We have studied the gas-separation properties of industrial polyvinyltrimethylsilane (PVTMS) membranes, as well as of experimental specimens of polyarylate siloxane, modified with ions C+, Ar+, B+, and N+.

Chromatographic determination of the Flory-Huggins parameter and solubility parameter of polyvinyltrimethylsilane

The thermodynamic properties of the glassy polyvinyltrimethylsilane (PVTMS) have been investigated by means of reverse gas chromatography. Values of the Flory-Huggins parameter in the range 25–230° were determined for systems of the types: polyvinyltrimethylsilane-hydrocarbons and polyvinyltrimethylsilane-alcohols. As the temperature rises the hydrocarbons become θ solvents for polyvinyltrimethylsilane, while the alcohols become good solvents.

Excess mixing functions in polymers and low-molecular weight solvents

The excess mixing functions of hydrocarbons of various structure and primary alcohols in glass-like polyvinyl trimethylsilane and hydrocarbons in natural rubber and PDMS are determined by a reverse gas chromatography method. The exothermal character of the mixing, the high entropy effects, and the marked dependence of the excess mixing functions on the molar volume of the sorbate in glass-like polymers and dissolution in associated liquids.

Use of the method of radiation graft polymerization for modifying polyvinyltrimethyl silane gas separating membranes

The authors investigate the possibility of modifying homogeneous and asymmetrical membranes of polyvinyltrimethyl silane by the method of radiation graft polymerization of AN. Radiation grafting was carried out by combined irradiation of the polymer membranes and monomer in the vapour phase. It was found that with increase in the γ-radiation dose graft polymerization of acrylonitrile on asymmetrical membranes proceeds at a much faster rate than on homogeneous films. It was shown that modified polyvinyltrimethyl silane membranes possess raised stability to the action of hydrocarbons. Increase in the PAN content in the membranes lowers the gas permeability coefficient and raises the selectivity of separation of the He/N 2 gas pair.

Temperature dependence of gas permeability of the asymmetrical polyvinyltrimethyl silane membrane

The temperature dependence of the gas permeability of an asymmetrical membrane of polyvinyltrimethyl silane is calculated as the sum of the temperature dependences of the Fick and capillary flows in the total flux of gases penetrating through inhomogeneous heterogeneous systems.

Translational and rotational mobility of low molecular weight substances in the plasticized polyvinyltrimethyl silane

The coefficients of diffusion of hydrocarbons and the rotation frequencies of spin probes plasticized with oligovinyltrimethyl silane ( M=600) have been measured. Plasticization results in a monotonic reduction in the glass transition temperature from 170 to 60° for a sample containing 43% of the oligomer. The general character dependences of the translational and rotational mobilities of various types of low molecular weight substances on the plasticizer concentration has been determined.

The ratio of permeability parameters for permanent gases and hydrocarbons in polymers

The published data on the coefficients of diffusion, solubility and permeability of C 1C 4 hydrocarbons in polymers have been analyzed from the view-point of their correlation with the permeability of permanent gases. The correlation dependences characterizing the permeability of permanent gases can be used for calculation of the above three coefficients of hydrocarbons in polymers. The characteristic dimensions of the C 1C 4 hydrocarbons, being effective in the diffusion process, have been determined relative to those of the permanent gases. The possibilities of the calculation have been demonstrated for polyvinyltrimethyl silane, polydimethyl siloxane, polydienes, polyolefins and fluorinated polymers.

Effects of thin carbon films on the selective gas permeability of a polymer membrane

Measurements have been made on the selectivity and gas permeability of a polyvinyltrimethylsilane (PVTMS) membrane bearing a thin carbon coating in the separation of gas mixtures containing CO2 and O2.

Permeability, diffusion and sorption of SO 2 in polyvinyltrimethyl silane membranes

The authors have studied the permeability of SO 2 through continuous and asymmetrical polyvinyltrimethyl silane membranes at 10–50°C and pressures 0–250 kPa. The special aspects of the transfer of SO 2 in polyvinyltrimethyl silane are the high values of the permeability coefficients P and the dependence of the permeability through the asymmetrical membranes on pressure (above 100 kPa), which is due to the concentration dependence of the diffusion coefficients of SO 2, the plasticizing effects of SO 2 and the non-linear character of its sorption isotherms. The form of the sorption isotherm agrees with the double sorption model. The parameters of this model are determined and for a number of polymers a correlation established between the adsorption capacity and glass transition point. The high P values for SO 2 in polyvinyltrimethyl silane are determined by the large diffusion coefficients.

Permeability of gases through an asymmetric polyvinyl trimethyl silane membrane

It was shown that gas flow through an asymmetric polyvinyl trimethyl silane membrane may be presented as flow consisting of three components—activated diffusion, Poiseuille viscosity flow and Knudsen capillary flow. By experimental measurement of the dependence of flow on pressure for nitrogen and argon the effect of each component on overall flow was calculated. Using the equations derived hydrogen and helium flow values were calculated from results for nitrogen and argon; deviation of calculated flow values from experimental results was less than ∼ 2%.

1H and 13C NMR analysis of the structure of chlorinated polyvinyltrimethyl silane

The structure of chlorinated polyvinyltrimethylsilane (CPVTMS) has been investigated by 1H and 13C NMR analysis. The NMR spectra of CPVTMS specimens were interpreted on the basis of the NMR spectra of model compounds, viz. chlorine derivatives of tetramethyl silane, and also in the light of calculations. It was found that chlorination covers only side groups of the polymer even when 2 Cl atoms per chain unit are introduced. On the basis of the data obtained it is concluded that very pronounced steric effects must be involved in the chlorination. Chemical shifts in the 13C NMR spectra have been tabulated for the chlorinated PVTMS and model compounds. Contents of six possible structures of chlorinated side groups have been calculated for chlorinated PVTMS with differing contents of Cl.

Physico-chemical analysis of the polyvinyltrimethylsilane mixture with cyclohexane and heptane

The temperature dependences of the heat content (C p=ƒ(T)) of polyvinyltrimethylsilane (PVTMS) binary blends with cyclohexane or heptane have been studied in an adiabatic vacuum calorimeter in the 80–300°K range. The C p=ƒ(T) diagrams showed glass transition of the cyclohexane or heptane solutions in the PVTMS and also crystallization, the solid-state transitions of the cyclohexane and heptane, and their melting when their contents in the blends with PVTMS exceeded solubility. The physical state diagrams were plotted for the above blends and allowed the determination of the number of such states, especially of the phases and of their physico-chemical nature as a function of the total mixture composition over a wide range of temperature.

Gas permeability of chlorinated polyvinyl trimethylsilane

By chlorination of polyvinyltrimethylsilane (PVTMS) by the action of molecular chlorine in a CCl 4 solution, initiated by visible light chlorinated PVTMS samples were obtained containing chlorine of n = 4·5, 18 and 78 Cl atoms per 100 Si atoms. Permeability factor P, coefficients of diffusion D and solubility σ of a number of gases (O 2, N 2, CH 4, C 2H 2, C 2H 4, SO 2, CH 3Cl, C 2H 3Cl) were determined with different degrees of chlorination. The rate of reduction of D with an increase in the degree of chlorination is dependent of the type of penetrating substance. For constant gases P decreases 4-fold with n = 78, whereas for SO 2, CH 3Cl and C 2H 3Cl P shows a much slighter dependence on n, which is due to the effect of the degree of chlorination of PVTMS on the coefficient of solubility of polar compounds.

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 effect of various factors on block copolymerization of nitrile monomers with vinyltrialkyl(aryl) silanes

A study has been made of the polymerization of acrylonitrile and methacrylonitrile by “living” polyvinyltrimethyl(phenyl)silane chains with lithium as the counter ion, in a hydrocarbon medium. It is shown the extent to which the original polyvinyltriorganosilane chains take part in formation of block copolymer increases as the concentration of initiator and nitrile monomer is increased. The efficiency of the macro-initiator is dependent also on its structure and on the nature of the polar monomer. It increases on passing from polyvinyltrimethylsilane to polyvinylphenyldimethylsilane “living” chains and from methacrylonitrile to acrylonitrile.