P. P. Chapala

New stationary phases for gas chromatography based on polymers with intrinsic porosity

Norbornene polymers with intrinsic porosity were investigated as candidates for polymeric stationary phases in capillary GC. Kinetic and thermodynamic characteristics of the stationary phases were evaluated and turned out that only polymer with vicinal distribution of trimethylsilyl groups (polymer II) provided properties making it potential candidate for application in capillary GC. Columns with stationary phase based on polymer II demonstrated unique selectivity, moderate thermostability and efficiency better than previously studied columns with stationary phase based on poly[(1-trimethylsilyl)-1-propine].

The equilibrium and kinetic rigidity of additive poly(trimethylsilyltricyclononenes) with one and two Si(CH3)3 groups in monomer unit

The homologous series of additive poly[3-(trimethylsilyl)tricyclononene-7] with two heminal substituents Si(CH3)3 in the side cycle of the monomer unit is studied for the first time via the methods of viscometry and static and dynamic light scattering in the range of molecular masses of (29–770) × 103. The scaling ratios for the intrinsic viscosity and the coefficient of translational diffusion of macromolecules in toluene at 298 K are obtained, and the equilibrium rigidity of the polymer chain is determined. The hydrodynamic and conformation properties of the polymer are compared to an analog with only one Si(CH3)3 substituent in the monomer unit. It is found that the introduction of the second side substituent in the heminal position increases the equilibrium rigidity of the additive poly[3-(trimethylsilyl)tricyclononene-7] by 1.4 times and has a far stronger effect on the kinetic rigidity of the polymer. With the use of the 1Н NMR relaxation method, it is shown that the mobility of side groups of the polymer with two substituents decreases significantly and the correlation times of hydrogen atoms of Si(CH3)3 groups exceed some 20 times the corresponding values for the analog with one Si(CH3)3 group in the monomer unit cycle.

Additive poly[3-(trimethylsilyl)tricyclononene-7]: Molecular properties and chain rigidity

With the use of the methods of hydrodynamics, the Kerr electrooptical effect, and dielectric polarization in solution, the molecular properties of a homologous series of poly[3-(trimethylsilyl)tricyclononene-7] samples synthesized via additive polymerization have been studied. Scaling relationships that describe how the intrinsic viscosities, diffusion coefficients, and sedimentation coefficients of macromolecules depend on their molecular masses in toluene at 298 K have been obtained. It has been shown that the additive poly[3-(trimethylsilyl)tricyclononene-7] has enhanced kinetic chain rigidity. According to hydrodynamic data, the length of the Kuhn segment for this polymer does not exceed 6.0 ± 0.6 nm, while the kinetic fragment estimated from electrooptical data is 4.3 nm. In terms of kinetic properties, the studied polymer is similar to wellknown poly[1-(trimethylsilyl)-1-propyne], with the specific morphology of its highly permeable films being determined by the large-scale mechanism of chain orientation.

Experimental and Theoretical Study of [2σ + 2σ + 2π]–Cycloaddition of Quadricyclane and Ethylenes Containing Three Silyl-Groups

The reaction of [2σ + 2σ + 2π]-cycloaddition of quadricyclane with olefins is an attractive way for regio- and sterospecific synthesis of norbornene derivatives (exo-tricyclononenes) with desired substituents. The presence of Cl3Si-containing groups in such compounds permits different monomer modifications for the development of new materials. Herein, for the first time the theoretical and experimental study of the behavior of different ethylenes containing three silyl-groups in the reaction of [2σ + 2σ + 2π]-cycloaddition with quadricyclane was systematically performed. Based on the data obtained for this reaction the activity scale of the ethylene derivatives was established, and the explanations for an ethylene activity were suggested. As a result, a new family of Si-containing tricyclononenes was successfully synthesized. As an example of a possible modification, the methylation of the sterically hindered cycloadducts was investigated and the conditions for full methylation were found. Considering that gas permeability of polymers increases with the increase of a number of the side Me3Si-groups, the compounds are interesting monomers for synthesis of membrane polymers possessing high gas permeability values.

Molecular Properties of Additive Poly(bis(trimethylsilyl)tricyclonones) with Vicinal and Geminal Side Substituents

The molecular properties of the additive poly(bis(trimethylsilyl)tricyclononene) with the vicinal position of two side groups Si(CH3)3 in the monomer unit are studied for the first time, and its conformational and kinetic properties are compared with those of the isomer with the geminal position of the same groups. Using the methods of static/dynamic light scattering and viscometry for the samples of the vicinal isomer, the hydrodynamic parameters of molecules are determined and their molecular mass dependences in toluene are ascertained. In addition, the Kuhn segment length of this isomer is estimated. The kinetic rigidity of vicinal and geminal isomers is evaluated by 1H NMR relaxation from the mobility of protons in Si(CH3)3 groups. The reasons behind different gas permeabilities of the films based on the polymers with the vicinal and geminal positions of Si(CH3)3 side groups in the monomer unit are discussed.

Microporous structure of highly permeable additive silicon-containing polytricyclononenes

The porosity of a number of additive silicon-containing polytricyclononenes from the class of highly permeable polymers has been systematically studied for the first time by the method of low-temperature nitrogen adsorption/desorption. It has been shown that these polymers have a large specific surface area (390−790 m2/g) and are microporous. Dominant pore size ranges from 7 to 10 A depending on the number of Me3Si groups in a monomer unit and their relative position.

Kinetics and thermochemistry of [2π + 2σ + 2σ]-cycloaddition of quadricyclane to tetracyanoethylene

Kinetic data for the unusual [2π + 2σ + 2σ]-cycloaddition of quadricyclane to tetracyanoethylene in toluene have been obtained for the first time. The same reaction in 1,4-dioxane appears to be the most exothermic among known cycloaddition reactions. The entropy of activation and reaction volume differ only slightly from the corresponding parameters of conventional Diels–Alder reactions.

Synthesis of 3,4-dihydroxyphenyl-containing polymeric materials from 1,2-polybutadiene and eugenol via thiol—ene addition

In a search for routes to new promising adhesive materials, 3,4-dihydroxyphenyl groups were introduced for the first time into syndiotactic polybutadiene (1,2-unit content >90%). Two ways of introduction were studied: cross metathesis and thiol—ene addition. Eugenol, an available product of plant origin, was used as a source of 3,4-dihydroxyphenyl groups following the protection of its oxygen-containing groups with Et3SiH in the presence of B(C6F5)3) as a catalyst. A cross metathesis reaction of polybutadiene with modified eugenol in the presence of the Grubbs catalysts of different generations resulted in considerable degradation of the polymer into the corresponding low-molecular-weight products. A new approach involving thiol—ene addition afforded 3,4-dihydroxyphenyl-containing polybutadienes with desired catechol contents and desired molecular weights.

New composites based on poly(3-trimethylsilyltricyclononene-7) and organic nature fillers (calixarenes & cyclodextrins)

Herein we describe new materials for membrane gas separation process with improved selectivities towards different pairs of gases. Organic nature fillers (modified calix[4]arenes, calix[8]arenes and modified α-, β-, γ-cyclodextrins) were used as additives to poly(trimethylsilyltricyclononene-7) (PTCNSi1)in order to study correlations between structure of the filling agent and gas transport parameters of the composite membranes. It was shown a positive influence of calixarenes and cyclodextrins as additives on permselectivity of the membranes. For instance, selectivity towards H2/CH4 gas pair increased almost in 2.4 times when calix[4]arene with Et- and tert-Bu- group was introduced into polymeric matrix. Detailed study of the PTCNSi1 adsorbtion/desortion data is presented. The obtained composites were characterized by TEM, WAXD, PALS and BET analysis.

Chromatographic determination of the diffusion coefficients of light hydrocarbons in polymers

Gas-chromatographic determination of the diffusion coefficients that allows for the compressibility of the mobile phase has been suggested. The diffusion coefficients were determined for light hydrocarbons С1–С4 in four polymers with a high free volume, which are candidates for use as gas-separating membranes. The diffusion coefficients calculated from chromatographic data were shown to be one or two orders of magnitude smaller than the values obtained by the membrane method. This may be due to the presence of an additional flow through the membrane caused by the pressure gradient across the membrane in membrane methods.