Search

The impact of double bond modification by gem-difluorocyclopropanation (gDFC) in poly(norbornenes) backbone on their gas transport properties was studied for the first time. With this aim the research of gDFC of polynorbornene (PNB) and poly(5-trimethylsilylnorbornene) (PNBSi) in the conditions of sodium chlorodifluoroacetate thermolyses at 180–190 °C in methyl benzoate solution were carried out. The starting poly(norbornenes) were synthesized via ring-opening metathesis polymerization of the corresponding monomers mediated by the first generation Grubbs’ catalyst. The degree of double bonds conversion into the gem-difluorocyclopropane and the molecular weight of modified polymers could be controlled by adjusting the reaction time, sodium chlorodifluoroacetate amount, and polymer concentration in reaction mixture, as well as by addition of inhibitor. The bulky Me3Si-substituent hindered the modification of double bonds in poly(norbornenes)’ backbone. The gDFC decreased the thermal stability of poly(norbornenes). However, the films of modified polymers demonstrated high stability during storage at the ambient conditions, especially in comparison with unmodified polynorbornene. The introduction of gem-difluorocyclopropane in poly(norbornenes) backbone increased their gas permeability coefficients P especially strongly for PNB. Simultaneously the values of ideal selectivity αij = Pi/Pj were not changed or slightly increased. The noted growth of P was caused by increases in the solubility coefficients S. To elucidate the role of the two types of modification fragment ( CF2 and O ) of double bonds a sample was prepared that included both types of the fragments. It was distinguished by increased P and αij values. So, a new and simple approach improving the gas permeation properties of metathesis polynorbornenes was developed. It may be extendable to broader families of polydienes and other polymers containing double bonds in the backbone.

Crystallinity of statistical multiblock copolymers of norbornene and cyclooctene with nearly equimolar composition and different degrees of blockiness is studied by differential scanning calorimetry including thermal fractionation by successive self-nucleation and annealing and by X-ray diffraction. The copolymers are synthesized via recently invented reaction of polymer cross-metathesis, as a result of interchain exchange between polynorbornene and polyoctenamer in the presence of Grubbs’ catalyst of the first generation. This catalyst raises the fraction of trans-octenylene units up to more than 80% promoting formation of triclinic crystals. The copolymer degree of crystallinity and melting peak temperature decrease with the cross-metathesis conversion. At the same time the equilibrium melting temperature predicted by the Flory theory of copolymer crystallization is not much affected by the interchange reaction. Compared with the pure polyoctenamer or its equimolar blend with polynorbornene, the norborene-cyclooctene copolymers form considerably smaller crystallites. Thermal fractionation makes it possible to find their size distribution, which correlates with the average length of trans-octenylene blocks. Short annealing the multiblock copolymers above their melting points gives rise to a small but persistent endotherm 5–10 degrees above the annealing temperature, which is absent in polyoctenamer and, therefore, may indicate mixing of segregated norbornene and cyclooctene blocks.

Cross-metathesis of 5-hydroxycyclooctene and norbornene homopolymers affords the multiblock copolymer possessing a broad range in the degree of blockiness (from 0.03 to 1).

Heterochain polycarbosilanes are well-known materials possessed important properties. Some of their applications, such as gas separation membranes, require polymers with high molecular weight that provide good film-forming and mechanical properties. In this research, the synthesis of poly(1,1-dimethyl-1-silapentene) via the ring-opening metathesis polymerization (ROMP) of 1,1-dimethyl-1-silacyclopentene and the acyclic dienes metathesis (ADMET) of diallyldimethylsilane mediated by Ru-carbene Grubbs complexes 1st - 3rd generations as well as Hoveyda-Grubbs 2nd generation catalyst were studied for the first time. High molecular weight poly(1,1-dimethyl-1-silapentene) was synthesized by ROMP of 1,1-dimethyl-1-silacyclopentene. Varying the type and loading catalyst, temperature and monomer concentration, we obtained poly(1,1-dimethyl-1-silapentene) with Mw = 100–143 kDa, which is significantly higher (5–7 times) than that reached previously by olefin metathesis polymerization. The activities of 1,1-dimethyl-1-silacyclopentene and cyclopentene in ROMP were compared using 1H NMR monitoring the conversion of their double bonds. The ADMET polymerization of diallyldimethylsilane led to oligomers with the average polymerization degree not exceeded 4.4.

Polymers of different classes are considered as membrane materials for separation of hydrocarbons C1–C4. It has been known for a long time that solubility controlled permeation is characteristic of rubbery polymers and in particular of the most permeable rubber polydimethylsiloxane. The transport properties of these polymers are considered. Discovery of poly(trimethylsilyl propyne) and other polyacetylenes showed that similar properties can be revealed in glassy polymers. As is discussed in this review, the most important properties are reduction of the permeability of light components (CH4) in the presence of more condensable penetrant (C4H10) and higher selectivity of mixture separation as compared with ideal separation factors measured in the experiments with pure gases. Recently, two other classes of glassy polymers with solubility controlled permeation were discovered: addition type Si-containing norbornene polymers and metathesis polynorbornenes with flexible Si–O bonds in side groups. The transport properties of these novel polymers are considered in detail. It was shown that for the former group of norbornene polymers the reasons for solubility controlled permeation is great and opened porosity just as is the case for polyacetylenes. For the latter group, the presence of flexible Si–O bonds in side groups is responsible for their transport properties.

The transport parameters (permeability coefficients, separation factors) were determined for the separation of mixtures of n-butane and methane. The content of butane in the feed was in the range 3.7–7.9% and simulated the composition of associated petroleum gas. The experiments were carried out at room temperature and feed pressure of 2–6 atm. Novel membrane materials – poly(trimethylsilylnorbornene) and poly(bis-(trimethylsilyl)tricyclononene) – were studied in the form of dense films. Both polymers reveal a distinct solubility controlled permeation: the permeate streams were strongly enriched (up to 58%) with the heavier component (C4H10), the permeability of methane was reduced by a factor 3–4 as compared to the permeability of pure methane, and high permeability of butane was observed. Novel Si-containing poly(cycloolefins) as membrane materials were compared with high permeability polyacetylenes.

Addition polymerization and copolymerization of bis(Me3Si)-substituted norbornene-type monomers such as 5,5-bis(trimethylsilyl)norbornene-2, 2,3-bis(trimethylsilyl)norbornadiene-2,5 and 3,4-bis(trimethylsilyl)tricyclo[4.2.1.02,5]nonene-7, in the presence of Ni(II) naphtenate/MAO catalyst were studied. Disubstituted norbornene and norbornadiene were found to be practically inactive in homopolymerization. On the other hand, their copolymerization with norbornene proceeded with moderate yields of copolymers containing predominantly norbornene units. Under studied reaction conditions 2,3-bis(trimethylsilyl)norbornadiene-2,5 was transformed into the only exo-trans-exo-dimer as a result of the [2+2]-cyclodimerization reaction. Moving Me3Si-substituents one carbon atom away from norbornene double bond made 3,4-bis(trimethylsilyl)tricyclo[4.2.1.02,5]nonene-7 active in homopolymerization and allowed to obtain addition homo-polymer with two Me3Si-substituents in each elementary unit. The reaction mechanism and steric effect of Me3Si-substituents are also discussed.

Polymerization of norbornene bearing Si(CH 3 ) 3 groups in the five position with the opening of double bonds was performed. By accurate selection of the ratios catalyst/co-catalyst and monomer/catalyst the samples with increased molecular mass (about 400,000) were obtained. Transport parameters of this, addition type poly(trimethylsilyl norbornene) (PTMSN) were measured using the gas chromatographic and mass spectrometric methods for different gases (H 2 , He, O 2 , N 2 , CO 2 , CH 4 , C 2 H 6 , C 3 H 8 and n -C 4 H 10 ). Temperature dependence of the permeability coefficients ( P ) indicated that low activation energies of permeation ( E P ) and diffusion ( E D ) are characteristic for PTMSN. In some cases (CO 2 , C 2 H 6 ) negative E P values were observed. Thermodynamics of vapor sorption in this polymer was studied using the inverse gas chromatography method. It was shown that PTMSN is characterized by very large solubility coefficients S similar to those of poly(trimethylsilyl propyne) (PTMSP). The comparison of the P , D , and S values of these highly permeable polymers showed that the greater permeability of PTMSP is determined by the larger D values. Application of different approaches for the determination of the size of microcavities in PTMSN indicated that this polymer is characterized by large size of microcavity (800–1200 Ǻ 3 ).

Addition polymerization of 5-trimethylsilyl- and endo -, exo -5,6-bis(trimethylsilyl)-norbornenes was studied in the presence of Ni-based catalytic systems: [π-C 5 H 9 NiCl) 2 ]-Et 3 Al 2 Cl 3 , Ni(II) naphtenate-methylaluminoxane (MAO) and (π-C 5 H 9 NiCl) 2 -MAO. Completely saturated and soluble in aromatic solvents poly(5-trimethylsilyl-2-norbornene) was obtained with the yields up to 80%. In the course of the reaction exo -conformer was consumed much faster than endo -form independently of the type of catalytic system employed. Exo -, endo -5,6-bis(trimethylsilyl)-2-norbornene was practically inactive in the presence of the studied Ni-catalysts. At the same time its addition copolymerization with norbornene and 5- n -hexyl-2-norbornene could be readily realized.

Thermodynamics of sorption of n-alkanes C4–C11 in poly(5,6-bis(trimethylsilyl)norbornene) was studied using the Inverse Gas Chromatography (IGC). Temperature dependences of the specific retention volume Vg and solubility coefficient S of various alkanes were obtained in the range 60–140 °C. For solubility coefficients, the following equation holds: ln S = 3.44 ( T c / T ) 2 − 3.90 , where Tc is the critical temperature of solutes, T is the experimental temperature and S is expressed in cm3(STP)/cm3 atm. The partial molar enthalpies ΔHm and entropies ΔSm of mixing of different n-alkanes in this glassy polymer vary in much wider range than in rubbers and display positive correlations: for more exothermic mixing process the larger negative ΔSm values are observed. It was shown that the ΔHm in poly(5,6-bis(trimethylsilyl)norbornene) pass through a minimum, when the size of solutes increases. The coordinates of ΔHm at minimum versus solute size provide an estimate of the size of free volume elements in this polymer. This conclusion was supported by variation of permeability in different glassy polymers studied using IGC and by the results of other methods for probing free volume in glassy polymers.

Using ring opening metathesis polymerization (ROMP) the novel linear polynorbornadiene and polynorbornene (PNB) derivatives bearing silicon-containing moieties were prepared in the presence of RuCl 3 ·3H 2 O, RuCl 2 (PPh 3 ) 3 , and WCl 6 /tetramethyldisilacyclobutane catalysts with the yields up to 98%. Gas permeation properties (permeability and diffusion coefficients) of the polymers obtained were measured. It was shown that polynorbornadiene containing the Si(CH 3 ) 3 group has the transport parameters similar to those of poly(trimethylsilyl norbornene) studied earlier. On the other hand, PNB bearing two Si(CH 3 ) 3 groups in each repeat unit reveals much greater gas permeability induced mainly by increased solubility coefficients. The latter result is consistent with the much higher glass transition temperature of this polymer.

A new series of tricyclononene derivatives with two and three silyl groups are successfully synthesized via [2σ+2σ+2π]-cycloaddition of silylethylenes to quadricyclane. The activity of the silylethylenes in the cycloaddition reactions was estimated.