N. V. Ushakov

Synthesis and gas permeation properties of new ROMP polymers from silyl substituted norbornadienes and norbornenes

Abstract 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.

Ring-opening metathesis polymerization of substituted norbornenes

Abstract Ring-opening metathesis polymerization of a series of substituted norbornenes was carried out. Special attention was paid to the polymerization of monomers bearing silicon-containing groups, e.g., trimethylsilylnorbornene. Various heterogeneous and homogeneous tungsten-, rhenium- and ruthenium-based systems were used as catalysts. It was possible to obtain polymers of some norbornenes having reactive SiCl and SiOR bonds as well as groups capable of polymerizing via different mechanisms. The latter remained unchanged during the ring-opening of the norbornenes and could be used for the further modification of these polymers. Some data on the polymerization of various cycloolefin pairs are presented. It was found that some of the new silicon-containing polynorbornenes belong to the group of the most permeable and rather permselective polymers.

Metathesis of silicon-containing olefins

Abstract The behaviour of various olefins containing SiC, GeC, SiSi, SiH, SiOSi and SiOC bonds has been studied in the presence of rhenium on alumina metathesis catalysts. Monovinyl-, allyl-, and butenylsilanes bearing alkyl, alkenyl, aryl, aralkyl, silacycloalkyl, siloxane and hydride substituents, as well as unsaturated silacarbon heterocycles, mono- and diallylgermanes, were used as substrates. Heterogeneous Re 2 O 7 /Al 2 O 3 SnBu 4 and Re 2 O 7 /Al 2 O 3 PbEt 4 catalysts showing good activity in metathesis were examined. Except for hydrides, allyl- and butenylsilanes or germanes were active in metathesis regardless of the nature of the substituents at the metal atom. On the other hand, all of the vinylsilanes used were practically inactive in the reaction. Except for vinyl derivatives, metathesis of di- and polyalkenylsilanes, disilanes, disiloxanes and germanes occurred via both intermolecular and intramolecular pathways. These were used to develop a novel effective synthetic method for producing linear 1,4-bis(triorganylsilyl)- (or germyl-) but-2-enes (including those with ferrocenyl substituents at the silicon) and six-membered mono- and disilacycloalkenes, as well as silaspirane structures. It was shown that α-olefin co-metathesis with allylsilanes (followed by protodesilylation) is a convenient method for increasing the length of an α-olefin hydrocarbon chain.

Melting and recrystallization processes in a rubbery polymer detected by vapor sorption and temperature-modulated DSC methods

Series of successive absorption runs of n-hexane vapor in films of semi-crystalline poly(dimethylsilatrimethylene) at 25 °C are presented. Sorption overshoots were observed in the uptake kinetic curves of first series of absorption runs in as-prepared films. The said overshoots were absent in the second series of runs, conducted after desorption, while the sorption isotherms of the two series were identical. The overshoots are attributable to penetrant-induced melting and recrystallization phenomena. Strong support to this interpretation is given by temperature-modulated DSC data obtained from the pure polymer, which reveal similar thermally induced phenomena at slightly higher temperatures.

Polycarbosilanes Based on Silicon-Carbon Cyclic Monomers

This review is devoted to analysis of the scientific data concerning polycarbosilanes and some of their functional derivatives, primarily, published in the last ten years. The scope is limited to highly molecular weight products of the above-mentioned type, prepared via polymerization of cyclic monomers as the most effective and flexible synthetic approach. The chapter consists of two main parts: heterochain and carbochain polycarbosilanes. It includes description of ring-opening polymerization (ROP) via rupture of endocyclic Si–C bonds in strained silacarbocycles, ring-opening metathesis polymerization (ROMP) via rupture of endocyclic C = C bond in silylcycloolefins, and vinyl type addition polymerization (AP) of silylnorbornenes. The review pays much attention to structure and physical chemical properties of the obtained polymers as well as possible ways for their applications. The mechanisms of some polymerization processes are also discussed.

Synthesis of silicon-carbon spiranes by metathesis on an aluminumrhenium catalyst

Dialkenyl derivatives of i-silacyclobutane and 1-silacyclopent-3-ene with double bonds β- and γ- to the silicon atom undergo metathesis over an aluminumrhenium catalyst to give silaspirocyclic compounds and open-chain organosilicon trienes containing the silacyclobutane and silacyclopentene fragments. Metathesis of allylbutenyl derivatives of silacyclobutane and silacyclopentene provides a convenient synthetic route to 4-silaspiro[3,5]non-6-enes and 5-silaspiro[4,5]deca-2,7-dienes.

Metathesis of dialkenylsilanes and polymerization of 1,1-dimethyl-1-sila-3-cyclopentene in presence of aluminum-rhenium catalysts

Conclusions1.It was shown that the efficient metathesis of dialkenylsilanes of variable structure in the presence of aluminum-rhenium catalysts is possible.2.Conditions were found for the preparative synthesis of 4,9-disila-4,4,9,9-tetramethy1-1,6,11-dodecatriene and 1,1-dimethyl-1-sila-3-cyclohexene via the inter- and intramolecular metathesis reaction.3.1,1-Dimethyl-1-sila-3-cyclopentene polymerizes to a linear polysilapentenomer in the presence of Al-Re catalysts.

Polydimethylsilalkylene-dimethylsiloxanes as advanced membrane materials for thermopervaporative recovery of oxygenates from aqueous reaction media

Polydimethylsildimethylene-dimethylsiloxane (PSDMS) and polydimethylsiltrimethylenedimethylsiloxane (PSTMS) have been first studied as pervaporation membrane materials for the recovery of butanol from aqueous media. New synthesis procedures that make it possible to obtain the monomers 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane (1) and 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane (2) in high yields and with high purity required for subsequent polymerization have been developed. The optimum concentration of the crosslinking agent (tetraethoxysilane (TEOS)) of 5% has been found, which provides the maximum degree of crosslinking without sacrificing high values of separation factor and permeate flux. It has been shown that the permselectivity of PSDMS or PSTMS for butanol–water is higher by a factor of 1.5 or- almost 2, respectively, than the selectivity of the industrial membrane polymer, PDMS, at comparable values of the butanol permeability coefficient.

Synthesis and polymerization ofSi-substituted silacyclobutanes

The synthesis and polymerization of silacyclobutane derivatives with ferrocenyl, 9-carbazolyl, and pentafluorophenyl fragments in substituents have been carried out. The effect of the replacement of H atoms by F in pendant groups of the polysiltrimethylene main chain on the glass transition temperature has been studied.

Synthesis of polysiltrimethylenes with trimethylsilyl groups in the branch of the main chain

The thermally initiated and platinum-catalyzed polymerization of 1-silacyclobutanes with substitutents containing a trimethylsilyl group was carried out. Soluble, high-molecular-weight, heterochain siltrimethylene polymers were obtained, containing trimethylsilyl groups removed from the main chain by various bridges.