K. L. Makovetskii

Effects of cis-trans-configurations of the main chains of poly(trimethylsilyl norbornene) on its transport and sorption properties as well as free volume

Samples of poly(trimetylsilyl norbornene) having different content of cis configurations of double bonds in the main chains were prepared by ring opening metathesis polymerization in the presence of the catalysts characterized by different stereoselectivity (Re2O7, RuCI3, WCI6). It was shown that the polymer obtained in the presence of the WCI6 catalysts having the closest content of the cis-and trans-configurations is distinguished by the largest gas permeability, diffusion, and solubility coefficients. Determination of the parameters of gas sorption isotherms and estimation of free volume using group contribution and positron annihilation methods allowed to conclude that microstructure of this polymer (cis/trans ratio) affects its free volume and, therfore, its transport and thermodynamic properties.

Study of the reactions of biscyclopentadienylnickel with tin halides and their use for the polymerization of butadiene

1. The polymerization of butadiene in the presence of catalytic systems based on biscyclopentadienyl-nickel (CPN) and tin halides was studied. The CPN-SnX4 systems are catalytical active only in the presence of excess CPN. 2. In the interaction of CPN with SnCl4, there is a redox reaction, leading to the formation of SnCl2. A true polymerization catalyst arises in the reaction of excess CPN with SnCl2. 3. It was hypothesized that the cause of the increased content of 1,4-trans-units in polybutadiene, obtained in the presence of CPN and tin chlorides, is an electron-donor action of compounds of divalent tin.

Study of the reactions of bis-cyclopentadienyl-nickel with titanium and aluminum halides and their use for the polymerization of butadiene

1. In the interaction of CPN with AlBr3 and TiCl4, donor-acceptor type complexes are formed, in which both cyclopentadienyl groups are bonded to a nickel atom. These complexes induce stereospecific polymerization of butadiene and its copolymerization with styrene. 2. The reaction of C5H5NiCl · PPh3 with AlBr3 leads to the formation of the complex C5H5NiCl · AlBr3, which catalyzes the polymerization of butadiene. 3. The mechanism of the formation of π-allyl-type active centers, which catalyze stereospecific polymerization, was discussed on the basis of the experimental data.

Polymerization of cyclopentene by the WCl6-phenylacetylene system activated by oxygen-containing compounds

The authors find that the activity of the WC1/sub 6/-PA system in the polymerization of cyclopentene (CP) may be markedly enhanced by the addition of small amounts of various oxygen-containing compounds. These additives shorten the polymerization induction period to 5-10 min and permit one to obtain an equilibrium yield of the polypentenamer, which is 86% under the conditions employed. The activating role of the oxygen-containing compounds is apparently a consequence of their capacity to form a W=O bond upon interaction with reduced tungsten compounds obtained in the reaction of WC1/sub 6/ with the monomer and phenylacetylene.

Polymerization of methylcyclooctadienes with ring opening

Conclusions1.The polymerization of 1-methyl-1,5-cyclooctadiene using metathesis catalysts proceeds with opening of the ring exclusively at the unsubstituted double bond.2.We were the first to polymerize 3-methylcyclooctadiene and dimethyl-1,5-cyclooctadiene (mixture of 3,7- and 3,4-isomers) with opening of the ring to respectively give 1,4-polypiperylene and the alternating copolymer of piperylene with budadiene.3.The reaction of 1-methyl-1,5-cyclooctadiene with WCl6 in the absence of cocatalysts leads to the formation of active centers, which are capable of initiating the polymerization of cycloolefins with opening of the ring.

Polymerization of cycloolefins in the presence of catalysts containing tungsten halides and allylsilanes

1. Allyl compounds of silicon in combination with tungsten halides effectively catalyze the ring-opening polymerization of cycloolefins. 2. Polymerization of cyclopentene by the catalyst system WCl6-tetraallylsilane between -20 and -78°C forms a polypentenamer with 94–99% cis-units. 3. We have studied the polymer-monomer equilibrium in the cis-polymerization of cyclopentene by the WC16- tetraallylsilane system and have determined some thermodynamic parameters for the process.

Role of carbene complexes in chain initiation and propagation of double-boot redistribution reactions

1. Catalytic decomposition of aliphatic diazo compound under the effect of tungsten chlorides leads to initiation of the chain process of opening of cycloolefins. 2. The possibility was shown on the example of the organotungsten compound (CH3)3SiCH2-WCl5 of using oxidation-reduction systems to generate carbene active centers at low temperatures. 3. Certain aspects of the chain stage of the double-bond redistribution process were examined in connection with the relative reactivity of carbene active centers.