Polymerization of Monoolefins

Egloff, G. Davis, R.F. Polymerization of monoolefins with solid phosphoric acid, XII International Congress of Pure and Applied Chemistry, New York, 1951 10-13. 

In the polymerization of ethylene by (Tr-CjHsljTiClj/AlMejCl [111] and of butadiene by Co(acac)3/AlEt2Cl/H2 0 [87] there is evidence for bimolecular termination. The conclusions on ethylene polymerization have been questioned, however, and it has been proposed that intramolecular decomposition of the catalyst complex occurs via ionic intermediates [91], Smith and Zelmer [275] have examined several catalyst systems for ethylene polymerization and with the assumption that the rate at any time is proportional to the active site concentration ([C ]), second order catalyst decay was deduced, since 1 — [Cf] /[Cf] was linear with time. This evidence, of course, does not distinguish between chemical deactivation and physical occlusion of sites. In conjugated diene polymerization by Group VIII metal catalysts -the unsaturated polymer chain stabilizes the active centre and the copolymerization of a monoolefin which converts the growing chain from a tt to a a bonded structure is followed by a catalyst decomposition, with a reduction in rate and polymer molecular weight [88]. 

Alcock and coworkers studied the polymerization of butadiene (as well as of monoolefins, acetylene and aromatic olefins) trapped within the tunnel clathrate system of tris((9-phenylenedioxy)cyclotriphosphazene, induced by Co-y-radiation. The host was used in order to find if the concatenation and orientation of the monomer molecules under the steric forces generated within the host crystal lattice will lead to stereospecific polymerization. The clathrate was prepared by addition of liquid butadiene to the pure host at low temperature. The irradiation was conducted at low temperatures. Irradiation of pure butadiene (unclathrated bulk monomer) leads to formation of a mixture of three addition products f,2-adduct, cis- and trons-f,4-adducts. In contrast, the radiation-induced polymerization within the tunnel system of the host yielded almost pure trans-1,4-polybutadiene. A small percentage of f, 2-addition product was observed, but no evidence for the formation of c/s-f,4-adduct was found, confirming the earlier observation by Fin ter and Wegner. The average molecular weight was about 5000,... 

Ethylene-propylene elastomers are made by solution polymerization of ethylene and propylene in a solvent such as hexane using Ziegler-Natta catalysts. EPDM terpolymers can be similarly made by adding 3 to 9% of any of the above dienes to the monoolefin mixture. 

Continuous Polymorization. A process for continuous polymerization of VF in aqueous medium has been described (76,78). A mixture of VF, water, and a water-soluble catalyst is stirred at 50-250°C and 15-100 MPa (150-1000 atm). A small amount of a monoolefin (C1-C3) is continnonsly introduced into the reactor to inhibit the bulk polymerization of VF to low molecular weight polmer. The water-soluble catalyst generates free radicals, which initiate the polymerization. Catalysts include ammonium persulfate, organic peroxides, and water-soluble azo initiators. In a two-stage continuous polsrmerization the polymer particles formed in the first stage act as nucleation sites for the second reaction zone (88). 

Homooligomerization of alkynes using palladium chloride as catalyst has been studied extensivelyHowever, few examples are known of cooligomerization of alkynes and monoolefins probably because of the difficulty due to the large difference in coordinalion ability between alkynes and alkenes to the metal center alkynes are more reactive to metals than alkenes are, which results in exclusive polymerization of the alkynes. Therefore, in order to accomplish the cooligomerization of alkynes and alkenes, it is very important to select suitable alkynic or alkenic compounds with similar orders of coordination ability to a metal, or to devise reactive conditions in which extensive alkyne polymerization is prevented. 

Concentrated sulphuric acid has been initially used for dimerization and oligomerization of cyclic monoolefins such as cyclohexene and diolefins such as cyclo-pentadiene, and later on for indene-coumarone fractions. Diluted sulphuric acid and benezenesulpho-nic acid have been further employed for the polymerization of more active cycloolefins like norbornene and dicyclopentadiene. In these reactions, monomer conversion, product yield and molecular mass depended largely on the acid concentration and monomer nature as well as on the other reaction parameters. Various compositions of initiators containing sulphuric acid in association with phosphoric acid, boric acid, sulphonic acids or inorganic sulphates of the type M (S04) (M = Al, Cr, Mg, Co, V) have also been reported for the polymerization of unsaturated alicyclic and cyclic fractions and for reactions with heavy aromatic fractions in hydrocarbon resin synthesis [2]. 

Loeb, W. E., Union Carbide Corp., Polymerization of a-Monoolefins in an Aqueous Diluent,... 

Butadiene and isoprene can be considered as both vinyl substituted 1.2 monoolefins and as 1.4 conjugated diolefins which can compete in polymerization. In this section we shall consider the conjugated dienes as vinyl substituted ethylenes which are polymerized to 1,2 (3—4)poly-dienes in competition with 1—4 polydienes of section III. 

Monomeric alkyl lithium polymerizes isoprene through an anionic type propagating species. The transition between cis 1,4 and trans 1,4 polymerization is not clear since mono-ene polymerization also occurs in this region. Increased dielectric constant of the media, the addition of ethers, or the use of high lithium alkyl concentrations increased the character from that weakly anionic for the cis-diene polymerization to the slightly more anionic requirements for 3.4-monoolefinic polymerizations. 

The most thoroughly investigated group of organolanthanide-catalyzed reactions are monoolefin transformations. These include the following processes a) hydrogenation, b) oligomerization, c) polymerization, d) hydroamination, e) hydrosilylation, and f) hydroboration, which will be discussed in the above order. 

Monoolefins higher than ethylene do not undergo a polymerization reaction of this type. Instead such compounds prefer to function as chain-transfer agents as do alkylaromatic compounds (5). 

The tendency to form carbonaceous deposits is increased as the hydrogen content of the nonaromatic hydrocarbons is lowered. Thus, it has been shown (Greensfelder and Voge, 13) that butadiene and iso-prene undergo more pronounced hydrogen transfer and polymerization than the corresponding monoolefins. The carbon formation amounted to 14 per cent in the case of isoprene, as compared with 6 per cent for n-pentenes. 

IV to VIII metals and base metal alkyls of Group II or III metals (Penczek and Premia, 2012 Boor, 1979 Ciardelli, 1992). It arose from the spectacular discovery of Ziegler et al. (1955) that mixtures of titanium tetrachloride and aluminum alkyls polymerize ethylene at low pressures and temperatures and from the equally spectacular discovery by Natta (1955) that the Ziegler catalysts can stereospecifically polymerize monoolefins to produce tactic, crystalline polymers. As can be imagined, these systems can involve many combinations of catalyst components, not all of which are catalytically active or stereospecific. However, we shall be concerned here only with polymerizations involving the commercial elastomers, principally polyisoprene, polybutadiene (Duck and Locke, 1977 Zohuri et al., 2012 Teyssie et al., 1988), and the ethylene-propylene copolymers (Schobel et al., 2012 Ver Strate, 1986 Davis et al., 1996 Noordermeer, 2003 Baldwin and Strate, 1972). 

Lehr, M. H. The active oxidation state of vanadium in soluble monoolefin polymerization catalysts. 

The copolymerization of nonconjugated dienes with monoolefinic vinyl monomers is also known.Depending upon the comonomer pair and the copolymerization conditions, the product copolymer may contain (1) cyclized units made from sequential addition of both ends of the diene monomer (2) cyclized units made from addition of one end of the diene followed by the monoolefin comonomer or one side of a second diene, followed by the other end of the first diene (3) non-cyclized diene units bearing pendant olefins, and (4) crosslinked dienes formed by incorporation of these pendant olefins into another polymer chain (Scheme 19.1). For symmetrical, nonconjugated dienes, it has been shown that all of the well-known methods of polymerization can be employed to... 

The monomer 7-methylnorbornadiene (7-MeNBD) also undergoes polymerization in the presence of several conventional metathesis catalysts to form poly(7-MeNBD). It is noteworthy that the catalyst OSCI3 (in 1 1 EtOH/PhCl) leads to polymer stereochemistry that is significantly different from that of poly(fl fi-7-MeNB). The OsC -derived polymer of the monoolefin contains predominantly atactic trans olefin structures, whereas the analogous diolefin polymer is composed of nearly exclusively cis alkene structures (97%) and predominantly syndiotactic dyads (r m = 75 25 through the NMR signals of the methyl substituent at 8 16.2-17.0 ppm)." The catalysts Reds... 

The copolymerizations between monoolefins and dienes have been considered to be of practical and theoretical importance. As reported in the literatures ethylene-butadiene and propylene-butadiene copolymers can be prepared with conventional Ziegler-Natta titanium-based or vanadium-based catalysts. The copolymer composition and monomer sequence distribution strongly depend on the catalyst system and polymerization conditions. Alternating copolymers were synthesized when the catalyst components were mixed at the... 

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