Polymerization aliphatic acetylenes

In the metal carbonyl catalysts, the use of a catalytic amount of Ph2CCl2 enables the omission of CGI4. For example, the polymerization of phenylacetylene with W(CO)6 in the presence of Ph2GGl2 in toluene upon photoirradiation proceeds homogeneously to give a polymer with of ca. 2 x 127,128 MW polymers > 10 ) are attainable from sterically bulky aromatic and aliphatic acetylenes. It is also effective to use a catalytic amount of Lewis acids instead of GGI4 in the M(GO)6-based catalysts (M = W, Mo). ... 

The Pd clusters have been produced by a recently developed high-frequency laser evaporation source, ionized, then guided by ion optics through differentially pumped vacuum chambers and size-selected by a quadrupole mass spectrometer [16-18]. The monodispersed clusters have been deposited with low kinetic energy (0.1-2 eV) onto a MgO thin film surface. The clusters-assembled materials obtained in this way exhibit peculiar activity and selectivity in the polymerization of acetylene to form benzene and aliphatic hydrocarbons [30]. 

Table 5 lists representative examples of polymerization of monosubstituted acetylenes, catalysts, and MWs of the polymers formed. Mo, W, and Rh catalysts, all of which involve transition metals, are particularly effective. Whereas Mo and W catalysts are sensitive to polar groups in the monomers, Rh catalysts are tolerant to such groups. Mo and W catalysts are effective toward sterically aowded monomers, while Rh catalysts are rather restricted to a particular type of monomers including propargyl esters, N-propargylamides, alkyl propio-lates, and PAs. Fe and Pd complexes are also useful in some cases. It is noted that not only sterically unhindered monomers but also very aowded ones afford high-MW polymers with W and Mo catalysts. An overview of typical monosubstituted acetylene monomers such as aliphatic acetylenes, ring-substituted PAs, and other aryl acetylenes is presented below. 

Butadiene is available commercially as a liquefied gas underpressure. The polymerization grade has a minimum purity of 99%, with acetylene as an impurity in the parts-per-million (ppm) range. Isobutene, 1-butene, butane and cis-l- and Zrc//7.s-2-butcnc have been detected in pure-grade butadiene (Miller, 1978). Typical specifications for butadiene are purity, > 99.5% inhibitor (/c/V-butylcatecliol). 50-150 ppm impurities (ppm max.) 1,2-butadiene, 20 propadiene, 10 total acetylenes, 20 dimers, 500 isoprene, 10 other C5 compounds, 500 sulfur, 5 peroxides (as H2O2), 5 ammonia, 5 water, 300 carbonyls, 10 nonvolatile residues, 0.05 wt% max. and oxygen in the gas phase, 0.10 vol% max. (Sun Wristers, 1992). Butadiene has been stabilized with hydroquinone, catechol and aliphatic mercaptans (lARC, 1986, 1992). 

One of the characteristic features of the metal-catalysed reaction of acetylene with hydrogen is that, in addition to ethylene and ethane, hydrocarbons containing more than two carbon atoms are frequently observed in appreciable yields. The hydropolymerisation of acetylene over nickel—pumice catalysts was investigated in some detail by Sheridan [169] who found that, between 200 and 250°C, extensive polymerisation to yield predominantly C4 - and C6 -polymers occurred, although small amounts of all polymers up to Cn, where n > 31, were also observed. It was also shown that the polymeric products were aliphatic hydrocarbons, although subsequent studies with nickel—alumina [176] revealed that, whilst the main products were aliphatic hydrocarbons, small amounts of cyclohexene, cyclohexane and aromatic hydrocarbons were also formed. The extent of polymerisation appears to be greater with the first row metals, iron, cobalt, nickel and copper, where up to 60% of the acetylene may polymerise, than with the second and third row noble Group VIII metals. With alumina-supported noble metals, the polymerisation prod-... 

As for the polymerization of unsaturated aliphatic compounds (olehns, diol ns and acetylene derivatives), due to their high intrinsic reactivity, their polymerization is extremely rapid, even at low temperatures. However, since these reactions represent the reverse of cracking, they are not favored from the thermodynamic standpoint in the operating cooditions of pyrolysis. 

Character of Center Nucleus.—As was stated in connection with anthracene itself we can not say positively as to the character of the center nucleus in either the hydrocarbon or the quinone. In anthracene the aliphatic character of this center nucleus is indicated by its formation from an ethane residue, by the tetra-brom ethane synthesis. This does not, however, preclude the possibility of its becoming a true benzene nucleus when condensed with two benzene rings, for benzene itself may be made from aliphatic hydrocarbons, from acetylene by polymerization (p. 478), and from hexane through hexa-methylene with the loss of hydrogen after the formation of the cyclo-paraffin (p. 469). Also naphthalene, in which there is no doubt of the benzene character of the two nuclei, may have one nucleus formed from an aliphatic chain as in the syntheses given (p. 767) from phenyl butylene bromide, from phenyl vinyl acetic acid and from tetra-carboxy ethane. In the same way the facts in regard to anthraquinone do not prove... 

The development of unsaturated polyanhydrides responded to the necessity of improving the mechanical properties of the polymers in applications such as the temporary replacement of bone. " Unsaturated polyanhydrides, prepared by melt or solution polymerization, include homopolymers of fumaric acid (FA), acetylene-dicarboxylic acid (ACDA), and 4,4 -stilbenzenedi-carboxylic acid (STDA). The chemical structures of poly(FA) and poly(ACDA) are shown in Table 1. These polymers are highly crystalline and insoluble in common organic solvents. The double bonds of these monomers make them suitable for further crosslinking to improve mechanical properties of polyanhydrides. When copolymerized with aliphatic diacids, less crystalline polymers with enhanced solubility in chlorinated solvents result. 

Another approach, which does not make use of either free or controlled radical polymerization, was demonstrated by Parrish et al. [20]. An aliphatic polyester with pendent acetylene groups was prepared via controlled ring-opening polymerization. Polyethylene glycol and the peptide sequence Gly - Arg - Gly - Asp - Ser (GRGDS) were functionalized with an azide moiety, and subsequently clicked to the pendent acetylenes in the... 

Acetylene, polymerization, 433-34 Acrylic polymers, 105 Aliphatic acid esters of wood,... 

Soon after the first preparation of vinyl acetate by the reaction of acetic acid with acetylene and its polymerization by Klatte [209] in 1912, methods for its industrial-scale synthesis were developed first in Germany, then in Canada [210]. At the same time, the chemistry was extended to the preparation and polymerization of vinyl esters of other aliphatic and aromatic carboxylic acids. The new polymers found immediate uses in paints, lacquers, and adhesives. Steady improvements in the industrial-scale monomer synthesis, particularly in the discovery of new catalysts for the acetic acid-acetylene condensation and development of a low-cost synthesis route based on ethylene have made vinyl acetate a comparatively inexpensive monomer. Besides the original applications, which still dominate the major uses of poly(vinyl acetate), this polymer finds additional utility as thickeners, plasticizers, textile finishes, plastic and cement additives, paper binders and chewing gum bases, among many others. At the same time, the uses and production of polymers of the higher vinyl esters have not kept pace with that of poly(vinyl acetate), primarily due to their higher cost. Consequently, the current worldwide production of these materials remains low. 

A novel acetylene monomer containing a cyanoterphenyl group, namely, l-[(4 -cyano-4-terphenyl)oxy]-3-octyne, has been polymerized with WCl6-Ph4Sn catalyst to yield a liquid crystalline aliphatic polyacetylene (54 in Figure 17). Polymer... 

The addition of carbamates to acetylene itself was also possible in the presence of ruthenium catalysts, namely RUCI3.3H2O and the polymeric [RuCl2(norbor-nadiene)] but in relatively modest yields of 10-46% [28, 29]. The formation of vinyl carbamates is restricted to terminal alkynes, which is in line with the formation of a metal vinylidene intermediate, and also to secondary amines. However, a catalytic reaction also took place under similar conditions with primary aliphatic amines but it led to the formation of symmetrical ureas [30, 31]. The catalytic system generated in this case is thought to proceed via a ruthenium vinylidene active species and is very efficient for the formal elimination of water by formation of an organic adduct. The proposed general catalytic cycle, which applies for the formation of vinyl carbamates and ureas, is shown in Scheme 7. 

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