Polymerization phenylacetylene

The use of palladium(II) sulfoxide complexes as catalyst precursors for polymerization has met with mixed results thus a report of a palla-dium(II) chloride-dimethyl sulfoxide system as a catalyst precursor for phenylacetylene polymerization suggests similar results to those obtained using tin chloride as catalyst precursor (421). However, addition of dimethyl sulfoxide to solutions of [NH fPdCh] decreases the activity as a catalyst precursor for the polymerization of butadiene (100). Dimethyl sulfoxide complexes of iron have also been mentioned as catalyst precursors for styrene polymerization (141). 

We found in 1974 that phenylacetylene polymerizes with tungsten hexachloride (WC16) and molybdenum pentachloride (MoC15) 6). Since then, we have exploited new effective catalysts, and polymerized various substituted acetylenes. An account of the polymerization by Mo and W catalysts has been reported7). 

The first group of catalysts is just MoCls and WC16. These metal chlorides polymerize various monosubstituted acetylenes. Table 4 demonstrates that WC16 and MoCl5 are specifically effective for phenylacetylene polymerization among various transition metal chlorides. It is noted that NbCl5 and TaCl5 selectively cyclotrimerize phenylacetylene, and that other metal chlorides hardly induce any reactions. 

In general, acetylenes are more reactive than olefins in a coordination reaction since the former have stronger coordinating ability, while vice versa in an cationic reaction because of the higher stability of carbocations formed from olefins. In the copolymerization of phenylacetylene with styrene by WC16—Ph4Sn, essentially only phenylacetylene polymerizes 86). This result supports the idea that the present polymerization is a sort of coordination reaction. 

Various Rh(i) compounds such as [RhTp(GOD)] (Tp = tris(pyrazolylborate)) and [Rh(acac)GOD], which are almost inactive in GH2GI2, became active catalysts for phenylacetylene polymerization in chloride-free ILs such as [C4CiIm]BF4 and... 

Hori, H. Six, C. Leitner, W. Rhodium-catalyzed phenylacetylene polymerization in compressed carbon dioxide. Macromolecules 1999, 32, 3178—3182. 

Another appHcation for this type catalyst is ia the purification of styrene. Trace amounts (200—300 ppmw) of phenylacetylene can inhibit styrene polymerization and caimot easily be removed from styrene produced by dehydrogenation of ethylbenzene using the high activity catalysts introduced in the 1980s. Treatment of styrene with hydrogen over an inhibited supported palladium catalyst in a small post reactor lowers phenylacetylene concentrations to a tolerable level of <50 ppmw without significant loss of styrene. 

The nature of this interaction is not yet clear, but there is no doubt that this is a manifestation of a polymer-monomer interaction, typical of PCSs. The process of polymerization of phenylacetylene on free ions is characterized by the 6th order in initiator and monomer and has an activation energy of=25 kJ/mol (6 kcal/mol). 

To be eligible to living anionic polymerization a vinylic monomer should carry an electron attracting substituent to induce polarization of the unsaturation. But it should contain neither acidic hydrogen, nor strongly electrophilic function which could induce deactivation or side reactions. Typical examples of such monomers are p-aminostyrene, acrylic esters, chloroprene, hydroxyethyl methacrylate (HEMA), phenylacetylene, and many others. 

Oxidative polymerization of trans-bis-deprotected 79 under Hay coupling conditions [54] yielded, after end-capping with phenylacetylene, the high-melting and readily soluble oligomers 80a-e with the poly (triacetylene) backbone [87,106] (Scheme 8). Poly(triacetylene)s [PTAs,-(C=C-CR=CR-C=C) -] are the third class of linearly conjugated polymers with a non-aromatic allcarbon backbone in the progression which starts with polyacetylene [PA,... 

Some transition metal catalysts induce the living polymerization of various acetylenic compounds.68,69 Such polymerizations of phenylacetylene catalyzed by rhodium complexes are used in conjunction with a quantitative initiation and introduction of functional groups at the initiating chain end (Scheme 16).70 The catalyst is prepared from an [RhCl(nbd)]2/Ph2C=C(Ph)Li/PPh3 mixture and proceeds smoothly to give quantitatively the polymer 54 with a low polydispersity ratio. 

Poly (acetylenes) [16], There are several catalysts available for polymerization of substituted acetylenes. Whereas Ziegler-Natta catalysts are quite effective for polymerization of acetylene itself and simple alkylacetylenes, they are not active towards other substituted acetylenes, e.g. phenylacetylenes. Olefin-metathesis catalysts (Masuda, 1985 Masuda and Higashimura, 1984, 1986) and Rh(i) catalysts (Furlani et al., 1986 Tabata, 1987) are often employed. In our experience, however, many persistent radicals and typical nitrogen-containing functional groups serve as good poisons for these catalysts. Therefore, radical centres have to be introduced after construction of the polymer skeletons. Fortunately, the polymers obtained with these catalysts are often soluble in one or other organic solvent. For example, methyl p-ethynylbenzoate can be polymerized to a brick-coloured amorph- See the Appendix on p. 245 of suffixes to structural formula numbers. 

Note Normally inhibited with 8-12 ppm 4-7er7-butylcatechol to prevent polymerization. According to Chevron Phillips Company (March 2002), 99.93% styrene contains the following components (ppm) benzene (<1), toluene (<1), ethylbenzene (50), a-meth ylstyrene (175), m + p-xylene (120), o-xylene (125), isopropylbenzene (100), / -propylbenzene (60), m + p-ethyltoluene (20), vinyltoluene (10), phenylacetylene (50), m + p-divinylbenzene (<10), o-divinylbenzene (<5), aldehydes as benzaldehyde (15), and peroxides as benzoyl-peroxides (5). 

Oligomerization and polymerization of terminal alkynes may provide materials with interesting conductivity and (nonlinear) optical properties. Phenylacetylene and 4-ethynyltoluene were polymerized in water/methanol homogeneous solutions and in water/chloroform biphasic systems using [RhCl(CO)(TPPTS)2] and [IrCl(CO)(TPPTS)2] as catalysts [37], The complexes themselves were rather inefficient, however, the catalytic activity could be substantially increased by addition of MesNO in order to remove the carbonyl ligand from the coordination sphere of the metals. The polymers obtained had an average molecular mass of = 3150-16300. The rhodium catalyst worked at room temperature providing polymers with cis-transoid structure, while [IrCl(CO)(TPPTS)2] required 80 °C and led to the formation of frani -polymers. 

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