Acetylene-Type Monomers

Copolymerization of substituted acetylenes with MA has received sparse 

Copolymerization of phenylacetylene with MA have been achieved with both y radiation and free-radical initiation/ Using y radiation, the highest conversion was obtained for a phenylacetylene MA ratio of 1 2 (versus 1 1 and 3 1) and yields increased with dose (42-1 012 rads/s). When polymerized in dioxane with free-radical initiators, the rate was 0.83 with respect to initiator and independent of monomer concentration.When heated at 98 C for 6.5 h copolymer of high molecular weight (up to 10 ) was obtained.Studies on photochemically initiated polymerizations resulted in the relationship [77] = 6.5 x cm /g (acetophenone, 29.6°C).  

It is doubtful, based on other efforts, that alternating copolymer is produced. The material most probably contains some poly(phenylacetylene) blocks. Since MA forms a CTC with poly(phenylacetylene) and copolymerization of the two materials can occur, the product from phenylacetylene-MA copolymerization could have a very complex structure.  

For p-dimethylaminophenylacetylene, various monomer mixtures were found to undergo thermal polymerization to produce, in each case, a copolymer having a 2 1 molar ratio of MA p-dimethylaminophenylacetylene. Studies showed that both types of copolymers exhibited paramagnetic properties. 

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Metal-containing polymers are also applied to the catalysis of other processes such as polymerization and copolymerization of butadiene and isoprene (see, e.g., ref. (64)), oopolymerization of diene and olefin monomers and polymerization conversions of acetylene-type monomers (65). Such investigations are likely to be oriented both theoretically and practically. Metallopolymers can be used as advantage in some other catalytic processes (54), among them hydrogenation of imsaturated carpounds, oxidative conversions of hydrocarbons, in hydroformylation, polycondensation and other processes, etc. (Table 4). Catalysis of almost all reactions obeys the same or similar principles as in the case of polymerization. The position of metallopolymers in catalysis and their links with traditional catalysts can be illustrated as follows ... 

Different carbon black types, as described in Table 1, were compared concerning their activity in plasma polymerization with acetylene as monomer Acetylene-plasma deposition was carried out with a monomer pressure of 27 Pa, a RF power of 250 W, and a treatment time of 1 h. 

The formation of triazole rings by the reactions of azides and acetylenes was first described by Huisgen and coworkers [48,49] and has recently been promoted as dick chemistry by Sharpless et al. [50,51]. This versatile [3 + 2] dipolar cycloaddition proved to be useful for the synthesis of hyperbranched polytriazoles via 1,3-dipolar polycydoaddition of AB2-type monomers 28 and 29 (Scheme 14) [52], The monomers exhibited very high reactivity the... 

Metal complexes bound to a polymer support most frequently induce ionic polymerization of olefins, dienes and acetylenes, and less commonly radical polymerization of vinyl-type monomers, acting at all reaction stages initiation, chain propagation and termination. Active sites for the addition of monomer molecules to the growing polymer chain can in many cases be regenerated yielding new polymer chains (catalysis via a polymer chain). 

Rh complexes are examples of the most effective catalysts for the polymerization of monosubstituted acetylenes, whose mechanism is proposed as insertion type. Since Rh catalysts and their active species for polymerization have tolerance toward polar functional groups, they can widely be applied to the polymerization of both non-polar and polar monomers such as phenylacetylenes, propiolic acid esters, A-propargyl amides, and other acetylenic compounds involving amino, hydroxy, azo, radical groups (see Table 3). It should be noted that, in the case of phenylacetylene as monomer, Rh catalysts generally achieve quantitative yield of the polymer and almost perfect stereoregularity of the polymer main chain (m-transoidal). Some of Rh catalysts can achieve living polymerization of certain acetylenic monomers. The only one defect of Rh catalysts is that they are usually inapplicable to the polymerization of disubstituted acetylenes. Only one exception has been reported which is described below. 

The use of benzocyclobutene as the source of the diene in a Diels-Alder polymerization offers a unique solution to the problems described above. Benzocyclobutene containing monomers can be stored indefinitely at room temperature without concern for further advancement of the molecular weight. It is only when benzocyclobutene is heated to temperatures of approximately 200 °C that the reactive diene, o-quinodimethane, is formed at a significant rate and enters into reaction with the dienophile. The only requirement of the dienophile is that it must be stable at these temperatures and not undergo reaction with itself. The most common dienophiles that have been successfully used in the formation of polymers from AB type benzocyclobutene monomers have been acetylenes, olefins and maleimides. 

They can be used to initiate the polymerization of monomers on several centres simultaneously, i. e. for the preparation of star polymers. Delocalized carbanions of a different type are formed by the deprotonation of acetylene copolymers [198]... 

Multiple bonds between the atoms in the molecules of conventional monomers may possess a relative excess or deficiency of electrons. In principle, only a few of these bond types exist nitrile, aldehyde, carbonyl, carboxyl, ester, vinyl and acetylene. In macromolecular chemistry, the reactions of anions with oxiranes, the amide and ester (in rings) and the siloxane bond are also of importance. 

Another type of reactivity change of the centres was observed in the polymerization of acetylene and its derivatives. The generated chain with conjugated double bonds makes possible a far-reaching delocalization of the unpaired electron. The reactivity of the active centre decreases with chain length [35, 36], so that the number of monomer additions is limited. 

Cyclotrimerization of polyfunctional aryl acetylenes offers a unique route to a class of highly aromatic polymers of potential value to the micro-electronics industry. These polymers have high thermal stability and improved melt planarization as well as decreased water absorption and dielectric constant, relative to polyimides. Copolymerization of two or more monomers is often necessary to achieve the proper combination of polymer properties. Use of this type of condensation polymerization reaction with monomers of different reactivity can lead to a heterogeneous polymer. Accordingly, the relative rates of cyclotrimerization of six para-substituted aryl acetylenes were determined. These relative rates were found to closely follow both the Hammett values and the spectroscopic constants A h and AfiCp for the para substituents. With this information, production of such heterogeneous materials can be either avoided or controlled. 

Acetylene (HCsCH) and benzene are very similar in their LCVD characteristics. Both compounds form plasma polymers with the least amount of hydrogen production (type I monomer), and their characteristics of copolymerization with N2 and/or H2O are nearly identical if we consider that one molecule of benzene is equivalent to three molecules of acetylene. Analysis of the gas phase in both closed and flow systems are given in Tables 7.5 and 7.6. 

The third type of monomer among Si-containing monosubstituted acetylenes is o-(trimethylsilyl)phenylacetylene (3). 

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