Metathesis condensation polymerization

Fig. 8.2 50 MHz NMR spectrum of the product of metathesis condensation polymerization of 4,4,7,7-tetramethyl-4,7-disiladeca-l,9-diene (Wagener 199If).

Keywords Acyclic diene metathesis polymerization, ADMET, Condensation polymerization Functionalized polymers, Negative neighboring group effect, Branched polyethylene... 

Smith Jr DW (1992) Unsaturated organosUicon polymers via acyclic diene metathesis (ADMET) condensation polymerization. PhD Dissertation, University of Florida, Gainesville, FL... 

These 1987 resnlts concluded that classical metathesis catalyst systems were not sufficient and that Lewis acid cocatalyst-free systems were necessary if successM ADMET condensation polymerization were to become a reality. The key to snccessM ADMET polymerization was demonstrated " nsing the Lewis acid-free tungsten alkylidene metathesis catalyst (5a), the structure of which had been reported by Schrock et just one year earlier. When this... 

J. G. Nel, Acyclic diene metathesis A new equilibrium step propagation, condensation polymerization, Ph.D. Dissertation, University of Florida, 1989. 

In a few words, the synthetic approaches can be presented as condensation polymerization, ring-opening metathesis polymerization and free and... 

Acyclic diene metathesis (ADMET) polymerization is an equilibrium step condensation during which the production and removal of C2H4 (when using terminal olefins) drive the reaction progress [18]. 

Olefin metathesis (OM) has proven to be one of the most important advances in catalysis in recent years based on the application of this chemistry to the synthesis of polymers and biologically relevant molecules [1-10]. This unique transformation promotes chain and condensation polymerizations, namely ring opening metathesis polymerization and acyclic diene metathesis polymerization (ADMET). Applications of metathesis polymerization span many aspects of materials synthesis from cell-adhesion materials [11] to the synthesis of linear polyethylene with precisely spaced branches [12]. 

Numerous friends and colleagues in the field of metathesis (the soldiers to whom we dedicate this book) have encouraged us to believe that a new book incorporating these recent developments would be both timely and welcome. We felt, however, that the book should still outline the historical development of the subject and not just be a supplement to the original book. This has necessarily meant some compression of earlier material and some restriction of discussion. The title has been expanded to include the words Metathesis Polymerization , which embraces not only ring-opening metathesis polymerization (ROMP), but also the metathesis condensation reactions of acyclic dienes (ADMET) and the addition reactions of acetylenes. The division of the material and the subjects of the chapters follow the same pattern as before. The literature has been covered up to mid-1996. 

The combination of a linear bifunctional telechelic precursor with a tricarboxylate counteranion produced a self-assembly that consisted of three polymer units and two counteranions under dilution. Subsequent heat treatment produced a pair of covalently fixed constitutional isomers, namely manacle-shaped and 0-shaped polymers (Scheme 18.3b) [6, 15]. These relevant pairs of polymeric isomers were formed from a self-assembly of two units of a three-armed star telechelic precursor and three units of a dicarboxylate counteranion [16], as well as from the double-metathesis condensation of an H-shaped telechehc polymer precursor having four alkene end groups (Scheme 18.3c) [17]. 

As has already been mentioned, divinyl silicon derivatives, similarly to monovinyl-substituted silicon compounds, are also completely inert to productive homometathesis, particularly as far as acyclic diene metathesis (ADMET) polymerization is concerned. However, we have shown in earlier reports that in the presence of ruthenium, rhodium and cobalt complexes containing or generating M-H and/or M-Si bonds, divinyl-substituted silicon compounds undergo de-ethenated (poly)condensation to yield a mixture of oligomers and cyclic unsaturated siloxanes, silazanes and caibosilanes, as shown in Scheme 2 [21-29]. 

Well defined high valent Schrock type carbene complexes of Mo or W with imido ligands are nowadays favoured as very active and selective catalysts for Ring opening Metathesis Polymerization (ROMP) and Acyclic Diene Metathesis Condensation (ADMET). Low valent Fischer type carbene complexes are less active and often need cocatalysts to enhance activities [1]. 

Using the above monomers several polymers have been prepared. Thus, monomer 46 has been polymerized by the acyclic diene metathesis polymerization method (ADMET) by using Grubb s catalyst to afford medium-molecular-weight polymers [41]. On the other hand, the reaction of the di-chloro derivative 42 with NaO- C6H4- -S02-C6H4-/7-0Na yields the polymer 49 (Fig. 4.23). Similarly the monomer 47 has been used in condensation polymerization with hexamethylenediisocyanate to afford the polyurethane 50. Polyimides such as 51 have been prepared by using monomer 48. 

Acyclic diene metathesis (ADMET) [75] is the process by which a transition metal catalyst leads to a stepwise condensation polymerization of diene monomers, characterized by loss of gaseous ethylene and the production of linear polyolefins containing regular unsaturations along the polymer backbone (Scheme 1.8). In fact, many of the polymeric structures accessible by ADMET can be made by alternate mechanisms (e.g., 1,4-polybutadiene made by ADMET polymerization of 1,6-hexadiene is more commonly made by the anionic polymerization of 1,4-butadiene). 

Tezuka, Y. and Ohashi, F. (2005) Synthesis of polymeric topological isomers through double metathesis condensation with H-shaped telecheUc precursors. Macromolecular Rapid Communications, 26,608-612. 

While ROMP chemistry is well understood, another means of producing polymers by metathesis has received less attention and is best described as acyclic diene metathesis (ADMET) polymerization. The chemistry, which also is illustrated in Figure 1, requires the condensation of an acyclic diene and produces a repeat unit which is identical to that generated by ROMP chemistry. The polymerization is driven by the removal of a small molecule. Figure 2 illustrates the structural change that occurs in diene monomers where the internal sp carbons form the link between growing monomer molecules, while the external sp carbons arc released as a small molecule. In this example ethylene is removed in order to drive this polymerization. The concept is not new, with results being published in the early 1970 s, yet all... 

Aqueous ring-opening metathesis polymerization (ROMP) was first described in 1989 (90) and it has been appHed to maleic anhydride (91). Furan [110-00-9] reacts in a Diels-Alder reaction with maleic anhydride to give exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3—dicarboxylate anhydride [6118-51 -0] (24). The condensed product is treated with a soluble mthenium(Ill) [7440-18-8] catalyst in water to give upon acidification the polymer (25). Several apphcations for this new copolymer have been suggested (91). 

Two-shot techniques for acyclic diene metathesis, 435-445 for polyamides, 149-164 for polyimides, 287-300 for polyurethanes, 241-246 for transition metal coupling, 483-490 Anionic deactivation, 360 Anionic polymerization, 149, 174 of lactam, 177-178 Apolar solvents, 90 Aprotic polar solvents, 185, 338 Aprotic solvents, low-temperature condensation in, 302 Aqueous coating formulations, 235 Aqueous polyoxymethylene glycol, depolymerization of, 377 Aqueous systems, 206 Ardel, 20, 22... 

The ruthenium catalyst system, 14, shown in Fig. 3, also carries out ADMET condensation chemistry, albeit with higher concentrations being required to achieve reasonable reaction rates [32]. The possibility of intramolecular compl-exation with this catalyst influences the polymerization reaction, but nonetheless, ruthenium catalysis has proved to be a valuable contributor to overall condensation metathesis chemistry. Equally significant, these catalysts are tolerant to the presence of alcohol functionality [33] and are relatively easy to synthesize. For these reasons, ruthenium catalysis continues to be important in both ADMET and ring closing metathesis chemistry. 

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