Metathesis ADMET polymerization

Acyclic diene molecules are capable of undergoing intramolecular and intermolec-ular reactions in the presence of certain transition metal catalysts molybdenum alkylidene and ruthenium carbene complexes, for example [50, 51]. The intramolecular reaction, called ring-closing olefin metathesis (RCM), affords cyclic compounds, while the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, provides oligomers and polymers. Alteration of the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

Olefin metathesis, an expression coined by Calderon in 1967,1 has been accurately described in Ivin and Mol s seminal text Olefin Metathesis and Metathesis Polymerization as the (apparent) interchange of carbon atoms between a pair of double bonds (ref. 2, p. 1). This remarkable conversion can be divided into three types of reactions, as illustrated in Fig. 8.1. These reactions have been used extensively in the synthesis of a broad range of both macromolecules and small molecules3 this chapter focuses on acyclic diene metathesis (ADMET) polymerization as a versatile route for the production of a wide range of functionalized polymers. 

K. B. Wagener, Acyclic Diene Metathesis (ADMET) Polymerization, in Synthesis of Polymers, A. D. Schluter (Ed.), Materials Science and Technology Series, Wiley, Weinheim, 1999. 

ADMET polymerization. See Acyclic diene metathesis (ADMET) polymerization... 

Wolfe and Wagener have developed main-chain boronate polymers (59) (Fig. 38) by the acyclic diene metathesis (ADMET) polymerization of symmetrical ,oj-dienes, containing both methyl- and phenyl-substituted boronate functionalities using Mo and Ru catalysts.84 The ring-opening metathesis polymerization (ROMP) of several norbornene monomers containing methyl- and phenyl-substituted boronates into... 

In the field of alkene metathesis ruthenium-allenylidene precursors have made, since 1998, an important contribution to catalysis [12, 31, 32], for the formation of cycles and macrocycles via RCM, ROMP and acyclic diene metathesis (ADMET) polymerization. 

However, the regio-random distribution of functional groups can be avoided by an acyclic diene metathesis (ADMET) polymerization technique using symmetric monomers (33). The molecular weights of these polymers are restricted to < 3 x 104 Dalton by ADMET. Due to their rich hydrocarbon content, the barrier properties in final ethylene vinyl alcohol copolymers are reduced. 

Acyclic diene metathesis (ADMET) polymerization of divinyl benzene, shown in Scheme 37, using an extremely reactive tungsten alkylidene catalyst (Schrock s catalyst) yielded PPV oligomers with DP of 8 [153]. In this example ethylene is formed as a side product of metathesis, and its removal by the use of high vacuum helps drive the polymerization in the forward direction. 

Fig. 1 Olefin metathesis reactions (a) ring-opening metathesis (ROM) and ring-closing metathesis (RCM), (b) self-metathesis (SM), (c) cross metathesis (CM), (d) ring-opening metathesis polymerization (ROMP), and (e) acyclic diene metathesis (ADMET) polymerization...

Cyclolinear carbosilane polymers with disilacyclobutane rings in the main-chain structure were prepared by means of acyclic diene metathesis (ADMET) polymerization of the corresponding l,3-dibutenyl-l,3-disilacyclobutanes in the presence of Grubbs catalyst (Scheme 13) <2003PP789, 2004MM5257, 2004PP118>. 

Olefin metathesis has quickly become one of the most widely used methods for mild carbon-carbon bond formation in organic synthesis [1,2]. With the development of highly active, fimctional group-tolerant catalysts, like Grubbs second generation catalyst ([Ru] ), metathesis has been successfully applied across many areas of research, and some reviews already exist that deal with metathesis catalysis and applications [1-5]. This review focuses on recent developments in acycUc diene metathesis (ADMET) polymerization chemistry and methodology that have been published over the past five years, starting with a short discussion on the history of olefin metathesis and ADMET polymerization. 

Matloka P (2004) The chemistry of latent reactive polycarbosUane/polycarbosUoxane elastomers via acyclic diene metathesis (ADMET) polymerization. Masters Dissertation, University of Florida, Gainesville, FL... 

Ring opening metathesis polymerization, which has been known since the discovery of the alkene metathesis reaction, has been given the acronym ROMP in recent years. In fact, the ROMP reaction was the first observation made in alkene metathesis chemistry, while the discovery of the exchange reaction in equation (1) actually occurred later. Acychc diene metathesis (ADMET) polymerization (equation 3) has only recently been shown to be a viable method for polymer synthesis, and it has been termed ADMET polymerization. ROMP reactions are driven by the release of ring strain from the monomer, while ADMET polymerization is driven by a shift in the equilibrium caused by the removal of one of the reaction products. 

ACYCLIC DIENE METATHESIS (ADMET) POLYMERIZATION CHEMISTRY... 

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]. 

Acyclic diene metathesis (ADMET) polymerization of dialkenyl-substituted oiganosilicon derivatives occurring in the presence of molybdenum, tungsten, and ruthenium alkylidenes has been commonly used for the synthesis of a wide range of linear unsaturated organosilicon polymers, e.g., polycarbosilanes, polycarbosiloxanes, and related polymers [1-8]. 

Lehman, S. E., Jr., Wagener, K. B. Catalysis in acyclic diene metathesis (ADMET) polymerization. (Late Transition Metal Polymerization Catalysis). 2003, 193-229... 

The next approach for obtaining higher molecular weight polymers was to explore acyclic diene metathesis (ADMET) polymerizations.The aim was to achieve higher molecular weight flame-resistant polymers. We modeled the reaction using aliphatic diene monomers such as 1,5-hexadiene and 1,9-deca-diene under test conditions to optimize conditions before making BPC-derived products. At this point, we decided to functionalize the BPC with an olefin. 

Wagener, K.B. Brzezinska, K. Acyclic diene metathesis (ADMET) polymerization Synthesis of unsaturated polyethers. Macromolecules 1991, 24, 5273-5277. 

Catalysis in Acyclic Diene Metathesis (ADMET) Polymerization... 

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