Olefin metathesis polymerization

Olefin metathesis is an important polymerization reaction that is particularly useful for cyclic compounds containing a double bond. Before going through this let us look at the olefin metathesis reaction. The latter can be represented by the following simple reaction [1-5] (see Eq. 2.28). 

The product in this reaction appears to arise as a result of splitting the reacting olefins exactly into two equal halves and allowing them to join again. This reaction is reversible and several versions are now known. 

The use of ROMP has been widely applied. Thus, cyclopentene can be polymerized by olefin metathesis to a linear pol5mier. In this reaction the cyclic hydrocarbon is opened up by the catalyst and joined together in a linear fashion (see Eq. 2.34). The catalysts that perform this operation are called ring-opening metathesis catalysts. 

Representative examples of the recent generation of metathesis catalysts are shown below (Fig. 2.29). Notice that these transition-metal derivatives contain an M=C bond. Such compounds are known as metal carbenes [18-20]. 

The mechanism of the olefin metathesis polymerization involves (a) an initial 2+2 cyclo-addition of a metal carbene with the cyclic olefin. This leads to the formation of a four-membered metallacyclobutane. The next steps (b) (c) and (d) show the polymer propagation reactions (Fig. 2.30). 

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Synthesis of Block Copolymers by Olefin Metathesis Polymerization... 

Recent examples of the first route have been described by Kobayashi and coworkers, who reported the synthesis and characterization of polymeric Pcs obtained through the olefin metathesis polymerization of terminal olefin groups in the side chains of unsymmetrical Pc monomers [159], X-ray analysis of the solid material indicates that the Pcs are ordered in stacks. 

The Development of Well-Defined Catalysts for Ring-Opening Olefin Metathesis Polymerizations (ROMP)... 

Ring-opening Olefin Metathesis Polymerization (ROMP) gives a mixture of linear high molecular weight polymer and a series of cyclic oligomers for a number... 

Schrock, Gibson et al. [52d] found that styrene and 1,3-pentadiene could be used as chain transfer reagents for the living ring-opening olefin metathesis polymerization of norbornene with molybdenum based catalyst 35a. Renewed norbornene addition to a polymerization mixture containing initiator 35a and 30 equivalents of styrene resulted in the formation of polynorbomene with a low polydispersity and a molecular weight controlled by the number of norbornene equivalents in each of the individual monomer solutions, Eq. (38). This method allows a more efficient use of the catalyst. 

Ring-Opening Olefin Metathesis Polymerization (ROMP) Dendrimers Polymers That Look Like Trees Silicones Summing Up References Cited Other Reading... 

His proposal involved a metal carbene and a metallocyclobutane intermediate and was the first proposed mechanism consistent with all experimental observations to date. Later, Grubbs and coworkers performed spectroscopic studies on reaction intermediates and confirmed the presence of the proposed metal carbene. These results, along with the isolation of various metal alkyli-dene complexes from reaction mixtures eventually led to the development of well-defined metal carbene-containing catalysts of tungsten and molybdenum [23-25] (Fig. 2). After decades of research on olefin metathesis polymerization, polymer chemists started to use these well-defined catalysts to create novel polymer structures, while the application of metathesis in small molecule chemistry was just beginning. These advances in the understanding of metathesis continued, but low catalyst stability greatly hindered extensive use of the reaction. 

Since ring-opening olefin metathesis polymerizations (ROMPs) [111, 112], yield polymers which contain at least one double bond in the backbone per monomer unit (Fig. 10-17), it is... 

Novak, B.M., Risse, W, Grubbs, R.H., 1992. The development of well-defined catalysts for ringopening olefin metathesis polymerizations (ROMP). Adv. Polym. Sd. 102, 47-72. 

Ruthenium catalysts are reactive only towards olefins. As a result, it is possible to introduce functional groups into the monomer prior to polymerizations. This was demonstrated by Hilf and Kilbinger [183] They demonstrated that small ring vinyl lactones and carbonates are efficient quenchers for the olefin metathesis polymerization. The slow kinetics of the reaction can be overcome by an excess of the reagent. The rapid termination of the polymerization reaction yields highly functionalized polymers with narrow molecular weight distribution ... 

Another example is ring-opening olefin metathesis polymerization (ROMP), as can be used for synthesis of polybutadiene from 1,5-cyclooctadiene. 

Important classes of olefin metathesis reactions include cross metathesis (CM), ring-closing metathesis (RCM), " acyclic diene metathesis polymerization (ADMET), and ringopening olefin metathesis polymerization (ROMP). > This chapter focuses on the last class of metathesis reactions, ROMP, and in particular on the stereochemistry of the resulting macromolecular products. 

Seehof, N. Risse, W. Ring-opening olefin metathesis polymerization of spiro(bicyclo[2.2.1]hept-2-ene-7,1 -cyclopropane).MacromoZecwZe 1993, 26, 5971-5975. 

Combination of Olefin Metathesis Polymerization with Click Chemistry... 

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