Acyclic diene metathesis polymers

TABLE 1. Selected acyclic diene metathesis polymers prepared using optically active monomers. 

TABLE 3. Physical properties of acyclic diene metathesis polymers illustrated in Tables 1 and 2. 

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. 

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... 

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

K. Nomura, H. Morimoto, Y. Imanishi, Z. Ramhani, and Y. Geerts, Synthesis of high molecular weight rra i-poly(9,9-di- -octylfluorene-2,7-vinylene) by the acyclic diene metathesis polymerization using molybdenum catalysts, J. Polym. Sci., Part A Polym. Chem., 39 2463-2470, 2001. 

Acyclic diene metathesis polymerization (ADMET) is a related polymerization in which an unconjugated diene polymerizes with loss of ethene [Lehman and Wagener, 2002, 2003 Schwendeman et al., 2002], ADMET is carried out using the Schrock and Gmbbs initiators at about 40-80°C. The process is a step polymerization, not a ROP chain reaction. The reaction is reversible, and high polymer MW is achieved by removal of ethene (usually by reduced... 

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. 

Dienes are cyclized by intramolecular metathesis. In particular, cyclic alkenes 43 and ethylene are formed by the ring-closing metathesis of the a,co-diene 46. This is the reverse reaction of ethenolysis. Alkene metathesis is reversible, and usually an equilibrium mixture of alkenes is formed. However, the metathesis of a,co-dienes 46 generates ethylene as one product, which can be removed easily from reaction mixtures to afford cyclic compounds 43 nearly quantitatively. This is a most useful reaction, because from not only five to eight membered rings, but also macrocycles can be prepared by RCM under high-dilution conditions. However, it should be noted that RCM is an intramolecular reaction and competitive with acyclic diene metathesis polymerization (ADMET), which is intermolecular to form the polymer 47. In addition, the polymer 47 may be formed by ROMP of the cyclic compounds 43. 

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>. 

A unique aspect of acyclic diene metathesis polycondensation is its ability to produce new polymer backbones by strategic monomer design [1]. 

Catalyst and monomer development in acyclic diene metathesis remains a subject of interest, the goal being to obtain macromolecules with well-defined backbone structures and architectures by easily accessible and less expensive means. By the application of an appropriate design of monomers and a careful choice of catalysts, a variety of non-functionalised and functionalised dienes have been polymerised via metathesis condensation to high molecular weight polymers. 

Telechelic dienes for metathesis polycondensation, containing functional groups such as those in alcohols, esters, carboxylic acids and imides, can be obtained via acyclic diene metathesis depolymerisation [64,65]. They can then be used in further reactions to create hydrophobic polyurethanes and other special-purpose polymers [1]. 

A new acyclic diene metathesis polymerization method has been developed using 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene)benzylidene mthenium(II) dichloride as catalyst. This reaction catalyst was used for preparing oligomers and polymers containing amino acids or polypeptides. 

Unsaturated polymers can be produced by means of ring-opening metathesis polymerization (ROMP) of cyclic alkenes. These unique polymers can also be produced via intermolecular Acyclic Diene Metathesis (ADMET). Dienes can also react intramolecularly via Ring Closing Metathesis (RCM) to afford cyclic products. RCM is often applied to synthesis of compounds for fine chemical and pharmaceutical application. Generic examples of these reactions are shown in Figure 2. 

Schwendeman JE, Wagener KB (2002) Polym Prepr 43 280 Brzezinska KR, Wagener KB, Burns GT (1999) J Polym Sci Pol Chem 37 849 Schwendeman JE (2002) Amorphous telechelic hydrocarbon diols and ethylene-based model copolymers via acyclic diene metathesis. PhD Dissertation, University of Florida, Gainesville, FL... 

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

ROMP Ring-opening metathesis polymerization ADMET Acyclic diene metathesis polymerization ALTMET Alternating diene metathesis polycondensation MCLCP Main chain liquid crystalline polymer SCLCP Side chain liquid crystalline polymer mru molecular repeating unit... 

To date there are only a few examples of polymers having a disilandiyl-carbon backbone, but they could not be synthesized by an olefin-metathesis process with Grubbs catalyst [4 - 6]. The aim of our work is to investigate the catalytic activity of the ruthenium-carbene complex RuCl2(PCy3)2(=CHPh) (Grubbs catalyst) in acyclic diene metathesis reactions of different unsaturated organodisilanes. 

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]. 

Fig. 14 Acyclic diene metathesis polymerization of 9 to give polymer 10.

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. 

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]. 

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