ADMET copolymerizations

The slower, more controlled hydrolysis of silicon-methoxy bonds enables the synthesis of a material diat is processable and extremely tough, yet flexible, with the degree of flexibility a direct result of the molar feed ratio of die two monomers since both are incorporated equally in the ADMET copolymerization. Therefore, a series of materials can be made where the properties are adjusted... 

There are several ways of using the olefin metathesis reaction to generate copolymers. Occasional reference has been made earlier to the formation of copolymers. Here we give further illustrations. For the ADMET copolymerization of linear dienes, see Section VII.C. 

Figure 6. Ester, urethane, poly-THF, and carbonate diene comonomers for ADMET copolymerization.

Siloxylene-vinylene-alkenylene Polymers via ADMET Copolymerization and Tandem ROIWCM Polymerization... 

High efficiency of the cross-metathesis of 1,9-decadiene and ROM/CM of cyclooctene with vinylsilanes points to a possibility of effective runs of the ADMET copolymerization of 1,9-decadiene [40] and tandem ROM/CM polymerization of cyclooctadiene [20], in both cases with divinylsilicon compounds. The reactions have proceeded according to Eq. 11, yielding polymeric material isolated and analyzed by GPC and NMR methods. 

Metathesis of 1,9-decadiene and cyclooctene with trialkoxy- and trisiloxy-substituted vinylsilanes in the presence of Grubbs catalyst, carried out in appropriate conditions, leads to the formation of bis(silyl)diene with a high yield. Similar processes performed with divinyl-substituted siloxane lead to the formation of silicon-containing polymers (via ADMET copolymerization and tandem ROM/CD polymerization), thus opening a new convenient route to synthesis of unsaturated organosilicon copolymers. 

ADMET copolymerization of 1,9-decadiene and 1,5-hexadiene [26] leading to perfectly random linear PBD-polyoctenamer copolymers was the first demonstration of the viability of this approach. The resulting copolymers contained comonomer ratios consistent with the monomer feed, and NMR analysis confirmed the random nature of the copolymer. Moreover, the same copolymers could be produced by the reaction of one comonomer with the homopolymer of the other comonomer for example, 1,9-decadiene with 1,4-PBD. This result further confirms the interchange reactions known to occur on the double bonds of the ADMET polymer backbone. 

This study was followed by a series of papers that examined the effect of the distance between the pendant fluorine [96], chlorine [97], or bromine [98] atoms. Later, a series of ethylene/vinyl halide polymers containing fluorine, chlorine, and bromine were created via ADMET copolymerization of a halogen-containing (x,K)-diene and 1,9-decadiene [99]. Thermal analysis of these statistically random copolymers showed a distinct difference between their crystallization behavior and that of their compositionally matched precise analogs. The sharp melting... 

Ferrocene is a very robust organometallic complex that has been incorporated into an impressive number of molecules with various applications and properties. Therefore, ferrocene-containing polymers have been pursued for many possible applications by different routes. Three metathesis-based approaches toward metallocene-containing polymers (mainly ferrocenes) have been reported so far (i) homo-ROMP or co-ROMP of olefins bearing a metallocenyl substituent, (ii) ROMP of strained an.ya-metallocenes, and (iii) ADMET polymerization of bis(alkenyl)metallocenes, including ADMET copolymerization with a.ty-dienes. 

The conjugated oligomers displayed low solubility in toluene. In order to overcome this limitation, ADMET copolymerization of l,l -divinylferrocene 2-1 with 1,9-decadiene was studied (Scheme 12.6) at 1 16 molar ratio. Random copolymers with M circa 3000 were obtained with the same monomer ratio as in the feed. 

ADMET copolymerization of divinyl-substituted silicon compounds with dienes... 

The cross-metatiiesis of a variety of (di)vinyl-substituted silanes, disiloxanes, and monovinyl-substituted siloxanes with olefins has proved to be a valuable method for the synthesis of unsaturated organosilicon derivatives and a model for the study of the synthesis of oUgo and polymeric products via ADMET copolymerization of divinyl-substituted silanes and disiloxanes with dienes. Furthermore, differently substituted vinylsiloxanes are valuable model compounds for studying poly(vinyl)siloxanes modification and cross-linking. 

While previous studies containing precisely placed methyl- and ethyl-branched PE copolymers via ADMET are perfectly sequenced models of EP and EB materials, copolymers of ethylene with a-olefins are obtained in a statistically random fashion using Ziegler-Natta or metallocene chemistry. Although these materials can be obtained totally randomized, imperfections over the branch identity are usually incorporated into the PE backbone due to tile chain nature of this chemistry. Randomly branched copolymers with only one kind of branch identity can be created using ADMET, copolymerization followed by exhaustive hydrogenation of a methyl-branched a,(o-diene with an unbranched a,to-diene yields statistically random EP copolymers. " Randomness in tiie final material is assured since copolymerization of both diene monomers is carried out, and no electronically or sterically major... 

The melting temperatures for model random EP copolymers follow a similar pattern to commercial materials obtained via chain chemistry. As the methyl branch content increases, the peak melting temperature, percent crystallinity, and heat of fusion decrease. " A decline in the melting temperature when methyl branches are incorporated into the PE backbone is observed, starting from perfectly linear PE with of 133°C, to PE with 55.6 methyl branches per 1000 carbon atoms with 7 of 52°C. Table 3 shows the peak melting temperature, heat of fusion, and percent crystallinity of all six materials obtained via ADMET copolymerization. 

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