Cyclopolymerization, nonconjugated dienes

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

As for olefins different from propene, molecular modeling studies have also been able to rationalize the dependence on metallocene symmetry of E-Z selectivity for 2-butene copolymerization as well as the stereoselectivity of the cyclization step, which determines the cis or trans configuration of the rings, for cyclopolymerization of nonconjugated dienes. 

The ionic chain polymerization of unsaturated linkages is considered in this chapter, primarily the polymerization of the carbon-carbon double bond by cationic and anionic initiators (Secs. 5-2 and 5-3). The last part of the chapter considers the polymerization of other unsaturated linkages. Polymerizations initiated by coordination and metal oxide initiators are usually also ionic in nature. These are called coordination polymerizations and are considered separately in Chap. 8. Ionic polymerizations of cyclic monomers is discussed in Chap. 7. The polymerization of conjugated dienes is considered in Chap. 8. Cyclopolymerization of nonconjugated dienes is discussed in Chap. 6. 

For reviews on enantioselective cyclopolymerization of nonconjugated dienes Coates GW (2000) Chem Rev 100 1223... 

Examples of intra intermolecular polymerizations are cyclic polymerizations of nonconjugated dienes. This can resemble cyclopolymerization by free-radical mechanism ... 

Cyclopolymerization. As discussed earlier, nonconjugated dienes can be polymerized with metallocene-based catalysts to afford cyclopol5miers. In contrast to linear polyolefins which have only two microstructures of maximum order (isotactic and syndiotactic), cyclic polymers have four microstructures due to the possibility of configurational isomerism (cis vs trans) in the main chain (Fig. 16). Of these the frares-diisotactic structure contains no mirror planes of S5unmetry and is chiral by virtue of its main-chain stereochemistry (481). Two criteria for chirality of this microstructure are the presence of trans rings and isotacticity (the same... 

Jayaratne, K. C. Keaton, R. J. Henningsen, D. A. Sita, L. R. Living Ziegler-Natta cyclopolymerization of nonconjugated dienes New classes of microphase-separated polyolefin block copolymers via a tandem polymerization/cyclopolymerization strategy. J. Am. Chem. Soc. 2000,122, 10490-10491. 

Cyclopolymerization of Nonconjugated Dienes with Nonmetallocene Catalysts 497... 

Polyolefins with cyclic units in the backbone show high TgS and high transparencies, and thus are suitable for optical and medical applications." " Even though they can be prepared by the copolymerization of ethylene and cyclic olefins (such as norbomene) using metallocene catalysts, the cyclopolymerization of nonconjugated dienes offers another access route into cyclopolymer materials. 

Ho, S. C. H. Wu, M. M. Xiong, Y. Novel cyclopolymerization polymers from nonconjugated dienes and 1-alkenes. PCT International Patent Application WO 95/06669 (Mobil Oil Corp.), March 9,1995. Hustad, P. D. Coates, G W. Insertion/isomerization polymerization of 1,5-hexadiene synthesis of functional propylene copolymers and block copolymers. J. Am. Chem. Soc. 2062,124, 11578-11579. Hustad, P. D. Tian, J. Coates, G. W. Mechanism of propylene insertion using bis(phenoxyimine)-based titanium catalysts an unusual secondary insertion of propylene in a group IV catalyst system. J. Am. Chem. Soc. 2002,124,3614-3621. 

This is the first example of cyclopolymerization of butadiene and of copolymerization to form the cyclopropane-containing polymer. 1,2-Inser-tion of the monomer leads to the r]1-polymer end with a vinyl group at the / -position. Further intramolecular insertion of the C=C bond of the vinyl pendant group into the Zr-C bond forms the cyclopropane group. Cyclopolymerization in nonconjugated cc,to-dienes is much more common, and is mentioned in the following section. 

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