Olefins isotactic copolymers with

A number of linear isotactic copolymers of 4-methyl-l-pentene with 1-hexene and functionalized olefins, such as 5-(trialkylsiloxy)-1-pentene, could be prepared under similar conditions (9). 

Styrene and ring-substituted styrenes also form copolymers with carbon monoxide, similarly to ethylene and a-olefins. These styrene/carbon monoxide copolymers are of alternating, highly regioregular head-to-tail structure and are characterised by different stereoregularity (syndiotactic, isotactic) [115-117]. 

The blends of EPDM terpolymers and isotactic PP with curing agents, such as peroxide, phenol resins, and sulfur, are termed as thermoplastic vulcanized elastomer (TPV) since the rubber domains are vulcanized. Polyolefin copolymers, such as random copolymer of propylene with ethylene, copolymers of other olefins, elastomeric PP, and elastomeric PE, are developed with recent advances of... 

The miscibility of olefin copolymers such as ethylene-a-olefin copolymers was found to be controlled by the structural composition and the primary strucmre of the copolymers. Using these copolymers, binary blends with various compatibilities were prepared and the effects of compatibihty on mechanical properties in the binary blends were investigated. The tensile properties in binary blends of iPP with rubbery olefin copolymers are considerably influenced by the miscibility between iPP and the copolymers. The miscibility of iPP with other polyolefins is described in detail based on the dynamic mechanical properties, morphology observation, and solidification process. It is found that EBR, EHR, and EOR having more than 50 mol% of a-olefin are miscible with iPP in the molten state. In the solid state, the miscible copolymers are dissolved in the amorphous region of iPP, although the copolymers are excluded from crystalhne lattice of iPP. The isotactic propylene sequence in the EP copolymers with a propylene-unit content of more than 84 mol% participates in the crystallization process of iPP, resulting that a part of the EP copolymers is included in the crystalline lattice of iPP. 

Helical conformations were also proposed for the isotactic copolymer derived from (i )-3,7-dimethyl-1-octene and styrene. The copolymer showed intense CD bands based on the styrene units incorporated into the polymer chain. The CD intensity was much larger than that of a model compound of an adduct of the chiral olefin and styrene. The helical structure of polyolefins has also been supported by force field calculations. These considerations are evaluated with reference to... 

Thus, it was not until 1990 that the group of Kaminsky and Arndt-Rosenau took a more detailed look at the homopolymerization of norbornene and the structures of the resulting polymers. Driven by the growing interest in copolymers with high norbornene contents and high glass transition (Tg) temperatures, as well as the unusual properties of PNBs, Arndt-Rosenau et al. used the hydrooligomerization technique to produce saturated model norbornene dimers and trimers with metallocene catalysts known to produce atactic, isotactic, and syndiotactic poly(a-olefins) (1-3, Table 16.1). 

The cooperative effect anticipated by the asymptotic dependence of chiroptical properties on the degree of tacticity is further evidenced by the study of the chiroptical properties of copolymers between optically active a-olefins and achiral comonomers. i Co-isotactic copolymers of (5)-4-methyl-l-hexene with 4-methyl-1-pentene show, at any composition, an optical rotation higher than the two homopolymer mixtures, thus indicating that 4-methyl-1-pentene (4MP) units in the copolymer contribute to optical rotation, the contribution being of the same sign as that of the (5)-4-methyl-l-hexene (4MH) units. By assuming that (Od )4mh is the same in the copolymer and in the homopolymer, the values of ( )4mp can be derived at each composition by the equation ... 

To deepen these results, the same OA alkyl a-olefins already mentioned were also copolymerized in addition to styrene, with 1-vinyl-naphthalene or 2-methylstyrene with the same Ziegler-Natta catalyst. Fractionation by solvent extraction as well as the optical properties and X-ray spectra demonstrate the formation of an isotactic copolymer which is, at the first sight predominantly random but also block formation seems to occur, depending on the reactivity of vinyl aromatic monomers with respect to the a-olefin and on the composition of the starting co-monomer mixture. The remarkable contribution to optical rotation by aromatic units observed in their copolymers with (/ )3,7-dimethyl-l-octene is at least 10—15% larger than predictable from the corresponding model. The CD spectra relative to the formally forbiden electronic transition of lowest energy (with very low ellipticity) of aromatic nuclei show that, when inserted in OA copolymers, they assume a preferential chiral conformation [171]. (see chapter of Chiellini etd.). 

Usually the Zigler-Natta co-ordination initiator system is used to graft oc-olefins onto other polymers to give stereo block/graft copolymers, which contain isotactic/atactic sequences. In the Zigler-Natta co-ordination catalyst [69] system, the diethyl aluminium hydride reacts with pendant groups to form macromolecular trialkyl aluminium. The residual initiator is freed by extraction methods. 

Present-day Ziegler-Natta catalysts are supremely suitable for the production of linear polyethylene and of highly isotactic polypropylene. They are also used to produce the softer ethylene-propylene copolymers, used for packaging and related purposes. Due to the presence of distinct catalyst sites in typical Ziegler-Natta catalysts, these copolymers suffer from non-uniformity however, and copolymers which contain increased amounts of higher ot-olefins, desirable for certain applications, cannot easily be made with these catalysts. 

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