Olefins atactic copolymers with

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). 

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. 

Nowadays commercial mixtures of bitumens with uncured synthetic elastomers are produced, e.g. ethylene-propylene-diene terpolymers (EPDM), styrene-butadiene sequence copolymers (SBS), and ethylene-acrylic ester-acrylic acid terpolymers (AECM). Mixtures with some thermoplastics are also commercial products, e.g. polyethylene (PE), ethylene-propylene copolymers (EPM), alpha-olefinic copolymers, atactic polypropylene (aPP), and ethylene-vinyl acetate copolymers (EVA). 

More importantly, while it is very difficult to control the nature of the site t)rpes on conventional heterogeneous Ziegler-Natta catalysts, metallocene catalysts can be designed to synthesize PP with different chain microstructures. PP chains with atactic, isotactic, isotactic-stereoblock, atactic-stereoblock and hemiisotactic configurations can be produced with metallocene catalysts (Figure 2). It is also possible to s)mthesize PP chains that have optical activity by using only one of the enantiomeric forms of the catalyst. Additionally, copolymers of propylene, ethylene and higher a-olefins made with metallocene catalysts have random (or near random) comonomer incorporation and narrow chemical composition distributions (CCD). 

New diblock copolymers of selected PHAs (PHB, PHBV, PHO) with atactic poly[(J ,5 )-3-hydroxybutyrate] (a-PHB) were obtained by using low-molecular weight macroinitiators derived from natural poly(3-hydro-jyalkanoates), which contain olefinic units and activated by 18-crown-6 ether carbojylic end groups. These new polymers are suitable for use as blend compatibilizers. ... 

In the absence of hydrogen, metallocene-based catalyst systems produce well-defined polymers which are olefin- or aluminum-terminated. Miilhaupt has polymerized propylene with a chiral metallocene and MAO under conditions where P-hydrogen elimination was the predominant chain transfer process. In a post-polymerization functionalization, the olefin endgroups of the highly isotactic polypropylene chains were converted to bromo-, epoxy-, anhydride-, ester-, amine-, carboxylic acid-, silane-, borane-, hydroxy-, thiol-terminated polymers as intermediates for the preparation of block copolymers. Using olefin-terminated atactic and isotactic polypropylene formed with MAO-activated Cp2ZrCl2 and (EBTHI)ZrCl2 Shiono has synthesized amine- and aluminum-terminated polymers." ... 

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