Alkene copolymers

In some very recent work by Karssenberg et al. [130], attempts have been made to improve the analytical ability of a technique like NMR spectroscopy to effectively predict the distribution of sequence lengths in polyethylene-alkene copolymers. They analyzed the entire [ C-NMR spectrum for homogeneous ethylene-propene copolymers. They used quantitative methods based on Markov statistics to obtain sequence length distributions as shown in Figure 22 [130]. The... 

The property of the polymers in question to form nonspherical nanostructures was confirmed in experimental studies. Shih et al. [29] synthesized alternating copolymers of 1-alkenes with maleic anhydride. The maleic anhydride units were hydrolyzed to maleic acid units. Fully hydrolyzed macromolecules associated into microstructures of cylindrical and ellipselike shape. The cylindrical shape was characteristic of copolymers with octadecene and hexadecene moieties, while the copolymers with lower alkene copolymers (tetradecene, dodecene, decene, octene) formed ellipsoidal structures. Wataoka et al. [30] investigated the formation of nonspherical helices in a system of maltopentaose-carrying polystyrene (PS). The polymer was synthesized via the homopolymerization of vinylbenzyl maltopentaose amide (Scheme 3). 

Random copolymers of ethylene and a-olefins (l-aUcenes) can be obtained with Ziegler-Natta catalysts, the most important being those of ethylene and 1-butene (LLDPE) and of ethylene and propylene (EPM or EPR and EPDM). Some reactivity ratios are listed in Table 9.5. Tha ratios vary with the nature and physical state of the catalyst and in most instances, r r2 is close to unity. However, all these values show that ethylene is much more reactive than higher alkenes. Copolymers produced using Ziegler-Natta catalysts usually have a wide range of compositions. This may be due to the presence of different active sites in the catalyst giving rise... 

Ethylene can be copolymerized with alkene compounds or monomers containing polar functional groups, such as vinyl acetate and acrylic acid. Branched ethylene/ alkene copolymers are essentially the same as LDPE, since in commercial practice a certain amount of propylene or hexene is always added to aid in the control of molecular weight. 

SFM studies of low crystallinity thermoplastic polyolefin elastomers based on polyethylene-alkene copolymers or stereoblock polypropylenes highlighted the importance of the crystalline regions as physical cross-links in these systems (173, 174). Even though crystallinity was very low in these materials, SFM provided sufficient contrast to interrogate the size and distribution of crystallites in the as-prepared and deformed materials (175). As will be discussed in the section under Polymer Crystallization, the crystallization process in such materials was also imaged in real time (176). 

Fig. 28 Dependence of elution volume on average chemical composition of copolymers, (a) ethylene-1-butene copolymers, (b) propylene-1-alkene copolymers stationary phase Hypercarb mobile phase gradient 1-decanol/TCB temperature 160°C detector ELSD. (Reprinted fi om [161] and [162] with permission of Springer Science -l- Business Media and Elsevier Limited)...

Experimental conditions have a determining influence, as in halogenation thus the hydrolysis of methyl trifluoroacrylate-a-alkene copolymer is difficult due to the complete lack of affinity of this copolymer for the alkali-methanol aqueous solution under reflux. 

The extensive overall crystallization kinetics that have been reported for blends of linear polyethylene with random ethylene-1-alkene copolymers cannot be analyzed in a consistent manner.(40) Hence, they are not reported here. The reason is that the crystallization temperatures were expressed in terms of an arbitrarily defined undercooling, Tq — Tq, where To is the peak crystallization temperature obtained by dynamic cooling. 

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