Isoprene-ethylene copolymer alternating

Alternating isoprene-ethylene copolymers (IER) were prepared with the same catalyst. Due to the strictly alternating sequences of diene and olefin units and the absence of chiral carbon atoms IER shows strain-induced crystallization, but at lower temperatures compared to natural rubber. 

The copolymers consist of strictly alternating sequences of diene and olefin. C-NMR measurements Showed the microstructure of the butadiene units in BPR to be exclusively of the trans-1,4 configuration (Figure 8). The isoprene units in isoprene-ethylene copolymer (IER) contain 84 % trans-1,4, 15 % cis-1,4, and 1 % 3,4 structures (Figure 9). Spontaneous crystallization in unstretched BPR samples was detected by dilatometry and confirmed by X-ray diffraction and DSC measurements. The extrapolated equilibrium melting point is about -10 °C. 

Other commercial copolymers which are typically random are those of vinyl chloride and vinyl acetate (Vinylite), isobutylene and isoprene (butyl rubber), styrene and butadiene (SBR), and acrylonitrile and butadiene (NBR). The accepted nomenclature is illustrated by EP, which is designated poly-ethylene-co-propylene the co designating that the polymer is a copolymer. When the copolymers are arranged in a regular sequence in the chains, i.e., ABAB, the copolymer is called an alternating copolymer. A copolymer consisting of styrene and maleic anhydride (SMA) is a typical alternating copolymer. 

Indicate cycloolefin monomers that will be polymerised by metathesis catalysts to polymers with a structure equivalent to polybutadiene, an alternating ethylene/ butadiene copolymer, an alternating butadiene / isoprene copolymer and polyacetylene. 

Thus a statistical copolymer of ethylene and propyiene is named poly(ethylene-stef-propylene), and an ABA tri-block copolymer of styrene (A) and isoprene (B) is named polystyrene-block-polyisoprene-block-polystyrene. In certain cases, additional square brackets are required. For example, an alternating, copolymer of styrene and maleic anhydride is named poly[styrene-d/f-(maleic anhydride)]. 

In a practical sense the hydrocarbon monomers that work best in anionic systems are styrene, a-methylstyrene, p-(tert-butyl)styrene, butadiene, isoprene, 2,3-dimethyIbutadiene, piperylene, stilbene, and 1,1-diphenylethylene. The latter two monomers give rise to alternating copolymers with other dienes but do not homopolymerize. Among the polar monomers (C) that can be polymerized are such monomers as 2-vinyIpyridine, pivalolactone, methacrylonitrile, methyl-methacrylate, ethylene oxide (not with Li-counterion), ethylene sulfide, and propylene sulfide. However, polymerization of many of these polar monomers suffers from side reactions and complicating termination or transfer reactions not present in the... 

Apart from the major reviews, numerous publications have appeared in the last two years which report new monomer combinations for alternating copolymerization or which seek to throw light on the numerous problems which still exist in this burgeoning field of study. Many comonomer systems have been reported in the last two years which give rise to alternating copolymers by one or more of the mechanisms which have been outlined, including acrylonitrile with acenaphthalene, cyclopenta-1,3-diene p-aminostyrene with p-nitro-styrene and other vinyl monomers butadiene with 1,2-dicarbomethoxy ethylenes, acrylonitrile, propylene, and others isoprene with mono-... 

Copolymers.—Both Monomers Vinyl. Ethylene-propylene copolymers have attracted the greatest attention,befitting their industrial importance. A variety of techniques has been used to assign the rather complex C spectra observed, including the synthesis of model oligomers and model polymers e.g. by hydrogenation of isoprene ). Propylene may add by either primary or secondary insertion, and a terpolymerization model has therefore been used to quantify the sequence distribution. Alternatively, Randall has proposed an analysis in terms of —CHa— or —CH(CHs)— units, rather than monomer residues. 

Modifications to the Ziegler-Natta catalyst system have led to the preparation of alternating copolymers from olefins, such as ethylene and propylene, and diolefins, such as butadiene and isoprene. In typical systems (Furukawa 1972, 1974a, b) the catalyst is prepared at very low temperatures (-70°C or below) from three components a... 

Similar crystallization behavior, where the ordered melt structure was destroyed upon crystallization and replaced by alternating lamellae with a spherulitic superstructure was also observed in diblock copolymers of poly(ethylene oxide-fe-(l,2-butylene oxide)) [109], poly(ethylene oxide-6-ethylethylene) [110],poly(ethylene oxide-6-isoprene) [111], poly(ethylene-6-(head-to-head propylene)) [112],poly(ethylene-6-ethylethylene) [113] and poly(ethylene-6-(ethylene-a/f-propylene)) [113], and a triblock copolymer of poly(ethylene oxide-6-styrene-6-ethylene oxide) [114]. In all instances, the solid-state morphology was characterized by a semicrystalline lamellar structure regardless of the initial melt morphology. 

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