Syndiotactic 1,2-polybutadiene applications

As regards high Irons- 1,4-poly butadiene, it has a few applications, especially as a blend with natural rubber. Syndiotactic 1,2-polybutadiene is a unique material that combines the properties of plastic and rubber. These properties lead to applications both as a thermoplastic resin and as a rubber. As regards isotactic 1,2-polybutadiene, one may note that its properties have not excited sufficient interest for commercial development. 

Figure 9.36 Raman spectra of polybutadiene-polystyrene copolymer in the C=Cstretching region showing three distinct bands of polybutadiene isomers cis-1,4 at 1650 cm-1, trans-1,4 at 1665 cm-1 and syndiotactic-1,2 at 1655 cm-1 (a) spectrum from the center of sample and (b) spectrum from the edge of sample. (Reproduced with permission from G. Turrell and J. Corset, Raman Microscopy, Developments and Applications, Academic Press, Harcourt Brace Company, London. 1996 Elsevier B.V.)...

MAJOR APPLICATIONS With one chiral center, l,2-p>olybutadiene can exist in the amorphous atactic form and two crystalline forms isotactic and syndiotactic. In the formation of 1,2-polybutadiene, it is believed that the syn p-allyl form yields the syndiotactic structure, while the anti p-allyl form yields the isotactic structures. The equilibrium mixture of syn and anti p-allyl structures yields heterotactic polybutadiene. At present, the two stereo-isomers that are most used commercially are the s5mdiotactic and heterotactic structures. ... 

Polybutadiene. Unlike cis- and trans-1,4-polybutadiene, high vinyl 1,2-polybutadiene has a chiral center which can exist in one of three different stere-ochemically related forms. The material can either be atactic, leading to an amorphous elastomer, or it can be isotactic or syndiotactic, both of which are crystalline. The elastomeric amorphous form has found utility in tire tread applications (271) and although certain molybdenum (272) coordination catalysts can produce this material, commercialization has focused on anionic alkali metal initiators modified with Lewis bases. Of the two crystalline forms, isotactic 1,2-polybutadiene with a melting temperature of 126° C is the most elusive isomer. A few chromium systems based on soluble salts and aluminum alkyls have been reported to give 45% of the isotactic polymer in a mixture of the atactic isomer (273,274). 

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See also in sourсe #XX -- [ ]

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