Isomers balata

This polymer is a hard plastic that occurs naturally as gutta-percha or balata. Since the trans isomer packs better than the cis isomer, it has a higher specific gravity, a higher degree of crystallinity, and a higher melting point (67 C) than the ds isomer of polyisoprene. The chemical and the solvent resistance of the trans polymer are simitar to those of the ds polymer. 

The polymer in natural rubber (from the Hevea bmsiliensis tree) is pure cis polyisoprene gutta percha and balata are composed of the trans isomer. 

Balata (guttapercha) is also 1,4-polyisoprene, but the polymer configuration is tram at the double bond (XII). The molecule is more extended and has symmetrical structure. The tram isomer is thus a nonelastic, hard and crystalline polymer. It is used as a thermoplastic. 

Poly(isoprene) occurs naturally as cis-l,4-poly(isoprene) (natural rubber) and as fraws-l,4-poly(isoprene) (gutta percha, balata). Both isomers can also be prepared synthetically. 

Balata, synthetic n. A stereospecific rubber, the trans isomer of polyisoprene, made by catalyzed addition polymerization of isoprene. 

Natural rubber is 1,4-polyisoprene and the polymer con guration is cis at each double bond in the chain, as shown in (XI). Consequendy, the polymer molecule has a bent and less symmetrical structure. Natural rubber does not crystaUize at room temperature and is amorphous and elastomeric. Balata (guttapercha) is also 1,4-poljdsoprene, but the polymer con guration is trans at the double bond (XII). The molecule is more extended and has symmetrical structure. The trans isomer is thus a nonelastic, hard, and crystalhne polymer. It is used as a thermoplastic. 

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