Cis- and Trans-1,4-Poly-l,3-Dienes

Stereoisomerism in 1,4-poly-l,3-dienes results in significant differences in the properties of the cis and trans polymers. The trans isomer crystallizes to a greater extent as a result of higher molecular syimnetry and has higher T and Tg values (Table 8-1). These trends are 

4- polyisoprene used commerically is the natural Hevea rubber.) cw-l,4-Polyisoprene is also found in the guayule bush. Other trees, mostly in Central America and Malaysia, yield gutta percha or balata rubber, which is predominantly the trans isomer. 

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