SOLUTION-GROWN CRYSTAL OF CIS-1,4 POLYISOPRENE

Synthetic cis-1,4 polyisoprene prepared by a Ziegler catalyst and natu rally occurring cis-1,4 polyisoprenes from Hevea brasiliensis and Lact arius volemus were crystallized at -80 to -45 degrees C from dilute he xane solution. The melting temperature, T-m, of these solution-grown c rystals in hexane solution was determined by differential scanning cal orimetry. The T-m value of natural rubber from Hevea brasiliensis was higher than that of low molecular weight rubber from Lactarius volemus and synthetic cis-1,4 polyisoprene, and was not varied by removing pr oteins, mixed fatty acids and linked fatty acids. For fractionated sam ples, the T-m value of rubber from Lactarius volemus decreased in prop ortion to the molecular weight, while that of natural rubber was indep endent of the molecular weight. (C) 1997 Elsevier Science Ltd.