English Abstract
Structure of Natural Rubber

Seiichi KAWAHARA1
Yasuyuki TANAKA2
1;Department of Materials Science and Technology, Nagaoka University of Technology, Nagaoka, Niigata , Japan.
2;Faculty of Engineering Tokyo University of Agriculture and Technology Koganei, Tokyo, Japan
Nippon Gomu Kyokaishi,(2009),82(10),417-423 General Review in Japanese

Abstract
Natural rubber, obtained from Hevea brasiliensis, consists of '-terminal, two trans-1,4-isoprene units, long sequence of cis-1,4-isoprene units and '-terminal ('-(trans)2-(cis)n- '), in this order, in which the ' and ' terminals represent unknown terminal groups attracted with proteins and phospholipids. The ' and ' terminals are analyzed in relation to structures of polyprenols such as (CH3)2C=CHCH2-(trans)2-(cis)n-OH and (CH3)2C=CHCH2-(trans)3-(cis)n-OH. The ' and ' terminals are found to play an important role in a formation of three dimensional networks of natural rubber, i.e. branching and crosslinking; the higher the molecular weight, the larger is the number of branching points. The formation of three dimensional networks is concerned with a biosynthesis of natural rubber on a surface of a rubber particle in latex stage.

Keywords:
Natural Rubber, Polyprenol, NMR, three dimensional networks, branching, crosslinking
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