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 ƒÖ'-terminal, two trans-1,4-isoprene units, long sequence of cis-1,4-isoprene units and ƒ¿'-terminal (ƒÖ'-(trans)2-(cis)n- ƒ¿'), in this order, in which the ƒÖ' and ƒ¿' terminals represent unknown terminal groups attracted with proteins and phospholipids. The ƒÖ' and ƒ¿' 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 ƒÖ' and ƒ¿ ' 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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