Discovery of island-nanomatrix structure in natural rubber

Natural rubber is a naturally occurring nanocomposite with an island-nanomatrix structure. It is composed of cis-1,4-polyisoprene particles with an average diameter of similar to 1 mu m dispersed in a nanomatrix (several tens of nanometers thick) of nonrubber components such as proteins and phospholipids. The island-nanomatrix structure is stabilized by physical and chemical pinning with proteins and phospholipids that is based on the fact that cis-1,4-polyisoprene of natural rubber is a branched polymer. In this paper, the effects of the island-nanomatrix structure on the mechanical properties of natural rubber are demonstrated with experimental results. Essential facts are described. First, the island-nanomatrix structure disappears, and the mechanical properties of natural rubber decrease, as proteins are removed from rubber. Second, the mechanical properties are recoverable to the original level when the island-nanomatrix structure reforms in natural rubber after protein is removed. Third, the outstanding mechanical properties of natural rubber are attributed to a ten-fold increase in the modulus of cis-1,4-polyisoprene present as a bound rubber in the nanomatrix. Fourth, the effects of the nanomatrix structure on the mechanical properties are confirmed by forming the island-nanomatrix structure in synthetic cis-1,4-polyisoprene.

Automated summary

Natural rubber is a nanocomposite material with an island-nanomatrix structure composed of cis-1,4-polyisoprene particles dispersed in a nanomatrix of proteins and phospholipids. The presence of this structure greatly enhances the mechanical properties of natural rubber. Experimental results demonstrate that the mechanical properties of natural rubber decrease when proteins are removed, but can be recovered when the island-nanomatrix structure reforms.