SEC‐MALS study of dynamic structuring of natural rubber: Comparative study of two Hevea brasiliensis genotypes

The dynamic structuring of natural rubber (NR) was studied selecting two specific Hevea brasiliensis genotypes (RRIM600 and PB235) to prepare model sam- ples. The mesostructure (macromolecular structure þ aggregates or gel) of NR samples was studied by SEC- MALS. The NR samples were analyzed after (i) slow struc- turing (18 months' storage at room temperature) and (ii) fast structuring (stored for 24 h on P2O5 at 60 � C). This study showed that the macromolecular structure, espe- cially Mn, and the total gel rates were dramatically modi- fied after fast structuring. For genotype RRIM600, the aggregates formed during fast structuring were essentially macroaggregates, whereas for genotype PB235 mostly microaggregates were formed. These results indicate that the dynamic structuring of NR is dependent on genotype. Depending on the genotype, for extreme conditions (fast structuring), it can be assumed there was percolation between elementary bricks, probably microaggregates, or no percolation. Although the mechanisms of dynamic structuring are quite complex and should be multifactors dependent, on the basis of our results, the degree of perco- lation seems to be partly dependent on the quantity of short polyisoprene chains initially present in the NR sam- ples. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 1570- 1577, 2012