Résumé
The different rheological behaviour of natural rubber (NR) compared to industrial synthetic poly(
cis-1,4-isoprene) (SR) has been attributed to the gel phase and long-chain branching. Previous studies on branching in NR were carried out using the fractionation technique by precipitation to obtain narrow molar mass distribution. In this study, chain branching of poly(
cis-1,4-isoprene) in NR was characterised by size-exclusion chromatography coupled with an online multi-angle light scattering detector (SEC-MALS). The nanoaggregates adsorbed on the column packing interfered with branching characterisation for short and medium chains (
M
w
<
1000
kg/mol). Using a master curve of linear standard poly(
cis-1,4-isoprenes), SEC-MALS revealed no or very little branching in the higher chains (1000
<
M
w
<
10,000
kg/mol) of natural rubber contrary to previous studies. This study showed that the soluble portion of NR samples was composed of almost linear poly(
cis-1,4-isoprene) and nanoaggregates with rather compact structures.