Quantitative determination of non-rubber components and construction of supramolecular network aggregation state structure of natural rubber

Natural rubber (NR), a natural polymer material, is widely used because of its great properties and supramolecule network aggregation structure. The non-rubber components (NRCs) in NR are very important to the structure and properties. They participate in the construction of the NR structure and make linear molecular chains transfer to the network structure. In this paper, from the horizontal dimension, the composition of various kinds of NR from different locations in China along with Thailand, Malaysia, and Indonesia was analyzed. It found that the Hevea brasiliensis itself, latex treatment mode, and other factors had different influences on the content of NRCs. From the longitudinal dimension, the content of free or binding proteins, phospholipids, and metal ions connected to the rubber molecular chains was quantitatively determined. In all kinds of NR, it contains on average 0.44 wt% binding proteins, 1.98 wt% binding phospholipids, 0.03 binding metal ions, 0.65 wt% other substances, and 96.90 wt% cis -1,4-polyisoprene in the NR molecular chains. At the same time, the role of NRCs in forming the aggregation structure of NR was analyzed. The molecular weight and gel content were used to evaluate the network structure of NR. It was found that phospholipid contributed more to the network structure of NR than protein. Quantitative analysis of the components of NR, coupled with the establishment of structural models, is of paramount importance for elucidating the intricate interactions between these components and rubber molecules. This understanding is crucial for deciphering the holistic performance of rubber materials and holds significant implications for the enhancement of their properties and the development of novel rubber products. Such an approach provides a scientific basis for the design of materials with a natural - rubber - like network structure in the industry. • Quantitative analysis uncovers key free/bound NRCs in NR structure. • Bound phospholipids affect NR’s solubility and properties. • The role of NRCs in forming the aggregate structure of NR was analyzed. • Phospholipid contributed more to the network structure of NR than protein.