Latex Serum-Derived Supramolecular Networks Enable Toughening of Natural Rubber.

Natural rubber (NR), derived from renewable latex, offers a sustainable alternative to petroleum-based elastomers and exhibits exceptional toughness via strain-induced crystallization (SIC). However, as a kinetically governed process, SIC manifests only below specific thresholds of temperature and strain rate, limiting its effectiveness under demanding conditions. Expanding this SIC-active regime remains a long-standing challenge. Here, we demonstrate that reintroducing dried latex serum (DS)-a waste byproduct of coagulation-substantially boosts SIC-driven reinforcement in NR by promoting supramolecular network formation. Mechanical testing shows that DS addition not only increases tearing strength but also expands the SIC-active window, raising the upper-limit temperature by about 20°C and the strain-rate threshold by more than several folds. Time-resolved wide-angle X-ray scattering reveals both earlier onset and higher crystallinity of SIC. Among DS constituents, L-quebrachitol-a five hydroxy polyol-is identified as a key contributor. Systematic screening highlights that polyols with more than three hydroxy groups are particularly effective in reinforcing SIC. Molecular dynamics simulations suggest that these polyols form bifurcated hydrogen bonds with ester-terminated polyisoprene chains, generating dynamic but persistent networks that facilitate SIC. This work provides a general and sustainable framework for designing SIC-toughened soft materials through supermolecular reinforcement, while valorizing latex waste.