Multifunctional Interfacial Design of Ladder-like Polysilsesquioxane (LPSQ)-Silica Hybrids for Advanced EV Tire Rubber Compounds

Among the various factors determining the durability of high-performance tires, interfacial compatibility across their constituent materials plays a particularly critical role. However, conventional silica fillers and cellulose nanofibers (CNFs), both rich in hydrophilic surface groups, suffer from poor adhesion to hydrophobic styrene-butadiene rubber (SBR) matrices and strong self-aggregation tendencies, critically deteriorating the processability and mechanical durability of eco-friendly green tire nanocomposites. To resolve these multi-phase interfacial defects, this study proposes a multifunctional interfacial design employing ladder-like polysilsesquioxane (LPSQ)-silica hybrids to simultaneously enhance dispersity and compatibilizing capability across the CNF-silica-SBR system. Two structurally robust LPSQs, an epoxy/alkyl-functionalized type and an acrylic/epoxy/alkyl-functionalized type, were synthesized. Afterwards their molecular weight distributions and functional groups confirmed by GPC and FT-IR. Furthermore, ²⁹Si-NMR verified the dominance of T³ environments, confirming successful ladder-structure formation. These LPSQs were then hybridized onto nanostructured silica surfaces via high-shear Henschel mixing to construct the designed interface. FE-SEM revealed significant mitigation of inter-particle aggregation through physical shielding of active silanol groups, while XPS elucidated the resulting surface chemical states, and TGA quantified the thermal decomposition behavior and loading efficiency of the LPSQ layers, with FT-IR cross-verifying the bonding evolution. Collectively, this interfacial engineering strategy transforms the hydrophilic silica surface into a compatibilizing platform bridging hydrophilic CNF and hydrophobic SBR, enabling exceptional filler dispersion and establishing a sustainable reinforcing platform for next-generation EV tire rubber compounds.