Highly Stretchable and Robust Composite Gel With Ultrahigh Inorganic Filler Loading

High inorganic particle loadings in soft gels typically compromise mechanical compliance, making the integration of high filling and large deformability of the composite gel a longstanding challenge. Here, we report a physically crosslinked poly(hydroxyethyl methacrylate-co-N-vinylformamide)/polyvinylpyrrolidone (P(HEMA-co-NVF)/PVP) polymer matrix that enables a record-high ZnO loading of 80 wt.% while achieving an ultrahigh fracture elongation of 650%. Through coordination and hydrogen bonding interactions between inorganic particles and the polymer network, ZnO particles are uniformly dispersed, ensuring structural integrity and broadly tunable mechanical properties: tensile strength could be precisely regulated from 63 to 682 kPa and toughness from 0.03 to 2.04 MJ/m³ by varying monomer composition. This developed strategy is generalizable to other fillers—including Al₂O₃, Fe₃O₄, and graphene—enabling diverse functional robust composite inorganic particle gels, showing improved thermal conductivity, electrical conductivity, or magnetic responsiveness. These high-filling, highly stretchable composite gels offer promising applications in flexible sensors, soft actuators, and robotics.