Vacuum-assisted interfacial engineering of elastomer and cellulose via octyl-aminated starch induced for strong, tough, hydrophobic, and biodegradable coated paper

Hydrophobic coating modification is a key approach for "paper-based substitution for plastics", yet interfacial bonding dominated by weak van der Waals forces between conventional coatings and cellulose paper severely limits coating performance and large-scale replacement of plastics. Herein, a vacuum-assisted interfacial engineering strategy is developed by introducing octyl-aminated starch to regulate the interfacial compatibility between thermoplastic polyurethane (TPU) and paper substrates. Protonatable amino groups enhance electrostatic interactions and hydrogen bonding with cellulose, while octyl chains improve interfacial compatibility and promote physical entanglement and mechanical interlocking between TPU and the paper substrate under vacuum conditions. As a result, a robust and stable interface is constructed, enabling simultaneous enhancement of the mechanical strength, toughness, and hydrophobicity of the paper substrate. Correspondingly, the tensile strength increases from 9.81 to 25.93 MPa, the fracture energy from 0.097 to 0.752 MJ m^-3, and the water contact angle from 0° to 100.64°, accompanied by a 40.83% reduction in water vapor transmission rate. In addition, the dynamic Schiff base linkages of CSO impart antibacterial activity, thereby extending the shelf life of perishable foods; this biodegradable system undergoes substantial degradation within 180 days, providing a sustainable alternative to conventional plastic packaging.