Polydopamine-functionalized graphene for stabilizing starch-based 3D networks and synergistically enhancing film properties.

Functional filler materials are often incorporated into films assembled from natural polymers to enhance their optical, mechanical, barrier, and preservative properties. However, the efficacy of these fillers depends on their compatibility with the surrounding polymer matrix. The application of carbon-based fillers in films is often limited by their strongly hydrophobic nature, which restricts their dispersion and interaction within hydrophilic polymer matrices. Inspired by mussel adhesion, we employed in situ dopamine self-polymerization to modify the surfaces of graphene nanosheets, which significantly improved their compatibility with hydrophilic starch matrices. The interfacial interactions of the graphene nanosheets with the starch matrix were analyzed using density functional theory (DFT) simulations. In addition, rheology and low-field nuclear magnetic resonance (LF-NMR) analyses indicated the formation of a stable three-dimensional network structure between the modified graphene fillers and the starch matrix. The formation of this network enhanced the structural integrity of the films and impeded crack propagation. As a result, the tensile strength of the composite film increased from around 14.8 to 27.9 MPa, while the water vapor and oxygen permeability were reduced by around 30 % and 40 %, respectively. This novel strategy could be extended to other biopolymers, thereby enabling the design of multifunctional, high-performance green composites for next-generation packaging and other applications.