Polymer‐Grafted Nanoparticles as Single‐Component, High Filler Content Composites via Simple Transformative Aging

Polymer‐grafted nanoparticles (PGNPs) are ideal additives to enhance the mechanical properties and functionality of a polymer matrix and can even potentially serve as single‐component building blocks for highly filled composites if the polymer content is kept low. The major challenge facing such syntheses is that PGNP‐based solids with short polymer brushes often have low mechanical strength and limited processability. It therefore remains difficult to form robust architectures with a variety of 3D macroscopic shapes from single‐component PGNP composites. Forming covalent bonds between cross‐linkable PGNPs is a promising route for overcoming this limitation in processability and functionality, but cross‐linking strategies often require careful blending of components or slow assembly methods. Here, a transformative aging strategy is presented that uses anhydride cross‐linking to enable facile processing of single‐component PGNP solids via thermoforming into arbitrary shapes. The use of low T g polymer brushes enables the production of macroscopic composites with > 30 vol% homogeneously distributed filler, and aging increases stiffness by 1–2 orders of magnitude. This strategy can be adapted to a variety of polymer and nanofiller compositions and is therefore a potentially versatile approach to synthesize nanocomposites that are functional, mechanically robust, and easily processable.