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

Abstract

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 Tg 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.