Precision Grafting-From of Diblock Copolymer Brushes on MXene Nanosheets

2D MXene materials offer outstanding optical, electrical, and mechanical properties, which can be used to produce multifunctional high-performance polymer-matrix composites. Here, we demonstrate the fabrication of robust covalently bonded polymer shells via the implementation of surface-initiated atom transfer radical polymerization (SI-ATRP) on heterogeneous 2D nanosheets. This robust grafting-from methodology was demonstrated through selective esterification of hydroxyl groups on Ti₃C₂T _x MXene with 2-bromoisobutyryl bromide. This approach enables the synthesis of diblock polymer brushes with sequential hydrophobic and hydrophilic blocks with predetermined, narrowly dispersed molecular weight and a low polydispersity index firmly bonded to the nanosheet surface. The high molecular weight of diblock copolymers was achieved by a precise design of molecular compositions (block ratio). By combining selective chain cleavage and monitoring the evolution of polymer shell morphology, we confirmed that the growth of polymer brushes falls in the near-brush regime with a high grafting density of 0.18-0.25 chains/nm² and shell thickness of 20-50 nm. Compared to common grafting-to and physical adsorption processes, the key benefits of this grafting-from approach lie in combining the 2D MXene nanosheets with the versatility of firmly grafted diblock copolymer functionalities and a core-shell brush architecture where MXene's inherent structure is protected in harsh chemical environments.