Hydrophobic Microphase Separation‐Driven Polycondensation and Carbonization for the Formation of Carbonized Polymer Dots

Hydrothermal synthesis has been widely used to prepare carbonized polymer dots (CPDs) in a one‐pot manner, yet how initial precursors evolve into nanoparticles in water‐rich environments remains poorly understood. Here, hydrophobic microphase separation is identified as a microenvironmental mechanism governing CPDs formation. CPDs are proved to possess a hydrophobic core and a hydrophilic shell, consistent with nanoscopic domains of reduced water accessibility during hydrothermal growth. These hydrophobic microphases locally shift reversible dehydration equilibria toward water loss, particularly dehydrative condensation, thereby sustaining polycondensation, crosslinking, and carbonization. The resulting microphase‐promoted dehydration process drives the nucleation and growth of CPDs. By independently tuning monomer hydrophobicity and crosslinking confinement, mechanism‐guided regulation of CPDs size and product fraction is achieved. These findings establish microphase‐promoted dehydration as a chemical principle for the rational hydrothermal synthesis of carbon nanomaterials.