Quantitative Distortionless Enhancement by Polarization Transfer (q‐DEPT) ¹³ C Nuclear Magenetic Resonance (NMR) Spectroscopy for Structural Elucidation of Hyperbranched Poly(glycerol) on Nanoparticles

Poly(glycerol) (PG) functionalization of nanoparticles (NPs) has attracted growing attention in biomedical research owing to its superior hydrophilic and stealth properties. However, the hyperbranched architecture of PG introduces structural ambiguity arising from the composition and arrangement of its subunits. Herein, we demonstrate that quantitative distortionless enhancement by polarization transfer (q‐DEPT) ¹³ C NMR gives more quantitative accuracy in structural characterization of PG subunit than the other NMR spectroscopies, including inverse‐gated ¹³ C NMR and even the other analytical methods including mass spectroscopies. Further structural elucidation is enabled by applying a topological rule in the PG chains; the number of the branching units is always two and one less than that of the terminal units in a free and a conjugated PG chain, respectively. By integrating q‐DEPT analysis with this topological rule, we establish a new analytical framework for determining the average chain and unit numbers of PG at the single‐chain level. This methodology is validated using various kinds of NPs, including nanodiamonds, boron nitride and boron carbide. Our framework resolves the long‐standing molecular‐level ambiguity of PG, enabling more reliable computational modeling and rational design in PG‐based nanomedicines. These findings may provide a general strategy for the structural elucidation of hyperbranched polymers.