Atomic Force Microscopy Visualization of Branches in Dendritic Hyperbranched Polymers Synthesized by One-Step Radical...

The development of hyperbranched polymers (HBPs) with controlled structures remains a significant challenge in polymer chemistry. A one-step synthesis of HBPs has been previously reported with controlled molecular weight and low dispersity by organotellurium-mediated radical polymerization (TERP) in the presence of an "evolmer," which induces controlled branch structure. Although indirect evidence supports the structural control of these HBPs, direct visualization of their branch architecture has been lacking. In this study, the use of atomic force microscopy (AFM) is demonstrated to directly visualize individual HBP molecules synthesized by this method using octadecyl acrylate (ODA) as an acrylate monomer. Two HBP samples with different branch molecular weights with a theoretical dendritic generation (G_n) of 4 are synthesized and analyzed on highly oriented pyrolytic graphite (HOPG) substrates. High-resolution AFM phase imaging successfully reveals dendritic branch structures with 16 branches, closely matching the theoretical values of 17 for a G_n = 4. These results provide direct evidence of the controlled dendritic architecture of HBPs synthesized by this method. This study thus represents a critical step toward advancing structurally defined HBPs for materials applications.