Synthesis, Isolation, and Solution Properties of 8-Shape and Tadpole-Shape Poly(ethylene glycol) and Their Topology Effect of Physisorption on Gold Nanoparticles.

Properties of polymers with diverse topologies are highly intriguing. The synthesis of 8-shape poly(ethylene glycol) (PEG) and its unique multicyclic topology effects including enhancement of the dispersion stabilization of gold nanoparticles (AuNPs) are studied. By employing liquid chromatography at critical conditions (LCCC), high-purity 8-shape and tadpole-shape PEGs were isolated, overcoming traditional difficulties in separating diverse molecular topologies with the same chemical structure in the repeating units. Through small-angle X-ray scattering (SAXS), it was demonstrated that increasing the number of rings significantly reduces the polymer's radius of gyration (Rg) in solution. When applied to AuNPs, 8-shape PEG facilitated even more robust physisorption than previously reported monocyclic PEG, generating a thick, protective layer without chemical bonding to the nanoparticle surface, as characterized by dynamic light scattering (DLS), ζ-potential measurements, ultraviolet-visible (UV-Vis) spectroscopy, and small-angle neutron scattering (SANS). This topological design of polymeric materials provides superior dispersion stability under environmental conditions, offering a highly efficient, noninvasive alternative to traditional chemical modification methods of nanoparticles in various applications.