Eunyong Seo

Precise control over molecular dispersity and supramolecular assembly is essential for designing nanostructures with targeted properties and functionalities. In this study, we explore the impact of molecular dispersity in BTA-oligo(AA)₃ oligomers on the formation and structural organization of Au nanomaterials in an aqueous system. Discrete and polydisperse BTA-oligo(AA)₃ samples are systematically synthesized and characterized to evaluate their role as templates for nanostructure formation. UV-vis spectroscopy and TEM analyses reveal distinct differences in the resulting nanostructures. Specifically, discrete oligomers facilitate the formation of well-defined, interconnected Au nanonetworks with high structural uniformity, even at elevated concentrations. In contrast, polydisperse oligomers facilitated the formation of isolated Au nanoparticles with limited control over morphology and connectivity. These differences are attributed to the greater molecular uniformity and enhanced self-assembly capabilities of the discrete oligomers, which serve as effective templates for directing Au precursor organization and reduction into ordered nanostructures. This study provides mechanistic insight into how molecular dispersity affects the templating and assembly of gold nanomaterials. The findings offer a promising strategy for developing tailored nanostructures with interconnected morphologies and controlled optical and structural properties, paving the way for advanced applications.

Control of polymer topologies is essential to determine their unique physical properties and potential applications. The polymer topologies can have a critical effect on pigment dispersion owing to their unique architectures; however, studies using polymer topologies on pigment dispersion in aqueous systems are scarce. Thus, this study proposes various topologies of polyether-based waterborne synergists, such as linear, hyperbranched, and branched cyclic structures. Specifically, we applied branched types of polyglycidols (PGs) as a synergist to provide polymer topology-dependent dispersibility for the surface-modification of Red 170 particles through adsorption and steric hindrance. The topology-controlled PG synergists (PGSs) were successfully prepared by post-polymerization modification with phthalimide and benzoyl groups. Particularly, the branched types of PGSs, branched cyclic PGS (bc-PGS), and hyperbranched PGS (hb-PGS) exhibited improved dispersibility through adsorption on top of the pigment, interaction between dispersant (BYK 190) and pigment, and steric effect. Surprisingly, hb-PGS conferred the Red 170 pigment particles with superior storage stability than that of bc-PGS despite their similar structural features. This study suggests the widespread potential application of PGSs as waterborne synergists for various dispersion applications.

We investigated the effect of polymer topologies on the efficiency of self-healing in polymer networks containing B-O bonds.

Controlling the topology of a polymer is essential in determining its physical properties and processing. Even after numerous studies, obtaining a diverse array of topologies, particularly within the framework of hyperbranched systems, remains challenging. Here, we propose a synthetic approach to obtain highly tunable hyperbranched polyglycidol (hb-PG) using a frustrated Lewis pair of pyridine or tributylamine along with tris(pentafluorophenyl)borane, B(C₆F₅)₃, that not only influences the preferred activated monomer mechanism through hydrogen bonding with the glycidol monomer, but also facilitates the formation of unique polymer topologies. Notably, the frustrated Lewis pair containing pyridine was found to yield a branched polymer carrying cyclic structures (branched cyclic polymers) with an increased degree of branching, whereas the more sterically hindered tributylamine yielded hb-PG without a cyclic structure; these results were confirmed by MALDI-ToF analyses. Based on the unique topologies of the PGs, significant correlations between the topology and the bulk and solution states were investigated using SEC, DSC, and ¹H NMR diffusion-ordered spectroscopy.

Ruthenium oxide (RuO₂) is the best oxygen evolution reaction (OER) electrocatalyst. Herein, we demonstrated that RuO₂ can be also efficiently used as an oxygen reduction reaction (ORR) electrocatalyst, thereby serving as a bifunctional material for rechargeable Zn–air batteries. We found two forms of RuO₂ (i.e. hydrous and anhydrous, respectively h-RuO₂ and ah-RuO₂) to show different ORR and OER electrocatalytic characteristics. Thus, h-RuO₂ required large ORR overpotentials, although it completed the ORR via a 4e process. In contrast, h-RuO₂ triggered the OER at lower overpotentials at the expense of showing very unstable electrocatalytic activity. To capitalize on the advantages of h-RuO₂ while improving its drawbacks, we designed a unique structure (RuO₂@C) where h-RuO₂ nanoparticles were embedded in a carbon matrix. A double hydrophilic block copolymer-templated ruthenium precursor was transformed into RuO₂ nanoparticles upon formation of the carbon matrix via annealing. The carbon matrix allowed overcoming the limitations of h-RuO₂ by improving its poor conductivity and protecting the catalyst from dissolution during OER. The bifunctional RuO₂@C catalyst demonstrated a very low potential gap (ΔE_OER-ORR = ca. 1.0 V) at 20 mA cm⁻². The Zn||RuO₂@C cell showed an excellent stability (i.e. no overpotential was observed after more than 40 h).

We herein report a facile synthetic method for preparing gold nanoparticles (Au NPs) with superior colloidal stability using a series of double hydrophilic block copolymers (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA), as a template (Au@DHBC NPs). Due to the presence of a well-defined polymeric shell around the Au NPs, this DHBC-based synthetic method provides superior stability when compared to conventional citrate-based synthesis. We have investigated NP performance by systematically varying the molecular weight of the interacting PAA block from 5000 g mol⁻¹ to 27 000 g mol⁻¹. Interestingly, the size of the Au NPs did not significantly depend on the molecular weight of the PAA block and the density of DHBC present around a single NP decreased upon an increase in the molecular weight of the PAA block. Cyanide etching of Au@DHBC NPs further confirmed the presence of DHBC with different densities around the NPs, resulting in tunable stability. Considering the structural variability of DHBCs, it is expected that the approach presented in this study will offer a new means for creating Au NPs with enhanced colloidal stability for potential biological and biomedical applications.

We report a facile green approach to the synthesis of silver nanoparticles (Ag NPs) on the surface of graphene oxide nanosheets functionalized with mussel-inspired dopamine (GO-Dopa) without additional reductants or stabilizers at room temperature. The resulting hybrid Ag/GO-Dopa exhibits good dispersity and excellent catalytic activity in the reduction of nitroarenes.