Effect of Initiator Density, Catalyst Concentration, and Surface Curvature on the Uniformity of Polymers Grafted from Spherical Nanoparticles

Yin, Rongguan; Wu, Hanshu; Hu, Xiaolei; Kim, Khidong; Lorandi, Francesca; D’hooge, Dagmar R.; Benetti, Edmondo M.; Bockstaller, Michael R.; Matyjaszewski, Krzysztof

doi:10.1021/acs.macromol.5c02737

Title: Effect of Initiator Density, Catalyst Concentration, and Surface Curvature on the Uniformity of Polymers Grafted from Spherical Nanoparticles

Journal Article · Tue Jan 06 00:00:00 UTC 2026 · Macromolecules

DOI: https://doi.org/10.1021/acs.macromol.5c02737 · OSTI ID:3015417

^[1]; Wu, Hanshu ^[1];

^[1]; Kim, Khidong ^[1];

^[2];

^[3];

^[2];

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^[1]

Carnegie Mellon Univ., Pittsburgh, PA (United States)
Univ. of Padua (Italy)
Ghent Univ. (Belgium)

Polymer-grafted nanoparticles (PGNPs) are versatile hybrid materials whose properties critically depend on brush dimensions, uniformity, and grafting density. Herein, we systematically investigated how initiator density, catalyst concentration, and nanoparticle curvature govern the growth of poly(methyl methacrylate) (PMMA) brushes grafted from spherical SiO₂ nanoparticles via surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP). By tuning the initiator density through a combination of “active” and “dummy” silane initiators anchored on the nanoparticles’ surface and controlling the catalyst concentration, we reveal that increased initiator crowding and smaller surface curvature amplify steric hindrance, leading to decreased initiation efficiency and broader molecular weight distributions. Correlation with the corresponding unattached chains by ARGET ATRP suggests the presence of permanently inaccessible (“buried”) initiation sites, which are a characteristic of surface-grafted systems. At sufficient Cu catalyst concentrations, uniform brush growth is attained across different initiator densities, whereas decreased catalyst concentrations accentuate nonconcurrent initiation and propagation. These findings provide mechanistic insights into the interplay of initiator density, catalyst concentration, and surface curvature, offering design principles for tailoring the PGNP architecture. These results can guide the structural engineering of densely grafted surfaces, including nanoparticles and flat substrates, for applications in nanocomposites, photonics, and functional coatings.

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Research Organization:: Carnegie Mellon Univ., Pittsburgh, PA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: SC0018784

OSTI ID:: 3015417

Journal Information:: Macromolecules, Journal Name: Macromolecules Journal Issue: 2 Vol. 59; ISSN 1520-5835; ISSN 0024-9297

Publisher:: American Chemical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
catalysts
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Title: Effect of Initiator Density, Catalyst Concentration, and Surface Curvature on the Uniformity of Polymers Grafted from Spherical Nanoparticles

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