Polymer-grafted nanoparticles stability and anomalous aggregation
Document Type
Presentation
Date of Original Version
3-27-2026
Abstract
Polymer-grafted nanoparticles (PGNPs) are a new class of hybrid materials that exhibit phase behavior distinct from classical polymer and colloidal systems. Their unique thermodynamic and dynamic behaviors make them incredible nanomaterials for applications in drug delivery and sensing technologies. This project has been published in the Macromolecules journal, and we investigate the stability and phase transitions of PGNPs. Notably, we assess functionalized gold nanoparticles (AuNPs) with polystyrene at different molecular weights ranging from 5 to 260 kDa. The graft thickness as a function of Mw follows a power-law dependence with a larger exponent in solution compared to dry-state measurements, confirming the swollen conformation of the grafted polymer in solution. Temperature-dependent measurements indicate that with decreasing temperature, the hydrodynamic diameter Dh of PGNPs decreases until reaching a critical temperature TUCST. Below the critical temperature, aggregation begins due to decreasing polymer-solvent interaction and increasing polymer-polymer interaction. Time-dependent aggregation measurements confirm that PGNP aggregation is in a diffusion-limited aggregation regime below TUCST, where the hydrodynamic size of the PGNP aggregates grows as a power law in time with an exponent α = 0.34 ± 0.06 independent of Mw. This exponent is dramatically different from the universal behavior of hard-sphere colloidal systems in which α = 0.55. We hypothesize that the different rate results from a combination of long-range polymer-polymer interactions and the viscoelastic relaxations of polymer grafted within the aggregate, allowing particles to rearrange. Furthermore, we observe a significant reduction in TUCST relative to that of free polymers, which we attribute to the lower entropy of mixing for grafted polymer chains. Our findings establish a PGNPs system in which their stability and phase behavior result from a combination of polymer thermodynamics and colloidal phenomena. Our investigation thereby provides crucial insights for designing nanomaterials with precise stability, self-assembly, and functionality for future technological and biomedical applications.
Recommended Citation
Abdi, Masoud; Amirsadri, David; Andreu, Irene; and Poling-Skutvik, Ryan, "Polymer-grafted nanoparticles stability and anomalous aggregation" (2026). Oral Presentations. Paper 26.
https://digitalcommons.uri.edu/gradcon2026-presentations/26