Thermal aggregation properties of nanoparticles modified with temperature sensitive copolymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Temperature-responsive polymers offer tunable properties for nanomaterial assembly.
• Gold nanoparticles (AuNPs) are versatile building blocks in nanoscience.

Purpose of the Study:

• To develop a method for reversible assembly of gold nanoparticles using temperature-responsive polymers.
• To investigate the influence of polymer conformation on nanoparticle aggregate structure.

Main Methods:

• Synthesis of thiol-modified poly(N-isopropylacrylamide-co-acrylamide) (pNIPAAm-co-pAAm) polymers with varying lower critical solution temperatures (LCST).
• Grafting polymers onto gold nanoparticles (AuNPs) of 11 and 51 nm.
• Characterization using transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance ((1)H NMR).
• Thermal response analysis via UV-visible spectroscopy (UV-vis) and dynamic light scattering (DLS).
• In situ small-angle X-ray scattering (SAXS) to study aggregate structure.

Main Results:

• Successfully synthesized and grafted temperature-responsive polymers onto AuNPs.
• Demonstrated reversible nanoparticle aggregation controlled by temperature transitions (T(C) = 51 and 65 °C).
• Observed polymer collapse and hydrophobic interactions driving aggregation above T(C).
• SAXS analysis revealed polymer conformation dictates interparticle distances in assembled aggregates.

Conclusions:

• Temperature-responsive polymers provide a controllable mechanism for reversible AuNP assembly.
• The polymer's phase transition behavior is key to initiating and controlling nanoparticle aggregation.
• This approach enables tunable nanoscale architectures with potential applications in sensing and catalysis.