Thermal Aggregation Properties of Nanoparticles Modified with Temperature Sensitive Copolymers
2013
Hamner, Kristen L. | Maye, Mathew M.
In this paper, we describe the use of a temperature responsive polymer to reversibly assemble gold nanoparticles of various sizes. Temperature responsive, low critical solution temperature (LCST) pNIPAAm-co-pAAm polymers, with transition temperatures (TC) of 51 and 65 °C, were synthesized with a thiol modification, and grafted to the surface of 11 and 51 nm gold nanoparticles (AuNPs). The thermal-responsive behavior of the polymer allowed for the reversible aggregation of the nanoparticles, where at T < TC the polymers were hydrophilic and extended between particles. In contrast, at T > TC, the polymer shell undergoes a hydrophilic to hydrophobic phase transition and collapses, decreasing interparticle distances between particles, allowing aggregation to occur. The AuNP morphology and polymer conjugation were probed by TEM, FTIR, and ¹H NMR. The thermal response was probed by UV–vis and DLS. The structure of the assembled aggregates at T > TC was studied via in situ small-angle X-ray scattering, which revealed interparticle distances defined by polymer conformation.
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