‘Smart’ materials that respond to external stimuli, such as a change in temperature, pH, ionic strength, light exposure, or electric field, are the subject of a large body of research for applications that range from artificial muscles to sensors to the delivery of therapeutics. The goal of this project was to combine special materials, namely gold nanoparticles and polymers, at the oil-water interface to afford new materials that hold great promise as highly functional, responsive systems. During this project, gold nanoparticles covered with responsive polymers were synthesized, characterized by a variety of techniques, and assembled at the oil-water interface by the addition of salt. This research was conducted in collaboration with Dr. Hongwei Duan, an expert in assemblies composed of polymer-covered particles, at Nanyang Technological University in Singapore.

Assembling polymer-nanoparticle composites into two- or three-dimensional structures affords properties distinct from the individual components that are broadly interesting for chemistry, physics, engineering, and biology. This project involved the incorporation of salt- and temperature-responsive zwitterionic polymers onto gold nanoparticles. The versatility of polymer chemistry lends itself to easily combine stimuli-responsive functional groups with moieties that facilitate cross-linking and binding to gold into the same polymer, while gold nanoparticles are ideal components of smart materials due to their biocompatibility and tunable optical properties. Gold nanoparticles covered with zwitterionic polymers having cross-linking units and ligands for binding gold were synthesized using a ligand exchange reaction. While the polymers alone assembled at the oil-water interface to create stable droplets, the polymer-gold nanoparticle composites remained in the aqueous phase. During this project, multiple approaches were explored to encourage the interfacial assembly of the composites, including modifying the surface of the polymer-covered gold particles by further ligand exchange reactions and by growing polymer chains from the surface of the nanoparticles. Assembly of the nanocomposites at the oil-water interface was eventually achieved by the addition of salt. Efforts are underway to afford assembly of these nanocomposites under no-salt conditions to take advantage of the salt-dependent behavior of the polymer and create new responsive materials. Importantly, this project provided a valuable opportunity for exchange of skills and technologies pertaining to polymers and nanoparticles as well as exposure to the vast amount of high quality research done in Singapore.

Last Modified: 02/28/2015
Modified by: Rachel A Letteri