Controlling Nanoparticle Size

Photo: Image of iron oxide nanoclusters with polymers

Growing particles within the confinement of polymer-based structures is one technique commonly used for controlling nanoparticle growth. After formation of the particles, the polymer matrix can be removed – or the resulting nanocomposite used for a variety of applications.

In a series of experiments, a research team from the Georgia Institute of Technology and Drexel University found a strong relationship between the chemical reactivity of the polymer and the size and shape of resulting nanoparticles.

"We have concentrated on the reactivity of the polymeric matrix and how that influences the growth of particles," explained Rina Tannenbaum, an associate professor in Georgia Tech's School of Materials Science and Engineering. "We found that in the melt the key parameter influencing particle size is actually the type of interaction with the polymer. The molecular weight of the polymer and the synthesis temperature are almost insignificant."

In a series of experiments, Tannenbaum and her collaborators created iron oxide nanoparticles within polymer films of different types, including polystyrene, poly(methyl methacrylate, bisphenol polycarbonate, poly(vinylidene di-fluouride) and polysulfone. The polymeric matrix was then decomposed using heat, leaving the particles to be characterized using transmission electron microscopy.

"These polymers spanned a variety of functional groups that differed in the strength and nature of their interactions with the iron oxide particles and in their position along with polymer chain," Tannenbaum explained. "We found that the characteristic nanoparticle size decreased with the increasing affinity – the strength of the interaction – between the polymer and the iron oxide particles."

COMPAMED.de; Source: Georgia Institute of Technology