Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers find new mechanism governing particle growth in nanocomposites

02.09.2005


Controlling nanoparticle size


Images show how the size and shape of iron oxide nanoclusters are controlled by interfacial interactions with polymers having various functional groups.



Because the properties of nanoparticles depend so closely on their size, size distribution and morphology, techniques for controlling the growth of these tiny structures is of great interest to materials researchers today.

A research team from the Georgia Institute of Technology and Drexel University has discovered a surprising new mechanism by which polymer materials used in nanocomposites control the growth of particles. Reported on August 28th at the 230th national meeting of the American Chemical Society, the findings could provide a new tool for controlling the formation of nanoparticles.


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, the research team 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."

Specifically, iron oxide particles formed in strongly interacting polymer media tended to be small (10-20 nanometers in diameter) and pyramid-shaped, while those formed in weakly-interacting media tended to be larger (40 to 60 nanometers in diameter) and spherical.

The researchers also found that the length of the polymer chain was only weakly related to the particle growth. "This means that for the same result, we can work in the melt with lower molecular-weight materials and have lower glass transitions," Tannenbaum explained.

Based on the experimental results, Tannenbaum and Associate Professor Nily Dan of Drexel’s Department of Chemical Engineering charted the relationship between average particle size and the reactivity of the polymer interface. That information should help other scientists as they attempt regulate the growth of nanoparticles using polymer reactivity.

Tannenbaum and Dan theorize that the polymer layer surrounding a nanoparticle while it grows favors an optimal interfacial curvature that sets the equilibrium particle characteristics. That may be related to the free energy of the adsorbed polymer layer.

While the researchers focused on iron oxide in this work, they believe the control mechanism should be broadly applicable to other particles and polymeric materials.

Next, the researchers plan to explore the influence of polymers in solution – a more complicated task involving more variables.

"In solution, the situation is much more complicated," Tannenbaum said. "The polymer chains are on the loose, and face competition from the solvent. The chains will be reluctant to adsorb onto the surface of the particles, so we may end up with larger particles than in the melt. In solution, molecular weight of the polymer will have an impact."

The work reported at the American Chemical Society meeting is part of a broader study of how nanoparticles interact with polymers – specifically, the interface between polymer chains and nanoparticles.

"The interface has important fundamental properties," Tannenbaum noted. "When you look at nanocomposites, the interface is a very large component of the whole structure. You can’t look at a nanocomposite as having just two components – the interface is really a third."

Beyond their use as a means for controlling nanoparticle size, nanocomposites may also have applications of their own. Their periodic structure, for instance, can be useful in optical and photonic applications.

John Toon | EurekAlert!
Further information:
http://www.edi.gatech.edu

More articles from Materials Sciences:

nachricht Watching atoms move in hybrid perovskite crystals reveals clues to improving solar cells
22.11.2017 | University of California - San Diego

nachricht Fine felted nanotubes: CAU research team develops new composite material made of carbon nanotubes
22.11.2017 | Christian-Albrechts-Universität zu Kiel

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

IceCube experiment finds Earth can block high-energy particles from nuclear reactions

24.11.2017 | Physics and Astronomy

A 'half-hearted' solution to one-sided heart failure

24.11.2017 | Health and Medicine

Heidelberg Researchers Study Unique Underwater Stalactites

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>