Iron containing nanoparticles
within a polymer matrix, as
photographed with a raster
electron microscope (SEM);
© Professor Stephan Förster,
University of Bayreuth
In science and industry polymer nanocomposites are increasingly regarded as materials that will significantly help to define progress in the 21st century. They consist of a polymer matrix and of nanoparticles which are inserted into the matrix as filler materials.
Nanoparticles are minute particles having a diameter of less than 100 nanometers. Unfortunately they have the tendency to aggregate within the polymer matrix. As such, they are not distributed as individual particles in all segments of the matrix, but rather form deposits in a limited number of locations in the matrix.
However, for industrial applications, nanocomposites are much more attractive if the individual nanoparticles are distributed separately in the polymer system. In this case, the new materials are characterized by significantly better transparency, whereas aggregated nanoparticles cause them to be dull and opaque. Additionally, the electrical and thermal conductivity of the materials are more pronounced, the more uniformly the nanoparticles are distributed in the polymer system. Finally, the resulting materials are then also more heat and fire resistant. But how can the aggregation of the nanoparticles in the polymer system be prevented?
The process begins with polymer chains. An adhesion molecule is attached to each chain. Just as with a grappling hook, the polymer chain attaches itself to a nanoparticle with the aid of this molecule; it does so in such a way that one end rests on the surface nearly vertically, whereas its other end points outwards.
Using this method, each nanoparticle obtains a complete surface coating consisting of polymer chains, giving the coating the appearance of a spherical brush. These polymer chains, pointing outwards just as bristles do, prevent the nanoparticles from coming too close to each other as they are introduced into the polymer matrix. They are preserved as individual particles whereas the polymer chains are processed into the polymer system.
This opens the door for producing highly advanced functional materials, in which separate nanoparticles are incorporated into all sections of the polymer system.
COMPAMED.de; Source: University of Bayreuth