Science at the Edge Seminar

                Friday, January 17, 2003 at 11:30 a.m.

         Room 1400 Biomedical and Physical Sciences Building

          Refreshments will be served at 11:15 a.m. in 1400A

Speaker:
                          Michael E. Mackay
       Department of Chemical Engineering and Materials Science
                      Michigan State University
                        East Lansing, MI 48824
                    www.memackay.com, mackay@msu.edu


Title:
                     Nanotechnology and Polymers

Abstract:

We found that adding nanoparticles to polymer melts causes unique effects
such as increased wetting behavior and a lowering of the melt viscosity.
One specific observation we have made is that addition of 10wt%
polystyrene nanoparticles (~ 10 nm in diameter) to a low molecular mass
linear polystyrene (4 kDa) eliminates/delays dewetting of thin spin
coated films. This is unique, although not unexpected, since we have
observed similar behavior by adding bucky balls and dendrimers. Another
observation is that the same nanoparticles reduce the viscosity of linear
polystyrene below that of the virgin polymer by a factor of two.

The key factors in producing these effects are: size, scale, solubility,
separation and structure of the nanoparticles. The size and scale of the
particles are taken relative to a polymer molecule and we believe that
when the nanoparticles are smaller in size than the linear polymer chain
then unique, non-continuum effects come into play. The solubility is also
an important factor since the nanoparticles must be dispersed to create
any unusual effect. Separation is related to the distance between the
nanoparticles. For a given particle volume fraction the separation
distance scales with the particle diameter and so nanoparticles can have
a very small separation at extremely modest loadings. It is believed this
factor especially contributes to some of the unusual effects that we
observe. Finally, the structure is important; particle porosity and shape
are certainly important factors, however, we have not yet tried to
manipulate these variables.

In this seminar, I will discuss the above observations and uniqueness of
nanoparticles when blended with linear polymers.