One of the most challenging
problems in polymer and materials science is an understanding of
the glass transition of polymers. It is now known that confined
polymers show different behaviours in thin films due to their
interactions with the substrate, However, even when no substrate
interactions exist the glass transition is not the same as that
in the bulk. The glass transition depends critically on factors
that can be studied in confined films such as chain dynamics, and
polymer conformation (on the sub-nanometre scale a uniform
polymer film is anything but!).
NMR and ellipsometry will be used
experimentally to determine the glass transition temperature in
thin polymer films. Transition temperatures will be studied as a
function of the sample-substrate interaction. These experimental
results will be used to verify and improve existing theoretical
understanding based on mode-coupling theory. NMR studies will be
carried out on small polystyrene spheres dispersed in water..
Scanning probe techniques can be used to measure the "hardness"
of polymer surfaces, a property which is sensitive to the glass
transition.
More details:
Ralf Seemann at the Max
Planck Institute for Self-organisation and dynamics in
Göttingen is in overall charge of this element of the
programme.
