Forces across polymer melts

The Structure of a composite material is influenced by the effective force between the filler particles in the polymer melt. Particles are well dispersed when this force is repulsive. If the interaction is attractive aggregates can form. Since the trend is towards using smaller and smaller particles, leading to nanocomposite materials with huge internal interfaces, knowledge of the force becomes more and more important. Unlike the situation for aqueous dispersions, our understanding of forces in polymer melts is still rudimentary.

We studied forces across different polymer melts including poly(dimethyl siloxane), poly(ethylmethyl siloxane), and poly(isoprene) with the atomic force microscope (AFM). Such experiments are not only important with respect to dispersing particles. A more fundamental interest is in the structure of confined polymers per se. In addition, force measurements provide information on the polymer-solid interface. In addition to monodisperse polymers we also studied mixtures of long and short chains and end-functionalized polymers.

• Sun, G. & H.-J. Butt: Adhesion between solid surfaces in a polymer melt: Bridging of single chains. Macromolecules 2004, 37, 6086-6089.
• Stark, R., M. Kappl & H.-J. Butt: Interaction of solids across mixtures of binary polymer melts. Macromolecules 2007, 40, 4088-4091.
• Wang, J. & H.-J. Butt: Force between thiolate-modified gold surfaces in a melt of end-functionalized polymers. J. Phys. Chem. B 2008, 112, 2001-2007.