Research in the group Materials Science and Technology of Polymers is focused on the molecular level understanding,
manipulation and control of polymeric materials. Work is carried out in three clusters.
The atomic force microscopy image shown here captures a snapshot of a crystallizing poly(e-caprolactone) melt obtained by hot-stage atomic force microscopy. The development of splaying and the growth of curved lamellar crystals can easily be seen. We have developed this approach to study the morphology development in semicrystalline polymers, in situ.
Our current interest focuses on imaging of the nucleation process on the nanoscale. In addition, we are interested in the effects of the primary macromolecular structure (such as chirality or stereoregularity) on the characteristics of the morphology.
Our work in this area also concerns with preparing fibers with diameters in the nanometer dimension, and their use in transparent composites.
Structure-property (morphology) studies of high-value added, nanostructured polymeric materials complement our work encompassing some direct application-oriented projects, which aim at nanocomposites, polymer surfaces and interfaces, coatings, and (molecular) adhesives. This “downstream” research component helps us to keep in touch with industries, it has significant relevance for valorization of the results of our generic research projects, it is crucial for educating future engineers, and it helps our students and graduates to find industrial employment upon graduation. Spin-offs, patents and direct industrial contacts facilitate utilization.
Functionalizing probe tips by self-assembled monolayers introduced a new dimension - that is, chemistry - to atomic force microscopy. It allows us, for example, to deliver reactants in preselected positions, to break and form complex guest-host chemical bonds, and to map the distribution of functional groups at polymer surfaces on the nanoscale. On the top of the scheme ester hydrolysis is captured which converts the reactant to an - OH terminated monolayer. The reaction is accompanied by a large change of force acting between the tip and the substrate, as a function of conversion. We use this effect to monitor chemical kinetics on the scale of 10-100 molecules. A typical example for guest-host interactions is also depicted, illustrating measurements of single-molecule interactions between ferrocene terminated monolayers and ß-cyclodextrin receptors, which are being studied in collaboration with the group of Prof. Reinhoudt. In another collaboration with Professor N. van Hulst we use single molecule fluorescent probes to study the nanoscale structure of free volume and molecular dynamics in polymeric glasses.
This figure illustrates how we use polymer chemistry and block copolymer self assembly to produce nanometer-sized patterns on silicon wafers and etch these patterns into the substrate in a simple, one-step reactive-ion etching process. A thin film of an organic-organometallic block copolymer on the substrate forms regularly arranged organometallic dots in the matrix of the organic component. The organometallic domains are highly resistant to reactive-ion etching due to the presence of iron and silicon in the polymer and could therefore be used as an effective etch barrier. We have sucessfully used this approach for example to etch single-domain ferromagnetic cobalt dots, in collaboration with the groups of Professor E.L. Thomas and C. Ross from MIT. Our current interest focuses on the synthesis of water-soluble polyanions and polycations of organometallic poly(ferrocenylsilanes) which possess iron in the main chain. These are candidates for layer-by-layer electrostatic self assembly from aqueous solutions, for example to modify electrode surfaces.