2008-08-26

New Properties for Plastics

Materials scientists at the University Jena generate new copolymer morphology

The materials scientists at the University of Jena seem to convince the experts in the field not only by their results, but also by their optics. The team of Prof. Dr. Klaus D. Jandt, Chair of Materials Science in Jena, again succeeded, within a short period of time, in presenting their newest research results on the front page of an internationally renowned journal.

In „Macromolecular Rapid Communications“ Dr. Thomas Keller shows how at the Institute of Materials Science and Technology (IMT) of the Friedrich-Schiller-University a new morphology of so called copolymers was generated for the first time. Copolymers consist of at least two different components, referred to as mers, within a single polymer chain. Such copolymers are mainly used as adhesives, for recycling of plastics, and for the development of new polymers with tunable properties (smart materials). It is also known that in nature copolymers are major building materials, like e.g. proteins or silk.

Stretching the “Polymer Fibers” from Random Coils

In his experiments in Jena, Dr. Keller first melted the copolymers. “From the melt we drew an extremely thin film which was approximately 100 nanometer thick, i.e. five hundredth of the diameter of the human hair”, says the scientist from Jena. This is astonishing, as both components usually prefer a large distance between them. Thomas Keller achieved the proximity of both components to only a few billion of a meter with a trick: The copolymers consist of molecular chains that normally are in a state of random coils. He aligned and oriented the chains along the drawing direction – similar to spaghetti, which are drawn from a plate with a fork. “While drawing, the different components approach each other and form a new morphology, which we called copolymer needles,” explains Dr. Keller. With his experiments, he was able to show that the morphology of a copolymer can be tuned with a comparatively easy procedure. This method potentially allows optimizing properties of optical guides, car tires or components of recycled plastics.

“The orientation of copolymer chains in a specified direction can increase the tensile strength of the films and therefore such materials are interesting for high-strength polymers or optical applications,” says the director of IMT, Prof. Jandt. For this, the next task of the materials scientists from Jena is the production of larger films.

Original publication:
T. Keller, C. Semmler, K. D. Jandt: „Strain-Induced Phase Morphology in Melt Drawn Ultrathin Highly Oriented Block Copolymer Films“, Macromol. Rapid Commun. 2008, 29, 876.