Influence of Shear Induced Inter-Chain Correlations on the Dynamics of Polymer Melts

PhD Thesis

Project Description: Unlike small molecules, polymers have a complex dynamic behavior due to the wide spectrum of length and time scales involved. A detailed microscopic understanding of the relaxation mechanisms is a prerequisite for understanding the macroscopic response of polymers. In melt state, polymer chains have large conformational entropy due to their Gaussian conformation. As a consequence, entropy dominates the enthalpic interactions and plays a deciding role on the dynamic behavior of polymers. Through dewetting experiments, we have recently created non-equilibrium experimental situations i.e. shear induced inter-chain correlations for highlighting the importance of enthalpic interactions on the dynamics of polymer melt. These experiments indicate the need for a new paradigm in polymer physics.

The potential candidate will investigate the following topics:

1)    The non-equilibrium situations as characterized by the stretching and alignment of the polymers will be utilized for highlighting the role of attractive enthalpic interactions on the dynamics of polymers with different chemical structures.

2)    A common behavior shared by the polymers with attractive enthalpic interactions is their ability to crystallize. Through dewetting experiments, we will obtain a network of highly sheared polymer filaments forming a structural mold for subsequent crystallization. Crystallization at such confined environments will produce novel ways for creating long lasting fibers, with high mechanical and thermal stability.

Combination of optically resolved microscopic techniques and atomic force microscopy will be utilized to perform measurements. These investigations will allow the candidate to create a new paradigm accounting for the importance of attractive enthalpic interactions on the dynamics of polymer melts.

What we offer: We are an experienced interdisciplinary group working on various fronts of soft matter science viz., Non-equilibrium properties of polymers, Self-assembly of small molecules, Bio-mimicking, Optical and Transport properties of conjugated polymers. This multi-disciplinary research will help the prospective student to have a broad view on soft matter. We have a close collaboration with theoreticians, chemists and engineering faculties through International Research Training Group, IRTG, chaired by Prof. Reiter (for more information: http://www.softmattergraduate.uni-freiburg.de/). This will provide enormous opportunities for the student in improving his/her scientific contacts, learning from the masters and so on. The students will also get opportunity for attending specialized workshops and schools organized by IRTG.

Requirements: We are looking for highly qualified and motivated graduates holding a master's degree (or equivalent) in physics, materials science or closely related areas. Applicants should be strongly interested to expand their horizon beyond the specific field of their major. An excellent proficiency in English is also expected from the applicants.

Applications (Cover letter and a complete CV) must be sent by email to sivasurender.chandran@physik.uni-freiburg.de and ag-reiter@physik.uni-freiburg.de.