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Edit Kutnyanszky (promotion date: 20 December 2012)

Addressable macromolecular architectures:

Towards stimuli promoted motion at the nanoscale

Promotion date: 20. December

Promotor: Prof.dr. Julius Vansco

Assistant promotor: Dr. Mark Hempenius

Addressable polymer structures play an increasingly important role in a variety of areas, such as surface engineering, drug delivery, and micro/nanofluidics. In these structures, addressability results from the sensitivity of incorporated polymer chains to variations in temperature, electric or magnetic field strength, pH, ionic strength, etc.

Macromolecules responsive to multiple types of stimuli are attracting increasing interest. Such molecules are often constructed from several building blocks where each constituent responds to a different stimulus. Although redox responsive polymers have received relatively little attention, redox is one of the very few stimuli that allows one to directly address single molecules.

To utilize stimulus responsive behavior and construct ’functioning’ molecular nanosystems such as molecular crawlers or motors, an external stimulus should be applied as a signal directly to a specific polymer chain, and be used for controlling its chain conformation and thus physical properties.

In order to lay the foundation of such systems, in this thesis several stimulus responsive macromolecules were studied based on two main polymer classes: (a) temperature responsive poly(N--‐isopropylacrylamides) (PNIPAM), and (b) redox--‐responsive poly(ferrocenylsilanes) (PFS). To address single chains and their assemblies, and to characterize their responsive behavior, Atomic Force Microscopy, dynamic light scattering and electrochemical measurements were used.

In what way did your thesis project progress?

The research area concerning stimulus responsive polymers is quite complex. In trying to accomplish a macromolecular single chain device that can move – a nano crawler – I succeeded in designing and synthesizing this kind of molecule, showing that the ultimate goal is within reach. The ‘backbone’ and ‘legs’ respond to electrochemical stimuli and to variations in temperature respectively . I guess a next generation of researchers will be able to carry on with these findings and may come up with a first prototype application.

My research was above all driven by scientific curiosity, though applications are thinkable in the future for example concerning drug delivery, surface engineering or functionalized chips.

Were your findings published?

In my project I gradually developed little steps. The single molecular experiments using atomic force microscopy - in order to characterize the functioning molecules - were among the first results I was happy to share. Publications appeared in the Journal of Chemical Physics Letters, by Elsevier, and the European Polymer Journal.

In what way did you develop personally, as a researcher and scientist?

I broadened my view in various ways on a wide range of chemical expertise areas. For example surface chemistry and physical chemistry are domains where I feel free to move in different research directions in the future, as I gained a lot of knowledge there. Also organic chemistry is among the specialist areas I learned a lot about.

What are your future plans?

The next few months I will be working as a post-doc on a subject closely related to this research, again being part of the Materials Science and Technology of Polymers group. I would like to explore some more years in academics before looking for a R&D job in industry. In these years I will be able to broaden my skills. I am looking forward to do so, as I like academic research very much.

Did you feel part of the Mesa+ institute during your PhD project?

We had some collaboration contacts with different groups, both within Mesa+ and abroad. The Mesa+ meetings I conceived of as very useful and also the collaboration moments with PhD colleagues. The access to the advanced instrumentation is one of the strong points Mesa+ can be proud to be associated with. I believe, Mesa+ should continue showing the results and research activities on an international scale and level for many more years to come.