Loopholes

Mikheil Doroshenko, PhD student at the Max Planck Institute for Polymer Research (MPI-P), was honored with the "Young Researchers Award" of the Springer publishing house at the "Conference on Diffusion in Solids and Liquids". His latest research results convinced the jury during the conference in Madrid from 24^th to 28^th June.

Doroshenko has designed a model structure with a cleverly devised combination of a silica inverse opal and a temperature responsive polymer for controlling diffusion processes. The silica inverse opal is a porous structure prepared by densely packing polystyrene nanoparticles and filling the gaps between them with silicon dioxide. After that the polystyrene particles are burned away at 500^oC to leave a well defined porous structure of silicon dioxide.

Doroshenko modified the inverse opal pores by attaching polymer chains to their surface. He used a PNIPAM that is a well-known thermo-responsive polymer exhibiting a sharp phase transition at a temperature near that of the human body. At around 20° Celsius the polymer chains are rigidly stretched thereby almost closing the pores. If the temperature rises to 35°C the chains collapse and pores open again. In this way, by changing the temperature one is able to tune the pore size and control the mobility of small molecules, proteins or polymers diffusing in the structure.

According to Mikheil Doroshenko, this is just the beginning. The aim is now to control the mobility by using other parameters, for example the pH value, instead of temperature.
Doroshenko is doing his doctorate under the supervision of Kaloian Koynov in the research group of Hans-Jürgen Butt.