Braun Group People
Nihan Yonet-Tanyeri
Graduate Student in Materials Science and Engineering
B.S. degree from Fatih University, Turkey (2002)
M.S. degree from Istanbul Technical University, Turkey (2004)
Understanding the diffusion of small molecules in polymeric materials is very important in various applications. This small molecule can be a drug molecule which is dissolved or dispersed in polymer matrix and in the most common release mechanism, the drug migrates from its initial position in the polymeric system to the polymer’s outer surface and then to the body. The small molecule can also be ions or charged molecules whose transport properties play a vital role in electronic devices. Additionally, diffusion of molecular additives in plastic products ranging from intravenous fluid bags to children’s toys is having big concerns in terms of safety. On the other hand, antioxidant or stabilizer additive migration can often limit the useful service life of a product.
My research focuses on designing quasi-two dimensional polymer brush based molecular conduits with the goal of regulating and controlling the diffusive transport of ionic, e.g. Ca ions, and protons molecular species, e.g. organic dyes along predefined 2-D pathways. Fluorescence recovery after photobleaching (FRAP) has been used to study the diffusion of Prodan in self-assembled monolayers [1] as well as solid-state PNIPAAm and poly(oligoethylene glycol) acrylate (POEGA) brushes under various levels of humidity. In my research, the transport of molecules in the patterned polymer brushes is studied using both confocal laser scanning microscopy and fluorescence microscopy. The patterned polymer brushes are formed by microcontact printing a silane initiator followed by atom transfer radical polymerization. The samples are characterized by ellipsometry, atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) to determine the thickness of the thin films, the quality of the patterning and the chemical composition of the polymers.
The molecular device, as shown in Figure 1, is composed of a hydrophilic POEGA brushes [2] which was selected because of its potential to dissolve a wide range of hydrophilic species. The transport of fluorescent species, HPTS, can be directly followed. We have demonstrated that HPTS diffuses much more rapidly along the predefined pathway than along the bare (polymer brush free) regions of the substrate (Figure 2).
Figure 1. Microfluidic dye delivery device.
Figure 2. Fluorescence micrographs of monitoring HPTS diffusion in the line-dot patterned
POEGA brush and diffusion profiles of HPTS in the line-POEGA.
1. Carla E. Heitzman, Huilin Tu, Paul V. Braun. Two-Dimensional Diffusion of Prodan on Self-Assembled Monolayers Studied by Fluorescence Recovery After Photobleaching. J. Phys. Chem B. 108, 13764 (2004).
2. Huilin Tu, Carla E. Heitzman, Rachel C. Evans, Paul V. Braun. Patterned Poly(oligoethylene glycol acrylate) Brushes on Silica Surfaces. Polymer Preprints 46, 444 (2005).
Professor Paul Braun • Phone: +1.217.244.7293 • Fax: +1.217.333.2736 • Email: pbraun@illinois.edu
Department of Materials Science and Engineering • University of Illinois at Urbana-Champaign