• Clerck, Karen De
• Hoogenboom, Richard

Abstract

The development of so-called smart materials, i.e. materials that are able to sense and respond to changes in theirenvironment, is a hot topic in today’s research. Halochromic dyes show high potential within this field aspH-changes are visualized by a fast and simple change of color.[1] A smart halochromic sensor can befabricated by incorporating such halochromic dye into a suitable matrix material, resulting in a custom,user-friendly product, providing clear information in a non-destructive way. Polymer nanofibers are a very wellsuited matrix material since nanofibrous nonwovens are characterized by a high specific surface area, small poresize, high pore volume and high absorbance capacity, making them ideal candidates for advanced,fast-responding sensor applications.[2] Dye-immobilization is, currently, a major challenge in nanofibroussensor design as dye-doped solvent electrospinning, i.e.the most commonly applied processing technique, suffersfrom leaching of the dye out of the nanofibrous network.[3] Our research focuses on dye-immobilization throughcovalent dye-modification, where the polymer backbone is modified with a halochromic dye before theelectrospinning process, providing a covalent linkage between the dye and the polymer. This technique is ofparticular interest for the application of natural (bio)polymers, such as chitosan.[4] The nanofibrous structure isideally produced via blend electrospinning, which allows for the selection of a suitable carrier polymer that iswidely available and well electrospinnable along with an appropriate amount of dye-modified polymer for thespecific application. Of course, the question arises, if the modification of the polymer has a significant influenceon the electrospinning process and, moreover, if the halochromic properties of the dye are maintained within thenanofibrous network. Within our research, chitosan was successfully modified and blend electrospun for theproduction of halochromic nanofibers. We found that the covalent modification could both positively as well asnegatively affect the electrospinnability of the polymer. Additionally, dye-migration was significantly reducedwithin the entire pH-range, without majorly affecting the halochromic properties of the dyes. Future work willinclude the selection of a dye with a suitable pH-range for the intended application, without negatively affectingthe electrospinning process. Nevertheless, our research already showed the great potential of the combination ofcovalent modification with electrospinning, especially for natural (bio)polymers, as it provides a universalmethod for versatile dye-functionalization of large-area nanofibrous nonwovens.

Topics

• impedance spectroscopy
• pore
• surface
• polymer
• leaching
• functionalization
• electrospinning