| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Friday Sessions |
| Session TF-FrM |
| Session: | Self-assembled Monolayers and Organic/Inorganic Interface Engineering |
| Presenter: | AnnaMaria Coclite, Graz University of Technology, Austria |
| Authors: | P. Salzmann, Graz University of Technology A. Perrotta, Eindhoven University of Technology, Netherlands A.M. Coclite, Graz University of Technology, Austria |
| Correspondent: | Click to Email |
Thermo-responsive polymers, like the Poly-(N Isopropylacrylamide) p(NIPAAm), change their properties (e.g. thickness and wettability) upon small changes in the environment temperature. This makes them suitable for interesting applications as smart sensors, artificial muscles or drug delivery systems. The change in the film properties arises from a coil to globule transition from a swollen hydrophilic state at temperatures below the lower critical solution temperature (LCST) to a shrunken hydrophobic state when the material is heated to temperatures higher than the LCST.
Cross-linked thin polymer films of NIPAAm were synthesized by initiated chemical vapor deposition (iCVD) and their thermoresponse was studied in-situ in water and in humidity by ellipsometry.
The film thicknesses were up to three times higher at temperatures below the LCST than at higher temperatures. Temperature cycles and different heating ramps revealed different mechanism of swelling and deswelling. The response during the cooling (i.e. during the swelling) was characterized by an LCST of 23°C. During the heating process (i.e. deswelling) the LCST was as high as 36°C. Similar discrepancies were also observed with another thermoresponsive polymer (N,N-Diethylacrylamide) deposited by iCVD. The reason was ascribed to different diffusion kinetics of water in the polymer meshes, and different arrangements of the polymer chains at the interface with water, depending on the rate of increase or decrease in temperature. A detailed investigation of these processes will be shown due to its importance for sensing applications.