Dresden 2003 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

CPP: Chemische Physik und Polymerphysik

CPP 22: POSTER C

CPP 22.62: Poster

Donnerstag, 27. März 2003, 12:00–14:00, ZEU/250

AFM-studies of the phase transition of Poly(N-isopropylacrylamide) (PNIPAM) and PNIPAM-co-poly(vinyl acetic acid) paricles in thin films — •Lothar Zitzler, Stephan Herminghaus, and Frieder Mugele — Abteilung Angewandte Physik, Universität Ulm

Poly(N-isopropylacrylamide) (PNIPAM) is a well known member of the class of responsive polymers. It has a lower critical solution temperature (LCST) at about 32˚C. This is attributed to the disruption of the hydrogen bonding of water molecules around the side chains of the PNIPAM molecules. As a result, the molecules show a conformational change from a coil to a globule state. In aqueous solutions this effect is well known and has been studied with neutron and light scattering. In this work we prepared thin films of PNIPAM with molecular weights from 10K to 465K on silicon and studied their behavior with AFM in ambient conditions. We found that the thickness of these films depends not only on the temperature but also on the relative humidity. Nevertheless, the swelling and shrinking of PNIPAM in thin films is much less pronounced than in solution. Additionally we also investigated the behavior of PNIPAM-co-poly(vinyl acetic acid) gel paricles with AFM in ambient conditions. Whereas in solution these particles show a change in diameter by a factor of 3, in ambient conditions the conformational change is only in the order of 10%. Therefor we repeated the measurements with AFM in solution.