Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster Session 2
CPP 37.1: Poster
Wednesday, April 2, 2014, 15:00–19:00, P3
Interactions between Water and Linear Poly(N-isopropylacrylamide) Chains Around the Phase Transition Investigated by Dielectric Relaxation Spectroscopy — •Marieke Füllbrandt1,2, Elena Ermilova3, Asad Asadujjaman1, Ralph Hölzel3, Frank F. Bier3, Regine von Klitzing2, and Andreas Schönhals1 — 1BAM Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin — 2Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin — 3Fraunhofer-Institut für Biomedizinische Technik IBMT, Am Mühlenberg 13, 14476 Potsdam
The molecular dynamics of linear poly(N-isopropylacrylamide) (pNIPAM) in aqueous media are investigated using dielectric relaxation spectroscopy in a frequency range from 0.1 Hz to 100 GHz. Below the lower critical solution temperature (LCST) two relaxation processes are observed located in the MHz and GHz region assigned to the reorientation of dipoles of the solvated polymer segments (p-process) and water molecules (w-process), respectively. Both relaxation processes are analyzed using the Havriliak-Negami (HN) functions taking special attention to the w-process. Above the LCST the dielectric spectra of the pNIPAM solutions resemble that of pure water showing only the high frequency relaxation process of the water molecules with more or less Debye-type behaviour. The non-Debye behaviour of the w-process below the LCST is mainly induced by the interactions between water and pNIPAM chains via hydrogen bonding. The relaxation time and strength of the w-process is studied in dependence on the concentration, temperature and the polymer chain length.