TY - JOUR A1 - Füllbrandt, Marieke A1 - Ermilova, E. A1 - Asadujjaman, Asad A1 - Hölzel, R. A1 - Bier, F.F. A1 - Von Klitzing, R. A1 - Schönhals, Andreas T1 - Dynamics of linear poly(N-isopropylacrylamide) in water around the phase transition investigated by dielectric relaxation spectroscopy N2 - The molecular dynamics of linear poly(N-isopropylacrylamide) (pNIPAM) in aqueous media at temperatures below and above the lower critical solution temperature (LCST) are investigated using broadband dielectric relaxation spectroscopy in a frequency range from 10–1 to 1011 Hz. Below the LCST, two relaxation processes are observed in the megahertz and gigahertz 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) function, 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 a more or less Debye-type behavior. The non-Debye behavior 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 with dependence on the concentration, temperature, and the polymer chain length (molecular weight). The information obtained is useful for a deeper understanding of the dehydration behavior at the phase transition. The suggestion of dehydration of the pNIPAM chains at the LCST is confirmed by calculating a dehydration number. PY - 2014 U6 - https://doi.org/10.1021/jp501325x SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 118 IS - 13 SP - 3750 EP - 3759 PB - Soc. CY - Washington, DC AN - OPUS4-30578 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -