Journal Article

PreJuSER-41827

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Thermally induced sign change of Soret coefficient for dilute and semidilute solutions of poly(N-isopropylacrylamide) in ethanol

Kita, R. ; Kircher, G. ; Wiegand, S.FZJ*

2004
American Institute of Physics Melville, NY

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Please use a persistent id in citations: http://hdl.handle.net/2128/1193  doi:10.1063/1.1803535

Abstract: We studied the thermal diffusion behavior of poly(N-isopropylacrylamide) (PNiPAM) in ethanol in a temperature range from T = 14.0 degrees C to T = 40.0 degrees C by means of thermal diffusion forced Rayleigh scattering. The obtained Soret coefficient S(T) of PNiPAM was positive for lower temperatures (T < 34 degrees C), while S(T) showed a negative value for higher temperatures (T > 34 degrees C). This means PNiPAM molecules move to the cold side for temperatures T < 34 degrees C, whereas they move to the warm side for T > 34 degrees C. This is the first nonaqueous polymeric system for which a sign change with temperature has been observed. We performed static and dynamic light scattering experiments in the same temperature range. The second virial coefficient determined from dilute solutions by static light scattering (SLS) was positive in the comparable temperature range. The results of SLS for the semidilute solution showed a strong repulsion among PNiPAM chains which was enhanced by increasing temperature. These results imply that the observed thermally induced sign change of S(T) does not depend on the intermolecular interactions among PNiPAM chains.

Keyword(s): J

Note: Record converted from VDB: 12.11.2012

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Contributing Institute(s):

1. Weiche Materie (IFF-IWM)

Research Program(s):

1. Kondensierte Materie (M02)

Appears in the scientific report 2004
Notes: This version is available at the following Publisher URL: http://jcp.aip.org

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