Ludwig-Soret Effect of Poly(N-isopropylacrylamide): Temperature Dependence Study in Monohydric Alcohols
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- 作者：Rio Kita ; Pavel Polyakov ; Simone Wiegand
- 刊名：Macromolecules
- 出版年：2007
- 出版时间：March 6, 2007
- 年：2007
- 卷：40
- 期：5
- 页码：1638 - 1642
- 全文大小：126K
- 年卷期：v.40,no.5(March 6, 2007)
- ISSN：1520-5835
文摘
We report the experimental results of the Ludwig-Soret effect for poly(N-isopropylacrylamide)(PNiPAM) in alcohols measured in the temperature range from 20 to 45 
C by means of thermal diffusion forcedRayleigh scattering (TDFRS). Alcohols, used in this study as solvent, are monohydric alcohols (methanol, ethanol,1-propanol, 2-propanol, 1-butanol, and tert-butanol). In the studied temperature range, PNiPAM in methanolshows a positive Soret coefficient, whereas PNiPAM has a negative Soret coefficient in larger alcohols, i.e.,1-propanol, 2-propanol, 1-butanol, and tert-butanol. In ethanol the temperature dependence of the Soret coefficientof PNiPAM shows a sign change from positive to negative with increasing temperature at T = 34 C. Thetemperature dependence of the Soret coefficients for these alcohol solutions is discussed in terms of cohesiveenergies such as the Hildebrand solubility parameter. It is indicated that the balance between the hydrogen-bonding capability and the hydrophobic association plays a dominant role for the sign change in the Soret coefficientand the thermal diffusion coefficient of PNiPAM.
C by means of thermal diffusion forcedRayleigh scattering (TDFRS). Alcohols, used in this study as solvent, are monohydric alcohols (methanol, ethanol,1-propanol, 2-propanol, 1-butanol, and tert-butanol). In the studied temperature range, PNiPAM in methanolshows a positive Soret coefficient, whereas PNiPAM has a negative Soret coefficient in larger alcohols, i.e.,1-propanol, 2-propanol, 1-butanol, and tert-butanol. In ethanol the temperature dependence of the Soret coefficientof PNiPAM shows a sign change from positive to negative with increasing temperature at T = 34 C. Thetemperature dependence of the Soret coefficients for these alcohol solutions is discussed in terms of cohesiveenergies such as the Hildebrand solubility parameter. It is indicated that the balance between the hydrogen-bonding capability and the hydrophobic association plays a dominant role for the sign change in the Soret coefficientand the thermal diffusion coefficient of PNiPAM.