Characterization of thermal diffusion in polymer solutions by thermal field-flow fractionation: effects of molecular weight and branching

Schimpf, Martin E.; Giddings, J. Calvin

doi:10.1021/ma00173a022

Cited by 126 publications

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“…23 There are several detailed and systematic studies of thermal diffusion phenomena of organic polymer systems covering scaling behavior, concentration effects, and preferential solvation effects in mixed solvents. [24][25][26][27][28][29] In contrast to those organic systems, there are only few studies for aqueous polymer solutions.Observations of the Ludwig-Soret effect in the vicinity of coil-globule transition of PNiPAM/water will illuminate the importance of segment-segment and segment-solvent interactions. These key features can be varied experimentally according to the consequence of coil-globule transition of PNiPAM.…”

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Soret Coefficient of Poly(N-isopropylacrylamide)/Water in the Vicinity of Coil−Globule Transition Temperature

Kita

Wiegand

2005

Macromolecules

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According to thermodynamics of polymer solutions, polymers show conformational changes depending on the solvent quality. A transition of single polymer chain induced by the solvent quality change, known as a coilglobule transition, has been extensively studied because of their importance in not only polymer physics but also application aspects for the collapse of a gel network, the folding of a protein, and so on. [1][2][3][4][5][6] Poly(N-isopropylacrylamide) (PNiPAM) chain in water has a Θ temperature at 30.6°C, where the second virial coefficient is zero, and shows the coil-globule transition by heating. Indeed, there are many reports studying PNiPAM solutions by scattering methods, 7-10 fluorescence, 11 electronic paramagnetic resonance, 12 IR spectroscopy, 13,14 and calorimetry. 15,16 A considerable amount of work on PNiPAM solutions is collected in a review. 17 However, thermal diffusion phenomena, also called the Ludwig-Soret effect, have not been studied with taking into account the coil-globule transition in the vicinity of the Θ temperature.The Ludwig-Soret effect accounts for a mass flux, J 1 , in a mixture which is induced by a temperature and a concentration gradient. [18][19][20][21] Under a steady temperature gradient a steady concentration gradient is built up, where the flux vanishes (J 1 ) 0). The Soret coefficient, S T , is expressed as where D is the translational mass diffusion coefficient, D T the thermal diffusion coefficient, c 1 the mass fraction of component 1, and T the temperature.The sign of S T indicates whether component 1 migrates to the warm side or the cold side of the fluid. 22 If the system is dominated by short-range interactions, the thermal diffusion behavior can be attributed to single particle and collective contributions. 23 There are several detailed and systematic studies of thermal diffusion phenomena of organic polymer systems covering scaling behavior, concentration effects, and preferential solvation effects in mixed solvents. [24][25][26][27][28][29] In contrast to those organic systems, there are only few studies for aqueous polymer solutions.Observations of the Ludwig-Soret effect in the vicinity of coil-globule transition of PNiPAM/water will illuminate the importance of segment-segment and segment-solvent interactions. These key features can be varied experimentally according to the consequence of coil-globule transition of PNiPAM. This approach will lead to deeper understanding of thermal diffusion behavior of aqueous polymer systems as well as provide new insight into the solution properties of PNiPAM in a thermodynamically nonequilibrium state.PNiPAM was purified by a fractionation method. 8 One fraction was used in this study which had the weightaveraged molecular weight M w ) 3.0 × 10 6 g/mol with a polydispersity M w /M n of 1.20. Details of sample preparation and characterizations are described elsewhere. 30 Water was deionized by a Milli-Q system. In this study 1.0 g/L PNiPAM in water was prepared with a tiny amount of the dye, Basantol Yellow 215. 31 ...

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Soret Coefficient of Poly(N-isopropylacrylamide)/Water in the Vicinity of Coil−Globule Transition Temperature

Kita

Wiegand

2005

Macromolecules

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“…Both measurement techniques, TC and TDFRS indicate that D T becomes constant and therefore independent of the molecular weight of the second component. This is also the behavior, which has been observed for infinite diluted solutions of polymers [145,124]. deviations larger than 30% in the entire molar mass range of the second compound.…”

Section: Thermal Diffusion Behavior Of N-decane In Various Alkane At supporting

confidence: 78%

“…thermogravitational columns [20], thermal lens [115], diffusion cells [188,121], thermal diffusion forced Rayleigh scattering technique [76,181], thermal field flow fractination [145] and microfluidic fluorescence [43]. However, only in the last decade it became possible to get reproducible values of S T with different methods for toluene/hexane mixture [188,75] and for binary mixtures of 1,2,3,4-tetrahydronaphthalene, n-dodecane and isobutylbenzene [116].…”

Section: Many Experimental Techniques Have Been Developed For Investimentioning

confidence: 99%

“…In some cases, even qualitative predictions, which are of practical importance, are impossible. The main practical applications are separation processes [145,29] such as thermal field flow fractionation of polymers and colloids or isotope separation, characterization of geochemical processes [66,30] and combustion [128].…”

Section: Introductionmentioning

confidence: 99%

“…The technical applications are isotope separation of liquids and gaseous mixtures [122], thermal field flow fractionation of polymers and colloids [145,29], identification and separation of crude oil components [30], coating of metallic items, etc. This phenomenon is supposed to play an important role in crystal growth [136] and combustion [128].…”

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