Correlation between the Soret coefficient and the static structure factor in a polymer blend
Physikalisches Institut, Universität Bayreuth, D-95440, Bayreuth, Germany
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Accepted: 21 October 2004
Published online: 16 November 2004
Mutual mass diffusion and thermal diffusion has been investigated in poly(dimethylsiloxane)/ poly(ethylmethylsiloxane) (PDMS/PEMS) polymer blends of equal weight fractions. Molar masses ranged from below 1 to over 20 kg/mol. Both the mutual mass (D) and the thermal diffusion (D T) coefficient contain a thermally activated factor with an activation temperature of 1415 K. The molar mass dependence of D T is due to an end-group effect of the local friction coefficient. The thermal diffusion coefficient in the limit of long chains and infinite temperature is D T 0,∞ = - 1.69×10-7 cm 2(sK)-1. The Soret coefficient S T of blends far enough away from a critical point is proportional to the static structure factor S(q = 0).
PACS: 61.25.Hq Macromolecular and polymer solutions; polymer melts; swelling – / 61.41.+e Polymers, elastomers, and plastics – / 64.60.Fr Equilibrium properties near critical points, critical exponents – / 66.10.Cb Diffusion and thermal diffusion –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2004