Europhys. Lett.
Volume 48, Number 4, November 1999
Page(s) 372 - 377
Section General
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00492-x

Europhys. Lett, 48 (4), pp. 372-377 (1999)

Molecular weight scaling in critical polymer solutions

Y. B. Melnichenko 1, G. D. Wignall 1 and W. A. Van Hook 2

1 Solid State Division, Oak Ridge National Laboratory - Oak Ridge, TN 37831, USA
2 Department of Chemistry, University of Tennessee - TN 37996, USA

(received 6 August 1999; accepted 13 September 1999)

PACS. 05.70Jk - Critical point phenomena.
PACS. 61.41${\rm +e}$ - Polymers, elastomers, and plastics.
PACS. 64.60Fr - Equilibrium properties near critical points, critical exponents.


In this letter we address the long-standing controversy which originated from differences between the experimental and theoretical values of the scaling exponent (n) for the critical amplitude $\xi_0$ of the correlation length in polymer solutions. Using small-angle neutron scattering we examine the dependence of $\xi_0$ on polymer molecular weight in polystyrene-methylcyclohexane- $\rm d_{14}$ solutions. We find that the experimental values of $n^{\rm cr}=0.195\pm 0.010$ in the critical region of phase demixing as well as $n^{\rm mf}=0.255\pm 0.009$ in the mean-field domain around the $\Theta$ temperature agree with the predictions of scaling theory $(n^{\rm cr}=0.185$, $n^{\rm mf}=0.25)$.


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