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Abstract : De Gennes 1 and Des Cloizeaux 2 have shown in what sense the problem of the configuration of chains in polymer solutions is related to the theory of critical phenomena. The exact result of Des Cloizeaux concerns the monomer concentration Cm dependence of the osmotic pressure. For semi dilute solutions 1 ≫ Cm ≫ C*m ~ N-4-5 he found π ~ C9-4m. Experimental methods have recently been developed 3, which allow the observation of more detailed quantities, such as the pair correlation functions neutron scattering, chain labelling by deuteriation. We have determined theoretically the concentration dependence of these quantities by analogy with the susceptibility of a magnetic system below Tc in the presence of an applied magnetic field. For semi dilute solutions the results are : Intensity for zero momentum transfer : Iq = 0 ~ C-1-4m response function for all chains labelled MATH response function for one labelled chain MATH mean square end to end distance ~ NC-1-4m screening length ξ ~ C-3-4m. The precision of the measurements is 5 %. Experimental results are in good agreement with these predictions 4. This agreement allows one to hope for an exact calculation of these quantities. However the theory consider a system of chains with sin undeterminated mass grand ensemble when the experiments are done with a system with a fixed molecular mass.

Autor: M. Daoud



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