J. Phys. II France
Volume 3, Number 6, June 1993
Page(s) 927 - 936
J. Phys. II France 3 (1993) 927-936
DOI: 10.1051/jp2/1993927

Direct osmotic pressure measurements on partially neutralized poly(acrylic acid) gels

C. Weill, T. Lachhab and P. Moucheront

Centre d'Enseignement et de Recherche en Analyse des Matériaux, Ecole Nationale des Ponts et Chaussées, I avenue Montaigne, 93167 Noisy le Grand Cedex, France

Received 18 September 1992, accepted in final form it February 1993

We present a new experimental device to measure the osmotic pressure in gels. The system has been tested on partially neutralized poly(acrylic acid) gels. The variation of the osmotic pressure with polymer concentration, Φ, and ionization degree, α, is linear, provided that α is not too high (I.e. the counterions do not condense on the chains). These results are in good agreement with theoretical models and with compressibility measurements obtained by light scattering experiments. The very charged gels are also studied, and the results are discussed in the frame of existing theories and experiments.

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