A SANS STUDY OF UNIAXIALLY ELONGATED POLYELECTROLYTE GELS

Polymer concentration fluctuations in poly(acrylic acid) gels subjected to uniaxial elongation are studied using small-angle neutron scattering (SANS). Different elongation ratios and neutralization degrees are considered. For non-ionized samples and for samples with added salt, the scattering intensity at small angles presents iso-intensity curves in the form of ''butterflies'', the absolute intensity in parallel direction being stronger than that in the perpendicular one. When the gel is sufficiently ionized, the ''butterfly'' patterns disappear and the intensity scattered in perpendicular direction is stronger than that in the parallel one, for the whole scattering wave vector range studied.