Scattering properties of weakly charged polyelectrolytes

The static properties of semi-dilute polysaccharide salt-free solutions as revealed by light scattering and small angle neutron scattering (SANS) are presented. As expected the results show the existence of a broad scattering intensity peak in the investigated range of polyelectrolyte concentration C-p and momentum transfer q in both light and SANS experiments. For all charge parameters, the positions of the peaks scale roughly as C-p(0.5). A new data treatment is proposed to analyze the effect of the polyelectrolyte concentration C-p and particularly the charge parameter lambda. The results reveal, for the investigated domain of concentration, a strong evidence of the chain coiling as the charge parameter lambda is decreased. This observation is valid for lambda < 1, i.e. above the Manning condensation limit. The case of polystyrene sulfonate is presented for comparison.