Testing Classical Approach to Polymer Solutions on SAXS Data of λ-Carrageenan, κ-Carrageenan and Methylcellulose Systems

In this paper we present the performance of the classical approach to polymer solutions in evaluation and interpretation of the experimental SAXS data obtained for aqueous solutions of two gelling polysaccharides κ-carrageenan and methylcellulose and a non-gelling polysaccharide λ-carrageenan. In a systematic structural SAXS study of various types of polymer solutions we pointed out and discussed the issues encountered and connected to the fact that the studied gels are obviously not "homogeneous gels" in terms of the structural details that the SAXS technique can resolve and the issues connected to the limited experimental resolution of the SAXS technique for such systems. In parallel the necessary modifications of the classical approach equations for the evaluation of the SAXS data are discussed. Furthermore, the detailed structural results of the studied aqueous polymeric systems in liquid state, during the onset of the gelation, and even in the gel state are presented.