Amphiphilic polysaccharides. Evidence for a competition between intra and intermolecular associations in dilute system

Abstract : Amphiphilic carboxymethylpullulans differing in their degree of octyl-bearing groups were investigated in dilute solution. Viscometry, flow field-flow fractionation with on-line coupling multi-angle laser light scattering (F4/MALLS) were used to examine conformations and aggregation states in dilute solutions. Polymer/polymer interactions tendency increases with grafting degree. At lower grafting degree, the main species in solution are composed of isolated chains, the conformation of which is close to the precursor. For greater grafting degree, strongly compact structure has been evidenced due to strong intramolecular hydrophobic associations. The transition between dilute and semi-dilute cannot be described by a classical overlapping of chains. The critical concentration (Ccr) appears to be largely function of the content of C8 groups and presents a minimum for about 20% of octyl groups: at this critical content aggregation trend is found maximum.