Temperature-induced self-assembly of degaloctosylated xyloglucan at low concentration

Xyloglucan is a natural polysaccharide having a hemicellulose backbone and hydroxyl groups-rich side-chains. In its native form the polymer is water-soluble and forms gel only in presence of selected co-solutes. When a given fraction of galactosyl residues are removed by enzymatic reaction, the polymer acquires the ability to form a gel in aqueous solution at physiological temperatures, a property of great interest for biomedical/pharmaceutical applications. This work presents data on the effect of a temperature increase on degalactosylated xyloglucan dispersed in water at concentration low enough not to run into macroscopic gelation. Results obtained over a wide interval of length scales show that, on increasing temperature, individual polymer chains and pre-existing clusters self-assemble into larger structures. The process implies a structural rearrangement over a few nanometers scale and an increase of dynamics homogeneity. The relation of these findings to coil-globule transition and phase separation is discussed. KEYWORDS: thermally responsive polymer, degalactosylated xyloglucan, self-assembly, mesoglobules, supramolecular structure