High-resolution nuclear magnetic resonance spectroscopy studies of polysaccharides crosslinked by sodium trimetaphosphate: a proposal for the reaction mechanism

An NMR spectroscopy study (31P, 1H, 13C) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl α-d-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPPg). On the one hand, STTPg can react with a second alcohol functionality to give a crosslinked monophosphate. On the other hand, a monophosphate (grafted phosphate) could be obtained by alkaline degradation of STPPg. NMR spectroscopy allows to detect the various species formed and to obtain the crosslinking density of STMP–polysaccharides hydrogels.

Graphical abstractReaction between methyl α-d-glucopyranoside and sodium trimetaphosphate (STMP) in alkaline medium was studied by nuclear magnetic resonance spectroscopy (31P, 1H, 13C). We have determined the various formed species and the reaction mechanism.