Starch Phosphate Hydrogels. Part I: Synthesis by Mono-phosphorylation and Cross-linking of Starch

Starch-based hydrogels were synthesized by cross-linking monostarch monophosphates (MSMP) with different di- and tricarboxylic acids such as succinic, adipic or citric acid. Phosphorylation of starch was performed in a semi-dry process using a mixture of primary and secondary sodium phosphates. The phosphorus content and degree of substitution of phosphate groups (DS(P)) of the resulting MSMP were determined using a photometric method. For structural characterization of starch phosphates (31)P NMR was used. Investigations showed that MSMP hydrogels were strong water absorbing polymer networks with a free swelling capacity (FSC) of up to 185 g water / g dry hydrogel.