Novel self-assembled hydrogels by stereocomplex formation in aqueous solution of enantiomeric lactic acid oligomers grafted to dextran.

This paper describes a novel hydrogel concept, which is based on self-assembling of enantiomeric lactic acid oligomers (stereocomplex formation) grafted to dextran. The hydrogels are prepared in an all-aqueous environment. For this purpose, l- and d-lactic acid oligomers were coupled to dextran, yielding dex−(l)lactate and dex−(d)lactate, respectively. Upon dissolving each product in water separately and mixing the solutions, we observed that a hydrogel is formed at room temperature as demonstrated by rheological measurements. The storage modulus of the obtained hydrogel strongly decreased upon heating to 80 °C, while it was restored upon cooling to 20 °C, demonstrating the thermoreversibility and the physical nature of the cross-links. Rheological experiments with monodisperse lactic acid oligomers grafted to dextran showed that the degree of polymerization (DP) of the lactic acid oligomers must be at least 11 to obtain a hydrogel. The hydrogel characteristics can be modulated by varying the degree of po...