DOSY NMR as a tool for predicting optimal conditions for hydrogel formation: The case of a hyperbranched polyglycidol cross-linked with boronic acids

This article demonstrates the utility of DOSY NMR for the determination of the optimal conditions for the efficient covalent, reversible cross-linking of macromolecules in water for hydrogel formation. The studied model system was hyperbranched polyglycidol (HbPGL) containing numerous diol groups in peripheral regions and two types of boronic acids, that is, B(OH)(4)(?) and benzene-1,4-boronic diacid, as cross-linking agents. Diffusion coefficient changes of a polymer in solution, under the influence of various concentrations of cross-linking agent and pH, which influences the equilibrium of the reaction between boronic acids and diols, were recorded. These data are consistent with the rheological properties, namely the G(max)() of hydrogels prepared under analogous conditions, from more concentrated solutions of HbPGL. This approach appears to be promising as it facilitates avoiding the loss of a large amount of polymer that is necessary for the elaboration of appropriate conditions for network formation in aqueous media. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2171-2178