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Sommer, J.-U. ; Dockhorn, R. ; Welzel, P. ; Freudenberg, U. ; Werner, C.
Swelling equilibrium of a binary polymer gel

The swelling properties of a new class of biohybrid gels made of heparin and 4-arm star-poly(ethylene glycol) (PEG) were studied using mean-field concepts. Heparin acts as a multifunctional cross-linker and is highly charged in aqueous environments allowing for the functionalization of the gels with a plethora of biologically active molecules. The elasticity of the gels is provided by the flexible arms of the PEG. Varying the mole fraction of the heparin at preparation changes both the elasticity and the charge of the gel. We combine the classical Flory-Rehner model with a free energy contribution due to trapped counterions and derive a general equation for the equilibrium swelling of the gel as a function of the heparin-content at preparation, size of PEG molecules and salt concentration of the solvent. Varying the heparin content in the state of preparation results in opposite tendencies of the swelling behavior in the limit of low and high salt concentrations. At intermediate salt concentrations we find a regime where the heparin concentration at equilibrium swelling is almost independent of the heparin concentration at preparation. This provides access to novel gel-based biomaterials where physical stimuli (modulus) and biomolecular signals (modulated by the heparin concentration) can be varied independently. Our results are in good agreement with experimental data obtained at various gel compositions and salt concentrations of the aqueous environments.

Macromolecules 44, 981–986


Erschienen am
January 2011