Strain stiffening and negative normal stress in alginate hydrogels. Issue 17 (24th May 2016)

• Record Type: Journal Article
• Authors: Hashemnejad, Seyed Meysam; Kundu, Santanu
• Is Part Of: Journal of polymer science. Volume 54:Issue 17(2016)
• Page Start: 1767
• Page End: 1775
• Publication Date: 2016-05-24
• Subjects: hydrogels -- negative normal stress -- polysaccharide -- rheology -- strain‐stiffening; 547
• DOI: 10.1002/polb.24081
• Languages: English
• ISSNs: 0887-6266

Abstract

ABSTRACT: Alginate hydrogels are polysaccharide biopolymer networks widely useful in biomedical and food applications. Here, we report nonlinear mechanical responses of ionically crosslinked alginate hydrogels captured using large amplitude oscillatory shear experiments. Gelation was performed in situ in a rheometer and the rheological investigations on these samples captured the strain‐stiffening behavior for these gels as a function of oscillatory strain. In addition, negative normal stress was observed, which has not been reported earlier for any polysaccharide networks. The magnitude of negative normal stress increases with the applied strain amplitude and can exceed that of the shear stress at large‐strain. Fitting a constitutive relationship to the stress‐strain curves reveals that the mode of deformation involves stretching of the alginate chains and bending of both the chains and the junction zones. The contribution of bending increases near saturation of G blocks as Ca 2+ concentration was increased. The results presented here provide an improved understanding of the deformation behavior of alginate hydrogels and such understanding can be extended to other crosslinked polysaccharide networks. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2016, 54, 1767–1775 Abstract : Alginate hydrogels are polysaccharide biopolymer networks widely used in biomedical and food applications. Strain‐stiffening behavior and negative normal stress in ionically cross‐linked alginate hydrogels have been captured using large amplitude oscillatory shear experiments. The rheological responses of these gels have been found to be dictated by stretching of the chains and bending of both the chains and the junction zones.