Refined control over the mechanical properties of hydrogels formed from cross-linking of polymers is increasingly regarded as critical for their successful application. In general, increasing the cross-linking density (ρ) of polymer gels raises the mechanical rigidity, but makes the gels more brittle. We proposed that controlling properties of the cross-linking junction and the cross-linking type would mediate the fracture response of the gels, and allow one to decouple the dependency of the mechanical stiffness and toughness from ρ of the gel. This possibility was investigated with alginate hydrogels, because alginate can be gelled via ionic or covalent cross-linking. Increasing ρ of the gels formed using covalent cross-linking with adipic acid dihydrazide or poly (acrylamide-co-hydrazide) raised the elastic modulus (E), but led to a reduction in the toughness of the gels. In contrast, increasing the number of calcium cross-links slowed the crack opening of the gels, and subsequently raised both E and work to fracture (W). From the results of this study, we could demonstrate a novel approach to regulate different mechanical properties of gels in an independent manner. This study provides a valuable guideline to the design of a broad array of polymer hydrogels.

Original languageEnglish (US)
Article numberY9.5
Pages (from-to)313-318
Number of pages6
JournalMaterials Research Society Symposium Proceedings
StatePublished - 2005

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials

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