Water-based semi-IPNs (Interpenetrating Polymer Networks) were prepared by mixing two biopolymers, alginate and hydrophobically modified ethylhydroxy ethyl cellulose (HM-EHEC), followed by crosslinking the alginate by in-situ release of calcium ions. It is known that HM-EHEC form physical gels by hydrophobic interactions, and the strength of these gels depend on the length of the hydrophobic moiety attached to the polymeric backbone, whereas alginate forms gels through ionic crosslinking. Thus by altering two different parameters, hydrophobic chain length and calcium crosslinker concentration, we were able to fine tune the rheological properties of the semi-IPNs. Rheological studies in the linear viscoelastic region indicate storage moduli comparable to soft tissue for hydrogels having 90 wt% water. To elucidate structure-property relationships for these materials, small angle scattering was performed to gain insight into the nano and micro scale structure.

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