Tailored Macromolecules Versus Nanoparticles as Additives for Mechanical Reinforcement of NCO-sP(EO-stat-PO) Hydrogels

Hydrogels are three dimensional networks of hydrophilic polymers that exhibit high equilibrium water contents (up to 99 w/w-%) in aqueous environment. Beside the manifold advantages such as intrinsic biocompatibility, low friction and enormous swelling behaviour, this high water content also results in an intrinsically low mechanical stability. Different reinforcement strategies have been developed that rely on the strengthening by a second component. In this study we present the improvement of six arm star-shaped poly(ethylene oxide-stat-propylene oxide) (sPEOPO) primary networks by two different strategies: incorporation of amino-functionalized silica nanoparticles (nanocomposites, NC) and generation of interpenetrating networks (IPNs) by addition of tailored linear triblock copolymers. The compression moduli and mechanical stress-at-break of both hydrogel systems are compared and discussed. In comparison to sPEOPO, the NC hydrogels demonstrate a strengthening effect with a 2.5 times higher compression stress-at-break whereas the IPN increases the modulus up to a factor of 1.5.