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

Abstract

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.

Mechanically Strong Microstructured Hydrogels Based on Reactive Star‐Shaped Prepolymers

“…[18] Synthesis of poly(tertbutyl glycidyl ether)-block-poly(ethylene oxide)-block-poly(tert-butyl glycidyl ether) was done as described earlier. [19] Briefly, 3 g PEO (M n ¼ 35000, PDI ¼ M w /M n ¼ 1.08; Polymer Source, USA) was activated with CsOH (99.5%) monohydrate, dried and transferred into a glove box. Subsequently, the calculated amount of protected glycidol monomer, t-BuGE (0.33 g) was added to the macroinitiator and the polymerization was completed for 5 days at 80 C. The obtained poly(tert-butyl glycidyl ether)-block-poly(ethylene oxide)-block-poly(tertbutyl glycidyl ether) (P(t-BuGE X -b-EO Y -bt-BuGE X )) was dissolved in a mixture of ethanol/distilled water ¼ 1/7 and the solution was placed into a cellulose dialysis membrane (Spectra/Por 1 -MWCO 500, Carl ROTH) and dialysed for 2 days.…”