Hydrogel-filled, semi-crystalline, nanoparticle-crosslinked, porous polymers from emulsion templating: Structure, properties, and shape memory

PolyHIPEs are porous polymers synthesized within high internal phase emulsions (HIPEs). This paper describes hydrogel-filled, shape-memory polyHIPEs (SMPHs) based upon a polyacrylate with crystallizable side-chains. These polyHIPEs had closed-cell-like voids with diameters ranging from 5 to 100 mm and a 200 nm thick hydrogel coating. The mechanical behavior was determined by the temperature and by the presence, and the state, of the hydrogel. The deformation during shape fixation, compression at 70 degrees C to 70% strain, depended on whether the polyHIPE was dry or hydrated. The hydrogel-filled SMPHs exhibited a partial "dual-lock" behavior. The crystalline element prevented recovery when below the melting point. The hydrogel element prevented full recovery in air above the melting point. A rapid, capillary-action-driven, full recovery could only be achieved through immersion in water at 80 degrees C, melting the crystalline element, plasticizing the hydrogel element, and allowing the elastomeric element to effect shape recovery. (C) 2015 Elsevier Ltd. All rights reserved.