Effect of matrix architecture on the elastic behavior of an emulsion-filled polymer gel

Abstract

This work aimed to address the effect of network architecture on the small deformation mechanical properties of emulsion-filled gelatin gels as a fat- or oil-filled composite food matrix. Through pH adjustment, filled gels could be produced with either a homogeneous or heterogeneous network architecture; the latter being characterized by droplet-rich, protein dense domains. Both systems displayed a characteristic filler-mediated reinforcement in the relative elastic modulus (Er), which was dependent on both droplet and matrix stiffness. The homogeneous system was affected by the filler modulus, but showed no dependence on gelator concentration. This trend followed the general behavior of the van der Poel model of particle reinforcement, but was also indicative of imperfect interfacial adhesion. Er of the heterogeneous composites could not be described by the van der Poel model, but exhibited power law scaling with filler content. This was attributed to an increase in the connectivity of the load-bearing network which translates stress through the material. The scaling factor decreased with increasing gelator concentration, indicating an interplay between the connectivity introduced by filler-rich domains and increasing crosslink density of the embedding network. This work demonstrates that network architecture plays a central role in determining the linear elastic response of fat-filled composite soft materials.