The effect of blob size in polymer networks on nanoparticle-mediated adhesion of hydrogels

Silica nanoparticles can be used as an adhesive for hydrogels or biological tissues due to their physical adsorption to polymer chains. Recently, we found that mesoporous nanoparticles were able to enhance the adhesion energy between hydrogels compared with non-porous nanoparticles because of the higher outer surface area of mesoporous silica nanoparticles. However, even in the case that the outer surface areas of mesoporous silica nanoparticles are similar, mesoporous nanoparticles with larger pore diameters showed significantly higher nanoparticle-mediated adhesion energy between hydrogels with a swelling ratio of 400%. Here, we have changed the swelling ratio of hydrogels in the preparation step so that the blob size in the polymer network changed accordingly. In experimental data, we found that the optimum pore size of mesoporous nanoparticles increased as the blob size increased for higher swelling ratio, which is ascribed to the larger blob size of polymer networks in hydrogels.