Interaction of Silica Nanoparticle/Polymer Nanocomposite Cluster Network Structure: Revisiting the Reinforcement Mechanism

The understanding of nanoparticle-polymer interaction is a key element to demystify the structure-property relationship for nanocomposites. The clusters composing poly(acrylamide) (PAM) grafted from silica nanoparticles (SNPs) were prepared according to the developed synthetic platform and analyzed by transmission electron microscopy and dielectric relaxation analysis. The morphological evolution of clusters was observed and correlated to the mechanical behaviors of nanocomposites. Dynamic dielectric analysis was conducted to examine the nature of the constrained polymer region in view of a reinforcement mechanism. The modulus enhancement of the nanocomposite hydrogels was found to correlate with the volume of constrained polymer chains, and a constrained region model for SNP/polymer nanocomposites was proposed. The strong interactions between SNPs and polymer chains affect the modulus of the nanocomposites that was predicted by the percolation model and contributed to the mechanical reinforcement. The interplay between filler-polymer interaction and network rearrangement during the deformations should be considered to propose the reinforcement mechanism.