Polymer-grafted nanoparticles (PGNPs) introduce an interesting complexity into polymer blend systems, where both entropic and enthalpic interactions come into play. In these systems, the dispersion of nanoparticles is often driven by maximizing the system’s configurational entropy, while the polymer chains also strive to maintain their conformational entropy and favorable enthalpic interactions. In this work, we investigate a binary blend of PGNPs with chemically distinct polymer brushes PMMA-g-SiO₂ and PSAN-g-SiO2 and explore how these factors affect their miscibility behavior compared to traditional polymer blends. We begin by studying a reference homopolymer blend system (PMMA/PSAN, with 14% AN content), where both polymers are matched in molecular weight to the grafted brushes and processed under identical thermal conditions. As expected, the homopolymer blend remains fully miscible across all compositions and temperatures studied, showing no phase separation. However, once these same polymers are tethered to nanoparticles, the story changes significantly. The PGNP blends undergo phase separation, especially near the 50/50 composition. This surprising shift in behavior is attributed to the loss of configurational degrees of freedom due to tethering, which weakens the entropic driving force for mixing and allows even modestly unfavorable enthalpic interactions to dominate. This occurs despite the fact that such enthalpic interactions are reduced due to limited interdigitation between brushes, especially in the concentrated polymer brush (CPB) regime.In addition, we explore the structural organization of single-component PGNP systems by casting thin films (50 nm and 150 nm) and annealing them under different conditions. Using atomic force microscopy (AFM) followed by 2D fast Fourier transform (FFT) analysis, we assess the degree of structural order and observe that the system approaches or enters a hyperuniform regime depending on annealing time, method, and film thickness.Together, our findings highlight how subtle changes introduced by grafting can dramatically influence phase behavior and nanoscale ordering in PGNP systems.
