Fractionated Crystallization Behavior of Low-Molecular-Weight Polyethylene Grafted onto SiO2 Nanoparticles

The synthesis of polymer-grafted nanoparticles is crucial for the development of polymer nanocomposites with excellent properties, but the synthesis of polyethylene (PE)-grafted SiO2 nanoparticles (PE-g-SiO2 NPs) remains a significant challenge due to the chemical inertia of PE. In this study, PE-g-SiO2 NPs with different grafting densities and molecular weights were successfully synthesized by a simple "grafting to" method, and differential scanning calorimetry was used to study the crystallization behavior of grafted PE. Some PE-g-SiO2 samples exhibited three crystallization peaks in the cooling curve (i.e., fractionated crystallization phenomena). Self-nucleation (SN) and successive SN and annealing (SSA) results reveal that the nanoparticles in PE-g-SiO2 samples provoke both confinement and nucleation effects on the grafted PE chains. For PE-g-SiO2 NPs with higher grafting density and molecular weight, the PE chains are more stretched and the interfacial chain segmental dynamics are less suppressed, which enhance the nucleation effect and weaken the confinement effect.