Research Interests:
- Phase behavior and stucture-property relationships in polymer blends and nanocomposite
- Polymer processing
- Advanced materials development
Presentation abstract:
Polymer-grafted nanoparticles (PGNPs) have been broadly recognized for their role in enhancing the mechanical and thermal stability of polymeric materials, making them ideal for applications in functional coatings, engineered surface nanopatterns, and lithography. In this study, we fabricated uniformly nanopatterned polymeric surfaces with a blend of poly (methyl methacrylate) (PMMA) and polystyrene (PS)-grafted titanium dioxide (TiO₂) nanoparticles of varying core sizes. Surface-initiated atom transfer radical polymerization (ATRP) was used to synthesize the PS-g-TiO₂ PGNPs. By examining the rate of surface pattern decay over time at different temperatures, we observed a dependence between enthalpy and entropy, specifically investigating the entropy–enthalpy compensation (EEC) effects. Our results show that PGNPs significantly improved pattern stability in PMMA films, retaining their structure at elevated temperatures up to 130°C. Additionally, PGNP inclusion slowed the relaxation dynamics of the patterned films, enhancing the thermal stability of the imprinted nanostructures. The compensation temperature (Tcomp) was found to be within the glass transition temperature (Tg) range of pure PMMA. Upon exceeding Tg, nanoimprints with PGNP inclusion exhibited superior structural reliability compared to the homopolymer, with a reduced rate of relaxation. Unlike previous studies that examined PGNPs in chemically compatible matrices, this study involves a PGNP with TiO₂ core and a PS brush that is chemically immiscible with the PMMA matrix. Prior studies attributed stabilization effects to either entanglement between the brush and matrix or increased viscosity due to PGNP inclusion, but this distinction remained unresolved. By studying this chemically immiscible system, we establish that the entanglement effect is suppressed, while viscosity plays a dominant role. These findings highlight the potential of polymer-grafted nanoparticles as stabilizers for nanopatterned structures in various polymer nanocomposite applications.
