Structural Relaxation of Polymer Nanospheres under Soft and Hard Confinement: Isobaric versus Isochoric Conditions
| Autor: | Rodney D. Priestley, Chuan Zhang, Maria D'Acunzi, Yunlong Guo, Christine Lai, George Fytas |
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| Rok vydání: | 2011 |
| Předmět: |
Time Factors
Materials science Physics::Medical Physics Physics::Optics General Physics and Astronomy Nanoparticle Condensed Matter::Disordered Systems and Neural Networks chemistry.chemical_compound Suspensions Hardness Polymer chemistry Transition Temperature General Materials Science Physics::Chemical Physics chemistry.chemical_classification Aqueous solution Isochoric process General Engineering Water Polymer Silicon Dioxide Condensed Matter::Soft Condensed Matter chemistry Chemical physics Polystyrenes Relaxation (physics) Isobaric process Glass Polystyrene Glass transition Nanospheres |
| Zdroj: | ACS Nano. 5:5365-5373 |
| ISSN: | 1936-086X 1936-0851 |
| Popis: | We have measured the glassy-state structural relaxation of aqueous suspended polystyrene (PS) nanoparticles (the case of soft confinement) and the corresponding silica-capped PS nanoparticles (the case of hard confinement) via differential scanning calorimetry. Suspended and capped PS nanoparticles undergo physical aging under isobaric and isochoric conditions, respectively. With decreasing diameter, suspended and capped PS nanoparticles exhibited reduced and bulk glass transition temperatures (T(g)), respectively. To account for T(g) changes with confinement, all physical aging measurements were performed at a constant value of T(g) - T(a), where T(a) is the aging temperature. With decreasing diameter, aqueous suspended PS nanoparticles exhibited enhanced physical aging rates in comparison to bulk PS. Due to differences in thermodynamic conditions during aging and interfacial effects from nanoconfinement, at all values of T(g) - T(a) investigated, capped PS nanoparticles aged at reduced rates compared to the corresponding aqueous suspended PS nanoparticles. We captured the physical aging behavior of all nanoparticles via the Tool, Narayanaswamy, and Moynihan model of structural relaxation. |
| Databáze: | OpenAIRE |
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