Structural relaxation of polymer nanospheres under soft and hard confinement: Isobaric versus isochoric conditions

Yunlong Guo, Chuan Zhang, Christine Lai, Rodney D. Priestley, Maria D'Acunzi, George Fytas

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


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 (Tg), respectively. To account for Tg changes with confinement, all physical aging measurements were performed at a constant value of Tg - Ta, 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 Tg - Ta 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.

Original languageEnglish (US)
Pages (from-to)5365-5373
Number of pages9
JournalACS Nano
Issue number7
StatePublished - Jul 26 2011

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


  • TNM model
  • confinement
  • core-shell nanoparticles
  • glass transition
  • nanoparticles
  • physical aging
  • structural relaxation


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