Suppression of the Fragility-Confinement Effect via Low Molecular Weight Cyclic or Ring Polymer Topology

Lanhe Zhang, Ravinder Elupula, Scott M. Grayson, John M Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

We used differential scanning calorimetry and spectroscopic ellipsometry to measure the molecular weight (MW) dependence of bulk fragility (mbulk) and spectroscopic ellipsometry to measure the thickness dependences of the glass transition temperature (Tg) and fragility (m) in supported thin films of low MW cyclic or ring polymer. The effects of confinement on Tg and m of thin polymer films are important in a range of advanced technology applications, including nanoimprinting. It has previously been shown that nanoconfined films of high MW linear polystyrene (PS) exhibit major Tg- and m-confinement effects whereas films of low MW cyclic PS (c-PS) show at most a very weak Tg-confinement effect. In the absence of chain ends, c-PS exhibits very weak Tg,bulk- and mbulk-MW dependences compared to linear PS. Despite low MW c-PS having mbulk values similar to that of high MW linear PS, we found that low MW c-PS films show a very weak m-confinement effect because of a weak free-surface effect; e.g., m for a 27 nm thick film of 3.4 kg/mol c-PS is the same as mbulk within error. Overall, these results support a strong correlation between the susceptibility of fragility perturbation and the susceptibility of Tg perturbation caused by MW reduction, chain topology, and/or confinement.

Original languageEnglish (US)
Pages (from-to)1147-1154
Number of pages8
JournalMacromolecules
Volume50
Issue number3
DOIs
StatePublished - Feb 14 2017

ASJC Scopus subject areas

  • Organic Chemistry
  • Materials Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry

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