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Article
Ultrathin Polymer Films: Rubbery Stiffening, Fragility and Tg Reduction
Macromolecules (2015)
  • Xiguang Li, Texas Tech University
  • Greg B. McKenna, Texas Tech University
Abstract
The mechanical and viscoelastic responses of poly(ethyl methacrylate)
(PEMA) ultrathin films over thicknesses ranging from 21 to 112 nm have been
studied using a nanobubble inflation method. The stress−strain response of the
PEMA thin films shows a rubbery stiffening as the film thickness decreases, and the
present results are combined with prior measurements of the rubbery stiffening index
S for multiple polymers. We find that S is linearly correlated with the dynamic fragility
index m. The results are also consistent with expectation from Ngai et al.’s [J. Polym.
Sci., Part B: Polym. Phys. 2013, 51 (3)] recent proposition based on his coupling
model but do not seem to correlate with the molecular composite concept proposed
by Page et al. [Nano Lett. 2014, 14 (5)] as a means to explain the dependence of the
rubbery stiffening on chemical structure of the polymer. In addition, we observe a
reduction in glass transition temperature of as much as 15.7 K for PEMA films of 21
nm thickness.
Keywords
  • thin polymer films,
  • nano- confinement,
  • Tg reduction
Publication Date
Summer August 18, 2015
Citation Information
Xiguang Li and Greg B. McKenna. "Ultrathin Polymer Films: Rubbery Stiffening, Fragility and Tg Reduction" Macromolecules Vol. 48 (2015) p. 6329
Available at: http://works.bepress.com/xiguang-luc-li/5/