Ultrathin Polymer Films: Rubbery Stiffening, Flagility, and T-g Reduction

Xiguang Li, Gregory McKenna

Research output: Contribution to journalArticle

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 thicknes
Original languageEnglish
Pages (from-to)6329-6336
JournalMacromolecules
DOIs
StatePublished - Sep 2015

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