Effects of Nanoscale Confinement and Interfaces on the Glass Transition Temperatures of a Series of Poly(n-methacrylate) Films

Rodney D. Priestley; Manish K. Mundra; Nina J. Barnett; Linda J. Broadbelt; John M. Torkelson

doi:10.1071/CH07234

RESEARCH ARTICLE

Effects of Nanoscale Confinement and Interfaces on the Glass Transition Temperatures of a Series of Poly(n-methacrylate) Films

Rodney D. Priestley ^A , Manish K. Mundra ^B , Nina J. Barnett ^B , Linda J. Broadbelt ^A and John M. Torkelson ^A ^B ^C

+ Author Affiliations

- Author Affiliations

^A Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, USA.

^B Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.

^C Corresponding author. Email: j-torkelson@northwestern.edu

Australian Journal of Chemistry 60(10) 765-771 https://doi.org/10.1071/CH07234
Submitted: 9 July 2007 Accepted: 24 August 2007 Published: 9 October 2007

Abstract

We use fluorescence from dye-labelled polymer to measure the glass transition temperatures (T_gs) across single-layer films and near surfaces and silica interfaces in bilayer films for a series of poly(n-methacrylate)s. With nanoscale confinement, the average T_g across a film supported on silica increases for poly(methyl methacrylate) (PMMA), decreases for poly(ethyl methacrylate) (PEMA) and poly(propyl methacrylate), and is nearly invariant for poly(iso-butyl methacrylate) (PIBMA). These trends are consistent with the relative strengths of local perturbations to T_g caused by surfaces and substrates as measured in bilayer films. The substrate effect, which increases T_g via hydrogen-bonding interactions between the polymer and hydroxyl groups on the silica surface, is stronger than the free-surface effect in PMMA. The free-surface effect, which reduces T_g via a reduction in the required cooperativity of the glass transition dynamics, is stronger than the substrate effect in PEMA. The substrate and free-surface effects have similar strengths in perturbing the local T_g in PIBMA, resulting in a net cancellation of effects when measurements are made across single-layer films.

Acknowledgements

This work was supported by the NSF-MRSEC program at Northwestern University (grants DMR-0076097 and DMR-0520513), Northwestern University, and a DFI fellowship (R.D.P.).

References

Effects of Nanoscale Confinement and Interfaces on the Glass Transition Temperatures of a Series of Poly(n-methacrylate) Films

Abstract

Acknowledgements

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