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On the glass transition in ultrathin polymer films of different molecular architecture
Author(s) -
Prucker Oswald,
Christian Stefan,
Bock Harald,
Rühe Jürgen,
Frank Curtis W.,
Knoll Wolfgang
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980701)199:7<1435::aid-macp1435>3.0.co;2-#
Subject(s) - glass transition , polymer , polymer science , polymer chemistry , materials science , composite material , chemical engineering , engineering
Optical waveguide spectroscopy has been employed to monitor the temperature dependence of the refractive index, k = ∂n/∂T , and of the thermal (linear) expansivity, ß = ( ∂d/∂T ) · d −1 , for thin poly(methyl methacrylate) (PMMA) films of thicknesses d > 0.2 μm independently from each other. A break in the linearized slope of n (and d ) was identified as the film glass transition temperature, T g . For thinner samples only surface plasmon resonances could be analyzed, but the kinetic mode, i.e. reflectivity‐ versus ‐temperature scans, still gave reliable T g values. The PMMA films of different thicknesses, ranging from d ∼ 3 nm to d ∼ 800 nm, were prepared by three different techniques: by spin‐casting from solution, by the grafting‐ from approach and by the Langmuir/Blodgett/Kuhn technique. We found that all these films prepared on hydrophobic substrates show the expected decrease of T g for ultrathin samples ( d < 100 nm). However, this behavior is independent of the strongly varying intramolecular architecture and organization of the macromolecular chains in the various films.