Journal ArticleDOI
Effect of strongly favorable substrate interactions on the thermal properties of ultrathin polymer films.
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TLDR
If one assumes that a region of reduced chain mobility exists near the solid substrate-polymer interface, an analysis of the measured thermal expansion behavior below the transition temperature indicates that the length scale of substrate interactions is on the order of the macromolecular size.Abstract:
The thermal behavior of ultrathin films of poly-(2)-vinylpyridine spin-cast on acid-cleaned silicon oxide substrates is considered. The interaction between the polymer and the substrate is polar in nature and very favorable. As a means of examining the thermal properties of the films, x-ray reflectivity is used to measure the temperature dependence of the film thickness. This experimentally measured thickness-temperature data is used to determine transition temperatures and thermal expansivities. Significantly increased transition temperatures (20-50 \ifmmode^\circ\else\textdegree\fi{}C above the measured bulk glass transition temperature) are observed in ultrathin polymer films. The transition temperature increases with decreasing film thickness, while the degree of thermal expansion below the transition temperature decreases with decreasing film thickness. If one assumes that a region of reduced chain mobility exists near the solid substrate-polymer interface, an analysis of the measured thermal expansion behavior below the transition temperature indicates that the length scale of substrate interactions is on the order of the macromolecular size.read more
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Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends.
Mariano Campoy-Quiles,Toby A. M. Ferenczi,Tiziano Agostinelli,Pablo G. Etchegoin,Youngkyoo Kim,Youngkyoo Kim,Thomas D. Anthopoulos,Paul N. Stavrinou,Donal D. C. Bradley,Jenny Nelson +9 more
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The distribution of glass-transition temperatures in nanoscopically confined glass formers
TL;DR: The distribution of Tgs across polystyrene films has been obtained by a fluorescence/multilayer method, revealing that the enhancement of dynamics at a surface affects Tg several tens of nanometres into the film.
Journal ArticleDOI
Effects of confinement on material behaviour at the nanometre size scale
TL;DR: In this article, the effects of size and confinement at the nanometre size scale on both the melting temperature and the glass transition temperature, Tm, are reviewed, and it seems that the existing theories of Tg are unable to explain the range of behaviours seen at the nano-scale.
Journal ArticleDOI
Quantitative equivalence between polymer nanocomposites and thin polymer films
Amitabh Bansal,Amitabh Bansal,Hoichang Yang,Hoichang Yang,Chunzhao Li,Kilwon Cho,Brian C. Benicewicz,Sanat K. Kumar,Linda S. Schadler +8 more
TL;DR: The thermomechanical properties of ‘polymer nanocomposites’ are quantitatively equivalent to the well-documented case of planar polymer films and it is conjecture that the glass-transition process requires that the interphase regions surrounding different particles interact.
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Model polymer nanocomposites provide an understanding of confinement effects in real nanocomposites.
TL;DR: It is shown that model nanocomposites provide a simple way to gain insight into the effect of interparticle spacing on Tg and to predict the approximate ageing response of real nanocomPOSites.