Molecular probe technique for determining local thermal transitions: The glass transition at Silica/PMMA nanocomposite interfaces Articles uri icon

publication date

  • October 2010

start page

  • 4891

end page

  • 4898

issue

  • 21

volume

  • 51

international standard serial number (ISSN)

  • 0032-3861

electronic international standard serial number (EISSN)

  • 1873-2291

abstract

  • Local glass transition temperatures (Tg) have been measured in the interfaces of solution blended silica/poly(methyl methacrylate) (PMMA) nanocomposites using florescence spectroscopy and compared with Tg measured by differential scanning calorimetry (DSC). It was found that the two types of measurements yielded significantly different information. Combinations of silanes and poly(propylene glycol)-based molecular spacers bound to fluorophores were covalently linked to the surface of the nanoparticles, allowing for variation of the fluorophore response with respect to the distance from the nanofiller surface. Increases in the bulk Tg from the neat PMMA value were found upon the addition of nanofillers, but were independent of the nanofiller concentration when the filler concentration was above 2% by weight. Furthermore, as the size of the grafted molecular spacer was increased, Tg values were found to decrease and approach Tg of the neat PMMA. Owing to variable conformations of the spacers, an effective distribution of fluorophore-silica distances exists, which influences the fluorophores' response to the transition.

keywords

  • Glass transition
    Nanocomposite
    Fluorescence spectroscopy