We have provided direct experimental evidence of dynamical facilitation occurring in organic glasses by manipulating the presence and position of mobile regions. Glasses of indomethacin (IMC) were prepared by vapor-deposition in isotopically labeled multilayers. The samples were annealed above Tg and measured with Secondary Ion Mass Spectrometry. For stable glasses we observe a growth front initiating at the free surface and no transformation at the glass/substrate interface. The number of growth fronts can be controlled by adding higher mobility layers that can be placed anywhere across the sample through ordinary glass depositions. The mobility in these regions does not remain isolated but gives rise to mobility in neighboring regions, thus enabling kinetic facilitation independently of free surface mobility. Capping the free surface eliminates surface mobility, impedes transformation and increases sample stability.

Direct observation of dynamical facilitation in organic glasses

244th National Meeting (2012)

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