Abstract
Positron annihilation lifetime spectroscopy (PALS) has been performed on a series of PMMA nanohybrids containing nanometric TiO2, which were produced by means of different preparation methods, i.e., melt mixing, electrospinning combined with solution mixing, or in-situ sol–gel growth methods, to study the effect of filler content and constituents on the free volume properties. The PMMA nanocomposites containing titania precursor or in-situ-formed TiO2 additives exhibit altered free volume properties compared to adding commercial TiO2 P25 fillers. The orthopositronium (o-Ps) lifetime (τ3) (free volume cavity size) was constant with composition in P25/PMMA nanohybrids due to the absence of interfacial interaction. However, in TiO2 precursor/PMMA composite fibers the free volume cavity size decreased substantially with hydroxyl group concentration and recovered after hydrothermal treatment. Additionally, a strong correlation between the glass transition temperature and the o-Ps lifetime in the nanohybrids wa...
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