Signatures of the fast dynamics in glassy polystyrene by multi-frequency, high-field electron paramagnetic resonance of molecular guests

Glassforming Liquids, Amorphous and Semicrystalline Polymers: Exploring their Energy Landscape and Dynamical Heterogeneity by Multi-frequency High-Field EPR

“…The present paper reviews in a concise way the experimental efforts carried out in Pisa using the HF-EPR spectroscopy to provide novel insight into a wide class of disordered systems both in the solid state, i.e., amorphous polymers [14][15][16][17][18][19][20], and in the liquid state, i.e., glassforming viscous liquids [21,22], polymer melts [21] and semicrystalline polymers [23,24]. For completeness, in addition to the previous studies, we also mention other investigations employing the same equipment [25][26][27][28][29][30][31].…”

“…Two main issues were addressed, namely the distribution of energy barriers which must be overcome by the spin probe during the reorientation process [14][15][16][17][18][19][20] and the spatial distribution of microscopic mobility [23,24]. The former aspect is strictly related to the features of the so-called "energy landscape" of glasses, whereas the latter, dubbed "dynamical heterogeneity" [36,37] is a distinctive feature of viscous liquids approaching the solidification process, known as glass transition, and is also present in semicrystalline polymers due to coexistence of liquid and solid fractions.…”