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A High-Field EPR Study of the Accelerated Dynamics of the Amorphous Fraction of Semicrystalline Poly(dimethylsiloxane) at the Melting Point |
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| Authors: | Carlo Andrea Massa Silvia Pizzanelli Vasile Bercu Luca Pardi Monica Bertoldo Dino Leporini |
| Institution: | 1. Istituto per i Processi Chimico-Fisici-Consiglio Nazionale delle Ricerche (IPCF-CNR), via G. Moruzzi 1, 56124, Pisa, Italy 2. Istituto di Chimica dei Composti Organometallici-Consiglio Nazionale delle Ricerche (ICCOM-CNR), via G. Moruzzi 1, 56124, Pisa, Italy 3. Department of Physics, University of Bucharest, Str. Atomistilor 405, Magurele, Jud. Ilfov, 077125, Bucharest, Romania 4. Dipartimento di Fisica “Enrico Fermi”, Universitá di Pisa, Largo B. Pontecorvo 3, 56127, Pisa, Italy |
| Abstract: | The reorientation of a small paramagnetic tracer in poly(dimethylsiloxane) (PDMS) has been investigated by high-field electron paramagnetic resonance spectroscopy at a Larmor frequency of 285 GHz. The tracer is confined in the disordered phase of the semicrystalline PDMS. A sudden change of the rotational dynamics is observed close to the melting point (213 K) of the crystallites. This points to strong coupling between the crystalline and the disordered fractions of PDMS. Below the glass transition ( \(T_\mathrm{g} \sim 150 \mathrm{K}\) ), the tracer reorientation occurs via small angle jumps, with no apparent distribution of the correlation times. Above \(T_\mathrm{g}\) , a power-law distribution of correlation times is evidenced. |
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