Dielectric spectroscopy investigation on relaxation in polyazomethine/fullerene C60 nanocomposites

• Polyazomethine/fullerene C60 nanocomposites varying in C60 content are prepared.
• C60 loading was shown to affect the side chain mesogen oscillations mobility.
• C60 loading was found to retard the α-relaxation.
• C60 loading increases both polymer fragility and glass transition temperature.

Nanocomposites based on polyazomethine (PAZ) matrix filled with fullerene C60 (0, 0.25, 0.5, 1, 1.5, and 2.5 wt%) were studied with broadband dielectric spectroscopy to investigate the filler effect on the molecular mobility of the polymer chains. The formalism of dielectric loss was used to analyze the dielectric response. Thus two low-temperature non-cooperative local β1- and β2-relaxations and one high-temperature cooperative segmental α-relaxation were found and observed. The increasing C60 content was shown to accelerate the rotational oscillations (β1-relaxation) and to retard the torsional oscillations (β2-relaxation) of the mesogens in the side chain of PAZ. The increasing C60 content (from 0 to 1.5 wt%) was found to enhance the attractive C60-polymer segments interaction resulting in retardation of the α-relaxation. As a consequence, the polymer fragility m increases and the glass transition temperature Tg of the PAZ/C60 nanocomposite increases strongly with increasing C60 loading. However, at the maximum C60 content (2.5 wt%), the C60 nanoparticles form percolation network resulting in enhanced conductivity of the nanocomposite and weakening the C60/polymer segments interaction. As a consequence, m decreases and Tg tends to decrease towards the value of the pristine PAZ.

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