The optical and the dielectric properties of an original nanocomposite based on the incorporation of carbon dots (C‐dots) in poly(methyl methacrylate) (PMMA) at several filler loading were studied. The optical characterization demonstrated the preservation of the excitation dependent intense emission of the C‐dots in the polymer, ascribed to the presence of organic fluorophores formed during the nanoparticle synthesis. The composite PMMA/C‐dots dielectric properties were investigated in the frequency range from 40 Hz to 1 MHz and over the temperature range from 200 to 400 K. The dielectric response was obtained using the complex permittivity or the modulus formalisms, depending on the concentration of filler in the polymer matrix. A relaxation phenomenon was induced by the incorporation of the C‐dots in the PMMA matrix. In addition, both the real and imaginary parts of the dielectric permittivity and electric modulus changed with the volume fraction of the C‐dots, suggesting that the presence of the fillers greatly affect the dielectric properties of the polymer matrix because of polarization phenomenon induced by the nanoparticles. POLYM. COMPOS., 40:E1312–E1319, 2019. © 2018 Society of Plastics Engineers

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The dielectric properties of biocomposite materials based on vinyl resin filled with microcrystalline cellulose, in the frequency range from 100 Hz to 1 MHz and in the temperature range from 280 to 400 K, are presented. Two dielectric relaxations were identified. The first one is attributed to the α-relaxation, associated with the glass transition of biocomposite, and the second one, appearing above the glass transition and at low frequencies, was identified as the interfacial polarization effect, which is attributed to the accumulation of charges at the cellulose microcrystalline/matrix interface. Furthermore, the thermal analysis of their relaxation frequency and the electrical conductivity behaviors showed that the activation energy of these composite is more pronounced for the temperatures above the glass transition temperature, suggesting that the interaction between MCC particles and polymeric matrix became significant with the increase of temperature.

The investigation of thermal and dielectric properties of carbon dots dispersed in PMMA has been conducted in freestanding thin solid films. Thermal properties were studied using differential scanning calorimetry. Impedance spectroscopy, in the frequency range 100 Hz to 100 kHz and temperatures between 200 and 390 K, was used for the electrical characterization. Using the electric modulus formalism, it has been found that the Havriliak‐Negami model of dielectric relaxation is adequate to fit the experimental data, from which the relaxation parameters can be calculated. The inclusion of C‐Dots in PMMA provides a plasticizing effect on the polymer structure, giving rise to an increase in the mobility of PMMA chains, and consequent changes in the relaxation parameters.

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