Dielectric relaxation analysis of hybrid acrylic–polyurethane gels

• Dielectric relaxations in chemically similar gels are found to depend on the synthesis conditions.
• Small angle X-ray diffraction also evidence differences.
• No differences are detected in their thermal properties.
• Results are rationalized in terms of PU bundle structures present in these hybrid gels.

In this paper we present a dielectric relaxation analysis of three acrylic–polyurethane gel samples in connection with their synthesis conditions. The dielectric analysis was carried out using broadband dielectric spectroscopy (BDS). Additionally, differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) measurements were performed. The thermodynamic characterization outcomes evidence very similar characteristics of the glass transition phenomena among the investigated samples without any signature of melting or crystallization. X-ray diffraction patterns evidence distinctive features for the three gel samples in two different regions, i.e., at high and low values of the scattering vector q. BDS measurements, identify three distinct dielectric relaxation processes above Tg. Particularly, differences in the dielectric parameters of the slowest relaxation process have been rationalized in connection with the synthesis method used. Our results show that the analysis of these acrylic–polyurethane gels by BDS – in combination with SAXS – provides access to characteristics of the network structure that would ultimately influence the properties of these materials.

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