Dielectric relaxation spectroscopy in interpenetrating polymer networks

The electrical and dielectric properties of Interpenetrating Polymer Networks (IPNs) based on crosslinked polyurethane (PUR) and copolymer of butylmethacrylate and dimethacrylate triethylene glycol were studied by means of broadband ac dielectric relaxation spectroscopy. Three relaxation processes were observed: secondary β-relaxation (due to copolymer), α-relaxation due to the glass-rubber transition of PUR phase and conductivity current relaxation due to space charges trapped at the interfaces of the material with different conductivity. The dipolar mechanisms (β,α) and the ac conductivity mechanism were studied in detail by analyzing the dielectric susceptibility data within the complex permittivity formalism, and modulus formalism. For the copolymer network the dielectric losses ε"(ω) show a strong secondary β-relaxation which becomes faster in the IPNs. The PUR network displays a relatively broad α-relaxation process which becomes slower in the IPNs. The energy and the shape parameters of the response were determined for both mechanisms at several temperatures