Poly(2-nonyl-2-oxazoline)₈₀-stat-poly(2-dec-9′-enyl-2-oxazoline)₂₀ and poly(2-dec-9′-enyl-2-oxazoline)₁₀₀ can be synthesized from the cationic ring-opening polymerization of monomers that can be derived from fatty acids from renewable resources. These (co)poly(2-oxazoline)s can be crosslinked with di- and trifunctional mercapto compounds using the UV-induced thiol-ene reaction. The complex permittivity of the corresponding networks increases with the temperature and decreases with the network density. In a frequency range from 10⁻² to 10⁶ Hz and at temperatures ranging from −20 to 40 °C, the changes of the real part of the complex permittivity as well as the loss factor can be explained by interfacial polarization within the material. At a temperature of 20 °C and a frequency of 50 Hz, the permittivity of the crosslinked (co)poly(2-oxazoline)s covers a range from 4.29 to 4.97, and the loss factors are in the range from 0.030 to 0.093. The electrical conductivities of these polymer networks span a range from 5 × 10⁻¹² to 8 × 10⁻⁹ S/m, classifying these materials as medium insulators. Notably, the values for the permittivity, loss factor and conductivity of these copoly(2-oxazoline)s are in the same range as for polyamides, and, hence, these copoly(2-oxazoline)-based networks may be referred to as “green” alternatives for polyamides as insulators in electronic applications.

In this study, epoxy-cubic boron nitride composites are fabricated, and their dielectric response is investigated. They exhibit the same trend as epoxy composites reinforced with other filler types. Thus, at low filler concentrations, they exhibit a lower relative permittivity than neat epoxy. As the fill grade further increases, the relative permittivity of the composites increases as well. It is suggested that two competing mechanisms, namely polymer re-organization and water uptake, mainly determine the dielectric response of epoxy composites. The former is related to the decrease while the latter to the increase of the relative permittivity. The experimental results clearly verify that water uptake strongly depends on the filler concentration and not only affects the dielectric response of epoxy composites but also it is one of the main mechanisms which dictate their dielectric behavior.