Refractive, dielectric and conductivity characteristics of photopolymerized NOA65 doped with ionic liquid

Conductive polymers that exhibit exceptional electrical conductivity have garnered significant interests in recent decades, disclosing remarkable potentials across a broad range of industries. In this study we investigated a series of Norland UV-curable optical adhesive (NOA65) doped with ionic liquid (1-hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide) at various concentrations from 0 wt% to 2.0 wt%. The refractive indices of the doped prepolymers and photopolymerized NOA65 were examined by Abbe refractometry with four wavelength filters at distinct temperatures. Moreover, the transmission spectra, frequency-dependent complex dielectric and conductivity properties of the composites were explored in comparison with their pristine precursor and photopolymer. Interestingly, by applying an alternating electric field within a specific frequency range, we found that these samples can undergo unique dielectric relaxation, and thus give rise to the observed heating effect. Our preliminary results demonstrate that the conductivity of the proposed polymer composites is significantly higher than that of the undoped counterpart, whereas the refractive index, dispersion, and transmission remain virtually unchanged, revealing great promise for real applications in optoelectronic technology.