Examining the varied localization of oxygen groups on graphene nanosheets and their entangled influence on electromagnetic waves’ absorption within polymeric coatings

Abstract

In this study, two distinct graphene nanosheets, featuring varying localization of oxygen groups, were synthesized to investigate their influence on the electromagnetic waves’ absorption properties of polymeric coatings. Natural graphite flakes and expanded graphite served as carbon precursors for synthesizing Edge-Functionalized Graphene Oxide (E-GO) and Basal-Functionalized Graphene Oxide (B-GO) nanosheets, respectively. Subsequently, polymer nanocomposite coatings were fabricated by dispersing E-GO and B-GO into a waterborne epoxy matrix. The dielectric properties of these coatings were measured post-in-situ thermal reduction at 225 °C. Results revealed that coatings containing B-GO nanosheets exhibited higher dielectric values compared to those with E-GO nanosheets. Furthermore, the electromagnetic properties of the coatings were examined to correlate the network formation findings obtained from dielectric studies and reflection loss values. It was demonstrated that an improved dispersion state of graphene nanosheets resulted in enhanced interphase formation between epoxy and graphene nanosheets, thereby improving interfacial polarization and dielectric permittivity values. Additionally, residual oxygen groups situated on the graphene basal plane induced dipolar polarization, consequently enhancing the reflection loss values of electromagnetic waves. Ultimately, the enhancements in electrical conductivity and dielectric permittivity contributed to reflection loss values reaching −52.67 dB in coatings with a thickness of 320 μm and a graphene loading level of 1.5 wt%, representing significant advancements compared to existing literature.