Aspect ratio dependent viscoelastic properties of graphene oxide liquid crystals

We present a systematic investigation of the size-dependent viscoelastic properties of aqueous suspensions of graphene oxide (GO). The study is performed on three different size graphene oxide dispersions with an average sheet surface area of 22.89, 126.42 and 173.83 mu m(2). The viscoelastic properties of the GO suspensions are found to be strongly dependent on the size of GO sheets. Irrespective of the size, all the GO dispersions revealed an isotropic phase at low volume fractions and a nematic liquid crystalline phase above critical volume fractions. Materials Chemistry and Physics 287 (2022) 126305 The formation of nematic liquid crystalline phase strongly depends on the size of GO sheets. The steady-state flow measurements confirmed the nematic liquid crystalline phase formation at a lower fraction (phi = 0.24%) for ultra-large GO sheet dispersion than small area graphene oxide dispersion (phi = 0.45%). Further, frequency sweep measurements of ultra-large GO suspension exhibit higher storage and loss moduli than small area gra-phene oxide dispersion for a particular GO concentration. The study also confirmed the gel-like phase formation at a higher GO fraction (phi > 0.73%), where both storage and loss moduli are nearly independent of frequency. The reported size-dependent viscoelastic properties of GO liquid crystals are very important for the fabrication of GO-based materials for various potential applications.