Flow-induced Alignment of Disk-like Graphene Oxide Particles in Isotropic and Biphasic Colloids

The flow-induced ordering of Graphene oxide (GO) particles was investigated in a tube flow of aqueous GO dispersions with varying GO concentrations. By measuring the average effective birefringence for the samples in a tube flow, we could quantitatively deduce the order parameter of GO particles. The flow-induced effective birefringence linearly increased as the GO concentration increased in isotropic phase, but the birefringence deviated from the linear tendency and increased more in biphase. We also calculated the S and P order parameters using the optical birefringence profile in the tube flow. The result showed that the S order parameter kept increasing as the GO concentration increased but the P order parameter decreased as the GO concentration increased. All these results indicate that the increase in inter-particle ordering interaction in biphase enhances the uniaxial S order parameter in the flow-induced ordering and suppresses the biased biaxial ordering.