Graphene oxide (GO) forms a well-aligned lyotropic liquid crystal (LC) phase in aqueous dispersions at relatively low concentrations. Under a remarkably wide range of shear rates, we report hitherto unobserved shear-induced polarized light image patterns, a Maltese cross combined with shear banding, recorded in real time and in situ during rheological measurements. This is shown to be a result of elastic flow instabilities that manifest as a helical flow in alternating bands of left- and right-handed helices, arising from a combination of shear flow and Taylor-type vortex flow. The instability is observed for LCs formed from large aspect ratio GO particles owing to their unique viscoelastic properties, but not for smaller aspect ratio particles. This phenomenon coincides with rheopecty and anomalous small-angle X-ray scattering patterns under shear flow, which confirm the instabilities. The results presented here could lead to advanced control over macroscopic periodic alignment in technologically relevant dispersions of two-dimensional material particles.

氧化石墨烯（GO）在较低浓度下在水性分散液中形成取向良好的溶致液晶（LC）相。在非常大的剪切速率范围内，我们报告了迄今未观察到的剪切诱导的偏振光图像模式，结合剪切带的马耳他十字形，在流变学测量中实时和原位记录。这是弹性流动不稳定性的结果，弹性流动不稳定性表现为剪切流和泰勒型涡流的组合所产生的左右旋螺旋交替带中的螺旋流。由于大的长径比的GO颗粒具有独特的粘弹性质，因此观察到由大长径比的GO颗粒形成的LC的不稳定性，而较小的长径比的颗粒则没有这种稳定性。这种现象与剪切流作用下的流变学和反常的小角度X射线散射图相吻合，证实了这种不稳定性。此处介绍的结果可能导致对二维材料颗粒的技术上相关的分散体中的宏观周期性对准进行高级控制。