Cellulose Nanocrystal well alignment with addition magnetic nanoplates in weak gradient magnetic field

Rod like Cellulose nanocrystal (CNCs) are emerging nanomaterials that form chiral nematic liquid crystals and the controlling of orientation of formed liquid crystal phased has attracted broad attention. To enhance the response of CNC rods in the magnetic field, barium hexaferrite (BF) nanoplates, with positive magnetic susceptibility and mean nanoplatelet magnetization is m_o= 2*10^-18 A m², were introduced. Here, we investigated the effect of addition BF nanoplatelets on the phase transition and orientation of CNCs suspension in a weak external gradient magnetic field (Several hundred Gauss) . We observed the nematic phase prefer to move to the lower magnetic field region and a floating nematic phase is formed when the direction of magnetic field is contrast with the gravity field. We also demonstrate the gradient magnetic field can accelerate the phase separation. Based on these, we establish a method to control the phase separation speed and the position of nematic phase, since the movement of nematic phase depends on the competition of magnetic and gravity field. Moreover, the nematic phase were nearly perfect alignment along the magnetic field, which indicate with the BF magnetic nanoplates, the CNCs can be aligned by very weak magnetic field.