ENHANCED ORDERING OF LIQUID-CRYSTALLINE SUSPENSIONS OF CELLULOSE MICROFIBRILS - A SMALL-ANGLE NEUTRON-SCATTERING STUDY

Small angle neutron scattering, SANS, was used to characterize the enh anced ordering induced by magnetic and shear alignment of chiral nemat ic liquid crystals of cellulose microfibrils in aqueous suspension. In a similar to 2 T magnetic field the chiral nematic phase exhibits a u niform orientation over an entire 10 mt sample. SANS data confirmed th at the cholesteric axis of this phase aligns along the magnetic field with implications that the distance between microfibrils is shorter al ong the cholesteric axis than perpendicular to it. This is consistent with the hypothesis that cellulose microfibrils are helically twisted rods. Under shear flow, the alignment of microfibrils changes from chi ral nematic to nematic with relative order increasing with increasing shear rate. The axial ratio (length/width) is the key parameter in det ermining the relative order achieved and in determining the relaxation behavior after shear ceases.