Wj. Orts et al., ENHANCED ORDERING OF LIQUID-CRYSTALLINE SUSPENSIONS OF CELLULOSE MICROFIBRILS - A SMALL-ANGLE NEUTRON-SCATTERING STUDY, Macromolecules, 31(17), 1998, pp. 5717-5725
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.