Abstract
Viscosity, flow birefringence, and sedimentation measurements are reported for suspensions of crystalline cellulose particles which were obtained by the hydrolysis of native celluloses with strong sulfuric acid (955 g./l. 24 hours, 40°C.). The hydrodynamic behavior of the particles was typical of rigid rods. The length of the equivalent prolate ellipsoid was much greater for suspensions made from bacterial cellulose than from ramie. In both cases, however, the hydrodynamic unit is an aggregate of microfibrillar fragments. Ultrasonic treatment of the suspensions from ramie fibers caused a marked reduction in the average length of the equivalent ellipsoid. The observed hydrodynamic properties after this treatment could be directly correlated with the size and length distribution of particles in the suspension as viewed in the electron microscope. The lateral dimensions of the latter particles indicate that they are derived by transverse cleavage of the microfibrils; hence a true suspension of cellulose crystallites was obtained. The possibility of using these suspensions as model systems of rigid rods for hydrodynamic studies is discussed.
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