Cellulose triacetate and triethyl cellulose have been crystallized from dilute solution into regular compact lamellar crystals of microscopic size (10–20 μ) and of the same type as the single crystals previously obtained from linear synthetic polymers The shape of the cellulose acetate crystals (pyramids with square base) conforms with the crystal lattice of cellulose triacetate II (pseudo‐orthorhombic unit cell) when the chains are at right angle to the base planes. Compact platelike crystals of pure cellulose containing the lattice of cellulose II (mercerized cellulose) have been prepared from aqueous solutions by slow saponification of water‐soluble cellulose acetates. At 90°C. the crystals can be grown to a regular diamond (lozenge) shape (15 × 30 μ in cross section) with a lattice order as good as or better than that of purified dried native cotton fiber or bacterial cellulose. The shape of the crystals conforms with the crystal lattice of cellulose II (monoclinic unit cell with the angle 60°) if the chains are a t right angle to the base planes. It is concluded that the crystals of cellulose and cellulose derivatives are single crystals of a structure analogous to that of synthetic polymers. This would require chain folding also for the cellulose molecules. From studies of molecular models of cellulose chains, a 180° fold is considered possible with about four glucose residues‐provided the consecutive units are rotated around the glycosidic bonds.
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Rånby et al. (1961) studied this question.