Abstract
A computer aided molecular design (CAMD) technique was applied to investigate a possible packing model for cellulose triacetate I (CTA I). The model was constructed based on structural data obtained by CP/MAS 13C NMR. The starting model was determined by molecular mechanics (MM) calculations on the basis of a model proposed previously by X-ray diffraction data. Molecular dynamics (MD) calculation data indicated the CTA I crystalline has a one-chain, monoclinic structure with unit cell parameters of a = 1.19 nm, b = 0.65 nm, c (fiber repeat) = 1.08 nm, and γ = 104°; the torsion angles χ (C4-C5-C6-O6) are gauche-gauche (gg); and that the side chains are one kind of conformation, respectively. This structure reveals that a glucopyranose residue becomes an asymmetric unit, whereas the previous model contains two independent chains per unit cell with P21. Hence, we propose a refined structure of CTA I.
