X-RAY AND ELECTRON-DIFFRACTION STUDY ON CELLULOSE BUTYRATE DIACETATE (CBDA, 2,3-DI-O-ACETYL-6-O-BUTYRYL CELLULOSE)

The unit lattice parameters and space group of cellulose butyrate diac etate (CBDA, 2,3-di-O-acetyl-6-O-butyryl cellulose) were determined th rough a combined X-ray fiber diagram of stretched and annealed film an d electron diffraction patterns of single crystal analysis. The unit l attice of CBDA is orthorhombic with space group P2(1)2(1)2(1) and para meters: a=1.544 nm, b=2.147 nm and c (fiber axis)=1.062 nm. Based on b oth these data and the observed density of the crystals, there exist f our chains per unit cell, which consists of two antiparallel and two p arallel chains, and the crystallographic repeat is the disaccharide un it in each chain. Taking unit lattice parameters and space groups of C BDA, cellulose triacetate and cellulose propionate diacetate (CPDA, 2, 3-di-O-acetyl-6-O-propionyl cellulose) into consideration, it is clear that the acyl substituents derived from secondary hydroxyl groups of the C(2) and C(3) positions play a decisive role in the conformation o f the cellulose ester.