CP MAS C-13 NMR-STUDY ON MICROBIAL CELLULOSE FLUORESCENT BRIGHTENER COMPLEXES/

The structures of microbial cellulose-fluorescent brightener complexes , produced from the Acetobacter culture in the presence of a fluoresce nt brightener, and the cellulose samples regenerated from them have be en examined by cross-polarization/magic-angle spinning (c.p./m.a.s.) C -13 n.m.r. spectroscopy. C4 and C6 resonance lines for the cellulose c omponents of the complexes appear at about 84.0 and 63.0 ppm, respecti vely, with the disappearance of their downfield crystalline components . Since the chemical shifts of the lines are in good accord with those of the non-crystalline component of native cellulose, it is concluded that the cellulose component of the complex is in the non-crystalline state. C-13 spin-lattice relaxation time (T-1C) measurements have als o confirmed that the T-1C values of the dried complexes are of the sam e order as those for the non-crystalline component of native cellulose . In contrast, the T-1C values of the non-dried complex are much short er than those of the dried complexes, indicating a much enhanced molec ular mobility in the non-dried complex. On the other hand, when the no n-dried complex is subjected to dye extraction, C4 and C6 resonance li nes assignable to the crystalline component can be observed in the c.p ./m.a.s. spectrum. Moreover, selective measurements of the spectrum of the crystalline component have revealed that cellulose I beta is pref erentially grown from the non-dried complex by dye extraction. In the case of the dried complexes, only very small amounts of cellulose I cr ystals are regenerated, possibly as a result of the formation of tight hydrogen bonds in the complex.