Double-Stranded Helix of Xanthan in Dilute Solution: Further Evidence

摘要: Viscosity measurements were made on ten samples of a bacterial polysaccharide xanthan in 0.1 M aqueous NaCl and cadoxen (at 25°C); the polymer dissolves as dimers former monomers latter. Intrinsic viscosities [η] function molecular weight fitted to Yamakawa–Yoshizaki’s theory for Kratky–Porod wormlike chain with linear mass density ML 1940 nm−1, persistence length 120 nm, diameter 2.0—2.5 nm. This corresponds 0.47 nm pitch (per main glucose residue) 51 double-stranded helix proposed crystalline structure xanthan, is consistent previous conclusion from light scattering that dimer has this helical structure. On other hand, values showed single solvent essentially flexible. Those mixtures water decreased sharply an increase composition range 60 70wt% cadoxen. The double-helical was not restored once dissociated into chains pure at 25°C or 95°C.