Miscibility of blends of Aeromonas gum or Erwinia gum with other polysaccharides

Aeromonas (A) gum and Erwinia (E) gum are acidic heteropolysaccharides, which exist in water as expanded chains caused by the electrostatic repulsion between the charged groups. A modified approach, which was suggested to estimate miscibility of stiff polymer in our previous study, was used to determine miscibility parameter mu for blends between A gum or E gum with other polysaccharides, by using viscometry in aqueous 0.1M NaCl solution. When weight ratios of E gum/pectin were in the range of 3:7 similar to 7:3, the blends in aqueous solution are miscible. The blends of A. gum/xanthan, A gum/pectin, and E gum/xanthan in aqueous solution are obviously immiscible. When the weight fraction (w(2)) of A gum or E gum in the mixture solution is 0.7, the mu predicts that the miscibility of blend films was on the order of E gum/pectin > E gum/xanthan > A gum/pectin > A gum/xanthan. These results are in good agreement with those observed by scanning electron microscopy and Fourier transform IR. (C) 1999 John Wiley & Sons, Inc.