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Ion complexation of biopolymers: Macromolecular structure and viscoelastic properties of gels
Author(s) -
Axelos M. A. V.
Publication year - 1990
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19900390128
Subject(s) - viscoelasticity , calcium , ion , ionic strength , viscosity , chemistry , sodium , salt (chemistry) , ionic bonding , shear modulus , modulus , chemical physics , materials science , chemical engineering , composite material , organic chemistry , aqueous solution , engineering
The effect of charge density and solvent conditions have been explored on sodium pectinate–calcium system undergoing gelation. Viscosity and shear modulus were determined respectively before and after the transition. More than 55% of sugar residues need to be charged to build a network. The amount of calcium required increases dramatically with the decrease of pH and ionic strength. Pectins in salt–free solutions are rapidly connected by calcium ions but the crosslink density remains lower than in NaCl‐rich solutions. Small angle X‐ray scattering indicates that the junction zones may be viewed as rod‐like cylinders whose cross–section radius increases from 3 to 6 and 8 Å when the ratio R = 2 (Ca 2+ )/(COO − ) changes from 0 to 0.5 and 0.75.