TY - JOUR
T1 - A small‐angle x‐ray scattering study of alginate solution and its Sol–Gel transition by addition of divalent cations
AU - Wang, Zheng‐Yu ‐Y
AU - White, John W.
AU - Konno, Mikio
AU - Saito, Shozaburo
AU - Nozawa, Tsunenori
N1 - Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.
PY - 1995/2
Y1 - 1995/2
N2 - The small‐angle x‐ray scattering (SAXS) technique has been applied to investigate solution and gel structures of alginate in the absence and presence of two divalent cations: Ca(II) and Cu(II). We have observed a broad maximum in the scattering curve, a characteristic of polyelectrolyte, for the purified alginate sample. The scattering maximum disappears in excess of added simple salt and shifts toward the higher angle region with increasing alginate concentration. Concentration dependence of the position and intensity of the maximum follows power law relations with exponents close to those predicted by theory. Data analysis shows an increase in correlation length ξ and cross‐sectional diameter d0, of polymer chains upon gelation and suggests that a dimeric structure is adopted in the junction zone, consistent with the “egg‐box” model previously proposed. In the Ca(II)–alginate system, the molecular parameters ξ and d0 are found to have good correlation with the macroscopic properties of gelation, such as gel point determined by viscosity measurements. However, for the Cu(II)–alginate system there is no clearly transitional behavior observed in ξ and d0, implying that the junction zone may be replaced by a more uniformly distributed site binding of Cu(II) ions to the carboxyl groups of both mannuronate and guluronate residues, in confirmation of previous 13C‐nmr results. © 1995 John Wiley & Sons, Inc.
AB - The small‐angle x‐ray scattering (SAXS) technique has been applied to investigate solution and gel structures of alginate in the absence and presence of two divalent cations: Ca(II) and Cu(II). We have observed a broad maximum in the scattering curve, a characteristic of polyelectrolyte, for the purified alginate sample. The scattering maximum disappears in excess of added simple salt and shifts toward the higher angle region with increasing alginate concentration. Concentration dependence of the position and intensity of the maximum follows power law relations with exponents close to those predicted by theory. Data analysis shows an increase in correlation length ξ and cross‐sectional diameter d0, of polymer chains upon gelation and suggests that a dimeric structure is adopted in the junction zone, consistent with the “egg‐box” model previously proposed. In the Ca(II)–alginate system, the molecular parameters ξ and d0 are found to have good correlation with the macroscopic properties of gelation, such as gel point determined by viscosity measurements. However, for the Cu(II)–alginate system there is no clearly transitional behavior observed in ξ and d0, implying that the junction zone may be replaced by a more uniformly distributed site binding of Cu(II) ions to the carboxyl groups of both mannuronate and guluronate residues, in confirmation of previous 13C‐nmr results. © 1995 John Wiley & Sons, Inc.
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U2 - 10.1002/bip.360350211
DO - 10.1002/bip.360350211
M3 - Article
AN - SCOPUS:0028891346
VL - 35
SP - 227
EP - 238
JO - Biopolymers
JF - Biopolymers
SN - 0006-3525
IS - 2
ER -