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Physicochemical studies of amylose and its derivatives in aqueous solutions: Thermodynamics of the iodine–triiodide complex
Author(s) -
Cesàro Attilio,
Jerian Edvino,
Saule Silvano
Publication year - 1980
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1980.360190806
Subject(s) - triiodide , chemistry , iodide , iodine , aqueous solution , amylose , complex formation , calorimetry , molecule , inorganic chemistry , thermodynamics , organic chemistry , electrolyte , physics , electrode , starch , dye sensitized solar cell
Thermodynamic properties of the amylose–iodine–triiodide complex have been studied by spectrophotometry and by calorimetry using previously studied samples of amylose ionic derivatives, carboxymethylamylose and diethylaminoethylamylose. The ratio of triiodide to total molecular iodine ([I 3 ] b /[I 3 − ] b + [I 2 ] b ) in the complex is ca. 0.3 over a range of iodide concentration from 10 −5 to 10 −4 M , and there is no evidence for an increasing charge at slightly higher iodide concentration. Direct calorimetric experiments have been carried out in different conditions of polymer, iodine, and iodide concentration in order to study the dependence of the heat of the complexation as a function of the above parameters. It is shown that the dependence of the measured Δ H on the iodide concentration simply derives from the rearrangement of the triiodide equilibrium because of the uptake of a fixed ratio of iodine and triiodide molecules in the complex.