On the poly(vinyl alcohol)–iodine complexes

Abstract

SYNOPSISThe color development due to the complex formation of poly(viny1 alcohol) (PVA) with iodine increased with increasing syndiotacticity of PVA. Isotactic PVA showed no color development. The color development of syndiotacticity-rich PVA film decreased with increasing annealing temperature for films before complexization, whereas that of atactic (commercial) PVA increased with it. Lower temperatures, the elongation of complex film, and the presence of boric acid enhanced the absorbance at 600 nm due to I;. The complexes are assumed to be made by incorporation of polyiodines into aggregates of syndiotactic sequences in PVA. The polarizability and electric conductivity of complex films are investigated. 0 1993 John Wiley & Sons, Inc.

Molecular iodine/polymer complexes

“…Very interesting research, still going on, is the study of the effect of tacticity, molecu lar weight and branching of PVA ( Figure 7B), and of the content of residual acetyl groups on the I 2 PVA complex formation [137][138][139][140][141][142]. The solutions of this complex were deep blue, green, redorange or yellow, depending upon the conditions.…”

Color Formation and Gelation of Xyloglucan Upon Addition of Iodine Solutions

“…[2] The other model proposed is the aggregate model for PVA and its iodine complex. [3,4] The iodine color reaction also occurs with cellulose, [5,6] which is composed of poly-(1-4)-b-glucose residues, but study of this situation is limited by the lack of effective solvents for cellulose. Cellulose derivatives also can form complexes with iodine molecules.…”

Polyvinyl Alcohol as a Useful Indicator on Iodometry: Volumetric and Spectrophotometric Studies on Iodine-PVA and Iodine-Starch Complexes

“…There are several unsolved problems for iodine-PVA complexes, irrespective of extensive investigations. [7][8][9][10][11][12][13] We have carried out MO calculations on iodine-PVA complexes assuming that they are composed of polyiodide with straight or zigzag-type structures to interpret the reason for the color appearance of those bands around 490 nm (λmax) or 640 nm (λmax); however, we could not obtain appropriate structures for the complexes until now. Hereafter, we will mainly use PVA of 88% saponification degree (average) with a polymerization degree of 1000 for convenience because of their plentiful supply.…”

“…Also, because the glycollate does not form a water-insoluble complex with iodine, the indicator may be added at any stage during titration, and the end-point is very sharp. On the other hand, we know that PVA (polyvinyl alcohol) [7][8][9][10][11][12][13] and chitosan 14 react with iodine to form a complex showing a color of bluish violet similar to that of the iodinestarch complex. We considered that PVA might be a more useful color reagent than starch or sodium glycolic acid, and we could determine a residual chlorine concentration of 0.…”