Iodine reaction of vinyl acetate‐vinyl propionate copolymers, VI, thermochromism of the iodine complex membranes of poly(vinyl acetate) and vinyl acetate‐vinyl propionate copolymers

Tanaka, Makoto; Mizutani, Katsumi

doi:10.1002/apmc.1979.050780115

Cited by 3 publications

(2 citation statements)

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“…4 The spectra of our iodine-PYA gels were very similar to those of the iodine-poly-( vinyl acetate) (PVAc) complexes reported by Hayashi et a/. 13 On the basis of Raman data, they concluded that the A.max due to 15 that of polycrystalline (benzamide hH + I 3 -used as the model substance. These considerations lead us to suppose that the shift of Amax from S20 nm to 620 nm, caused by increased D.H. and decreased temperature, may be attributed to the increase in the number of iodine atoms in a polyiodine chain.…”

Section: Resultssupporting

confidence: 54%

“…The sudden beginning of stress relaxation in Figure 8 indicates a discontinuous increase in the mobility of the network chains at the temperature, implying a kind of transition in PV A gels. It has been reported 15 that the iodine-PVAc complex suddenly disappears when the temperature is over the glass transition point of the polymer. In our case, the decrease of the amount of complex occurs gradually, suggesting that the transition at 20oc is not 'the Tg where the chain mobility changes from that of solid to that of liquid.…”

Section: Resultsmentioning

confidence: 99%

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Effects of the Degree of Hydration of Water Swollen Poly(vinyl alcohol) Films on Their Iodine Complexation

Oishi

Mlyasaka

1986

Polym J

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ABSTRACT:PYA films with a wide span of hydration (swelling) were soaked at different temperatures in iodine aqueous solutions to make the iodine-PYA complex, with a particular concern for the effects of the degree of hydration (D.H.) on the complex formation. The visible absorption maximum A.m., increased with D.H., while it decreased with temperature. The equilibrium amount of the complex increased with D.H. at a given concentration of iodine below 20°C. However, the effects of D. H. on the amount of complex deteriorated with increasing temperature and at 45°C became reversed to those at low temperature. When the samples soaked at soc were heated in the solution, the amount of complex suddenly began to decrease at 20oC; this corresponded to the sudden stress relaxation of water swollen PV A films. This transition seems to have great effect on the complexation. Poly(vinyl alcohol) (PYA) forms a complex with iodine, changing the color from brown to blue. 1 • 2 The most important application of the complex is use as sheet polarizers with a high quality of dichroism. 3 The polarizer is usually prepared by soaking PYA films in the iodinepotassium iodide solution with boric acid and by subsequent drawing to cause a high degree of uniaxial orientation. The iodine-PYA complexation occurs both in the aqueous solution and swollen gel states of PYA depending on the iodine concentration and temperature. For example, in solution, the amount of increases with increasing concentrations of PYA, iodine and boric acid. 4 The complex disappears during heating and again appears during cooling, resulting in color changes between blue and brown. 2 • 5 • 6 The extension of PYA gels enhances the complexation, 5 • 7 suggesting that the extended conformation of PYA chain segments is favorable for complexation. The strain-induced complexation is reversed on removal of the strain. 7 Many studies have been made also on the structure of the complex. For example, Zwick hypothesized a structure in which a linear polyiodine chain is included by helical PYA chains going around, 4 according to the structure of the iodine-amylose complex. 8 Inagaki et a/. 9 support this structure with the similarity between the raman spectra of iodine-PYA and iodine-amylose complexes. On the other hand: Rundle et a/. 10 proposed another one in which a polyiodine chain lies parallel to an extended part (segment) of a PYA chain. Tebelev 11 supports Rundle's model and further proposes that the iodine chain is surrounded by several extended PYA segments. In spite of these propositions, the structure has not been explicitly determined. We have been interested in 307

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%