Structure and properties of poly(vinyl alcohol)–iodine complex formed in the crystal phase of poly(vinyl alcohol) films

摘要

AbstractThe structure and optical properties of the complex formed in the crystal phase of PVA that is caused by soaking at very high iodine concentration are investigated. In the resonance Raman spectra of lightly and heavily iodinated specimens, two Raman shifts appeared at 109 and 161 cm−1. The 109 cm−1peak due to the I −3mode was much stronger than the 161 cm−1peak in a heavily iodinated specimen, whereas the peak was comparable with the 161 cm−1peak in a lightly iodinated specimen. The complex formed in the crystal phase is identified as the I −3mode complex. It has an averaged iodine–iodine distance of 3.2 Å, which is different from the 3.08 Å of the I −5mode complex formed in the amorphous phase. The effect of KI concentration in the soaking solution on the formation of the complex is also examined. The increased KI concentration in the soaking solutions at a fixed iodine concentration increases the amount of the complex formed in the crystal phase. The change in the hydrogen‐bonding state in the crystal phase with the complex formation can be evidenced by IR and NMR. ©