Quantitative Crystal Structure Analysis of Poly(vinyl Alcohol)–Iodine Complexes on the Basis of 2D X-ray Diffraction, Raman Spectra, and Computer Simulation Techniques

The crystal structures of the two types of iodine complexes (complex I and II) of poly(vinyl alcohol) (PVA), which were prepared respectively from the KI/I2 aqueous solution of middle (0.1–0.5 mol/L) and high (1–3 mol/L) concentration of I2, have been analyzed quantitatively on the basis of 2-dimensional X-ray diffraction diagrams and Raman spectral data in addition to the computer simulation method. In the crystal lattice of the original PVA, the PVA chains of zigzag conformation are packed together by intermolecular hydrogen bonds. Once the I3– ions migrate into the crystal lattice of PVA, these hydrogen bonds are deconstructed and the PVA chains are displaced from the original positions so that the I3– ions can be coupled together with the PVA chains through the charge-transfer between the I3– and hydroxyl groups, resulting in the formation of complex I. In this complex, the averaged occupancy of I3– ions is about 0.2, and the PVA–iodine pairs and the original PVA chain pairs coexist to form a kind of ...