Formation of poly(vinyl alcohol)-iodine complex in aqueous solution: a SEM study of the freeze-dried substances

✍ Scribed by Noguchi, Hiroji; Jodai, Hiroshi; Yamaura, Kazuo; Matsuzawa, Shuji

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 348 KB
• Volume: 47
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199812)47:4<428::aid-pi56>3.0.co;2-w

✦ Synopsis

The freeze-dried samples prepared from dilute PVA aqueous solutions and PVAÈiodine complex aqueous solutions have been examined using a scanning electron microscope. The samples prepared from syndiotacticity-rich PVA (S-PVA) solutions were found to have a network structure due to the formation of intermolecular hydrogen bonds, whereas in the case of atactic PVA (A-PVA) a network structure was not found. The network structure became more Ðnely structured with increasing syndiotacticity. The structure of the freeze-dried sample of the complex solution prepared from S-PVA having a syndiotactic diad content of 63É8%, and iodine, was coarse in comparison with that of the freezedried sample of the S-PVA solution. In addition, the formation of spherical bulges, which are considered to correspond to microgels in the aqueous solution, were observed in several places. In the S-PVA having a syndiotactic diad content of 57É8%, the spherical bulges were not observed, whereas the absorbance of the aqueous solution was the highest. Although A-PVA did not form a PVAÈ iodine complex at 30¡C in solution, the frozen solution turned blue due to the formation of aggregates. These phenomena were conÐrmed by the degree of crystallinity estimated from IR spectra, and the amount of iodine estimated from X-ray microanalysis of the freeze-dried samples. The PVAÈiodine complexes are formed by the interaction of the aggregates of PVA molecules with iodine molecules. However, the PVA microgels do not interact with iodine. Society ( 1998 of Chemical Industry