Structure and processability of iodinated poly(vinyl alcohol) (III)‐structure of films iodinated in solution before casting

Abstract

Films iodinated at solution before casting (IBC films) were prepared by casting aqueous solutions of 10 wt % poly(vinyl alcohol) (PVA) containing selected quantities of I 2 /KI. The quantity of I 2 /KI was controlled to obtain 15.2, 39.8, 83.2, 117.0, and 140.1%. The Thermogravimetry (TG) curves of the IBC film exhibited three distinct zones corresponding to the evaporation of H 2 O and I 2 molecules (zone I), evaporation of I 2 and partial decomposition of side groups (OOH) (zone II), degradation of the remaining side groups and partial degradation of the main chain (zone III-1), and degradation of the remaining main chain and the char zone corresponding to KI. The crystalline structure of the film with a weight gain of 15.2% was almost the same as that of the pure PVA, and the film with the weight gain of 140% was almost amorphous. The differential scanning calorimetry (DSC) thermograms of the IBC films with a weight gain of 15.2% and 39.8% indicated endothermic single or double peaks at around 180°C, corresponding to the crystal melting and degradation of side groups; those with weight gains of 83.2% and above indicated exothermic peaks at around 170°C, corresponding to crystallization, and broad endothermic peak at around 180 -200°C, corresponding to the crystal melting and degradation of side groups. The dynamic mechanical ␣ a transition of the IBC film with the weight gain of 140.1% appeared at around 20°C. X-ray diffraction and DSC analysis of deiodinated films show that the crystal structure, on deiodination of all the IBC films, regardless of crystallinity, returned to that of the pure PVA.