Polarizer effect and structure of iodinated before and after casting poly(vinyl alcohol) film



Poly(vinyl alcohol) (PVA)/iodine polarizing film was manufactured as follows: PVA iodinated in solution before casting (IBC film) and iodinated again after casting (IBC + IAC film) and then the IBC + IAC film was drawn in boric acid aqueous solution (IBC + IAC polarizing film), to improve the durability of the polarizing film under a humid and warm atmosphere. These effects were examined by investigating the structural and optical properties of the IBC, IBC + IAC, and IBC + IAC polarizing films. In the IBC state, the PVA chain segments that combined boric acid and iodine were regarded as defects of the crystal, the formation of I3 decreased with respect to weight gain of boric acid. In the IBC + IAC state, the strength of the peak corresponding to I3 decreased and the I5 peak increased. The iodine ions penetrated into crystal of the IBC state during the IAC process and formed a new PVA/iodine complex crystal at the 2θ = 20° in the X-ray diffraction curves. In the IBC + IAC polarizing film state, another type of polarizing film (IBC + IAC polarizing film-H) containing I3 ions mainly was manufactured as well as the IBC + IAC polarizing film to compare the effects of the I3 and I5 ions on the durability of the polarizing films. The durability of the I3 ions that were complexed with the PVA chain was higher than the I5 ions, which could possibly be separated to I3 and I2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010