Optical, electrical and chemical properties of PEO:I-2 complex composite films

Synthesized PEO:I-2 complex composite films with different I-2 concentrations were deposited onto fused silica substrates using a dip-coating method. Incorporation of PEO films with I-2 increases the electrical conductivity of the composite, reaching a maximum of 46 mS/cm for 7 wt% I-2. The optical and optoelectronic properties of the complex composite films were studied using the transmittance and reflectance spectra in the UV-Vis region. The transmittance of PEO decreases with increasing I-2 content. From this study, the optical bandgap energy decreases from 4.42 to 3.28 eV as I-2 content increases from 0 to 7 wt%. In addition, the refractive index for PEO films are in the range of 1.66 and 2.00.H-1 NMR spectra of pure PEO film shows two major peaks at 3.224 ppm and 1.038 ppm, with different widths assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase, respectively. By adding I-2 to the PEO, both peaks (amorphous and crystal) are shifted to lower NMR frequencies indicating that I-2 is acting as a Lewis acid, and PEO is acting as Lewis base. Hence, molecular iodine reacts favorably with PEO molecules through a charge transfer mechanism, and the formation of triiodide (I-3(-)), the iodite (IO2-) anion, I-2 center dot center dot center dot PEO and I-2(+) center dot center dot center dot PEO complexes. PEO:I-2 complex composite films are expected to be suitable for optical, electrical, and optoelectronic applications.