Spectroscopic and sub-bandgap optical properties of gamma-irradiated cellulose triacetate polymer

Abstract

The effect of gamma irradiation on the optical and sub-bandgap properties of cellulose triacetate (CTA) films is studied. Sellmeier and Wemple–DiDomenico models are used to study the optical dispersion. The refractive index is decreased with increasing irradiation dose, revealing the existence of chain scission. An increase in Urbach energy is obtained, confirming the existence of bond breaking and chain scission mechanism. Phonon assisted optical transition exists with no appreciable change in the bandgap energy values. Such behaviour indicates that the optical properties of the irradiated CTA polymer are attributable to changes in the linear electronic polarizability of the material rather than its bandgap or electronic structure. The obtained tunability in the optical properties of gamma-irradiated CTA polymer makes it of great interest in a number of optical applications.