Influence of the Substitution Degrees on the Optical Properties of Cellulose Acetates

Cellulose acetates with different substitution degrees possess a set of properties that makes them highly suitable for optical applications. This article discusses some of these properties, namely refractivity, dielectric properties, and transmittance. The contribution of the ratio between the molar refraction, which is proportional to the induced dipole moment, and the molar volume for the different atoms present in the studied polymers to the optical properties was investigated. The study illustrates the importance of such structural and compositional characteristics in tailoring some specific optical applications. Furthermore, optical transmission has been investigated in the 200-1000 nm range. To obtain the optical parameters, the approach proposed by Tauc for amorphous semiconductors has been used because of the similarity of the absorption edges. The values of pseudogap energy ranged between 3.44 and 4.70 eV, whereas those of Urbach energy were modified in the 18-37 meV range. All parameters determined have been related to the influence of the substitution degrees and of the synthesis condition. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1751-1757, 2010