ABSTRACT
The interaction between polymer molecules and the Ultraviolet (UV) component in sunlight can lead to dissociation of σ-bonds and is a principal cause of photodegradation of polymers. Aromatic structures have delocalized electrons and exhibit strong UV absorption at very short wavelengths. The UV–visible part of the electromagnetic spectrum corresponds to electronic excitation and the energy levels depend on the chemical bonds within the specimen, σ-electrons, absorb high energy photons in the UV region, whereas π-electrons absorb photons at longer wavelengths. One of the most useful applications of UV—visible spectroscopy to polymers is the measurement of the length of conjugation in unsaturated molecules. A modern application is in the analysis of rigid rod molecules with liquid crystal properties. The chapter shows that the measurement of the conjugation length is an important application of UV—visible spectroscopy that follows directly from the theoretical analysis.
