Photodegradation chromophore concentration

Further test Six selected Aromatic Dyes with various chromophores were UV-irradiated at X = 253.7 nm to explore the reaction pathways and decay rates of photo-degradation under different initial pH levels and pH buffers. The concentrations of the dyes during photodegradation were determined by HPLC. 

At low concentrations (0.025 M) the photolysis of these polymers resulted in the decoloration due to the degradation of the azo dye.260 After the cationic cyclopentadienyliron moieties are cleaved from the polymer, they form complexes with the azo chromophore, which then leads to photodegradation of the azo chromophore. 

Since a polymer must contain a chromophore before photodegradation takes place, the fundamental step in investigating the process is to identify the chromophore. Thereafter the initial photochemistry is that of the chromophore modified by the physical nature of the glassy or highly viscous medium. Distinction must be made between spurious absorbing species present as low concentration impurities and chromophores present as an integral part of the polymer structure. Apart from the obvious difference in concentrations of the two species it has to be stated that frequently polymer chemists have little knowledge or control of the former and consequently this review will only consider the photoreactions of what can be described as planned and identified chromophores. 

---