Photo-dimerization in Green Polymers

D. MARTINO; D. REYNA

Bristol RI USA

Conferencia; Gordon Conference on Green Chemistry; 2004

For centuries, nature has been the sole supplier of natural macromolecules ranging from cotton, wool, silk to natural rubber. Now a day, these renewal resources coming from plants, animals and microorganisms can be modified to meet specific needs. With advances in chemistry and materials science, a vast array of novel synthetic polymers has been introduced virtually in every aspect of modern society. However, the growing reliance on synthetic polymers has raised a number of environmental and human health concerns. Most plastic materials, for instance, are not biodegradable and are derived from nonrenewable resources. These problems have focused our attention on polymers that are derived from biological precursors or mimic biological processes. We performed studies in water-soluble thymine containing polymeric systems. It is known that when thymine is irradiated with short UV light (~ 265nm) it undergoes a dimerization reaction. This photoreaction initiates a cross-linking mechanism, where neighboring strands are "tied" together, leading to insolubilization. The applicability of these biopolymers can be extended by the addition of photosentitizers molecules, which absorb light of longer wavelength (long UV ~ 365 nm or visible range) and induce the cross-link of the polymer. Different dye molecules at several concentrations were used as sensitizers. Dye-polymer interactions appear to orient the polymer in a way that enhances the photoreaction. By optimizing the conditions for these interactions, it is possible to improve the cross-linking mechanism.