STRATEGIES FOR THE INCORPORATION OF PORPHYRINS IN POLYSILOXANES AND THEIR APPLICATIONS

Abstract

Porphyrins are a class of natural and synthetic aromatic macrocycles that have received extensive investigation because of their unique chemical and optoelectronic properties. They are excellent ligands, photosensitizers and catalysts and serve critical roles in numerous biochemical reactions. Their properties and diverse applications have fascinated chemists from multiple fields, and porphyrins have been investigated in applications such as dye-sensitized solar cells, cancer treatments, and conjugated polymers among others. While porphyrins have made in-roads in multiple fields they have received at best minimal attention in the field of polysiloxane chemistry. Polysiloxanes are a class of inorganic polymers widely used in industrial applications that possess properties including low glass transition temperatures, high thermal and oxidative stabilities, high optical transparency, and low refractive indices that are largely unmatched by organic polymers. These properties, if properly utilized, could compliment those possessed by porphyrins and lead to the development of new applications in the fields of porphyrin and polysiloxane chemistry. Unfortunately, porphyrins and polysiloxanes are not readily compatible with one another and synthetic techniques must be developed to allow for the reliable incorporation of porphyrins into polysiloxane matrices. The objectives of this thesis are to develop strategies that allow for the ready incorporation of porphyrins into polysiloxane materials to improve existing and develop new applications for porphyrin-polysiloxane materials. These investigations led to the development of two techniques for the incorporation of porphyrins into polysiloxanes, the Piers-Rubinsztajn reaction, and ionic crosslinking. Several siloxane and polysiloxane porphyrins were prepared utilizing the Piers-Rubinsztajn reaction. These porphyrins were easily incorporated into silicone elastomers that could be utilized as dielectric, or reactive oxygen species-generating elastomers. Alternatively, ionic crosslinks could be utilized to incorporate the natural porphyrin hemin into silicone elastomers. Elastomers manufactured via this method retained the catalytic capabilities of hemin, opening the door to a new class of synthetic peroxidases. Regardless of the method of application controlling the natural tendency of porphyrins to aggregate was essential to achieving the desired properties.