Visible Light-Absorbing Polymers
Polymeric nanomaterials have been well established as drug delivery systems as they can protect therapeutic payloads from the harsh in vivo environment, minimize degradation of therapeutics upon administration, allow for delivery of higher concentrations, and minimize unwanted side effects. These materials can be tailored to respond to a variety of external and biological stimuli such as pH, enzymes, redox molecules, light, and heat. Light is an attractive trigger because it is not limited by physiological conditions and can be controlled remotely. This provides great spatial and temporal control of the triggered reaction. In the past decades, most light-responsive materials have utilized UV due to the large library of molecules that absorb that wavelength and its efficient one-photon absorption mechanism. However, its poor penetration depth and deleterious health effects has made it less attractive. As an alternative, near-infrared (NIR) responsive materials have been explored. Although NIR is biologically benign and can penetrate much deeper than UV, it can be disadvantageous as it is much lower in energy and would require materials to upconvert or undergo inefficient two-photon absorption to trigger its photochemistry. Visible light provides a great middle ground as it is higher in energy than NIR and much less deleterious than UV. However, despite the decades of research, very few materials have been developed that utilize visible light for polymeric nanomaterials. To further advance this field, research into visible light responsive polymers is described in this dissertation. In chapter 1, a fluorescent dye was conjugated onto an established visible light polymer to allow for in vivo tracking and monitoring. In chapter 2, a dinitro derivative of bisstyrylthiophene was explored as a potential visible light polymer. Additionally, a biphenyl visible light chromophore was conjugated onto dextran to be explored as a visible light responsive polymer. In chapter 3, the visible light responsive materials that were developed are used to assess their absorption of blue visible light from ambient sunlight.