Polymer sensors and actuators: synthesis and characterization of polythiophenes modified with benzospiropyran derivatives

The aim of this thesis is to understand the basic physico/chemical behaviour of novel nitrospiropyran-substituted-(poly)terthiophene materials. Attractive characteristics that distinguish these materials include electrochemical/photochemical-switching processes. Understanding the fundamental behaviour of these new derivatives is the key to taking advantage of these characteristics. The stimuli induced isomerisation between the colourless spiropyran and the highly coloured merocyanine is the key-process studied in this research. Chapter 2 reports the electrochromic behaviour of spiropyran, through irreversible electrooxidative isomerisation in at least two merocyanine isomers. The molecular photophysical processes of the electrochemically-generated polymer are reported and the properties studied. In Chapter 3 a new monomer, which differs by a single methylene group in the linking ester-linker functionality from the previous one, will be introduced. A nitrospiropyran was used as a reference, and a detailed spectroscopy analysis will help in the description of the thermodynamic properties. Chapter 4 highlights how the polymeric molecular switches can bind an important extracellular protein, fibronectin, and explores by means of microscopy the on-demand tuning of the protein adhesion. A new derivative is presented in Chapter 5, wherein a spiropyran moiety is intercalated between two thiophenes. The electrochemical and optical switching of the spiropyran and thiophene groups were investigated. In Chapter 6 three new spiropyran-based derivatives are presented, and routes to multi-modal switching behavior are explored via photochemical, electrochemical and chemical stimuli, such as pH. Their reversibility and their properties are investigated using both spectroscopic and electroanalytical methods. The final chapter outlines future work and initial progress related to the integration of spiropyran-thiophene polymers into photo-electro active portable analytical devices.