Chromism of spiropyrans: from solutions to surfaces

Smart molecular systems in which spiropyran based molecular switches play a key role are the central focus of this thesis. These systems respond to stimuli (e.g., light, pH, electricity, etc.) through a change in molecular, and thereby material, properties such as color, acidity, or conductivity, amongst others. Although spiropyrans and related compounds have been known for over a hundred years, they are still ever-present in the contemporary scientific literature and, increasingly, in commercial uses (for example the sunglasses that change color). The key challenge with such functional molecules is to translate the changes that occur in a single molecule to the macroscopic world so that we can experience the result and put it to use.
In this thesis first the proof of principle was demonstrated by synthesizing and characterizing model compounds that are capable of generating polymers effectively, after which their switching between properties was restored. This knowledge is then applied to create functional polymers of spiropyran, through which new responses were uncovered. One of these happened to be inherent to the spiropyran molecule, being seemingly overlooked all this time, thus being fully explored in a separate chapter. Finally, a new variation is explored through fusing of two spiropyrans together, yielding new and, moreover, interesting new responses.
As a whole, this thesis contributes to the advancement of the exciting field of spiropyran photochromes and at the same time we have answered key fundamental questions regarding the coloration of spiropyrans. Of course many more questions have been raised in the process.