My afternoon has been mostly attending Session II2: Mechanochemistry in Polymers. I decided to go learn something completely new today -- and indeed, mechanochemistry is something I know little about. When I think chemistry, I think reactions -- dump a few things and together, perhaps add some heat, and something happens. But imagine designing a system where you are able to push or pull a molecule by certain atoms in such a way that it changes conformation, properties, or even drives a reaction in a certain way. I found the color changing polymers particularly interesting, as examples of "mechanophores". It's a simple concept -- take a molecule like spiropyran, attach it to a polymer (the example given was polyurethane), and stretch the polymer to induce conformational change in the spiropyran and change it to merocyanine, which gives the polymer a purple color. Pretty cool :-)