Fig. 1. General structures of four main-chain polymers derived from four regioisomers of a spiropyran scaffold. The sole difference among these regioisomers is the relative position (with respect to the benzopyran oxygen) of the ester group (–OCOR) on the chromene moiety of the spiropyran. We demonstrate dramatic effects of these minor difference on the photo- and halochromism of the resulting polymers. Note that the covalent connection to the chromene moiety can be realized through the carbonyl carbon (–COOR), which is critically different from our design.
