Pendant Photochromic Conjugated Polymers Incorporating a Highly Functionalizable Thieno[3,4- b]thiophene Switching Motif.

The ability to externally modulate conjugated polymer optoelectronic properties is an important challenge for modern organic electronics. One attractive approach entails the incorporation of stimuli-responsive molecular systems, such as diarylethenes, into polymeric materials. Our approach involves the design of polymers possessing photochromic moieties pendant to the main conjugated chain to allow for electronic influence along the polymer backbone while avoiding substantial conformational demands that may affect solid-state performance. Herein, we report the synthesis of a series of thieno[3,4- b]thiophene (TT)-based photochromes that demonstrate drastically different optoelectronic properties upon cyclization. Experimental and computational investigations of aryl-extended model compounds provided crucial insight on the interplay between electronic structure and photochromic activity, thus allowing for the realization of pendant photoswitchable conjugated copolymers that reflect the activity found in the related model systems.