Enabling Lower Energy Light Harvesting in Stilbene-Based Photomechanical Polymers via Triplet Sensitization

Photoresponsive polymers, typically activated with direct excitation of an azobenzene moiety, are an intriguing class of materials for application as adaptive structures. Here, we introduce triplet excited state sensitization as a mechanism to harness light in a stilbene-based photopolymer (i.e., the carbon analogue of azobenzene). While the undoped film shows no response, the sensitized film exhibits polarization dependent bending under 445 nm irradiation via (1) sensitizer excitation, (2) triplet energy transfer, (3) stilbene isomerization, and (4) subunit reorientation. This work is the first to demonstrate stilbene-based photopolymers and triplet sensitization as a low energy light harvesting mechanism in photomechanics.