Photoplastic Transformation Based on Dynamic Covalent Chemistry

The magical fantasy of decades-old transformer characters is becoming closer to scientific reality, as transformable materials can change their shapes in response to thermal, mechanical, electrical, and chemical stimuli. However, precise and prompt control of plastic shaping remains to be wanted. Photoresponsive materials provide a promising alternative for rapid optomechanical shaping with limited success. Here, we report a new class of photoplastic transformation based on dynamic covalently crosslinked polytriazole (PTA) networks, in which crosslinking points are comprised of photocleaveable hexaarylbiimidazole (HABI). Upon sub-500 nm light irradiation, HABI is dissociated into two triphenylimidazole radicals (TPIRs) followed by spontaneous recombination back to the initial state. This photoswitching effect is demonstrated to generate nonthermal shape change in the PTA-HABI gel network at will upon light stimulus. A unique photoalignment phenomenon has also been discovered which can form oriented nanosc...