Fatigue‐Resistant Crosslinked Azopolymers with Inhibited H‐Aggregation for Efficient Photopatterning

Abstract

The ability to repeatedly record information with external stimuli, in particular light, is of fundamental importance for the development of photoresponsive materials. Here, we demonstrated a photo-patterning system by using crosslinked azopolymers incorporating meta-substituted azobenzene (M-azo) moieties into dodecyl glyceryl itaconate (DGI) polymer networks. M-azo inhibited H-aggregation and showed efficient trans-to-cis photoisomerization in the crystal and film states, making photopatterning of the crosslinked polymers fully reversible. Macro-or microscale patterning could be written and erased in a reversible manner using light on the polymer film with fast response, high resolution, and flexibility. Moreover, these polymer films exhibited good fatigue resistance, which enabled hundreds of cyclic photo-writing and erasing tests without any decay under alternating UV/Vis irradiation. The high fatigue resistance indicates the ability of the azopolymers to repeatedly harvest and convert light energy into chemical conformation in the polymer networks by taking advantages of efficient photoisomerization.

Visible‐light‐switchable azobenzenes: Molecular design, supramolecular systems, and applications

“…The second challenge is determining the total photoisomerization efficiency of the AB system. The photoisomerization of AB molecules in solution is efficient, whereas in the solid state, it is difficult to achieve efficient photoisomerization owing to the π–π stacking (e.g., H‐aggregation) of chromophores 12,150 . For AB polymers, π–π stacking of incorporated AB moieties can be avoided by using meta ‐substituted AB 12 or nonplanar AB, such as ortho ‐methoxy AB with a twisted conformation 150 .…”

“…The photoisomerization of AB molecules in solution is efficient, whereas in the solid state, it is difficult to achieve efficient photoisomerization owing to the π–π stacking (e.g., H‐aggregation) of chromophores 12,150 . For AB polymers, π–π stacking of incorporated AB moieties can be avoided by using meta ‐substituted AB 12 or nonplanar AB, such as ortho ‐methoxy AB with a twisted conformation 150 . However, another problem arises as the limited irradiation depth of the AB polymers due to the high molar extinction coefficient of AB moieties, which causes the photoreactions to occur only on the sample surface, hindering further photoresponsive processes 17 .…”

“…For other photoswitchable molecules, such as diarylethenes, the photoswitching processes are associated with bond cleavage (ring‐opening) and bond formation (ring‐closing) with significant difference in their electronic state between the open and closed forms. In some cases, the inevitable side‐reactions happened in these photoisomerization processes 11,12 . Additionally, AB are versatile molecules, and their electronic absorption band can be tuned from UV to visible‐red regions by various ring substitutions.…”

“…In some cases, the inevitable side-reactions happened in these photoisomerization processes. 11,12 Additionally, AB are versatile molecules, and their electronic absorption band can be tuned from UV to visible-red regions by various ring substitutions. When incorporated AB into polymers or other systems, it is able to achieve a rapid and reversible control over a variety of chemical, mechanical, electronic, and optical properties.…”

Photo-Controlled Adhesives Based on Photoinduced Solid-to-Liquid Transition of an Azobenzene Compound

“…18 The introduction of this asymmetric methyl also weakens the H-aggregation in the molecules. 19 The introduction of long alkyl chains at both ends increases the flexibility of azobenzene molecules, and makes azobenzene molecules more prone to photoisomerization. 20 Under UV irradiation, the lattice structure of small molecules is broken, then isomerizes to a cis-structure and quickly changes to liquids.…”