Designing Molecular Photoswitches for Soft Materials Applications

Abstract

In order to respond to light stimuli, materials and devices thereof must contain a photoresponsive component. Ideally, this response is reversible and can be tuned depending on the desired application. In the context of soft material development, the integration of molecular photoswitches has proven a viable strategy. This Progress Report outlines molecular design principles to successfully transfer beneficial photoswitching performance from solution to the bulk. Selected examples of the most prominently used classes of photoswitches and their use in actuating and self‐healing materials as well as optoelectronic and microfluidic devices are highlighted. The current state of the art is critically discussed with emphasis on both the scientific challenges and the future promise for light‐responsive, smart soft matter technologies.

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

“…[1][2][3][4] Despite over 100 years of study, new applications both in research and materials (not least in light responsive sun glasses) emerge owing to the wide and diverse range of building blocks available. [5][6][7][8][9][10][11][12][13] The known photochromes include a range of switches that have been proven versatile to chemical modification, enabling changes to, enhancement of, and sometimes even completely novel, functionality. Several classes of molecular switch have featured prominently such as the azobenzenes, 14,15 dithienylethenes 16,17 and spiropyrans.…”

Visible Light—Responsive Drug Delivery Nanoparticle via Donor–Acceptor Stenhouse Adducts (DASA)

“…The majority of examples of light‐induced drug delivery occur by irradiation with UV light (250–400 nm) [ 5 ] such as the isomerization of azobenzenes, diarylethene, and spyropirans. [ 1,2,6,7 ] However, the disadvantages of UV light includes low tissue penetration as well as phototoxicity. [ 8,9 ] To deal with these challenges are being tackled with visible‐light responsive photoswitchable molecules.…”

Strong, Self‐Healable, and Recyclable Visible‐Light‐Responsive Hydrogel Actuators

“…However, despite the progress made in achieving light‐induced shape changing hydrogels, many significant issues remain as impediments to application. Most systems use high intensity short‐wavelength UV light . Moreover, the photoresponsive hydrogels typically suffer from poor mechanical properties, namely fatigue‐related failure.…”