Optical Input/Electrical Output Memory Elements based on a Liquid Crystalline Azobenzene Polymer

Abstract

Responsive polymer materials can change their properties when subjected to external stimuli. In this work, thin films of thermotropic poly(metha)acrylate/azobenzene polymers are explored as active layer in light-programmable, electrically readable memories. The memory effect is based on the reversible modifications of the film morphology induced by the photoisomerization of azobenzene mesogenic groups. When the film is in the liquid crystalline phase, the trans → cis isomerization induces a major surface reorganization on the mesoscopic scale that is characterized by a reduction in the effective thickness of the film. The film conductivity is measured in vertical two-terminal devices in which the polymer is sandwiched between a Au contact and a liquid compliant E-GaIn drop. We demonstrate that the trans → cis isomerization is accompanied by a reversible 100-fold change in the film conductance. In this way, the device can be set in a high- or low-resistance state by light irradiation at different wavelengths. This result paves the way toward the potential use of poly(metha)acrylate/azobenzene polymer films as active layer for optical input/electrical output memory elements.

Towards low-energy-light-driven bistable photoswitches: ortho-fluoroaminoazobenzenes

“…In particular, many applications benefit from switching with lowenergy and low-intensity light as well as from high thermal stability of the metastable cis-isomer. These attributes are crucial for switches used in living systems 19 or memories 20 and often times advantageous for applications in solar thermal fuel systems 21,22 and soft-robotic materials [23][24][25] as well: high-energy irradiation generally has a degrading effect on the switch and its surroundings 26,27 and, on the other hand, constant illumination is not always possible.…”

Supramolecular design principles for efficient photoresponsive polymer–azobenzene complexes

“…Additionally, many device applications demonstrated to date in covalent systems that benefit from photoresponsive azopolymers, such as photonic components, 67,164 organic lasers 165,166 and conductivity switching, [167][168][169] could benefit from employing the supramolecular materials for optimizing, e.g., the azobenzene content for the described application. Ionic bonding, on the other hand, is generally more stable thermally and temporally, whereas hydrogen-and halogenbonded small molecules are more susceptible to partial loss at higher temperatures or under vacuum drying.…”

Photo-Responsive Graphene and Carbon Nanotubes to Control and Tackle Biological Systems

“…Among the molecular switches, azobenzenes and spiropyrans have been widely studied (Raymo and Giordani, 2001 ; Raymo et al, 2003 ) and employed to fabricate responsive materials because they can be reverted to their more stable isomer either photochemically or thermally. They provide an easy access to switchable materials with a relatively ease of synthesis, high chemical stability (in both isomeric forms) and the possibility to incorporate multiple organic functional groups to allow the coupling with biomolecules as well as several types of materials, including polymers (Mosciatti et al, 2016 ) and nanomaterials (Weber et al, 2016 ) (Scheme 1 , Table 1 ).…”