Search

Azobenzene‐doped glassy polyimides (azo‐polyimides) offer some of the most efficient optomechanical power densities to date rivaling electrostrictive polymers. Despite such potential attributes, the optomechanical efficiency remains low in comparison to other smart materials. Using high‐fidelity coarse‐grained molecular dynamics simulations, the authors reconcile both experimental and theoretical challenges to understand the limiting factors for the optomechanical conversion in photostrictive polymers. Interestingly, the ideal optomechanical efficiency of 10–24% for a single‐chain azo‐imide monomer predicted here is equal to or a little higher than experimental reports, suggesting experimental design space. The time‐dependent optomechanical efficiency of bulk azo‐polyimide is quantified, for the first time, to be strongly correlated with the initial free volumes, a measure of polymer conformational freedom. This trend is elaborated by conformational order parameters and viscoelastic relaxation moduli. Resembling the role of porosity in azobenzene‐contained metal/covalent organic frameworks to enhance the photo‐switching efficiency, a larger conformational freedom enables >10 times increase in optomechanical efficiency comparing to existing experiments. This is primarily due to facilitated viscoelastic relaxation after photo‐switching which alleviates residual stresses quickly and reduces heat dissipation. These findings suggest opportunities to improve the optomechanical performance through targeted strategies, such as porosity control and thermal annealing. [ABSTRACT FROM AUTHOR]

"Communicating particles" are reported that combine an identification (ID) taggant and a temperature recorder in one single entity—a micron‐scaled supraparticle. The optical information carriers within the hybrid inorganic‐organic supraparticles are three different types of luminescent nanoparticles, which can be read‐out using single‐wavelength excitation. These three nanoparticle types are assembled into a core‐satellite structure via a two‐step droplet evaporation technique. The core is built‐up from Tb3+ and Eu3+‐doped nanophosphors, providing an environmentally stable ID that is easily tunable through ratiometric spectral coding. This core is surrounded by organic, dye‐doped polymer nanoparticle satellites, acting as thermal‐history‐recorders of their environment. Exposed to a threshold temperature, the luminescence of the utilized 7‐diethylamino‐4‐methylcoumarin‐doped polymer nanoparticles is irreversibly quenched. This "turn‐off " signal response is attributed to conformational changes in the dyes' excited state and an alteration of their molecular environment, respectively, triggered by the polymer nanoparticles' glass transition. Thus, the sensitivity of the temperature recorder can be configured over a wide temperature range by varying the dye‐hosting polymer. At the same time, the ID of the particle, stemming from its inorganic building blocks, stays unaffected, thus stable against thermal changes. The idea of communicating particles introduces a promising concept for smart additives. [ABSTRACT FROM AUTHOR]

The indispensable transformation to a (more) sustainable human society on this planet heavily relies on innovative technologies and advanced materials. The merits of nanoparticles (NPs) in this context are demonstrated widely during the last decades. Yet, it is believed that the impact of particle‐based nanomaterials to sustainability can be even further enhanced: taking NPs as building blocks enables the creation of more complex entities, so‐called supraparticles (SPs). Due to their evolving phenomena coupling, emergence, and colocalization, SPs enable completely new material functionalities. These new functionalities in SPs can be utilized to render six fields, essential to human life as it is conceived, more sustainable. These fields, selected based on an entropy‐rate‐related definition of sustainability, are as follows: 1) purification technologies and 2) agricultural delivery systems secure humans "fundamental needs." 3) Energy storage and conversion, as well as 4) catalysis enable the "basic comfort." 5) Extending materials lifetime and 6) bringing materials back in use ensure sustaining "modern life comfort." In this review article, a perspective is provided on why and how the properties of SPs, and not simply properties of individual NPs or conventional bulk materials, may grant attractive alternative pathways in these fields. [ABSTRACT FROM AUTHOR]