Influence of Chromophoric Electron-Donating Groups on Photoinduced Solid-to-Liquid Transitions of Azopolymers

Abstract

The photoinduced solid-to-liquid transitions property of azobenzene-containing polymers (azopolymers) enables azopolymers with various promising applications. However, a general lack of knowledge regarding the influence of structure of the azobenzene derivatives on the photoinduced liquefaction hinders the design of novel azopolymers. In the present study, a series of azopolymers with side chains containing azobenzene unit bearing alkyl electron-donating groups were synthesized. The photoisomerization and photoinduced liquefaction properties of newly synthesized azopolymers were investigated. Alkyl-based electron-donating group significantly facilitate the photoisomerization process of azopolymers in solution, as the electron-donating ability of substituents increased, the time required for photoisomerization of azopolymers continually deceased. Meanwhile, the electron-donating group can drastically accelerate photoinduced solid-to-liquid transitions of azopolymers, the liquefaction rate of obtained azopolymers gradually getting quicker as the electron-donating ability of substituents increased. This study clearly demonstrates that the electron-donating group that bearing in the azobenzene group of polymer side chain play an essential role on the photoinduced solid-to-liquid transitions of azopolymers, and hence, gives an insight into how to design novel azopolymers for practical applications.

A Comparative Study on the Oxidation Mechanisms of Substituted Phenolic Pollutants by Ferrate(VI) through Experiments and Density Functional Theory Calculations

“…It was reported that the energy of the highest occupied molecular orbital ( E HOMO ) reflects the electron-donating ability of a molecule, and thus phenols with a higher E HOMO value were more susceptible to oxidation . As for the five phenols studied in this work, −Cl (−X) and −(CO)– are electron-withdrawing groups with the electron-withdrawing capacity of −(CO)– greater than that of −Cl, while −R is an electron-donating group. , The presence of electron-withdrawing groups decreased the E HOMO value, which will enhance the stability of compounds toward oxidation . By contrast, the electron-donating groups can increase a compound’s reactivity with ferrate­(VI).…”

“…28 As for the five phenols studied in this work, −Cl (−X) and −(C�O)− are electron-withdrawing groups with the electron-withdrawing capacity of −(C�O)− greater than that of −Cl, while −R is an electron-donating group. 29,30 The presence of electron-withdrawing groups decreased the E HOMO value, which will enhance the stability of compounds toward oxidation. 31 By contrast, the electron-donating groups can increase a compound's reactivity with ferrate(VI).…”

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

“…These asymmetric molecules have been carefully discussed in a study by Akiyama et al 17 The introduction of this asymmetric methyl can weaken the π-π interaction in the molecule, which weakens the compactness of the molecular packing. 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.…”

Cold crystallization and photo-induced thermal behavior of alkyl-derivatized diarylethene molecules

“…[19][20][21][22][23][24] They absorb ultraviolet (UV) and/or visible light, and molecular photoisomerization occurs. The isomerization is sometimes accompanied by a solid-liquid transition, 25,26 and the transition energy can be stored by light irradiation. [27][28][29][30] The combination of cold crystallization and photoisomerization is a promising method for nding new functional energy storage systems.…”