Jilei Wang

Fast Photoinduced Large Deformation of Colloidal Spheres from a Novel 4-arm Azobenzene Compound

A novel 4-arm shaped amphiphilic azobenzene compound was synthesized. The tetraphenylethylene (TPE) core precursor was prepared and further modified by azo coupling reaction at the four peripheral groups. Colloidal spheres could be directly prepared by self-assembly of the prepared amphiphilic azobenzene compound in selective solvents (THF/H2O), which were characterized by using transmission electron microscopy. The colloid diameters could be controlled by adjusting the initial compound concentration and water-adding rate in the preparation processes. By irradiation with visible linearly polarized LED light (450 nm), fast photoinduced deformation of the colloidal spheres along the polarization direction was observed. A very large deformation degree (l/d > 4) could be easily obtained.

Synthesis of Y-shaped amphiphilic copolymers by macromolecular azo coupling reaction

The synthesis of AB2 Y-shaped amphiphilic block copolymers by macromolecular azo coupling reaction is reported. The hydrophobic block with the functional group at the end of the polymeric chain was prepared by controlled radical polymerization methods such as RAFT and ATRP. The hydrophilic block with diazonium salt group was obtained by the diazotization of V-shaped aniline-functionalized PEG. Then Y-shaped block copolymers were easily prepared through macromolecular azo coupling reactions between the abovementioned two polymeric blocks. The results of experiments showed that the position of the functional group suitable for azo coupling reaction in the polymeric chain has considerable effect on the efficiency of macromolecular azo coupling reaction. It was easier for the macromolecular diazonium salts to attack the functional groups when they were at the end of the macromolecular chains instead of in the middle. The self-assembly properties of the obtained Y-shaped amphiphilic block copolymers were also studied. Colloidal spheres were prepared by gradual hydrophobic aggregation of the polymeric chains in a THF–H2O dispersion medium.

Photoswitchable aggregation-induced emission polymer containing dithienylethene and tetraphenylethene moieties

A photochromic aggregation-induced emission (AIE) active polymer containing dithienylethene (DTE) and tetraphenylethene (TPE) moieties was synthesized through a nucleophilic substitution reaction between 1,2-bis[5′-(4′′-hydroxyphenyl)-2′-ethylthien-3′-yl]perfluorocyclopentene and 1,2-bis[4-(bromomethyl)phenyl]-1,2-diphenylethene. The prepared polymer is soluble in various organic solvents and can be easily processed into thin film. The DTE chromophores in the polymer can undergo reversible photoisomerization between their open and closed forms upon irradiation with UV and visible light. Thus, the fluorescence of the prepared AIE polymer can be photoswitched.

Photocleavable amphiphilic diblock copolymer with an azobenzene linkage

Amphiphilic diblock copolymers with an azobenzene linkage were synthesized by a macromolecular azo coupling reaction between a PEG based macromolecular diazonium salt and a PS based polymeric block with a functional terminus. Colloidal aggregates could be directly prepared by self-assembly of the prepared amphiphilic copolymer in selective solvents (THF/H2O). By irradiation with UV light, the azobenzene linkage in the block copolymer can be efficiently photocleaved. Thus, the colloidal aggregates of the amphiphilic diblock copolymer will be disrupted due to the cleavage of the azobenzene junction.