New amphiphilic diblock copolymers composed of poly(ethylene glycol) and a thermotropic liquid crystalline polymer have been synthesized and demonstrated to form well-defined unilamellar vesicles in water by cryo-electron microscopy.
A series of azobenzene-containing isotropic/nematic/isotropic liquid crystal (LC) triblock copolymers (PBMA-b-PMAazo444-b-PBMA) with different block ratios was synthesized by atom transfer radical polymerization (ATRP). The central block PMAazo444 is an azobenzene-containing side-on nematic liquid crystalline polymer and PBMA a coil polymer. These azo-triblock copolymers were prepared and studied with the aim of producing, in the future, photoresponsive elastomers with lamellar structure. Kinetic studies on the polymerization of the azobenzene-containing LC monomer demonstrate that its polymerization is a controlled process. A LC homopolymer with narrow molecular weight distribution (M w /M n ) 1.13) was used as a difunctional macroinitiator to prepare the triblock copolymers by ATRP. The triblock copolymers were characterized by NMR, SEC, DSC, and POM. A triblock copolymer with 47 wt % of LC part self-assembles into a lamellar phase as evidenced both by SAXS and by TEM. The surface alignment of this lamellar phase on a silicon substrate was studied by AFM and compared with its nonphotosensitive triblock homologue (PBA-b-PA444-b-PBA). For this nonphotosensitive triblock copolymer the lamellas aligned parallel to the substrate, while for the azobenzene-containing triblock copolymer they organized perpendicular to the substrate.
Multistage hydrophilic core/hydrophobic shell latexes containing carboxyl groups were prepared via multistep seeded emulsion copolymerization, and particles with different morphologies were obtained after alkali post-treatment. Influences of the type and content of unsaturated acid monomer on the polymerization and the particle morphology were investigated based on conductometric titration and TEM observation. Results showed that the hydrophilic core/hydrophobic shell particles could be easily formed using methacrylic acid (MAA) instead of acrylic acid. When MAA was 12.2 wt % in the core latex preparation, only fine pores existed inside the alkali-treated particles. With MAA increased from 20.0 to 30.0 wt %, the alkali-treated particle morphology evolved from porous, hollow to collapse structure. When MAA further increased to 40.0 wt %, it was difficult to prepare uniform multistage particles and distinct morphologies including solid, deficient swelling, hollow and collapse structure were coexistent in the alkali-treated particles. Moreover, the forming mechanism of different morphologies was proposed.
Exploring highly efficient catalysts with excellent photothermal conversion and further unveiling their catalytic mechanism are of significant importance for photothermal catalysis technologies, but there remain grand challenges to these activities. Herein, we fabricate a nest-like photothermal nanocatalyst with Pd decorated on a N-doped carbon functionalized Bi 2 S 3 nanosphere (Bi 2 S 3 @NC@Pd). Given its well-dispersed ultrafine Pd nanoparticles and the excellent photothermal heating ability of support material, the Bi 2 S 3 @NC@Pd composite exhibits a superior activity and photothermal conversion property to commercial Pd/C catalyst for hydrogenation of organic dyes upon exposure to near-infrared (NIR) light irradiation. In addition, the photothermal effect (temperature rise) and activity enhancement of the heterogeneous catalysis system are further probed by comparing the reaction rate with and without the NIR light irradiation. Furthermore, the catalytic behaviors of the Bi 2 S 3 @NC@Pd catalyst under conventional and photothermal heating are investigated at the same reaction temperature. This work not only improves our fundamental understanding of the catalytic behavior in heterogeneous liquid−solid reaction systems under near-infrared irradiation but also may promote the design of catalysts with photothermally promoted activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.