Sufang Chen

Self-assembly of amido-ended hyperbranched polyester films with a highly ordered dendritic structure.

Self-assemblies fabricated from dendrimers and amphiphilic polymers have demonstrated remarkable performances and a wide range of applications. Direct self-assembly of hyperbranched polymers into highly ordered macrostructures with heat-resistance remains a big challenge due to the weak amphiphilicity of the polymers. Here, we report the self-assembly of amphiphilic amido-ended hyperbranched polyester (HTDA-2) into millimeter-size dendritic films using combined hydrogen bond interaction and solvent induction. The self-assembly process and mechanism have been studied. Hydrogen bond interaction between amido-ended groups assists the aggregation of inner and outer chains of the HTDA-2, resulting in phase separation and micelle formation. Some micelles attach to and grow on the glass substrate like seedlings. Other micelles move to the seedlings and connect with their branches via solvent induction and hydrogen bond interaction, leading to the fabrication of highly ordered crystalline dendritic films that show high heat-resistance. HTDA-2 can further self-assemble into sheet crystals on the dendritic films.

Synthesis of a Degradable High-Performance Epoxy-Ended Hyperbranched Polyester

Degradation and recycling of cured thermosetting epoxy resins are major challenges to the industry. Here, a low-viscosity, degradable epoxy-ended hyperbranched polyester (DEHP) is synthesized by a reaction between epichlorohydrin and a carboxyl-ended hyperbranched polyester (DCHP) obtained from an esterification between citric acid and maleic anhydride. The chemical structures of DCHP and DEHP were characterized by Fourier transform infrared and 1H NMR. DEHP has a positive effect on reinforcing and toughening of the diglycidyl ether of bisphenol-A (DGEBA). With an increase in the content and molecular weight of DEHP, the mechanical performances of the cured DEHP/DGEBA composites, including the tensile, flexural, and impact strengths, increase first and then decrease. The improvements on the tensile, flexural, and impact strengths were 34.2–43.4%, 35.6–48.1%, and 117.9–137.8%, respectively. Moreover, the DEHP also promotes degradation of the cured DEHP/DGEBA composites. The degree of degradation of the cured DEHP/DGEBA composites increases with an increase of the DEHP content and molecular weight. The composites containing 12 wt % DEHP can be degraded completely in only about 2 h at about 90 °C, compared with the degradation degree (35%) of cured DGEBA, indicating good degradation and recycling properties of the DEHP.

Influence of the molecular weights of amino-ended hyperbranched polyamide template on the morphology of self-assembled ZnS nanoparticles

Zinc sulfide (ZnS) as an important photocatalytic material in photodegrading organic dyes has attracted increasing attention to obtain high activity crystal structures. Here we report synthesis of wurtzite ZnS nanoparticles using amino-ended hyperbranched polyamide (AEHPA) with different molecular weights as templates. The microstructure, morphology and optical properties of the self-assembled ZnS particles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra and UV-vis absorption. The molecular weight of the template has a remarkable influence on the microstructure and photocatalytic property of the self-assembled ZnS. Photocatalytic tests showed that the ZnS nanoparticle obtained using the AEHPA with a moderate molecular weight as template performed the best function in degradation of Rhodamine B under UV irradiation.

Synthesis and Degradation Mechanism of Self-Cured Hyperbranched Epoxy Resins from Natural Citric Acid

Rapid and highly efficient degradation of cured thermoset epoxy resins is a major challenge to scientists. Here, degradable self-cured hyperbranched epoxy resins (DSHE-n, n = 1, 2, and 3) were synthesized by a reaction between 3-isocyanato-4-methyl-epoxy-methylphenylcarbamate and degradable epoxy-ended hyperbranched polyester (DEHP-n) prepared from maleicanhydride, citric acid, and epichlorohydrin. The chemical structure of DSHE-n was characterized by Fourier transform infrared and 1H NMR spectra. With an increase in DSHE-n molecular weight, the adhesion strength of self-cured DSHE-n films increases distinctly from class 1 to 4, and their pencil hardness remains about class B–2B. The study on the self-cured behavior and mechanism of DSHE-n shows that the carbamate group of the DSHE-n is decomposed into diamine group to react with epoxy group and form a cross-linked structure. The self-cured DSHE-n films were degraded completely in 2 h at 90 °C in the mixed solution of hydrogen peroxide (H2O2) and N,N-dimethylformamide under atmospheric pressure and produced the raw material citric acid, indicating good degradation performance and recyclable property of DSHE-n.

Preparation of SBA-15 with penetrating pores and their performance in Fischer–Tropsch synthesis

A novel SBA-15 (2.5N-SBA-15) with pores penetrating into the silica walls has been synthesized with amino-ended hyperbranched polyamide (AEHPA) and P123 as co-templates. This novel template method successfully imprints mesoporous cavities into the silica structure. The obtained composites are used as a Co (15 wt%) catalyst support for Fischer–Tropsch Synthesis (FTS). The catalytic activity and product selectivity are significantly influenced by the support structure. Compared with the conventional 15Co/SBA-15 catalyst, the 15Co/2.5N-SBA-15 catalyst with a penetrating pore structure shows improved reducibility of cobalt species, leading to better catalytic properties with respect to CO activity and C5+ selectivity during the FTS reaction.