Template-free uniform-sized hollow hydrogel capsules with controlled shell permeation and optical responsiveness

This study has established a robust and straightforward method for the fabrication of uniform poly(vinylamine) hydrogel capsules without using templates that combines the dispersion polymerization and the sequential hydrolysis/cross-linking. The particle sizes are determined by the degree of cross-linking as well as by the cross-linking reaction time, while the shell thickness is independent of these variables. Diffusion-limited reactions occur at the periphery of the particles, leading to the formation of hydrogel shells with a constant thickness. The treatment of the surfaces of hollow hydrogel capsules with oppositely charged biopolymers limits the permeability through the shell of species even with low molecular weights less than 400 g/mol. Furthermore, we demonstrated that the hydrogel shell phase decorated with Au nanoparticles can be optically ruptured by exposure to laser pulse, a feature that has potential uses in optically responsive drug delivery.     

Template synthesis of hydrogel composite hollow spheres against polymeric hollow latex

Hierarchically structured hydrogel hollow spheres with functional hydrogels located at desired sites are expected to have new properties. We have developed a facile swelling polymerization route using a polymer hollow sphere as template to synthesize hierarchically structured hydrogel hollow spheres. It is significant to pre-swell the template shell with good solvents, such as chloroform containing oil-soluble initiators to control interaction, thus, polymerization locus of different water-soluble functional monomers. Some representative hydrogel composite hollow spheres such as poly(N-isopropylarylamide) and poly(acrylic acid) with different morphologies have been synthesized. Hydrogels with functional groups can favorably complex with desired materials; hierarchically structured inorganic or polymer composite hollow spheres are synthesized by a sol–gel process of the inorganic precursor by using different hydrogel composite hollow spheres as templates.     

Stimuli-responsive properties of N-isopropylacrylamide-based ultrathin hydrogel films prepared by photo-cross-linking

To develop stimuli-responsive ultrathin polymer films on a solid substrate, a novel photo-cross-linkable polymer with both temperature- and pH-responsive properties was prepared. The photoreactive 4-aminobenzophenone (BP) was introduced onto the side groups of poly(N-isopropylaclylamide-co-2-carboxyisopropylaclylamide) [poly(NIPAAm-co-CIPAAm)]. This copolymer was designed for highly random sequences of comonomers. After the formation of spin-coated polymer films on a solid substrate, UV-light irradiation started the cross-linking reaction. The spin-coating processes and stability of the polymer films were quantitatively monitored by a quartz crystal microbalance (QCM), and the thickness was estimated using an atomic force microscope (AFM). These measurements confirmed the formation of a very plain polymer film, and the film thickness was precisely controlled by the concentration of the polymer solution used for spin coating. Moreover, the obtained films showed a high stability due to the cross-liking reaction and UV irradiation. Cyclic voltammetry using potassium ferricyanide revealed that the ions could permeate the photo-cross-linked ultrathin polymer films. The permeability of the ultrathin hydrogel films was dramatically changed by varying the pH and temperature of the aqueous media. These observations suggest that the preparation of isopropylacrylamide-based stimuli-responsive ultrathin hydrogel films is possible.     

An efficient and robust synthesis of amorfrutin A

Amorfrutin A was synthesized via a short sequence in an overall yield of 41% using a green, aerobic oxidation/re-arrangement process as the key-step.     

Fabrication and biocompatible characterization of magnetic hollow capsules

Monodispersed Fe3O4/polypyrrole （PPy） hollow particles were synthesized via controllable in-situ deposition and polymerization techniques using poly（styrene-co-acrylic） （PSA） latex as template. Field-dependent magnetization plot illustrates that the capsules are superparamagnetic at 300 K. FTIR spectrum confirms that the myoglobin （Mb） molecule adsorbed on the surface of Fe3O4/PPy hollow particle essentially retains its native structure. Furthermore, direct electrochemistry of Mb can be realized on Fe3O4/PPy capsules modified pyrolytic graphite disk electrode, which indicates that the magnetic conductive polymer capsules can promote the electron transfer of protein.     

Smart hybrid magnetic self-assembled micelles and hollow capsules

Novel magnetic nano-composites are obtained by the self-assembly in water of polypeptide-based diblock copolymers polybutadiene-b-poly(glutamic acid) combined with hydrophobically modified γ-Fe₂O₃ nanoparticles. These hybrid supramolecular objects are either filled micelles (3-d) or hollow vesicles with a magnetic membrane (2-d), deformation of which under an applied magnetic field has been evidenced. These nanoparticles are also able to respond to stimuli such as pH and ionic strength due to the presence of the polypeptide block, thus forming what we called multi-responsive nanocapsules. These superparamagnetic hybrid self-assemblies offer attractive potentialities in biomedicine and biotechnology due to their dimensions (0.1–0.5 μm) small enough to stay for some time in the blood circulation, and due to the properties brought about by the iron oxide nanoparticles: possible manipulation by an external magnetic field gradient, local heating by a radio-frequency field for cancer radio-therapy, labeling of organs to enhance the contrast in Magnetic Resonance Imaging.     

Formation of fractal-like structures driven by carbon nanotubes-based collapsed hollow capsules

Carbon nanotubes (CNTs) based hollow capsules were obtained by degradation under acidic conditions of core-shell nanocomposites build up upon adsorption of multilayers of CNTs (shell) onto melamine-formaldehyde (MF) spheres (core). By evaporation of the dispersions obtained, polymeric fractal patterns from the degradation products of the MF core were formed onto silicon wafers. The proposed mechanism for the formation of these structures is based on the role of the capsules as arrangements of heterogeneities that facilitate the dewetting of the liquid polymeric films.     

In-situ constructing robust cellulose nanocomposite hydrogel network with well-dispersed dual catalysts for the efficient,stable and recyclable photo-Fenton degradation

Cellulose - The hydrogel supported catalyst is explored as an efficient strategy for water remediation due to its combination of absorption and degradation, while it remains great challenge to...     

Short and efficient synthesis of a stock material of dihydroxyacetone phosphate from glycidol

As enzymatic syntheses are expensive for a large-scale preparation of DHAP, a precursor leading to DHAP was synthesized in three steps starting from (±) glycidol; the stable benzylated stock material afforded by hydrogenolysis DHAP in high purity, which may be used directly without purification in enzymatic aldol synthesis.     

Large-scale synthesis of bismuth hollow nanospheres for highly efficient Cr(vi) removal

Bismuth hollow nanospheres were successfully synthesized via a facile solvothermal method and exhibit highly efficient Cr(vi) removal capacities in a wide pH range (2-11).     

Dye decolorisation by laccase immobilised in lens-shaped poly(vinyl alcohol) hydrogel capsules

In this study, laccase (from Trametes versicolor, 8.3 U mg _enz ^?1 ) was used for the decolorisation of Saturn Blue L4G (10 mg L^?1). The efficiency of the decolorisation (ratio between the amount of decolorised dye and initial amount of dye) by a free enzyme was 48 % and the decolorisation rate was determined at 2.11 × 10^?3 mg_dye mg _enz ^?1 min^?1. After immobilisation in lens-shaped poly(vinyl alcohol) hydrogel capsules LentiKats® Biocatalyst (LB) (concentration of immobilised enzyme: 4 mg per g of particles; volume-loading rate of LB: 10 g per 100 mL of medium), the enzyme retained 16.1 % of its original activity (1.34 U mg _enz ^?1 ). Immobilised laccase was used for the dye decolorisation in 130 repeated batch tests with 71 % efficiency (LB activity: 7 × 10^?3 mgdye min^?1 g _LB ^?1 ). In continuous mode (after 716.5 h), the efficiency of the dye decolorisation was 48 % (LB activity: 3.3 × 10^?4 mg_dye min^/?1 g _LB ^?1 ).     

Cyclohexadiene-trans-diols as versatile starting material in natural product synthesis: short and efficient synthesis of iso-crotepoxide and ent-senepoxide

A new synthesis of ent-senepoxide and iso-crotepoxide starting from microbially produced(+)-trans-2,3-dihydroxy-2,3-dihydrobenzoic acid via regio- and stereoselective epoxidation is described.     

Low-density polycarbonate composites with robust hollow glass microspheres by tailorable processing variables

Polycarbonate (PC) composites with low weight have been required for mobile applications. Herein, the incorporation of 15 phr (parts per hundred of resin) soda-lime borosilicate hollow glass microspheres (HGMs) into a PC matrix reduced the specific gravity by 15.2%. The microsphere preservation rate was systematically examined depending on HGM compressive strength, and processing conditions for extrusion (side-feeding vs. main-feeding vs. screw configuration) and injection molding (mild condition for edge gate vs. extreme condition for pinpoint gate). Various transition temperatures such as glass transition temperatures and heat distortion temperature were investigated as a function of HGM. The coefficient of thermal expansion of the 15 phr HGM-embedded PC composites was reduced by 51.9%. The rheological behavior of the composites was also probed. The toughness was reduced due to the ductile-to-brittle transition of PC caused by the incorporation of fillers despite the enhanced modulus. The incorporation of the robust hollow glass microspheres into a PC composite via a delicately designed screw configuration and suitable processing conditions can be used for low-density composites such as mobile applications.     

Interface-directed self-assembly of gold nanoparticles and fabrication of hybrid hollow capsules by interfacial cross-linking polymerization

Amphiphilic gold nanoparticles (AuNPs) were produced at liquid-liquid interface via ligand exchange between hydrophilic AuNPs and disulfide-containing polymer chains. By using oil droplets as templates, hybrid hollow capsules with AuNPs on the surfaces were obtained after interfacial cross-linking polymerization. The volume ratio of toluene to water exerts an important effect on the size of capsules. The average size of the capsules increases with the volume ratio. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the hollow structures. In this research, not only one-component but also multicomponent hollow capsules were prepared by copolymerization of acrylamide and hybrid AuNPs at liquid-liquid interface. Because of the improvement in hydrophilicity of the hollow capsules, the average size of multicomponent capsules is bigger than one-component ones in aqueous solution.     

Spherical carbon capsules with hollow macroporous core and mesoporous shell structures as a highly efficient catalyst support in the direct methanol fuel cell

Carbon capsules with hollow core and mesoporous shell (HCMS) structures were used as a support material for Pt(50)-Ru(50) catalyst, and the catalytic performance of the HCMS supported catalyst in the direct methanol fuel cell was described; the HCMS carbon supported catalysts exhibited much higher specific activity for methanol oxidation than the commonly used E-TEK catalyst by about 80%, proving that the HCMS carbon capsules are an excellent support for electrode catalysts in DMFC.     

Synthesis and characterization of core-shell selenium/carbon colloids and hollow carbon capsules

A novel Se/C nanocomposite with core-shell structures has been prepared through a facile one-pot microwave-induced hydrothermal process. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS).