Mozhen Wang

Fabrication of raspberry SiO2/polystyrene particles and superhydrophobic particulate film with high adhesive force

We report a facile and novel strategy on the fabrication of well-defined raspberry SiO2/polystyrene (SiO2/PS) particles via radiation miniemulsion polymerization. Starting from methacryloxypropyltrimethoxysilane (MPS)-functionalized SiO2 particles (176 nm), raspberry SiO2/PS particles (257 nm) with a submicron SiO2 core decorated by nano-sized PS latex particles (58 nm) are obtained after γ-ray induced miniemulsion polymerization of styrene (St). It is found that MPS grafted density on the surface of submicron SiO2 particles, the weight ratio of St to SiO2 particles (WSt/o-SiO2), as well as the surfactant concentration will affect the morphology and wettability of the resultant SiO2/PS hybrid particles. When the well-defined raspberry SiO2/PS particles are deposited on a blank glass substrate, a dual-size roughness surface topology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). This film has a static water contact angle as high as 151°. However, this film exhibits a large contact angle hysteresis (∼116°) and strong adhesion to water. Furthermore, this kind of superhydrophobic particulate film can be used as a “mechanical hand” for transportation of small water droplets without loss, thus it may have potential applications in industrial fields.

Fabrication of fibrous amidoxime-functionalized mesoporous silica microsphere and its selectively adsorption property for Pb2+ in aqueous solution

Fibrous cyano-modified mesoporous SiO2 microspheres with specific surface area of ca. 300 m(2) g(-1) have been successfully fabricated respectively by in-situ synthesis and post-modification methods, based on the hydrolysis of ethyl silicate in the presence of (2-cyanoethyl)triethoxysilane at a certain condition. TEM observations show that the average diameters of the prepared fibrous cyano-modified SiO2 microspheres by these two methods are 68 and 211 nm, respectively. The N2 adsorption-desorption isotherms analysis on the fibrous SiO2 microspheres show sharp peaks in the 10-20 nm range. After the cyano groups transformed to amidoxime groups, the adsorption behavior of the fibrous amidoxime-functionalized mesoporous SiO2 microspheres for Fe(3+), Cu(2+), and Pb(2+) was investigated. The results show that the prepared SiO2 microspheres can selectively adsorb Pb(2+). The maximum equilibrium adsorption capacity for Pb(2+) could reach 284 mg/g. The desorption of Pb(2+) in 2M HNO3 completes within 60 min. The efficiency of the desorption is as high as 96.2%. This work provides the methods to prepare amidoxime-functionalized SiO2 microsphere with high specific surface area and total pore volume, which has the potential to be applied as an efficient adsorbent for specific heavy metal ions.

The mechanism of the formation of multihollow polymer spheres through sulfonated polystyrene particles.

Multihollow poly(methyl methacrylate) (PMMA) particles were successfully fabricated simply by gamma-ray radiating emulsions consisting of MMA monomers, sulfonated polystyrene (SP) particles, and water. The mechanism on the formation of the holes was studied in detail. It was found that there were two routes to achieve two different multihollow structures dependent on the initial location of SP particles before emulsification. If SP particles first located in the water phase, cage-like hollow PMMA particles were obtained through the formation of a Pickering emulsion. Otherwise, if SP particles first located in the oil (MMA) phase, a different multihollow structure would be produced via the formation of a multiple emulsion. This work provides a simple method to fabricate two different structured multihollow particles using the same conditions.

Novel Walnut-like Multihollow Polymer Particles: Synthesis and Morphology Control

Novel walnut-like multihollow polymer particles were first prepared by gamma-ray radiation emulsion polymerization using cross-linked and sulfonated polystyrene spheres (CSPs) as the template. The formation process was studied in detail, and the morphology of walnut-like multihollow polystyrene particles could be controlled by the content of cross-linking agent, sulfonation time of CSP particles, and the weight ratio of monomer/CSP. In addition, an application of walnut multihollow polymer particles on bonding Ag nanoparticles onto the surface was achieved, which could be extended to other noble metal nanoparticles and could have a wide range of potential applications, such as catalysts, sensors, solar cells, and photonic crystals.

Preparation of three-dimensional inverse opal SnO2/graphene composite microspheres and their enhanced photocatalytic activities

Three-dimensional inverse opal SnO2/graphene (IO-SnO2/graphene) microspheres with a size of several tens of microns are first prepared by a well-designed two-step calcination of polystyrene (PS) colloidal crystal template balls infiltrated with the sol precursors of SnO2 and graphene oxide. The polystyrene colloidal crystal template balls are formed by the self-assembly of monodispersed PS microspheres confined in water droplets of an inverse emulsion induced by the slow evaporation of water. Characterization with scanning electronic microscopy, Raman spectra, X-ray diffraction and X-ray photoelectron spectroscopy proved the ordered macroporous inverse opal composed of crystalline SnO2 and in situ reduced GO during the calcination. The pore size depends on the PS microspheres. The UV-vis diffusive reflectance spectra show that the light absorption edge of the prepared IO-SnO2/graphene microspheres can shift more than 400 nm. The photoluminescence spectra indicates that the IO structure and the introduction of rGO make the charge carriers transfer fast and retard the hole/electron recombination in the IO-SnO2/graphene microspheres so that their photocatalytic performance on the UV photolysis of methyl orange is considerably better than that of commercial SnO2 nanoparticles. However, the photocatalytic performance also depends on the content of GO. The addition of 0.06 wt% of GO achieves the best photocatalytic effect. Excessive GO will result in a diminished catalytic activity. This work provides a way to fabricate a new morphological SnO2 based materials with enhanced photocatalytic activity, which helps in the exploration of new photocatalysts with high performance.

Colloidal silver deposition onto functionalized polystyrene microspheres

This paper presents a facile method for the preparation of silver/polystyrene (Ag/PS) composite microspheres. PS microspheres with carboxyl and nitrile groups on the surfaces were synthesized via a two-step dispersion copolymerization of styrene, itaconic acid, and acrylonitrile in ethanol–water media. Ag/PS composite microspheres were prepared successively by addition of AgNO3 aqueous solution to the dispersion, absorbing to the surfaces of functional PS microspheres, and then reduction of Ag+ ions to silver nanoparticles by aqueous hydrazine hydrate. The results showed that Ag nanoparticles with size of about 50 nm were located on the shell of PS microspheres due to the combined interactions between the carboxyl and nitrile groups of PS microspheres and the in situ formed silver nanoparticles. The as-prepared Ag/PS microspheres showed good catalytic properties.

Fabrication of High-Performance Magnetic Lysozyme-Imprinted Microsphere and Its NIR-Responsive Controlled Release Property

The preparation of efficient and practical biomacromolecules imprinted polymer materials is still a challenging task because of the spatial hindrance caused by the large size of template and target molecules in the imprinting and recognition process. Herein, we provided a novel pathway to coat a NIR-light responsive lysozyme-imprinted polydopamine (PDA) layer on a fibrous SiO2 (F-SiO2) microsphere grown up from a magnetic Fe3O4 core nanoparticle. The magnetic core-shell structured lysozyme-imprinted Fe3O4@F-SiO2@PDA microspheres (MIP-lysozyme) can be easily separated by a magnet and have a high saturation adsorption capacity of lysozyme of 700 mg/g within 30 min because of the high surface area of 570 m(2)/g and the mesopore size of 12 nm of the Fe3O4@F-SiO2 support. The MIP-lysozyme microspheres also show an excellent selective adsorption of lysozyme (IF > 4). The binding thermodynamic parameters studied by ITC proves that the lysozyme should be restricted by the well-defined 3D structure of MIP-lysozyme microspheres. The MIP-lysozyme can extract lysozyme efficiently from real egg white. Owing to the efficient NIR light photothermal effect of PDA layer, the MIP-lysozyme microspheres show the controlled release property triggered by NIR laser. The released lysozyme molecules still maintain good bioactivity, which can efficiently decompose E. coli. Therefore, this work provides a novel strategy to build practical NIR-light-responsive MIPs for the extraction and application of biomacromolecules.

Formation of cagelike sulfonated polystyrene microspheres via swelling-osmosis process and loading of CdS nanoparticles.

In this report, we studied the formation mechanism of cagelike polymer microspheres fabricated conveniently and efficiently through a swelling-osmosis process of sulfonated polystyrene (SPS) microspheres in a ternary mixed solvent (water/ethanol/heptane). The scanning electron microscopy and transmission electron microscopy observations indicated that the morphology of the final cagelike SPS microspheres is mainly controlled by the composition of the mixed solvent and the swelling temperature. Considering the solubility parameters of related reagents and the low interface tension of heptane and the aqueous solution of ethanol (only 6.9 mN/m), we confirm that the porogen procedure starts from the swelling of SPS microspheres by heptane, followed by the osmosis process of water molecules into the swollen SPS microspheres forced by the strong hydrophilicity of -SO3H group. The water molecules permeated into SPS microspheres will aggregate into water pools, which form the pores after the microspheres are dried. These prepared cagelike SPS microspheres are further served as the scaffold for the in situ generated CdS nanoparticles under γ-ray radiation. The CdS/SPS composite microspheres show good fluorescence performance. This work shows that the cagelike SPS microspheres have a wide industrial application prospect due to their economical and efficient preparation and loading nanoparticles.

The comparison of the ringed spherulite morphology of PCL blends with poly(vinyl chloride), poly(bisphenol A carbonate) and poly(hydroxyether of bisphenol A)

The crystallization and ringed spherulite morphology of poly(e-caprolactone) (PCL) in the miscible blends of PCL/poly(vinyl chloride) (PVC), PCL/poly(hydroxyether of bisphenol A) (phenoxy resin) and PCL/poly(bisphenol A carbonate) (PC) were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Through the comparison of the PCL crystalline morphology with the interaction energy density B between the miscible components in these blends, it was found that the addition of the non-crystallizable component had great effect on the regularity of the ringed spherulite, which was coincided with the change of the interaction energy density B. To grow regular ringed spherulites in the PCL miscible blends, it was most important that the crystallization rate of PCL in the blends must be matched with the diffusion rate of the non-crystallizable component. Such a matching relation in the process of the ringed spherulite growth was a most important condition for the regular twisting of PCL lamellae.

Compositional heterogeneity, thermostable, and shape memory properties of ethylene oxide-ethylene terephthalate segmented copolymer with long soft segment

Ethylene oxide-ethylene terephthalate segmented copolymers (EOET) with long PEO segment or high PET content have showed an obvious compositional heterogeneity. The EOET copolymers with compositional heterogeneity could be separated into soluble and insoluble fractions by extraction with chloroform. 1 H-NMR measurements showed that the former contains much lower PET content than the average content value, and the latter is in reverse. DSC results revealed that PET segments in the latter would crystallize more easily, but in the former PEO segments exhibits more intensive melting peak. The thermogravimetric behaviors of EOET copolymers were between PEO and PET homopolymers. The EOET copolymers with serious compositional heterogeneity showed two stages of weight loss. TGA was sensitive to indicate the compositional heterogeneity in EOET copolymers. The compositional heterogeneity could impart a great influence on the shape memory behavior of EOET copolymers. The recovery curve of EOET copolymers with serious compositional heterogeneity also can exhibit two stages of deformation recovery. Generally, the component with worse memory behavior in EOET copolymer is an unfavorable factor, and the addition of EOET copolymer with better memory behavior into the blend is a favorable factor for the blend system.