Sulfonated poly(ether ether ketone)/polypyrrole core–shell nanofibers : a novel polymeric adsorbent/conducting polymer nanostructures for ultrasensitive gas sensors

Conducting polymers-based gas sensors have attracted increasing research attention these years. The introduction of inorganic sensitizers (noble metals or inorganic semiconductors) within the conducting polymers-based gas sensors has been regarded as the generally effective route for further enhanced sensors. Here we demonstrate a novel route for highly-efficient conducting polymers-based gas sensors by introduction of polymeric sensitizers (polymeric adsorbent) within the conducting polymeric nanostructures to form onedimensional polymeric adsorbent/conducting polymer core−shell nanocomposites, via electrospinning and solution-phase polymerization. The adsorption effect of the SPEEK toward NH3 can facilitate the mass diffusion of NH3 through the PPy layers, resulting in the enhanced sensing signals. On the basis of the SPEEK/PPy nanofibers, the sensors exhibit large gas responses, even when exposed to very low concentration of NH3 (20 ppb) at room temperature.

Polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-bpolystyrene triblock copolymers as potential carriers for hydrophobic drugs

A simple and effective method is introduced to synthesize a series of polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-b- polystyrene (PSt-b-POEOMA-b-PSt) triblock copolymers. The structures of PSt-b-POEOMA-b-PSt copolymers were characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopy. The molecular weight and molecular weight distribution of the copolymer were measured by gel permeation chromatography (GPC). Furthermore£ the self-assembling and drug-loaded behaviours of three different ratios of PSt-b-POEOMA-b-PSt were studied. These copolymers could readily self-assemble into micelles in aqueous solution. The vitamin E-loaded copolymer micelles were produced by the dialysis method. The micelle size and core-shell structure of the block copolymer micelles and the drug-loaded micelles were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The thermal properties of the copolymer micelles before and after drug-loaded were investigated by different scanning calorimetry (DSC). The results show that the micelle size is slightly increased with increasing the content of hydrophobic segments and the micelles are still core-shell spherical structures after drug-loaded. Moreover, the glass transition temperature (Tg) of polystyrene is reduced after the drug loaded. The drug loading content (DLC) of the copolymer micelles is 70%-80% by ultraviolet (UV) photolithography analysis. These properties indicate the micelles self-assembled from PSt-b- POEOMA-b- PSt copolymers would have potential as carriers for the encapsulation of hydrophobic drugs.

Preparation and characterization of natural rubber/silica nanocomposites using rule of similarity in latex

Rule of similarity and latex compounding techniques were combined for the first time to prepare natural rubber/nanosilica (NR/SiO2) nanocomposite with core-shell nanosilica-poly (methyl methacrylate) (SiO 2-PMMA) particles and PMMA-modified natural rubber matrix (NR-PMMA). The microstructure of SiO2 and nanocomposites with different SiO 2 contents was characterized by fourier transform infrared spectroscopy (FTIR); the morphology of nanocomposites was investigated with scanning electron microscopy (SEM); the tensile strength was characterized by tensile testing machine and the thermal stability of composites was studied by thermal gravimetric analysis. Results showed that PMMA chains have successfully grafted onto the surface of SiO2, and the core-shell SiO 2-PMMA nanoparticles and NR-PMMA latex have been perfectly incorporated. SiO2-PMMA nanoparticles are evenly distributed over the NR matrix with an average size in the range of 60-100 nm at the low content (SiO2? 3 wt%), while aggregations are apparently observed when 5 wt% SiO2 is loaded. In addition, NR/SiO2 composities possess a considerable improvement in ageing resistance compared with the pure NR. The tensile strength of composite increases from 6.99 to 12.72 MPa, reaching the highest value at a 0.5 wt% SiO2 loading, and then the figure decreases gradually because of the aggregation of SiO2 nanoparticles. It is anticipated that the reported process is to provide a simple and economic way for preparing NR composites.

Composite yarns fabricated from continuous needleless electrospun nanofibers

In this work, a spinning metal wire collector was employed to continuously collect polyacrylonitrile (PAN) nanofibers produced by a disc fiber generator and coil them around a polyethylene terephthalate (PET) yarn. The obtained composite yarns exhibited a core/shell structure (PET yarn/PAN nanofibers) with nanofibers orderly arranged on the surface of the PET yarn. The electric field analysis showed that the position of metal wire had insignificant effect on the formed electric field and high intensity electric field was formed at the disc circumferential area, which provided a constant electric field for the production of uniform nanofibers. The spinning solution, spinning speed of metal wire, and winding speed were found to play an important role in producing good quality nanofiber yarns, in terms of morphology, strength, and productivity. Pure nanofiber yarns were obtained after dissolving the core yarns in a proper solvent. This method has shown potential for the mass production of nanofiber yarns for industrial applications.

Ultrafine PDMS fibers: Preparation from in situ curing-electrospinning and mechanical characterization

Polydimethylsiloxane (PDMS) fibers with unexpected elasticity were prepared by a modified core-shell electrospinning method using a commercially-available liquid PDMS precursor (Sylgard 184) and polyvinylpyrrolidone (PVP) as core and sheath materials, respectively. The liquid PDMS precursor was crosslinked in situ to form a solid core when the newly-electrospun core-sheath nanofibers were deposited onto a hot-plate electrode collector. After dissolving the PVP sheath layer off the fibers, net PDMS fibers showed larger average diameter than core-sheath fibers, with an average diameter around 1.35 μm. The tensile properties of both single fibers and fibrous mats were measured. Single PDMS fibers had a tensile strength and elongation at break of 6.0 MPa and 212%, respectively, which were higher than those of PDMS cast film (4.9 MPa, 93%). The PDMS fiber mat had larger elongation at break than the single PDMS fibers, which can be drawn up to 403% their original length. Cyclic loading tests indicated a Mullin effect on the PDMS fiber mats. Such a superior elastic feature was attributed to the PDMS molecular orientation within fibers and the randomly-orientated fibrous structure. Highly-elastic, ultrafine PDMS fibers may find applications in strain sensors, biomedical engineering, wound healing, filtration, catalysis, and functional textiles. © The Royal Society of Chemistry 2014.

Epitaxial growth of multi-structure sno2 by chemical vapor deposition

The nanowire and whisker heterostructures of tin dioxide were fabricated by the chemical vapor deposition technique. It was demonstrated that various structures of tin oxide can be obtained by controlling the thickness of gold layer and the partial pressure of source vapor at growing sites. 12.5 and 25 nm thicknesses are preferable for the epitaxial growth of nanowires and heterostructure through vapor-liquid-solid mechanism, respectively. The tin dioxide whiskers with core-shell structure were fabricated by vapor-solid mechanism. Meanwhile, the influences of various factors on the tin dioxide growth are also discussed.

Novel approach to trigger nanostructures in thermosets using competitive Hydrogen-Bonding-Induced Phase Separation (CHIPS)

A new route to prepare nanostructured thermosets by the utilization of intermolecular hydrogen-bonding interactions is demonstrated here. In this study, competitive hydrogen-bonding-induced microphase separation (CHIPS) in epoxy resin (ER) containing an amphiphilic block copolymer poly(ε-caprolactone)-block-poly(2-vinylpyridine) (PCL-b-P2VP) is investigated for the first time. The phase separation takes place due to the disparity in the hydrogen-bonding interactions in ER/P2VP and ER/PCL pairs leading to the formation of ordered nanostructures in the ER/block copolymer blends. SAXS and TEM results indicate that the hexagonally packed cylindrical morphology of neat PCL-b-P2VP block copolymer remains but becomes a core-shell structure at 10 wt % addition of ER, and changes to regular lamellae structures at 20-50 wt % then to disordered lamellae with 60 wt % ER. Wormlike structures are obtained in the blends with 70 wt % ER, followed by a completely homogeneous phase of ER/P2VP and ER/PCL. The formation of nanostructures and changes in morphologies depend on the relative strength of hydrogen-bonding interactions between each component block copolymer and the homopolymer. This versatile method to develop nanostructured thermosets, involving competitive hydrogen-bonding interactions, could be used for the fabrication of hierarchical and functional materials.

A novel and facile approach to fabricate a conductive and biomimetic fibrous platform with sub-micron and micron features

The demands of multifunctional scaffolds have exceeded the passive biocompatible properties previously considered sufficient for tissue engineering. Herein, a novel and facile method used to fabricate a core-shell structure consisting of a conducting fiber core and an electrospun fiber shell is presented. This multifunctional structure simultaneously provides the high conductivity of conducting polymers as well as the enhanced interactions between cells and the sub-micron topographical environments provided by highly aligned cytocompatible electrospun fibers. Unlimited lengths of PEDOT:PSS-Chitosan-PLGA fibers loaded with an antibiotic drug, ciprofloxacin hydrochloride, were produced using this method. The fibers provide modulated drug release with excellent mechanical properties, electrochemical performance and cytocompatibility, which hold great promise for the application of conductive electrospun scaffolds in regenerative medicine.

Interactions between fibroin and sericin proteins from antheraea pernyi and bombyx mori silk fibers

Silkworm silk fibers are core-shell composites of fibroin and sericin proteins. Studying the interactions between fibroin and sericin is essential for understanding the properties of these composites. It isobserved that compared to the domestic silk cocoon Bombyx mori (B. mori), the adhesion between fibroin and sericin from the wild silk cocoon, Antheraea pernyi (A. pernyi), is significantly stronger with a higherdegree of heterogeneity. The adsorption of A. pernyi sericin on its fibroin is almost twice the value for B.mori sericin on fibroin, both showing a monolayer Langmuir adsorption. 1H NMR and FTIR studiesdemonstrate on a molecular level the stronger interactions and the more intensive complex formation between A. pernyi fibroin and sericin, facilitated by the hydrogen bonding between glycine and serine.The findings of this study may help the design of composites with superior interfacial adhesion between different components.

Layer-by-layer structured membranes of silk fibroin and polyethylenimine on electrospun silk fibroin nanofibers

Self-assembled silk fibroin (SF)-polyethylenimine (PEI) multilayered films were fabricated on ethanol treated electrospun SF nanofibrous substrates via the electrostatic layer-by-layer (LBL) adsorption. The film coated membranes were characterized using scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectrophotometer (XPS). The SEM images showed that the multilayers of SF-PEI were formed on the surface of the ethanol treated SF nanofibres. The characteristics such as the fiber shape and porous structure were well maintained as the number of the coated SF-PEI bilayers was less than five. However, obvious adhesive substances and blocked pores were observed on the surface of the fibers as the number of bilayers of SF-PEI increased to six. Furthermore, the obvious core-shell structures were observed by TEM. The thickness of five SF-PEI bilayers was approximately 80nm. Additionally, the XPS results also revealed that the SF-PEI multilayer composite membranes formed. The adsorption mainly depended on a simple electrostatic interaction between the layers of SF and PEI. These SF-PEI multilayer assembled nanofibrous membranes could be a promising material for use as a sensor, gene delivery agent and scaffolds.

Reverse microemulsion-mediated synthesis of SiO2-coated ZnO composite nanoparticles : multiple cores with tunable shell thickness

Monodispersed SiO₂-shell/ZnO-core composite nanospheres have been prepared in an oil-in-water microemulsion system. By using cyclohexane as the oil phase and Triton X-100 as the surfactant, composite nanospheres with high core loading levels and tunable shell thickness were obtained. Utilization of PVP capping agent on ZnO allowed the synthesis of composite nanospheres without forming any coreless SiO2 spheres or shell-less ZnO particles. The photoactivity of ZnO nanoparticles was greatly reduced by SiO2-coating, which enables their applications as durable, safe, and nonreactive UV blockers in plastics, coating, and other products.