Novel fabrication of magnetic thermoplastic nanofibers via melt extrusion of immiscible blends

A novel technique of fabricating magnetic thermoplastic nanofibers by the control of the phase separation of immiscible polymer blends during melt extrusion was presented. The magnetic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE)/Fe₃O₄ composite nanofibers were prepared via the melt extrusion of cellulose acetate butyrate matrix and PVA‐co‐PE preloaded with different amounts of Fe₃O₄ nanoparticles. The morphologies of magnetic composite nanofibers were characterized by scanning electron microscopy. The uniform dispersion of Fe₃O₄ nanoparticles in nanofiber matrixes and crystal structures were confirmed using transmission electron microscopy and wide angle X‐ray diffraction. Thermogravimetric analysis was employed to quantify the exact loading amount of Fe₃O₄ nanoparticles in the composite nanofibers. The magnetic measurements showed that composite nanofibers displayed superparamagnetic behavior at room temperature. With increasing content of Fe₃O₄ nanoparticles, the saturation magnetization of the magnetic composite nanofiber significantly improved. The prepared magnetic composite nanofibers might have found potential applications in the sensors and bio‐molecular separation fields. Copyright © 2012 John Wiley & Sons, Ltd.     

A Novel Fission Process in Mini-emulsion RAFT Polymerization: Shell Crosslinked Nanoparticles as a Model

Shell crosslinked nanoparticles, prepared from copolymerization of styrene and disulfide crosslinker, using poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) as stabilizer and macroinitiator, exhibited a special fission behavior during the mini-emulsion RAFT polymerization process.     

Atom Transfer Radical Polymerization of MMA Initiated by 2‐(4‐chloromethyl‐phenyl)‐benzoxazole and Fluorescent Property of PMMA

Atom transfer radical polymerization (ATRP) of MMA was conducted using 2‐(4‐chloromethyl‐phenyl)‐benzoxazole as initiator, CuCl as catalyst, and PMDETA as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (Mn/Mw range from 1.30 to 1.45). The structure of PMMA was analyzed by ¹H‐NMR and proved the polymerization could be controlled to some degree. The optical property of the initiator was well preserved in the resulting PMMA, and the end‐functionalized PMMA exhibited fluorescent emission at 360 nm whether in DMF solution or in film state.     

Dihydromyricetin

A study on the efficiency of bio-based compound as stabilizer for linear low density polyethylene (LLDPE) is reported. A water extract from Ampelopsis grossedentata (Dihydromyricetin) is used. Its stabilizing activity is compared with two commercial phenolic antioxidants: methyl gallate (MG) and Irganox 1010. Based on the measurement of the oxidation onset temperature (OOT) of LLDPE/antioxidant samples, it is found that the antioxidant ability of the three kinds of antioxidants is in the following order: DMY > 1010 > MG. The antioxidant ability and thermal decomposition activation energy (E _a) of antioxidants are further examined by thermal gravimetric analysis. The effects of water extraction on the migration resistance of LLDPE/antioxidants are also evaluated by monitoring the OOT change, demonstrating that DMY retained high stability against migration.     

Synergistic effects between silicon-containing flame retardant and potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) on flame retardancy and thermal degradation of PC

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) and diphenylsilanediol through solution polycondesation and it was used together with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) to prepare a flame-retardant system for polycarbonate (PC). The structure and thermal property of PSiN were characterized by Fourier transform infrared spectroscopy (FTIR), ¹HNMR and thermogravimetric analysis (TG) tests. Flammability and thermal behaviors of PC/KSS/PSiN systems were estimated by limited oxygen index (LOI), cone calorimeter, vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and char residues of PC/KSS system were improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% KSS were incorporated, the LOI value of PC was found to be 46, and class V-0 of the UL-94 test. Moreover, both the heat release rate and the total heat release of PC/KSS/1 mass% PSiN decreased compared with those of PC and PC/KSS systems. The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for PC/KSS/PSiN system hold a more cohesive and denser char structure when compared with the pure PC and PC/KSS system.     

Direct electrochemistry of hemoglobin on graphene/Fe3O4 nanocomposite-modified glass carbon electrode and its sensitive detection for hydrogen peroxide

Graphene/Fe₃O₄ nanocomposite was prepared for the immobilization of hemoglobin (Hb) to improve the electron transfer between Hb and glass carbon electrode (GCE). The characterization of nanocomposites was described by transmission electron microscopy, Fourier transform infrared, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemistry of Hb on the graphene/Fe₃O₄-based GCE was investigated by cyclic voltammetry and amperometric measurement. The modified electrode showed a wide linear range from 0.25 μmol/L to 1.7 mmol/L with a correlation coefficient of 0.9967. The detection limit of the H₂O₂ biosensor was estimated at 6.0?×?10^?6?mol/L at a signal-to-noise ratio of 3.     

Future of the Particle Replication in Nonwetting Templates (PRINT) Technology

Particle replication in nonwetting templates (PRINT) is a continuous, roll‐to‐roll, high‐resolution molding technology which allows the design and synthesis of precisely defined micro‐ and nanoparticles. This technology adapts the lithographic techniques from the microelectronics industry and marries these with the roll‐to‐roll processes from the photographic film industry to enable researchers to have unprecedented control over particle size, shape, chemical composition, cargo, modulus, and surface properties. In addition, PRINT is a GMP‐compliant (GMP=good manufacturing practice) platform amenable for particle fabrication on a large scale. Herein, we describe some of our most recent work involving the PRINT technology for application in the biomedical and material sciences.