Preparation and characterization of a poly(vinylbenzyl sulfonic acid)‐grafted FEP membrane

In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP‐g‐PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base‐catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM‐EDX. A chemical stability study performed with Fenton's reagent (3% H₂O₂ solution containing 4 ppm of Fe²⁺) at 70 °C revealed that FEP‐g‐PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)‐grafted membranes (FEP‐g‐PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010     

Phosphorus ligands for iron(III)‐mediated ATRP of styrene via generation of activators by monomer addition

Styrene polymerization via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) has been examined extensively with bulk FeX₃ and FeX₂ at 110 °C in conjunction with various phosphorus‐bearing ligands. It was found that GAMA possesses advantages over normal ATRP. Most importantly, narrower polydispersity index (PDI) values were observed from the styrene polymerizations with Fe(III) over those with Fe(II). Every instance of 2‐(diphenylphosphino)‐N,N′‐dimethyl‐[1,1′‐biphenyl]‐2‐amine and 2‐(diphenylphosphino) pyridine with the Fe(III) system were controlled excellently without addition of any radical initiator or reducing agent additives. Initiator type was found to exert a significant factor to influence on the controllability of polymerization. The initiation of 1‐phenylethyl chloride and methyl‐2‐chloropropionate gave rise to formation of polymers with narrow PDI (1.05–1.20), whereas those from 1‐phenylethyl bromide increased to 1.35. The GAMA of bulk styrene exhibited the best performance in terms of both rate and controllability compared with toluene and anisole. Both formation of block copolymer from the macroinitiator and efficient perturbation of polymerization with 2,2,6,6‐tetramethylpiperidine 1‐oxyl provided firm evidence to support the living and radical characteristics for the GAMA of styrene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 144–151, 2010     

Hydrophilic functionalization of syndiotactic polystyrene via a combination of electrophilic bromination and Suzuki–Miyaura reaction

Postfunctionalization of high‐molecular‐weight syndiotactic polystyrene (sPS) was achieved via combination of electrophilic bromination at the para‐position of the polymer aromatic ring and subsequent Suzuki–Miyaura cross‐coupling reactions with functionalized phenylboronic acids. The concentration of brominated styrene repeating unit in sPS was conveniently controlled by changing the ratio of added bromine relative to the polymer repeating unit. Brominated sPS (8.5 mol %) was converted quantitatively to other polar functional groups via Suzuki–Miyaura cross‐coupling reactions with various functional group‐substituted phenylboronic acids. The surface properties of functionalized sPS were studied by measuring water contact angles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4335–4343, 2010     

SSA-MOA: a novel CTC isolation platform using selective size amplification (SSA) and a multi-obstacle architecture (MOA) filter

Circulating tumor cells (CTCs) have gained increasing attention as physicians and scientists learn more about the role these extraordinarily rare cells play in metastatic cancer. In developing CTC technology, the critical criteria are high recovery rates and high purity. Current isolation methods suffer from an inherent trade-off between these two goals. Moreover, ensuring minimal cell stress and robust reproducibility is also important for the clinical application of CTCs. In this paper, we introduce a novel CTC isolation technology using selective size amplification (SSA) for target cells and a multi-obstacle architecture (MOA) filter to overcome this trade-off, improving both recovery rate and purity. We also demonstrate SSA-MOA's advantages in minimizing cell deformation during filter transit, resulting in more stable and robust CTC isolation. In this technique, polymer microbeads conjugated with anti-epithelial cell adhesion molecules (anti-EpCAM) were used to selectively size-amplify MCF-7 breast cancer cells, definitively differentiating from the white blood cells (WBCs) by avoiding the size overlap that compromises other size selection methods. 3 μm was determined to be the optimal microbead diameter, not only for size discrimination but also in maximizing CTC surface coverage. A multi-obstacle architecture filter was fabricated using silicon-on-glass (SOG) technology-a first such application of this fabrication technique-to create a precise microfilter structure with a high aspect ratio. The filter was designed to minimize cell deformation as simulation results predicted that cells captured via this MOA filter would experience 22% less moving force than with a single-obstacle architecture. This was verified by experiments, as we observed reliable cell capture and reduced cell deformation, with a 92% average recovery rate and 351 peripheral blood leukocytes (PBL) per millilitre (average). We expect the SSA-MOA platform to optimize CTC recovery rates, purity, and stability, increasing the sensitivity and reliability of such tests, thereby potentially expanding the utilization of CTC technologies in the clinic.     

Chromatographic separation and mass spectrometric identification of positional isomers of polyethylene glycol-modified growth hormone-releasing factor (1-29)

A one-step chromatographic method capable of separating all isomers of polyethylene glycol (PEG)-growth hormone-releasing factor (GRF) (1-29) conjugates was developed. The unmodified GRF (1-29) and seven different isomers of PEG-GRF (1-29) conjugates were separated by using a simple reversed-phase HPLC method depending on the differences of hydrophobicity due to the number and site of PEG attachment. The PEGylation sites of all isomers of PEG-GRF (1-29) conjugates were identified by determining the molecular masses of the Lys-C digested fragments with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This study is a first report for the separation of all PEG-conjugate isomers and would be useful for further studies to find the promising conjugate by evaluating biological activity and stability of each isomer.     

Azido- or hydroxyl-capped half-cubanes containing Cp*Rh fragments: [Cp*3Rh3(mu-X)3(mu3-X)]2+ (X-=OH- or N3-)

Treatment of [Cp*Rh(H(2)O)(3)](OTf)(2) (1) with Me(3)SiNH-t-Bu in acetone gave a hydroxyl-capped half-cubane [Cp*(3)Rh(3)(mu-OH)(3)(mu(3)-OH)](OTf)(3)(t-BuNH(3)) (2). Slow diffusion of Me(3)SiN(3) in diethyl ether into compound in acetone produced an azido-capped half-cubane [Cp*(3)Rh(3)(mu-N(3))(3)(mu(3)-N(3))](OTf)(2) (3). On the other hand, treating 1 with Me(3)SiN(3) in acetone gave an azido-bridged, dinuclear rhodium(III) complex [Cp*Rh(mu-N(3))(OH(2))](2)(OTf)(2) (4). Complexes 2 and 3 represent the first azido- or hydroxyl-capped, incomplete cubane-type Rh clusters. Under appropriate conditions, complexes 2 and 3 could be converted to complex 4. The structures of all products were determined by X-ray diffraction.     

Preparation of water‐soluble,syndiotacticity‐rich,low molecular weight poly(vinyl alcohol) microfibrils in high yields with the low‐temperature polymerization of vinyl pivalate in tetrahydrofuran and saponification

To prepare water‐soluble, syndiotacticity‐rich poly(vinyl alcohol) (PVA) microfibrils for various industrial applications, we synthesized syndiotacticity‐rich, low molecular weight PVA by the solution polymerization of vinyl pivalate (VPi) in tetrahydrofuran (THF) at low temperatures with 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN) as an initiator and successive saponification of poly(vinyl pivalate) (PVPi). Effects of the initiator and monomer concentrations and the polymerization temperature were investigated in terms of the polymerization behaviors and molecular structures of PVPi and the corresponding syndiotacticity‐rich PVA. The polymerization rate of VPi in THF was proportional to the 0.91 power of the ADMVN concentration, indicating the heterogeneous nature of THF polymerization. The low‐temperature solution polymerization of VPi in THF with ADMVN proved to be successful in obtaining water‐soluble PVA with a number‐average degree of polymerization (P_n) of 300–900, a syndiotactic dyad content of 60–63%, and an ultimate conversion of VPi into PVPi of over 75%. Despite the low molecular weight of PVA with P_n = 800, water‐soluble PVA microfibrillar fibers were prepared because of the high level of syndiotacticity. In contrast, for PVA with P_n = 330, shapeless and globular morphologies were observed, indicating that molecular weight has an important role in the in situ fibrillation of syndiotacticity‐rich PVA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1103–1111, 2002     

1,3-Dipolar cycloaddition of azides with electron-deficient alkynes under mild condition in water

We report a simple synthetic protocol for the 1,3-dipolar cycloaddition of azides with electron-deficient alkynes. Alkyne with at least one neighboring electron-withdrawing group proceeds with the cycloaddition successfully without any catalysts at room temperature in water. Under this simple condition, we evaluated a series of small molecule model reactions and then coupled an azido-DNA molecule with electron-deficient alkynes for the formation of [1,2,3]-triazole heterocycle, providing a potential method for introducing functional groups to DNA under biological conditions.     

Kopsifolines A–F: a New Structural Class of Monoterpenoid Indole Alkaloids from Kopsia

Six new indole alkaloids, named kopsifolines A–F ( 1 – 6 ), with an unprecedented hexacyclic carbon skeleton, constituting a new structural group of monoterpenoid indole alkaloids, were obtained from the leaf extract of a Malayan Kopsia species, and their structures were established by spectroscopic analysis.     

Roles of metal nanoparticles on organosulfur-conducting polymer composites for lithium battery with high energy density

Ag nanoparticles were added to DMcT-PAn composites to improve charge-discharge performance of the composites as a cathode material for lithium rechargeable batteries. Addition of Ag nanoparticles successfully enhanced the redox activity of the composites, possibly due to electrocatalytic activity of the nanoparticles. Increased conductivity of the composite films could be another possible origin for the enhanced redox activity. UV/vis spectroscopic analysis suggested strong interactions between DMcT and nanoparticles, while only weak interactions were observed between PAn and nanoparticles. XPS measurements further confirmed the interactions between DMcT and Ag nanoparticles based on a signal indicative of a silver-sulfur bond.