Inorganic–Organic Heteropolyacid–Gold(I) Hybrids: Structures and Catalytic Applications

Gold(I)‐polyoxometalate hybrid complexes 1 – 4 ([PPh₃AuMeCN]_xH_4?xSiW₁₂O₄₀, x=1–4) were synthesized and characterized. The structure of the primary gold(I)–polyoxometalate 1 (x=1) was fully ascertained by XRD, FTIR, ³¹P and ²⁹Si magic‐angle spinning (MAS) NMR, mass spectroscopy, and SEM–energy dispersive X‐ray spectroscopy (EDX) techniques. Moreover, this complex exhibited better catalytic activity and selectivity compared with standard, homogeneous, gold catalysts in the new rearrangement of propargylic gem‐diesters.     

Synthesis and Characterization of Novel Organic／Inorganic Hybrid Polymers Containing Polyhedral Oligosilsesquioxanes

Hybrid polymers, poly(vinyl pyrrolidone-co-isobutyl styryl polyhedral oligomeric silsesquioxanes)s (PVP-POSS) were synthesized by one step polymerization and characterized using GPC and DSC. Addition of POSS significantly increases the Tg of polyvinylpyrrolidone at a fair high POSS content and obtained high molecular weight polymers with very narrow molecular distribution. The POSS content in the resulted hybrids can be controlled by varying the POSS feed ratio.     

Highly Extensible Bio‐Nanocomposite Fibers

Here, we show that a poly(ethylene oxide) polymer can be physically cross‐linked with silicate nanoparticles (Laponite) to yield highly extensible, bio‐nanocomposite fibers that, upon pulling, stretch to extreme lengths and crystallize polymer chains. We find that both, nanometer structures and mechanical properties of the fibers respond to mechanical deformation by exhibiting strain‐induced crystallization and high elongation. We explore the structural characteristics using X‐ray scattering and the mechanical properties of the dried fibers made from hydrogels in order to determine feasibility for eventual biomedical use and to map out directions for further materials development.

     

Inorganic–organic hybrids involving poly(ε‐caprolactone) and silica network: Hydrogen‐bonding interactions and isothermal crystallization kinetics

Inorganic–organic hybrids mediated by hydrogen‐bonding interactions involving silicon oxide network and poly(ε‐caprolactone) (PCL) were prepared via an in situ sol–gel process of tetraethoxysilane in the presence of PCL. Fourier transform infrared spectroscopy indicated that there were hydrogen‐bonding interactions between carbonyls of PCL and silanol hydroxyls that were formed by incomplete polycondensation in the sol–gel process. In terms of the frequency shift of the hydroxyl stretching vibration bands, it is concluded that the strength of the interassociation between PCL and silicon oxide networks is weaker than that of the self‐association in the control silica network. The phenomenon of equilibrium melting point depression was observed for the PCL/silica system. The hybridization of PCL with silica network causes a considerable increase in the overall crystallization rate and dramatically influences the mechanism of nucleation and growth of the PCL crystallization. The analysis of isothermal crystallization kinetic data according to the Hoffman‐Lauritzen theory shows that with increasing silica content in the hybrids, the surface energy of extremity surfaces increases dramatically for the hybrids. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2594–2603, 2005     

A Cationic Water‐Soluble Poly(p‐phenylenevinylene) Derivative: Highly Sensitive Biosensor for Iron‐Sulfur Protein Detection

Summary: A new water‐soluble cationic ammonium‐functionalized poly(p‐phenylenevinylene) (PPV‐NEtMe) was successfully synthesized and exhibited high sensitivity (K_sv = 6.9 × 10⁷ M ⁻¹) on rubredoxin, a type of anionic iron‐sulfur (Fe‐S) proteins. Further investigation showed that the biosensitivity of the cationic conjugated polymer is strongly dependent on the nature of the buffer solution and the concentration of the conjugated polymer used in the analyses.

The schematic diagram of anionic rubredoxin detected by PPV‐NEtMe.     

Poly(N‐vinylpyrrolidone)‐Modified Surfaces for Biomedical Applications

Poly(N‐vinylpyrrolidone) (PVP), an important water soluble synthetic polymer, has many desirable properties including low toxicity, chemical stability, and good biocompatibility. Since PVP is hemocompatible and physiologically inactive, it has been used as a blood plasma substitute. Surface modification with PVP has been investigated extensively over the past few years as a means of preventing nonspecific protein adsorption. PVP may therefore be seen as a promising antifouling surface modifier comparable to poly(ethylene glycol) (PEG). In this review, various approaches for the design and preparation of PVP‐modified surfaces are summarized and potential biomedical applications of these PVP‐modified materials are indicated. Finally, some perspectives on future research on PVP for surface modification are discussed.

     

Synthesis of polydopamine‐coated graphene–polymer nanocomposites via RAFT polymerization

Graphene‐polymer nanocomposites have significant potential in many applications such as photovoltaic devices, fuel cells, and sensors. Functionalization of graphene is an essential step in the synthesis of uniformly distributed graphene‐polymer nanocomposites, but often results in structural defects in the graphitic sp² carbon framework. To address this issue, we synthesized graphene oxide (GO) by oxidative exfoliation of graphite and then reduced it into graphene via self‐polymerization of dopamine (DA). The simultaneous reduction of GO into graphene, and polymerization and coating of polydopamine (PDA) on the reduced graphene oxide (RGO) surface were confirmed with XRD, UV–Vis, XPS, Raman, TGA, and FTIR. The degree of reduction of GO increased with increasing DA/GO ratio from 1/4 to 4/1 and/or with increasing temperature from room temperature to 60 °C. A RAFT agent, 2‐(dodecylthiocarbonothioylthio)?2‐methylpropionic acid, was linked onto the surface of the PDA/RGO, with a higher equivalence of RAFT agent in the reaction leading to a higher concentration of RAFT sites on the surface. Graphene‐poly(methyl methacrylate), graphene‐poly(tert‐butyl acrylate), and graphene‐poly(N‐isopropylacrylamide) nanocomposites were synthesized via RAFT polymerization, showing their characteristic solubility in several different solvents. This novel synthetic route was found facile and can be readily used for the rational design of graphene‐polymer nanocomposites, promoting their applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3941–3949     

Resistive‐type humidity sensors based on PVP–Co and PVP–I2 complexes

Poly(vinylpyrrolidone) films containing cobalt chloride or iodine were investigated to obtain information on their possible use as a humidity sensor element. FTIR and UV‐VIS spectroscopies were used to characterize the PVP–I₂ and PVP–Co complexes. Infrared spectroscopy revealed a structural change of both shape and intensity of the carbonyl and lactam bands, indicating the formation of an ion‐coordination polymer. The J–E curves for pure PVP, PVP–I₂, and PVP–Co films obey ohm's law at low voltages, deviate from the linear response at higher voltages, and finally display breakdown behavior. An increase in current density of the PVP matrix with iodine or cobalt doping is attributed to the formation of charge transfer complexes. The observed hysteresis of the I–V characteristics implies that there was some standing voltage in the film, which could be attributed to a disorientation of polar side groups of PVP. The electrical conductivities of the polymeric complexes were very sensitive to environmental humidity. An explanation of the humidity‐sensing behavior of the PVP–I₂ and PVP–Co complexes is presented. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 459–469, 2001     

Synthesis and characterization of pH‐sensitive PAMPS/PVP nanogels in aqueous media

A novel method for preparing poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS) and poly (vinylpyrrolidone) (PVP) complex nanogels in PVP aqueous solution is discussed in this paper. The PAMPS/PVP complex nanogels were prepared via polymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) monomer in the presence of PVP nanoparticles which formed in water/acetone cosolvent in presence of N, N′‐methylenebisacrylamide (MBA) as a crosslinker, N, N, N′, N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H NMR spectra indicated that the compositions of PAMPS/PVP are consistent with the designed structure. TEM micrographs proved that PAMPS/PVP nanogels possess the spherical morphology before and after swelling. These PAMPS/PVP nanogels exhibited pH‐induced phase transition due to protonation of PAMPS chains. The properties of PAMPS/PVP nanogels indicate that PAMPS/PVP nanogels can be developed into a pH‐controlled drug delivery system. Copyright © 2009 John Wiley & Sons, Ltd.     

First Successful Post‐Synthetic Self‐Assembly of Polyaniline with Poly(N‐vinylpyrrolidone) into Aqueous Nanocolloids

Summary: Polyaniline (PANI) is successfully self‐assembled with poly(N‐vinylpyrrolidone) (PVP) into aqueous nanocolloids. The typical morphology of the colloids is studied by atomic force microscopy (AFM), which reveals spherical nanoparticles with a diameter of 80–150 nm. A possible mechanism for such a post‐synthetic self‐assembly process is proposed.

AFM micrograph of PANI aqueous nanocolloids stabilized by PVP via a novel post‐synthetic self‐assembly method.     

Poly(vinylpyrrolidone)‐based films grown on copper surfaces

The influence of molecular weight and the amount of the poly(vinylpyrrolidone) (PVP) on the growth of poly(vinylpyrrolidone)–based films on copper surfaces was studied by electrochemical, infrared and electronic spectroscopy, and thermogravimetric methods. Complex polymer/metal ions were deposited onto a copper surface, as the result of the electrochemically generated reaction of copper cations with PVP and SCN^?, in sulfuric acid media. Spontaneous film growth on copper surfaces was generated and characterized as a Cu(II)/PVP/SCN^? complex. Infrared spectra and thermal gravimetric curves of the films generated at + 0.7 V were compared with the chemically synthesized complex, and show the same patterns. The oxidation process can be described as: Cu(0)→Cu(I) and Cu(I)→Cu(II), and the copper complex formed at more positive potentials was characterized as Cu(II)/PVP/SCN^?, with copper bonded to the oxygen atom of PVP and thiocyanate ligand N‐linked. This study focuses on the complex formation on a copper surface in acid media and its characterization through electrochemical and spontaneously generated reactions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2206–2214, 2009     

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

Au nanoclusters with an average size of approximately 1 nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) into 2,5‐furandicarboxylic acid (FDCA). It achieved >99 % yield of 2,5‐furandicarboxylic acid in water under mild conditions (60 °C, 0.3 MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO₂, CeO₂, and Mg(OH)₂) and channel‐type zeolites (ZSM‐5 and H‐MOR). Detailed characterizations, such as X‐ray diffraction, transmission electron microscopy, N₂‐physisorption, and H₂‐temperature‐programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA.     

Bifunctional Polyacrylonitrile Fiber‐Mediated Conversion of Sucrose to 5‐Hydroxymethylfurfural in Mixed‐Aqueous Systems

A highly efficient catalytic system composed of a bifunctional polyacrylonitrile fiber (PANF‐PA[BnBr]) and a metal chloride was employed to produce 5‐hydroxymethylfurfural (HMF) from sucrose in mixed‐aqueous systems. The promoter of PANF‐PA[BnBr] incorporates protonic acid groups that promote the hydrolysis of the glycosidic bond to convert sucrose into glucose and fructose, and then catalyzes fructose dehydration to HMF, while the ammonium moiety may promote synergetically with the metal chloride the isomerization of glucose to fructose and transfer HMF from the aqueous to the organic phase. The detailed characterization by elemental analysis, FTIR spectroscopy, and SEM confirmed the rangeability of the fiber promoter during the modification and utilization processes. Excellent results in terms of high yield (72.8 %) of HMF, superior recyclability (6 cycles) of the process, and effective scale‐up and simple separation procedures of the catalytic system were obtained. Moreover, the prominent features (high strength, good flexibility, etc.) of the fibers are very attractive for fix‐bed reactor.     

Exfoliated Polylactide/Clay Nanocomposites by In‐Situ Coordination–Insertion Polymerization

Poly(L ‐lactide)/layered aluminosilicate nanocomposites were synthesized in bulk by ring‐opening polymerization in the presence of two organo‐modified montmorillonites. When the organo‐modifier consisted of an ammonium cation bearing primary hydroxyl groups, polymerization was initiated by the alcohol functions after adequate activation. The growing polymer chains were directly “grafted” onto the clay surface through the hydroxyl‐functionalized ammonium cations yielding exfoliated nanocomposites with enhanced thermal stability.

TEM image of a fully exfoliated Cloisite®30B‐based nanocomposite, showing delamination of the silicate layers.     

Core–shell functionalized MWCNT/poly(m‐aminophenol) nanocomposite with large dielectric permittivity and low dielectric loss

Core–shell carboxyl‐functionalized multiwall carbon nanotube (c‐MWCNT)/poly(m‐aminophenol) (PmAP) nanocomposite were prepared through in‐situ polymerization of m‐aminophenol (m‐AP) in the presence of MWCNTs, and explicated as a dielectric material for electronic applications. The formation of thin PmAP layer on individual c‐MWCNT with excellent molecular level interactions at interfaces was confirmed by morphological and spectroscopic analyses. Here we conducted a comparative study of the dielectric performances of PmAP based nanocomposite films with pristine MWCNTs and c‐MWCNTs as fillers. Compared to PmAP/MWCNT nanocomposites, the PmAP/c‐MWCNT nanocomposites exhibited higher dielectric permittivity and lower dielectric loss. The well dispersed c‐MWCNTs in PmAP/c‐MWCNT nanocomposite produce huge interfacial area together with numerous active polarized centers (crystallographic defects), which in turn intensified the Maxwell‐Wagner‐Sillars (MWS) effect based on excellent molecular level interactions and thus, produce large dielectric permittivity (8810 at 1 kHz). The percolation threshold of PmAP/c‐MWCNT nanocomposites is found lower than that of the PmAP/MWCNT nanocomposites, which could be attributed to homogeneous distribution of c‐MWCNTs and strong c‐MWCNT//PmAP interfacial interactions in the nanocomposites. Copyright © 2016 John Wiley & Sons, Ltd.     

A Novel Inorganic-Organic Composite Constructed from Cobalt（Ⅱ）-Monosubstituted Polyoxometalates and Poly（amidoamine）-NH2 DendrimersA Novel Inorganic-Organic Composite Constructed from Cobalt（Ⅱ）-Monosubstituted Polyoxometalates and Poly（amidoamine）-NH2 Dendrimers

An inorganic-organic composite was prepared by poly（amidoamine） （PAMAM） dendrimer reacting with cobalt（Ⅱ）-monosubstituted polyoxometalates Na5Co^Ⅱ（H2O）PW11O39 （PW11CO） in an aqueous solution. The hybrid composite PW11Co/PAMAM was characterized by FT-IR, UV-Vis diffuse reflectance spectra （DR-UV-Vis）, XPS, XRD and TG/DTA, indicating that the PWI iCo was chemically anchored to PAMAM. The morphologies of the title composite were characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The catalytic activity was evaluated by oxidation of isobutyraldehyde （IBA） to isobutyric acid （IBAc） in MeCN under mild conditions （20 ℃, ambient pressure）, showing that the title compound is a more effective and recoverable catalyst than corresponding PW11Co.     

固体杂多酸在生物质水解转化中的应用

随着化石资源的日益枯竭,寻求可替代清洁能源已成为全球重大课题。生物质是一种可再生的清洁能源,目前人们尝试通过利用生物质转化缓解日益增长的能源需求。杂多酸是应用在清洁工艺中的重要催化剂,结构和酸度的设计调变性及较高的热稳定性,使其广泛用于生物质的水解转化反应平台。目前固体杂多酸在水溶剂、有机溶剂及两相体系中降解生物质有着各自不同的优缺点。本文综述了杂多酸在不同反应体系中水解转化生物质制备精细化学品的研究进展,并对其在生物质水解转化利用中的应用前景进行了展望。