bluuebunny/crossref_metadata_2025_split huggingface dataset:
N‐Heterocyclic Carbene‐Mediated Organocatalytic Transfer of Tin onto Aldehydes: An Easy Access to syn‐Diols and Mechanistic Studies
Authors: Blanc Romain , Nava Paola , Rajzman Michel , Commeiras Laurent , Parrain Jean‐Luc 
Published: July 2012

AbstractAn update of our preliminary communication concerning an efficient organocatalytic procedure for the transfer of tin onto aldehydes is presented. This update combines (i) a full study of the preparation of γ‐silyloxyallylstannanes from β‐substituted enals, (ii) a “one‐pot” sequence (in inter‐ and intramolecular version) including N‐heterocyclic carbene (NHC)‐catalyzed silylstannation reaction/Lewis acid‐promoted allylstannation reaction to furnish the corresponding syn‐diols, and (iii) mechanistic studies on the organocatalytic 1,2‐addition.
Access to Both Enantiomers of α‐Chloro‐β‐keto Esters with a Single Chiral Ligand: Highly Efficient Enantioselective Chlorination of Cyclic β‐Keto Esters Catalyzed by Chiral Copper(II) and Zinc(II) Complexes of a Spiro‐2,2′‐bischroman‐Based Bisoxazoline Ligand
Authors: Li Jie , Pan Wei , Wang Zheng , Zhang Xumu , Ding Kuiling 
Published: July 2012

AbstractThe spiro‐2,2′‐bichroman‐based chiral bisoxazoline ligands (SPANbox) were found to be highly efficient in copper(II)‐ and zinc(II)‐catalyzed asymmetric chlorinations of cyclic β‐keto esters with N‐chlorosuccinimide (NCS) as the chlorination reagent, to give the corresponding α‐chloro‐β‐keto esters in excellent yields in 5–30 min with ee values up to 97%. The copper(II) triflate and zinc(II) triflate complexes of a single SPANbox ligand demonstrated complementary results to each other with respect to the enantioselection, affording both antipodes of the chlorinated product enantiomers with good to excellent optical purities.
Study of the compositional heterogeneity of ethylene/1–hexene copolymers produced over supported catalysts of different composition
Authors: Matsko Mikhail A. , Echevskaya Ludmila G. , Vanina Marina P. , Nikolaeva Marina I. , Mikenas Tatyana B. , Zakharov Vladimir A. 
Published: June 2012

AbstractSeparation into narrow MWD fractions (liquid–liquid fractionation) and preparative TREF (temperature rising elution fractionation) with subsequent analysis of fractions by GPC, FTIR, and 13C NMR spectroscopy were used to study the comonomer distribution of ethylene/1–hexene copolymers produced over highly active supported titanium‐ and vanadium‐magnesium catalysts (TMC and VMC) and a supported zirconocene catalyst. These catalysts produce PE with different MWD: Mw/Mn values vary from 2.9 for zirconocene catalyst, 4.0 for TMC, and 15 for VMC. 1‐Hexene increases polydispersity to 25 for copolymer produced over VMC and hardly affects MWD of the copolymer produced over TMC and zirconocene catalysts. The most broad short chain branching distribution (SCBD) was found for ethylene/1–hexene copolymers produced over TMC. VMC and supported zirconocene catalyst produce copolymers with uniform profile of SCB content vs. molecular weight in spite of great differences in Mw/Mn values (22 and 2.5 respectively). TREF data showed that majority of copolymer produced over supported zirconocene catalyst was eluted at 70–90°C (about 85 wt %). In the case of VMC copolymer's fractions were eluted in the broad temperature interval (40–100°C). Accordingly, TREF data indicate a more homogeneous SCBD in copolymer, produced over supported zirconocene catalyst. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)
Authors: Arigonda Mahesh , Deshpande Abhijit P. , Varughese Susy 
Published: June 2012

AbstractDevelopment of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis and characterization of ternary‐copolymer of soluble fluorinated polyimides based on 1,4‐bis (4‐amino‐2‐trifluoromethylphenoxy) benzene
Authors: Fang Cheng , Zhou Yuming , He Man , Bu Xiaohai , Yin Kang , Weng Jiajia , Zhang Zewu 
Published: June 2012

AbstractA series of novel ternary‐copolymer of fluorinated polyimides (PIs) were prepared from 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene (pBATB), commercially available aromatic dianhydrides, and aromatic diamines via a conventional two‐step thermal or chemical imidization method. The structures of all the obtained PIs were characterized with FTIR, 1H‐NMR, and element analysis. Besides, the solubility, thermal stability, mechanical properties, and moisture uptakes of the PIs were investigated. The weight‐average molecular weight (Mw) and the number‐average molecular weight (Mn) of the PIs were determined using gel‐permeation chromatography (GPC). The PIs were readily dissolved not only in polar solvents such as DMF, DMAc, and NMP, but also in some common organic solvents, such as acetic ester, chloroform, and acetone. The glass transition temperatures of these PIs ranged from 201 to 234°C and the 10% weight loss temperatures ranged from 507 to 541°C in nitrogen. Meanwhile, all the PIs left around 50% residual even at 800°C in nitrogen. The GPC results indicated that the PIs possessed moderate‐to‐high number‐average molecular weight (Mn), ranging from 9609 to 17,628. Moreover, the polymer films exhibited good mechanical properties, with elongations at break of 8–21%, tensile strength of 66.5–89.8 MPa, and Young's modulus of 1.04–1.27 GPa, and low moisture uptakes of 0.54–1.13%. These excellent combination properties ensure that the polymer could be considered as potential candidates for photoelectric and microelectronic applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Extensional viscosity measurements and characterization of poly (vinyl chloride‐co‐vinyl acetate) plastisols and foams
Authors: Zoller Agnes , Marcilla Antonio 
Published: July 2012

AbstractThe foaming of PVC‐VA [Poly (vinyl chloride‐co‐vinyl acetate)] plastisols is a complex combination of processes involving the simultaneous curing of the paste with the evolution of gases caused by the decomposition of the chemical blowing agent. The extensional viscosity is a fundamental characteristic of the material, responsible for the behavior of the system when undergoing the extensional stress produced by the released gases. Nevertheless, such changes have not been considered to the same extent as the complex viscosity evolution or the thermal processes suffered by PVC‐VA plastisols. The objective of the present work is to study the extensional viscosity of the PVC‐VA plastisols prepared with three plasticizers of similar structure, but with different curing and rheological behavior in order to investigate its influence on the quality of the foams obtained. Extensional viscosity measurements under forced prestretch conditions revealed that depending on the structure and consequently on the compatibility of the plasticizer used, each plastisol develops its properties and structure accordingly. DINCH plasticizer (Diisononyl cyclohexane‐1,2‐dicarboxylate presenting alicyclic ring) seems to be the less compatible compared with the other two studied (both presenting aromatic rings) according to its behavior during the curing and foaming processes and may not be able to withstand the pressure evolved by the released gases during the foaming process yielding foams of poorer quality. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis and characterization of glucosamine modified poly(ethylene glycol) hydrogels via photopolymerization
Authors: Wang Qunfang , Ren Li , Xu Caixia , Zhai Zhichen , Zhou Jia‐an , Yao Yongchang , Xia Huan , Wang Yingjun 
Published: June 2012

AbstractThis study presented the synthesis and characterization of glucosamine (GlcN) modified poly (ethylene glycol) (PEG) hydrogels. The chemical structure was characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The morphology of hydrogels was observed by scanning electron microscopy (SEM). The results indicated that GlcN was successfully incorporated into PEG hydrogel network. Moreover, the data of the swelling ratio showed that the ratio of GlcN‐modified PEG hydrogels was lower than that of pure poly(ethylene glycol) diacrylated (PEGDA). Biocompatibility of unreacted GlcN monomer and GlcN‐modified hydrogels was also evaluatedin vitro. Compared with glucosamine hydrochloride, 2 and 5 mMN‐acroloyl‐glucosamine monomer exhibited no toxicity against bone marrow stromal cells (BMSCs), while with the concentration increased to 10 mM, cell viability appeared to decrease. However, when BMSCs were encapsulated in GlcN‐modified hydrogels via photopolymerization method, cells remained vigorous viability. Metabolic activity of the encapsulated cells demonstrated GlcN‐modified hydrogels was favorable for cell proliferation. Compared with free GlcN, covalent binding GlcN showed lower cytotoxicity and higher cell proliferation properties. As a result, GlcN‐modified PEGDA hydrogels could be used as safe and injectable cell carriers forin situtissue engineering applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis of sulfated β‐cyclodextrin/cotton/ZnO nano composite for improve the antibacterial activity and dyeability with Azadirachta indica
Authors: Sundrarajan M. , Selvam S. , Ramanujam K. 
Published: June 2012

AbstractThe sulfated β‐cyclodextrin (sb‐cd) was prepared from β‐cyclodextrin and the sb‐cd was crosslinked with cotton fabric using ethylenediaminetetraacetic acid (EDTA) as crosslinker. After crosslinking, the synthesized ZnO nanoparticles were padded on this fabric surface. Then, the treated fabrics were dyed with neem extract. The synthesized polymer, crosslinked and nanoparticle‐treated cotton fabrics were characterized using fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), particle sized analyzer, and transmission electron microscopy (TEM) studies. The antibacterial test was done against Staphylococcus aureus and Escherichia coli bacterium. The composite coated with neem dyed cotton fabric has exhibited 71% of dye uptake with 2–3 fastness grade and it has 99% of antibacterial efficiency for S. aureus and 97% for E. coli bacterium. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Thermal, mechanical, and morphological properties of maleated polypropylene compatibilized Borassus fruit fiber/polypropylene composites
Authors: Sudhakara P. , Kamala Devi A. P. , Venkata Prasad C. , Obi Reddy K. , Dong Woo L. , Kim B. S. , Song J. I. 
Published: June 2012

AbstractWith a view of exploring the potential use of natural recourses, we made an attempt to fabricate new Borassus fruit fiber/polypropylene composites by melt mixing method using 5 wt % of fiber. Fibers were chemically modified by alkali treatment using maleated PP (MAPP) as compatibilizer to improve the adhesion between fibers and matrix. Thermal, mechanical, and morphological properties of untreated, alkali treated, and MAPP modified fiber reinforced composites were explored by thermogravimetric analysis, differential scanning calorimetry, universal testing machine, and scanning electron microscopy (SEM), respectively. Thermal stability of the composites was enhanced to some extent on alkali treatment and addition of MAPP. The tensile strength and modulus, flexural strength and modulus, and impact strength were increased for alkali treated/MAPP composites by 4.5%, 17%, 17.2 %, 9%, and 10% respectively. SEM studies on tensile fractured specimens of unmodified composites reveal the poor fiber‐matrix interaction, whereas the interaction is strong with enhanced mechanical properties for modified fiber composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Photostabilization of polystyrene/montmorillonite nanocomposite. A factorial experimental design 24
Authors: Oliveira Camila F. P. , Cremm Silvio R. , Cruz Gerson H. S. , Fechine Guilhermino J. M. 
Published: June 2012

AbstractThe weathering behavior of polystyrene (PS) and PS/montmorillonite nanocomposite with and without addition of ultraviolet (UV) absorber and/or antioxidant was investigated. Samples were exposed to UV radiation in the laboratory for periods of up to approximately 12 weeks. The samples were exposed for various irradiation intervals, and their tensile and impact strength was monitored through a factorial experimental design 24. The molecular weight, yellowness, and fracture surface were also monitored. The results generated by analysis of variance (ANOVA) Table showed that UV absorber and exposure time had the most important effects positive and negative, respectively. These results could be seen for neat PS and PS/MMT nanocomposite. The presence of antioxidant alone did not have any significant effect but when mixed with UV absorber presented a small synergism. These results corroborate with molecular weight, yellowing and fracture surface of tensile and impact samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis, characterization, and film properties of crosslinked chitosan with pentaerythritol tris[3‐(1‐aziridinyl) propionate]
Authors: Soucek Mark D. , Yi Ying 
Published: June 2012

AbstractThe novel crosslinked chitosan derivative (CMCSCL) has been synthesized via carboxymethyl chitosan with pentaerythritol tris[3‐(1‐aziridinyl)propionate] (PEN) as crosslinking reagent. Its structure has been proved by Fourier transform infrared spectroscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis and atomic force micrograph. The mechanical properties and water uptake of CMCSCL films have been measured. The results show that CMCSCL film with 4% PEN crosslinker has a high tensile strength (TS) 17.1 MPa, 13.1% elongation at break, and 99% water uptake. The film with 6% PEN has a TS 15.2 MPa, 10.2% elongation at break, and 111% water uptake. The dosage of the crosslinking agent is the principal factor affecting the mechanical properties and water uptake of these films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Study on the molecular behavior of hydrophobically modified poly(acrylic acid) in aqueous solution and its emulsion‐stabilizing capacity
Authors: Li Quanwei , Yuan Rui , Ying Li  
Published: June 2012

AbstractIn this article, molecular conformation and aggregation behavior of partly hydrophobically modified poly(acrylic acid) (HMPAA) in aqueous solution has been studied by mesoscale simulation approach dissipative particle dynamics for the purpose to find out how the chemical structure and environmental conditions effect its capacity. It has been found that, as a kind of pH‐sensitive polymer, the chemical structure variation of HMPAA carried by adjusting pH and grafting degree influence the taking place of intermolecular and intramolecular associations, which induced the formation of molecular network and help to maintain high bulk phase viscosity of its aqueous solution in larger pH range or under higher salinity comparing with PAA. There exists an optimum grafting degree, above which the increase of the possibility of the intramolecular associations enhance the coiling of the polymer chain and result in destroy of the network. The experimental determination of properties of aqueous solutions of poly(acrylic acid) (U10) and poly alkyl acrylate (U20), such as the bulk phase viscosity and oil/water interface tension, accord well with the molecular simulation conclusion, by which the mechanisms of elevated stability of surfactant‐free O/W emulsion stabilized by the HMPAA comparing with PAA has been discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Novel Ni and Pd(benzocyclohexan‐ketonaphthylimino)2 complexes for copolymerization of norbornene with octene
Authors: Liu Yueman , Ouyang Meng , He Xiaohui , Chen Yiwang , Wang Kaiti 
Published: June 2012

AbstractTwo novel late transition metals complexes with bidentate OˆN chelate ligand, Mt(benzocyclohexan‐ketonaphthylimino)2 {Mt(bchkni)2: bchkni C10H8(O)C[N(naphthyl)CH3]; Mt  Ni, Pd}, were synthesized. In the presence of B(C6F5)3, both complexes exhibited high activity toward the homo‐polymerization of norbornene (NB) (as high as 2.7 × 105
gpolymer/molNi·h for Ni(bchkni)2/B(C6F5)3 and 2.3 × 105
gpolymer/molPd·h for Pd(bchkni)2/B(C6F5)3, respectively). Additionally, both catalytic systems showed high activity toward the copolymerization of NB with 1‐octene under various polymerization conditions and produced the addition‐type copolymer with relatively high molecular weights (0.1–1.4 × 105g/mol) as well as narrow molecular weight distribution. The 1‐octene content in the copolymers can be controlled up to 8.9–14.0% for Ni(bchkni)2/B(C6F5)3 and 8.8–14.6% for Pd(bchkni)2/B(C6F5)3 catalytic system by varying comonomer feed ratios from 10 to 70 mol %. The reactivity ratios of two monomers were determined to be r1‐octene = 0.052, rNB = 8.45 for Ni(bchkni)/B(C6F5)3 system, and r1‐octene = 0.025, rNB = 7.17 for Pd(bchkni)/B(C6F5)3 system by the Kelen‐TÜdÕs method. The achieved NB/1‐octene copolymers were confirmed to be noncrystalline and exhibited good thermal stability (Td > 400°C, Tg = 244.1–272.2°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Polypyrrole/graphene composite films synthesized via potentiostatic deposition
Authors: Lim Y. S. , Tan Y. P. , Lim H. N. , Tan W. T. , Mahnaz M. A. , Talib Z. A. , Huang N. M. , Kassim A. , Yarmo M. A. 
Published: June 2012

AbstractA one‐step electrochemical process has been employed to synthesize composite films of polypyrrole/graphene (PPy/GR) by electrochemical polymerization on indium tin oxide (ITO) from an aqueous solution containing pyrrole monomer, graphene oxide (GO) nanosheets and sodium p‐toluenesulfonate (NapTS). Thermogravimetric analysis (TGA) confirmed the formation of a composite; the degradation temperature of the new hybrid was between those of PPy and GO. Moreover, the bulbous surface of PPy and the almost transparent tissue‐like GO nanosheets were replaced by the new appearance of the composite where the surface was flat but creased. As GO is nonconductive, we deduced that it had been reduced to conducting graphene in the composite film during the electrodeposition process, based on an electrical conductivity study measured with a four‐point probe. On average, the electrical conductivity of the PPy/GR composites was twofold higher than that of the pure PPy film, indicating that the incorporation of graphene was able to enhance the conductivity of PPy film. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Effect of monomer composition on the properties of biodegradable poly(NIPAAm‐AA‐PCLdA) copolymeric hydrogels
Authors: Lee Wen‐Fu , Cheng Tzu‐Shen 
Published: June 2012

AbstractA series of biodegradable hydrogels were prepared from N‐isopropylacrylamide (NIPAAm), acrylic acid (AA), and a biodegradable crosslinker, poly(caprolactone) diacrylate (PCLdA). The effect of the different molar ratios of NIPAAm and AA in the poly(NIPAAm‐co‐AA) copolymeric hydrogel on the swelling behaviors and physical properties were investigated. The results showed that the swelling ratio in deionized water and in phosphate buffer solution increased with an increase of the content of AA in the copolymeric hydrogel, and the critical gel transition temperature (CGTT) of the copolymeric hydrogel crosslinked with PCLdA was lower than the hydrogel crosslinked with N,N'‐methylenebisacrylamide (NMBA). The compressive modulus decreased with an increase of AA content in the copolymeric hydrogels. The gels showed good pH/temperature sensitive behavior. The results also showed that the hydrogel crosslinked with PCLdA has higher crosslinking density (ρx) and higher mechanical strength than the hydrogel crosslinked with NMBA. The influence of the copolymeric composition on the drug release behavior in the poly(NIPAAm‐co‐AA) hydrogels was also investigated in this study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Preparation and characterization of nanohydroxyapatite strengthening nanofibrous poly(L‐lactide) scaffold for bone tissue engineering
Authors: Han Wanqing , Zhao Jianhao , Tu Mei , Zeng Rong , Zha Zhengang , Zhou Changren 
Published: June 2012

AbstractA biomimetic nanofibrous poly(L‐lactide) scaffold strengthened by nanohydroxyapatite particles was fabricated via a thermally induced phase separation technique. Scanning electron microscopy results showed that nanohydroxyapatite particles uniformly dispersed in the nanofibrous poly(L‐lactide) scaffold (50–500 nm in fiber diameter) with slight aggregation at a high nHA content, but showed no influence on the interconnected macroporous and nanofibrous structure of the scaffold. The nanofibrous poly(L‐lactide) scaffold presented a specific surface area of 34.06 m2 g−1, which was much higher than that of 2.79 m2 g−1 for the poly(L‐lactide) scaffold with platelet structure. Moreover, the specific surface area of the nanofibrous scaffold was further enhanced by incorporating nanohydroxyapatite particles. With increasing the nanohydroxyapatite content, the compressive modulus and amount of bovine serum albumin adsorbed on the surface of the nanofibrous composite scaffold were markedly improved, as opposed to the decreased crystallinity. In comparison to poly(L‐lactide) scaffold, both the nanofibrous poly(L‐lactide) and poly(L‐lactide)/nanohydroxyapatite scaffolds exhibited a faster degradation rate for their much larger specific surface area. The culture of bone mesenchymal stem cell indicated that the composite nanofibrous poly(L‐lactide) scaffold with 50 wt % nanohydroxyapatite showed the highest cells viability among various poly(L‐lactide)‐based scaffolds. The strengthened biomimetic nanofibrous poly(L‐lactide)/nanohydroxyapatite composite scaffold will be a potential candidate for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013