bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailor‐made hybrid nanostructure of poly(ethyl acrylate)/clay by surface‐initiated atom transfer radical polymerization
Authors: Datta Haimanti , Bhowmick Anil K. , Singha Nikhil K. 
Published: June 2008

AbstractHybrid nanoarchitecture of tailor‐made Poly(ethyl acrylate)/clay was prepared by surface‐initiated atom transfer radical polymerization (SI‐ATRP), by tethering ATRP initiator on active hydroxyl group, present in surface as well as in the organic modifier of the clay used. Extensive exfoliation was facilitated by using these initiator modified clay platelets. Poly(ethyl acrylate) chains with controlled polymerization and narrow polydispersities were forced to be grown from within the clay gallery (intergallery) as well as from the outer surface (extragallery) of the clay platelets. The polymer chains attached onto clay surfaces might have the potential to provide the composites with enhanced compatibility in blends with common polymers. Attachment of the initiator on clay platelets was confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), elemental analysis, Wide‐angle X‐ray diffraction (WAXD), and microscopic analysis. Finally, end group analysis (by Matrix‐Assisted Laser Desorption Ionization Mass Spectrometry, and chain extension experiment) of the cleaved polymer and morphological study (by WAXD, Transmission Electron Microscopy), performed on the polymer grafted clays examined the effect of grafting on the efficiency of polymerization and the degree of dispersion of clay tactoids in polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5014–5027, 2008
Self‐assembly of thermo‐ and pH‐responsive poly(acrylic acid)‐b‐poly(N‐isopropylacrylamide) micelles for drug delivery
Authors: Li Guiying , Song Sen , Guo Lei , Ma Songmei 
Published: June 2008

AbstractSelf‐assembled thermo‐ and pH‐responsive poly(acrylic acid)‐b‐poly(N‐isopropylacrylamide) (PAA‐b‐PNIPAM) micelles for entrapment and release of doxorubicin (DOX) was described. Block copolymer PAA‐b‐PNIPAM associated into core‐shell micelles in aqueous solution with collapsed PNIPAM block or protonated PAA block as the core on changing temperature or pH. Complexation of DOX with PAA‐b‐PNIPAM triggered by the electrostatic interaction and release of DOX from the complexes due to the changing of pH or temperature were studied. Complex micelles incorporated with DOX exhibited pH‐responsive and thermoresponsive drug release profile. The release of DOX from micelles was suppressed at pH 7.2 and accelerated at pH 4.0 due to the protonation of carboxyl groups. Furthermore, the cumulative release of DOX from complex micelles was enhanced around LCST ascribed to the structure deformation of the micelles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5028–5035, 2008
β‐Cyclodextrin polymer brushes based on hyperbranched polycarbosilane: Synthesis and characterization
Authors: Tian Wei , Fan Xiao‐Dong , Liu Yu‐Yang , Jiang Min , Huang Yi , Kong Jie 
Published: June 2008

AbstractIn this article, our main goal is to combine hyperbranched polymer with β‐cyclodextrin (β‐CD) to establish a novel functional polymer species with core‐shell structure and supramolecular system for further application in inclusion technologies and the complex drugs delivery system. Therefore, two β‐CD polymer brushes based on hyperbranched polycarbosilane (HBP) as a hydrophobic core and poly(N,N‐dimethylaminoethyl methacrylate) (PDMA) carrying β‐CD units as a hydrophilic shell were synthesized. Hyperbranched polycarbosilane macroinitiator carrying Cl groups (HBP‐Cl) was also prepared by using 1,1,3,3‐tetrmethyldisiloxane, allyl alcohol, and chloroacetyl chloride as reagents. The molecular structures of HBP‐Cl macroinitiator and β‐CD polymer brushes were characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR) spectroscopies, size exclusion chromatography/multi‐angle laser light scattering (SEC/MALLS) and laser particle size analyzer. The results indicate that the grafted chain length of two β‐CD polymer brushes can be controlled by changing the feed ratio. Differential scanning calorimetry (DSC) results show that two β‐CD polymer brushes have two glass transition temperatures (Tgs) from a hydrophobic core part and a hydrophilic shell part, respectively, and the Tg from PDMA is higher than that of HBP‐g‐PDMA. Thermalgravimetric analyzer (TGA) analysis indicates that the thermostability of two β‐CD polymer brushes is higher than that of HBP, but is lower than that of HBP‐g‐PDMA. Using phenolphthalein (PP) as a guest molecule, molecular inclusion behaviors for two β‐CD polymer brushes were studied. It reveals that two β‐CD polymer brushes possess molecular inclusion capability in PP buffer solution with a fixed concentration. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5036–5052, 2008
Ways of selective polycondensation of L‐lysine towards linear α‐ and ε‐poly‐L‐lysine
Authors: Ho Chau Hon , Odermatt Erich , Berndt Ingo , Tiller Joerg C. 
Published: June 2008

AbstractPolylysines (PL) are highly interesting polymers due to their biocompatibility and their high number of reactive amino groups. So far it was not possible to synthesize them directly from L‐lysine. Here, we describe two different synthesis routes to selectively polymerize lysine in one batch without the use of protection groups. Applying 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide as activating agent for the polycondensation of L‐lysine in water gave selectively linear ε‐PLL. In contrast to this, the polymerization of L‐lysine in chloroform in the presence of dicyclohexyl carbodiimide and 18‐crown‐6 ether selectively afforded pure α‐PLL. We also assessed the capability of polylysine derivatization by polymer analog reactions with acetic anhydride, methyl iodide and 2,4,6‐trinitrobenzenesulfonic acid. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5053–5063, 2008
Dendronized tricyanopyrroline‐based chromophores in nonlinear optical active host polymer
Authors: Hoang Mai Ha , Kim Myung Hee , Cho Min Ju , Kim Kyung Hwan , Kim Kyu Nam , Jin Jung‐Il , Choi Dong Hoon 
Published: June 2008

AbstractWe synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008
One‐pot synthesis and characterization of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids and multihydroxyl secondary amines
Authors: Lin Ying , Dong Zhongmin , Li Yuesheng 
Published: June 2008

AbstractA convenient and cost‐effective strategy for synthesis of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids (A2) and multihydroxyl secondary amine (CB2) has been developed. By optimizing the conditions of model reactions, the AB2‐type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB2 intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester‐amide)s bearing multi‐hydroxyl end‐groups. The FTIR and 1H NMR spectra indicated that the polymerization proceeded in the proposed way. The DBs of the resulting polymers were confirmed by a combination of inverse‐gated decoupling 13C NMR, and DEPT‐135 NMR techniques. The DBs of the hyperbranched poly(ester‐amide)s were in the range of 0.44–0.73, depending on the structure of the monomers used. The hyperbranched polymers exhibited moderate molecular weights with relatively broad distributions determined by SEC. All the polymers displayed low inherent viscosity (0.11–0.25 dL/g) due to the branched nature. Structural and end‐group effects on the thermal properties of the hyperbranched polymers were investigated using DSC. The thermogravimetric analysis revealed that the resulting polymers exhibit reasonable thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5077–5092, 2008
End group transformations of RAFT‐generated polymers with bismaleimides: Functional telechelics and modular block copolymers
Authors: Li Ming , De Priyadarsi , Gondi Sudershan R. , Sumerlin Brent S. 
Published: June 2008

AbstractEnd group activation of polymers prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of thiocarbonylthio end groups to thiols and subsequent reaction with excess of a bismaleimide. Poly(N‐isopropylacrylamide) (PNIPAM) was prepared by RAFT, and subsequent aminolysis led to sulfhydryl‐terminated polymers that reacted with an excess of 1,8‐bismaleimidodiethyleneglycol to yield maleimido‐terminated macromolecules. The maleimido end groups allowed near‐quantitative coupling with model low molecular weight thiols or dienes by Michael addition or Diels‐Alder reactions, respectively. Reaction of maleimide‐activated PNIPAM with another thiol‐terminated polymer proved an efficient means of preparing block copolymers by a modular coupling approach. Successful end group functionalization of the well‐defined polymers was confirmed by combination of UV–vis, FTIR, and NMR spectroscopy and gel permeation chromatography. The general strategy proved to be versatile for the preparation of functional telechelics and modular block copolymers from RAFT‐generated (co)polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5093–5100, 2008
Side chain liquid crystal poly(fumarate)s bearing tolane‐based mesogens
Authors: Noguchi Hiroshi , Michinobu Tsuyoshi , Fujii Nozomu , Funahashi Masahiro , Tokita Masatoshi , Watanabe Junji , Shigehara Kiyotaka 
Published: June 2008

AbstractCyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (Mn) of ∼ 104 and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10−4–10−5 cm2 V−1 s−1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008
Synthesis and characterization of a novel polymer based on anthracene moiety for organic thin film transistor
Authors: Li Yinam , Kim Tae‐Hoon , Zhao Qinghua , Kim Euh‐Kyung , Han Seung‐Hon , Kim Yun‐Hi , Jang Jin , Kwon Soon‐Ki 
Published: June 2008

AbstractWe have designed and synthesized a new polymer, which could be used in the organic thin film transistor (OTFT). Poly[2,6‐bis(3′‐dodecythiophene‐2′‐yl)anthracene] (PDTAn), which is composed with anthracene moiety and dodecyl alkyl thiophene, was synthesized by oxidative polymerization using iron (III) chloride. The mole ratio of FeCl3 and monomer (4.2:1), keeping low temperature during the initiation reaction, amount of solvent, and dropping order were very important for oxidative polymerization without crosslinking. The molecular weight of the polymer (Mw) was measured to be 40,000 with 2.85 of polydispersity index by GPC. The physical and optical properties of the polymer were characterized by differential scanning calorimetry (DSC), cyclic voltammetry (CV), and optical absorption and photoluminescence (PL) spectroscopy. A field‐effect mobility of 1.1 × 10−4 cm2 V−1 S−1, a current on/off ratio of 105, and the Vth at −15.2 V had been obtained for OTFTs using this polymer semiconductor by solution coating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5115–5122, 2008
Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles
Authors: Zhu Yanguo , Li Zhiqiang , Zhang Di 
Published: June 2008

AbstractThe polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm−1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008
Crystallization behavior of some unimodal and bimodal linear low‐density polyethylenes at moderate and high supercooling
Authors: Krumme Andres , Lehtinen Arja , Adamovsky Sergey , Schick Christoph , Roots Jaan , Viikna Anti 
Published: June 2008

AbstractEffect of molar mass distribution (MMD) and composition distribution (CD) on crystallization behavior of linear low‐density polyethylene materials at moderate and high supercooling was studied using differential scanning calorimetry, hot‐stage polarized light microscopy, small‐angle light scattering, and chip nanocalorimetry methods. A set of uni‐ and bimodal materials having small variation in average molar mass, density, and melt flow rate, but large differences in MMD and CD, was investigated. The results indicate a clear effect of structural heterogeneity on morphology and crystallization behavior of the materials. Broader MMD and CD increased in average radius of superstructures, melting, crystallization temperatures, and isothermal crystallization rate at different supercoolings. Origin of such behavior is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1577–1588, 2008
Modeling on swelling behavior of a confined polymer network
Authors: Li Xue‐Mei , Shen Zhou , He Tao , Wessling Matthias 
Published: June 2008

AbstractPolymeric membranes suffer from plasticization in gas separation, extensive swollen in pervaporation, nanofiltration, and fuel cells by losing performance. Growing research has experimentally realized that the membrane performance could be stabilized by blending with inert second polymer or imbedding in a porous inert confinement. In this article, we introduce a generic model based on Flory–Rehner's swelling theory to describe various membrane processes using a measurable parameter. We assume the membrane polymer to be a network and the constraint as an expandable structure with an energy density equal to its E‐Modulus. The model reveals that the isotropic constraint is far more efficient in swelling control. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1589–1593, 2008
Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement
Authors: Wang Jiku , Liu Xuyan , Choi Ho‐Suk 
Published: June 2008

AbstractAfter one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008
Near infrared analysis of blends of sulfonated polystyrene ionomers and poly(ε‐caprolactam)
Authors: Ghebremeskel Yacob , Weiss R. A. 
Published: June 2008

AbstractNear infrared spectroscopy (NIR) was used to characterize the nature of specific interactions in blends of lightly sulfonated polystyrene ionomers (M‐SPS where M = Zn+2, Mn+2, or Li+) and polycaprolactam (PA6). The assignments of the NIR overtone bands that arise due to the interactions between the cation of the ionomer, and the amide groups were made using spectra of model compounds. The relative populations of the different environments of the NH groups were qualitatively determined by deconvoluting the NIR spectra into five absorbances representing hydrogen‐bonded NH in crystalline and amorphous phases and an ion‐amide complex. The ion‐amide complex was specific for the blends. The interpolymer interactions were sensitive to composition and temperature, but qualitatively the behavior was the same for all three ionomer salts investigated. © 2008 Wiley Periodicals, Inc. JPolym Sci Part B: Polym Phys 46: 1602–1610, 2008
HIF‐1α: A key survival factor for serum‐deprived prostate cancer cells
Authors: Thomas Rusha , Kim Myoung H. 
Published: June 2008

AbstractBACKGROUNDHypoxia‐inducible factor‐1α (HIF‐1α) is commonly overexpressed in prostate cancer (PCa) cells. As PCa cells are known to survive serum deprivation, we investigated the effect of prolonged serum deprivation on HIF‐1α expression, and the function of HIF‐1α in regulating the survival of normoxic serum‐deprived PCa cells.METHODSHIF‐1α protein was assessed by immunoblots. Cell viability and proliferation were assessed by trypan blue assay and flow cytometric analysis. Transcriptional activity was assessed by luciferase reporter assay and RT‐PCR. HIF‐1α expression was suppressed with siRNA. Activities of HIF‐1α‐target genes were inhibited with neutralizing antibody.RESULTSProlonged serum deprivation is a potent inducer of HIF‐1α in PC‐3 and LNCaP PCa cells, despite normal oxygen conditions. In contrast, cells grown in the presence of serum did not show HIF‐1α protein accumulation. Moreover, HIF‐1α protein increase during serum deprivation correlated with increased cell survival, while suppression of HIF‐1α expression significantly decreased PCa cell viability. Our results further demonstrate that HIF‐1α protein increase is due to increased HIF‐1α protein synthesis. First, there was no significant increase in HIF‐1α mRNA. Secondly, cycloheximide, a protein synthesis inhibitor, prevented HIF‐1α protein increase in serum‐deprived PCa cells. Moreover, the expression of HIF‐1α‐target genes, VEGF and IGF‐2, was concomitantly increased in serum‐deprived PCa cells, while suppression of HIF‐1α expression significantly inhibited their induction. Furthermore, inhibition of IGF‐2 activity resulted in a significant decline in PCa cell survival.CONCLUSIONPCa cells counteract the stress of prolonged serum deprivation by upregulating HIF‐1α protein which increases IGF‐2 expression to promote cell survival. Prostate 68: 1405–1415, 2008. © 2008 Wiley‐Liss, Inc.
Knockdown resistance to DDT and pyrethroids: from target‐site mutations to molecular modelling
Authors: Davies TG Emyr , O'Reilly Andrias O , Field Linda M , Wallace BA , Williamson Martin S 
Published: June 2008

AbstractNaturally derived insecticides such as pyrethrum and man‐made insecticides such as DDT and the synthetic pyrethroids act on the voltage‐gated sodium channel proteins found in insect nerve‐cell membranes. The correct functioning of these channels is essential for the normal transmission of nerve impulses, and this process is disrupted by binding of the insecticides, leading to paralysis and eventual death. Some insect pest populations have evolved modifications of the sodium channel protein that inhibit the binding of the insecticide and result in the insect developing resistance. This perspective outlines the current understanding of the molecular processes underlying target‐site resistance to these insecticides (termed kdr and super‐kdr), and how this knowledge may in future contribute to the design of novel insecticidal compounds. Copyright © 2008 Society of Chemical Industry
Intensity and temperature dependent characterization of eta solar cell
Authors: Musembi Robinson J. , Rusu Marin , Mwabora Julius M. , Aduda Bernard O. , Fostiropoulos Konstantinos , Lux‐Steiner Martha Ch. 
Published: June 2008

AbstractTemperature‐dependent electrical characterization of a highly structured TiO2/In(OH)x Sy /Pb(OH)x Sy /PEDOT:PSS eta solar cell has been carried out. The transport mechanism in this type of solar cell has been investigated. A schematic energy band diagram which explains the photoelectrical properties of the device has been proposed. The solar cell has been characterized in the temperature range 200–320 K at illumination intensities between 0.05 mW/cm2 and 100 mW/cm2. The diode ideality factor A under illumination has been found to vary between 1.2 and 1.6, whereas in the dark 6.9 ≤ A ≤ 10.1. The device has been found to undergo a thermally activated recombination under illumination, while tunnelling enhanced recombination has been established to dominate the current in the dark. The solar cell efficiency shows a logarithmic dependence on illumination in the whole temperature range investigated, achieving its maximum at an illumination of ∼45 mW/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)