bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polypropylenimine dendrimers: Improved synthesis and characterization
Authors: De Brabander E. M. M. , Brackman J. , Mure‐Mak M. , De Man H. , Hogeweg M. , Keulen J. , Scherrenberg R. , Coussens B. , Mengerink Y. , van Der Wal S. J. 
Published: March 2011

AbstractBoth the Michael addition and the hydrogenation steps in the large scale synthesis of polypropylenimine dendrimers have been improved: by adding ammonia during the hydrogenations the substrate concentrations can be increased 8 times, the catalyst concentration can be lowered 10 times and the average selectivity remains > 99.5% per conversion. The dimensions of the dendrimers have been studied with SANS and with molecular calculations.
Dendritic polyols based on carbosilanes ‐ lipophilic dendrimers with hydrophilic skin
Authors: Frey Holger , Lorenz Klaus , Mülhaupt Rolf , Rapp Uwe , Mayer‐Posner Franz J. 
Published: March 2011

AbstractCarbosilane dendrimers with up to 108 end groups were prepared by a divergent synthetic route via repeated alternating Grignard‐reaction with allylmagnesium bromide and hydrosilylation. Quantitative hydroboration of the dendrimers was achieved with 9‐BBN/H2O2,OH−. Employing this synthetic route, rather monodisperse dendritic polyols with lipophilic carbosilane core and hydrophilic shell were prepared. All dendrimers were characterized with MALDI‐TOF, showing low polydispersities. The novel dendritic polyols constitute interesting molecular scaffolds for the preparation of unusual supermolecules. As an example, reaction with cholesteryl chloro‐formiate was used to prepare a series of dendrimers with 12, 36 and 108 mesogenic cholesteryl end groups.
Polyrotaxanes: Past, present and future
Authors: Gibson Harry W. , Liu Shu 
Published: March 2011

AbstractThe threading process in polysebacate‐crown ether rotaxanes prepared by the acid chloride method was examined by systematic study of the effects of 1) the size of the macrocycle, 2) the equilibration time between the diol and the macrocycle before addition of sebacoyl chloride, 3) the molar ratio of crown ether to diol, 4) the length of the α,ω‐diol and 5) the temperature of equilibration and reaction. It was concluded that the threading process is based on hydrogen bonding interactions of the diol with the crown ether, predisposing the latter to threading as the ester bond is formed. The lack of “stoppers” or “knots” at the chain ends is believed to allow loss of macrocycles in the initial precipitation, after which loss of macrocycles is very slow due to chain folding. All of these polyester rotaxanes, except the 30‐crown‐10 case, display crystalline phases for both the backbone and the cyclic components. All of the polyrotaxanes complex alkali metal ions.
Stereocomplex formation in AB DI‐block copolymers of poly(ϵ‐caprolactone) (a) and poly(lactide)(B)
Authors: Stevels Willem M. , Ankoné Marc J. K. , Dijkstra Pieter J. , Feijen Jan 
Published: March 2011

AbstractThe thermal properties of two series of AB di‐block copolymers of poly(ϵ‐caprolactone) (A) and poly(lactide) (B) and their blends were studied. Each series contained poly(lactide) blocks of opposite chirality. The length of the poly(ϵ‐caprolactone) blocks was not varied (DP = 70), whereas the poly(lactide) blocks were of varying length (DP = 5 − 80). Blends of polymers containing blocks of opposite chirality were prepared by mixing in solution. The melting temperature of the PLA phase was raised by approximately 55 °C in the blends due to stereocomplex formation. The melting temperatures of the crystalline PCL and PLA phases strongly depended on the composition of the block copolymers.
Optical and charge transport properties of DI‐n‐hexyl substituted polysilylene and polygermylene
Authors: van Der Laan Garrelt P. , De Haas Matthijs P. , van Walree Cornelis A. , van Slageren Joris , Jenneskens Leonardus W. , Frey Holger 
Published: March 2011

AbstractOptical and charge transport properties of poly(di‐n‐hexylsilylene), PD6S, and poly(di‐n‐hexylgermylene), PD6G, have been studied. The main‐chain σ‐conjugation in both polymers leads to intense σ‐σ* UV‐absorptions. A hypsochromic shift is observed for both polymers at the transition from a crystalline solid phase to a columnar mesophase. This transition is accompanied by disordering of the polymer backbone which results in a decrease of the radiation induced microwave conductivity by a factor of 26 for PD6S and a factor of 4 for PD6G. In the disordered mesophase a charge carrier mobility of ca. 0.6×106 m2/Vs is found for both polymers. Charge carrier mobilities of 15×106 m2/Vs and 2.4×10‐6.m2/Vs are found in the crystalline phase of PD6S and PD6G respectively, indicating a more ordered backbone for PD6S compared with PD6G.
Spectroscopic and thermodynamic characterization of the adsorption of plasma proteins onto cellulosic substrates
Authors: Müller M. , Werner C. , Grundke K. , Eichhorn K. J. , Jacobasch H.‐J. 
Published: March 2011

AbstractThe sorption of the plasma proteins human serum albumin (HSA) and human fibrinogen (FIB) onto hemodialytic cellulosic substrates was investigated by the surface sensitive ATR‐FTIR‐spectroscopy. By means of this method we monitored the protein sorption kinetics onto acetylated and unmodified cellulose (AKZO‐NOBEL). Furthermore, secondary structure alterations of the adsorbed proteins as well as changes of the composition in sorbed layers consisting of two proteins were detected. These findings were compared with results of the zeta potential and contact angle measurements on comparable sorption experiments.
Water soluble nucleic acid analogs: Preparation and properties
Authors: Takemoto Kiichi 
Published: March 2011

AbstractIn order to prepare water soluble natural and synthetic polymers, which contain nucleic acid base units as the functional side groups, a different sort of polymers, such as poly(ethyleneimine), poly(amino acids) and so on were used as the base materials. The properties of the polymers derived, in particular the specific interaction between nucleic acid base containing complementary polymers was studied in detail. Introduction of the base units onto hyaluronic acid was also carried out. Applicabilities of these polymers obtained, for example as the controlled release system by using reversible photodimerization reaction of thymine bases were also shown.
Polymeric prodrugs of mitomycin C
Authors: Soyez Heidi , Schacht Etienne , De Marre Anne , Seymour Leonard W. 
Published: March 2011

AbstractPoly‐[N‐(2‐hydroxyethyl)‐L‐glutamine] (PHEG) prodrugs of the cytotoxic agent Mitomycin C were synthesized using peptidyl spacers to link the drug to the polymeric carrier. The influence on the length and detailed structure of the oligopeptide on the rate of drug release was investigated in buffer, in the presence of lysosomal enzymes (tritosomes, cathepsin B and D) and metalloprotease type IV collagenase. It was observed that tetra‐ and hexapeptide based conjugates generally release Mitomycin C (MMC) more effectively than tripeptide derivatives. The gly‐phe‐ala‐leu conjugate released MMC very rapidly both in presence of lysosomal enzymes and collagenase IV. Only in the presence of the aspartic protease cathepsin D, the gly‐phe‐leu‐gly‐phe‐leu derivative turned out to be a better substrate. In vivo studies against C26 solid tumour bearing mice suggest that PHEG‐spacer‐MMC conjugates act as prodrugs of MMC: antitumour efficacy of the macromolecular prodrugs was better than free MMC both in inhibition of tumour growth and increasing survival.
Micro and nano layered polymers
Authors: Baer Eric 
Published: March 2011

AbstractThe crazing behavior of coextruded microlayer sheets consisting of alternating layers of polycarbonate (PC) and styreneacrylonitrile copolymer (SAN) was investigated as a function of PC and SAN layer thicknesses. In this study, the total sheet thickness remained essentially constant and the PC and SAN layer thicknesses were changed by varying both the total number of layers from 49 to 1857 and the PC/SAN volume ratio.[1,2] Photographs of the deformation processes were obtained when microspecimens were deformed under an optical microscope. Three different types of crazing behavior were identified: single crazes randomly distributed in the SAN layers, doublets consisting of two aligned crazes in neighboring SAN layers, and craze arrays with many aligned crazes in neighboring SAN layers. The transition from single crazes to doublets was observed when the PC layer thickness was decreased to 6 microns. Craze array development was prevalent in composites with PC layer thickness less than 1.3 microns. It was concluded that SAN layer thickness was not a factor in formation of arrays and doublets; formation of craze doublets and craze arrays was dependent only upon PC layer thickness.
Morphological alignment of liquid crystalline conducting polyacetylene derivatives
Authors: Akagi Kazuo , Shirakawa Hideki 
Published: March 2011

AbstractWe have synthesized novel liquid crystalline conducting polymers by introducing liquid crystalline group into acetylene monomer and polymerizing them with Ziegler‐Natta [Fe(acac)3 ‐ AlEt3] and metathesis [M0Cl5 ‐ Ph4Sn] catalysts. The liquid crystalline group is composed of a phenylcyclohexyl (PCH) or biphenyl (BP) moiety as a mesogenic core, a trimethylene chain [‐(CH2)3‐] as a spacer, and an alkyl chain (‐CnH2n+1, n = 2, 3, 5 ∼ 8) as a terminal group. The polymers are abbreviated as PPCHn03A and PBPn03A.All polymers prepared exhibited solubility in organic solvents and smectic liquid crystallinity characterized with fan‐shaped texture in polarizing optical microscopy. Phase transitions and the corresponding enthalpy changes were also evaluated by means of differential scanning calorimetry (DSC). Macroscopic alignments of the polymers were performed in the liquid crystalline phase by shear‐stress or magnetic force field of 0.7 − 1.0 tesla, which resulted in an enhancement by two orders in electrical conductivity of iodine‐doped cast films. Changes of the electronic and geometrical structures of the polymer upon the iodine‐doping were elucidated by examining the effective conjugation length of a polyene chain, cis and trans thermal isomerization, and spin distribution of unpaired electrons through ultraviolet / visible (UV‐Vis) and electron spin resonance (ESR) measurements.
On the formation of liquid crystalline texture in epoxy resins
Authors: Grebowicz Janusz S. 
Published: March 2011

AbstractThree epoxy resins and two curing agents were studied in their monomeric as well as polymeric states. Two monomers were monotropic liquid crystals. Characterization of liquid crystallinity before, during and after curing reaction was carried out by DSC, optical microscopy and WAXS. It was found that LC texture develops in every epoxy/(curing agent) system studied in this work. Nucleation and growth is a physical mechanism for the formation of initial liquid crystallinity. The final texture is not well defined and likely contains nematic, poorly ordered smectic and isotropic phases. Schematic diagram of the possible states of LCTs is discussed.
Synthesis of biodegradable polymers catalyzed by macromolecule ‐ bimetal complexes
Authors: Yang Shu‐Ying , Fang Xing‐Gao , Chen Li‐Ban 
Published: March 2011

AbstractA series of biodegradablc modified aliphatic polycarbonates were synthesized from carbon dioxide and relevant comonomers using a macromolecule ‐ bimetallic catalyst. The work was done to help the elimination of the pollution both from polymeric rubbish and from the greenhouse gas CO2.
Polymeric complex membranes for olefin/paraffin separation
Authors: Hsiue Ging‐Ho , Yang Jin‐Sheng 
Published: March 2011

AbstractSemi‐crystalline polyethylene (PE), rubbery silicone rubber (SR) and glassy poly[(l‐trimethylsilyl)‐l‐propyne] (PTMSP) were modified for olefin/paraffin separation. The polymers were first grafted with the acrylic acid (AA) and then incorporated with silver ions for forming the complex membranes such as PE‐g‐AA‐Ag+, SR‐g‐AA‐Ag+ and PTMSP‐g‐AA‐Ag+ The complex membranes were activated by glycerol solvation and subsequently showed high selectivity in olefin/paraffin separation. The silver ion distribution, the kinetics of olefin binding to PE‐g‐AA‐Ag+, the gas permeation properties and the sorption behaviors were studied. A novel dry complex membrane for olefin/paraffin separation based on AgClO4 complexing with PTMSP main‐chain was also studied.
Analysis of charge transfer distance between Ru(bpy)32+ complexes incorporated into a nafion film as studied by spectrocyclic voltammogram
Authors: Zhang Jian , Yagi Masayuki , Kaneko Masao 
Published: March 2011

AbstractAn ITO electrode was coated by a Nafion film incorporating Ru(bpy)32+ complex as redox centers either by mixture casting method, adsorption method, or swelling method and the electrochemical reactivity of the modified electrode was determined by the in‐situ spectrocyclic voltammogram (SCV) in a sodium perchlorate aqueous solution at pH 1.2. A modified Poisson statistics equation was used to estimate the charge transfer distance (Ro) between the Ru(bpy)32+ complexes. The estimated charge transfer distances for the electrodes prepared by swelling method (Ro = 1.63 nm for the electrode modified in M/W 1:10, and 1.69 nm in M/W 1:2) and adsorption method (Ro = 1.61 nm) were longer than that for mixture casting method (Ro = 1.5 nm). Based on the different procedure of Ru(bpy)32+ complex incorporation in the Nafion film, the reasons that affect the apparent charge transfer distance were discussed.
Molecular design of catalysts on the basis of functionalized poly(ethylene oxide) and block copolymers of ethylene oxide and propylene oxide
Authors: Karakhanov E.A. , Maksimov A.L. , Predeina V.V. , Utukin A.M. , Filippova T. Yu. 
Published: March 2011

AbstractTransition metal complexes based on polyethylene oxide and copolymers of ethylene oxide and propylene oxide functionalized by dipyridyl, acetylacetone and catechol have been prepared. Macrocomplexes showed high activity and selectivity as catalysts in oxidation of cyclohexane, hydroxylation of benzene, epoxidation of hexene and allylic alcohol bound by hydrogen peroxide, oxidation of ethylbenzene by dioxygen.
Polymer‐protected bimetallic clusters with various alloying structures
Authors: Toshima Naoki 
Published: March 2011

AbstractColloidal dispersions of polymer‐protected bimetallic cluster can be prepared by refluxing the alcoholic solutions of two kinds of metal ions in the presence of poly(N‐vinyl‐2‐pyrrolidone). The bimetallic clusters thus prepared had higher activity as catalysts than the corresponding monometallic clusters. The structure of bimetallic clusters, analyzed by an Extended X‐ray Absorption Fine Structure(EXAFS) technique as well as ultraviolet‐visible(Uv‐vis) absorption spectra, depends on the preparation method. Some of them have a special core‐shell structure. The order of the tendency to be a core is estimated to be Au>Pt>Pd>Rh. This order could be explained by the redox potential of the corresponding metal ion and the coordination ability of the metal to polymer.
Novel polymer‐supported chiral catalysts for asymmetric synthesis
Authors: Itsuno Shinichi , Kamahori Koichi , Watanabe Katsuhiro , Ito Koichi 
Published: March 2011

AbstractHydroxy amino acid monomers 3, 5 and amino acid monomers 10, 11 were prepared. Suspension polymerization of these chiral monomers with styrene and crosslinking agent afforded insoluble chiral polymers which were used as chiral ligands of the enantioselective Diels‐Alder reaction catalysts. A continuous flow system using polymeric catalyst was also successfully achieved in the same reaction.
Synthesis of rare‐earth metal‐containing polymers and their fluorescence properties
Authors: Zhou Yimin , Liu Rongqiang , Kong Deling , Sun Juntan 
Published: March 2011

AbstractFour kinds of polymeric β‐diketone compounds, including poly(vinylbenzyldibenzoylmethane)(1), poly(vinylbenzylacetoacetone)(2), poly(vinylbenzyl‐2‐thenoyltrifluoroacetone)(3) and poly(p‐benzoylacetylstyrene)(4) were synthesized. And then polymeric β‐diketone‐europium(III), ‐terbium(III), ‐samarium(III), ‐dysprosium(III), ‐europium(III)‐gadolinium(III), ‐terbium(III)‐gadolinium(III), and ‐europium(III)‐terbium(III) chelates were also synthesized. The chelate structures were confirmed. The influence of the structure on the fluorescence properties was investigated. The fluorescence intensity of polymeric rare‐earth metal complexes is closely related to the ligand and metal content. Polymeric complexes possess a higher fluorescence stability than that of corresponding low‐molecular‐weight complexes.
Precise pariser‐parr‐pople molecular orbital calculations using new‐γ. A novel guiding principle for the design of functional materials
Authors: Tokita Sumio , Hiruta Kimihiro , Nishimoto Kichisuke 
Published: March 2011

AbstractFor precise Pariser‐Parr‐Pople molecular orbital (PPP MO) calculations, the values of the spectrochemical softness parameter k of a new two‐center electron repulsion integral new‐γ were evaluated based on an appropriate partial structure of polycyclic aromatic hydrocarbons (PAHs). The spectroactive aromatic sextet resonance system (ASRS) was defined as a spectroactive partial structure of a molecule. The calculated excitation energies of the p‐band of PAHs accurately reproduced the observed ones.
Computer design, synthesis and investigation of gradient‐modulus polymers
Authors: Askadskii Andrey , Goleneva Lidiya 
Published: March 2011

AbstractGradient‐modulus polymeric materials have been prepared, which show a continuous transition, within the same sample, from rubber to plastic without any junctions, joints, etc. These materials are elastic and have a modulus ranging from 4.5 to 2000 MPa. The properties of the materials were calculated before their synthesis. It was shown that a prerequisite of such materials is a network structure comprising rigid bulky crosslinked points and short flexible linking chains. Another prerequisite of such materials is the occurrence of microphase separation.
Topological nanoinhomogeneities in polymer networks
Authors: Dušek Karel , Šomvársky Ján 
Published: March 2011

AbstractSmall‐size topological inhomogeneities in polymer networks characterized by differences in composition are formed as a consequence of history‐determined covalent linking of units differing in some property into chemical clusters (topological inhomogeneities). This process is possibly assisted by physical association (segregation) of units of different types. Evolution of hard clusters in mixtures of long and short chains crosslinked with a common crosslinking agent and multicomponent polyurethane networks have been treated as examples of evolution of topological inhomogeneities. Simple mean‐field models based on the statistical theory of branching processes (TBP) have been developed for modelling of the topological inhomogeneities (molecular weight averages, functionality averages, percolation threshold, etc.) in dependence on initial composition, reactivities of the functional groups, or history of network formation. Such characterization was possible by distinguishing bonds between e.g. soft‐soft, soft‐hard, and hard‐hard units. More sophisticated models view inhomogeneities formation as a kinetic process where effective reactivity of functional groups in reactions, by which inhomogeneities are formed, depends on the size and composition of a given chemical cluster. This model is based on Monte‐Carlo simulations of the generalized Smoluchowski coagulation process.
Pseudo interpenetrating polymer networks and interpenetrating polymer networks of zeolite 13 X and polystyrene and poly(ethyl acrylate)
Authors: Frisch Harry L. , Xue Yong‐peng , Maaref Shahin , Beaucage Gregory , Pu Zhengcai , Mark James E. 
Published: March 2011

AbstractFree‐radical polymerization of liquid styrene and ethyl acrylate with or without ethylene dimethacrylate crosslinker in the presence of zeolite 13 X produces interpenetrating polymer networks (IPN's) or pseudo IPN's in which polymer chains have grown and filled internal pores of the zeolite. A variety of methods of characterization including, solubility studies, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), 13C solid‐state nuclear magnetic resonance (NMR) and small‐angle X‐ray scattering (SAXS) provide supporting evidence for this. The polymer chains within the internal pores do not exhibit a bulk glass transition. This is part of a larger study of the glass transition of polymers confined to cavities or pores of various sizes.
Morphology and domain size of a model graft copolymer
Authors: Matsushita Yushu , Noda Ichiro 
Published: March 2011

AbstractWe prepared well‐defined styrene (S)‐2‐vinyl‐pyridine (P) graft copolymers of the ABB type or SPP graft copolymers, in which as block chain is grafted at the center of a block chain, as a model graft copolymer by anionic polymerization and coupling reaction. The composition dependence of morphology of SPP graft copolymers is qualitatively the same as that of SP diblock copolymers, but the composition range of each structure is shifted to the higher volume fraction of S block chain. The molecular weight dependence of lamellar domain size of SPP graft copolymers is almost the same as that of SP diblock copolymers, but the magnitudes are smaller. These experimental results are well explained by the difference in chain architectures.
Composites obtained via matrix and pseudo‐matrix processes (polymerization and new phase formation)
Authors: Papisov Ivan M. , Litmanovich Andrey A. , Bolyachevskaya Klavdiya I. , Yablokov Yuriy S. , Prokofev Aleksandr I. , Litmanovich Ol'ga Ye. , Markov Sergey V. 
Published: March 2011

AbstractA variety of composites comprising complexes between macromolecules and growing species such as macromolecules or particles may be prepared using matrix or pseudo‐matrix processes. Matrix polycondensation of silica acid in the presence of poly(ethylene glycol) and other polymers in benzene resulting in formation of interpolymer complex (IPC) poly(silica acid)‐matrix or composites including the IPC is regarded as an example of matrix processes providing the possibility to synthesize an IPC or composite which cannot be (or hardly may be) obtained by other ways:Theoretical aspects of pseudo‐matrix processes in which pseudo‐matrix macromolecule recognizes (i.e., forms a complex with) a particle of forming new phase and terminates its subsequent growth are discussed. Experimental data dealing with reduction of Ni(II) in polymer solutions and formation of nano‐composites ‘polymer ‐ metallic nickel’ including small particles (3–5 nm in diameter) with narrow size distribution are presented.
The topological structure of hypersurfaces of conformational energy levels and physical mechanisms of the internal mobility of proteins
Authors: Shaitan Konstantin V. 
Published: March 2011

AbstractThe interrelationship between the general characteristics of structure of biopolymer conformational energy hypersurface and possible mechanisms of conformational movements and elementary acts of functional processes is considered. The fundamental principle underlying regulation and control within biological systems at the macromolecular level are discussed. A new approach to modeling the dynamics of functional processes is proposed.
Effect of tertiary diamines on anionic polymerization of polar vinyl monomers
Authors: Marchal Jérǒme , And Yves Gnanou , Fontanille Michel 
Published: March 2011

AbstractTertiary diamines that exhibit chelating capability to lithium are shown to decrease the reactivity of growing species when used in classical anionic polymerization of methacrylic monomers. Out of the different diamines investigated, sparteine turns out to be the most efficient chelating agent. The beneficial effect of the latter additives on the overall reactivity of methacrylic anions was exploited to prepare poly(MMA) samples of controlled size at room temperature. The decrease in reactivity was also demonstrated from a kinetic point of view, upon measuring the actual rate constant of propagation using vinyl pyridine as model monomer.