bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lamellar structure of poly(ethylene oxide) molecular complexes
Authors: Dosière M. 
Published: March 2011

AbstractThe phase diagrams of some binary systems such as poly(ethy lene oxide)‐p‐dihalogenobenzene, poly(ethylene oxide)‐resorcinol and poly(ethylene oxide)‐p‐nitrophenol show the existence of molecular complexes with a well definite stoichiometry. The crystal structure of these molecular complexes has been determined by wide‐angle X‐ray diffraction. The morphology of these molecular complexes crystallized from the melt is investigated by differential scanning calorimetry and small angle X‐ray scattering. PEO‐p‐dichlorobenzene and PEO‐resorcinol complexes crystallize from the melt as extended chains (EC) or integral folded chain (IFC) lamellar crystals. As observed for PEO oligomers, the fraction of EC crystals of PEO‐resorcinol increases with the crystallization temperature. However EC crystals are present in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO‐p‐nitrophenol complex crystallizes over all the studied crystallization temperature range as stable non integral folded chain (NIFC) crystals. Explanations related to the crystal structure of these complexes and to their mode of growth are invoked to explain these two deeply different lamellar morphologies.
Local microstructure dependence of PVC interaction with solvents. A FTIR verification
Authors: Gómez‐Elvira J.M. , Tiemblo P. , Martínez G. , Millán J. 
Published: March 2011

AbstractThe occurrence of local configuration based PVC‐solvent interactions, specifically, is demonstrated by studying, first, the changes in FTIR frequency of both the solvent carbonyl band and the PVC C‐Cl stretching bands with the composition of PVC‐solvent mixtures; and, secondly, the FTIR dichroic behaviour of the same bands upon stretching PVC films containing traces of solvent. The latter turns out to be an original path to investigate polymer interactions.
Order ‐ disorder transitions in comb‐like polymer‐surfactant systems involving hydrogen bonds
Authors: ten Brinke Gerrit , Huh June , Ruokolainen Janne , Torkkeli Mika , Serimaa Ritva , Ikkala Olli 
Published: March 2011

AbstractConditions to obtain micro‐phase separated morphologies in polymer‐surfactant systems involving hydrogen bonds have been investigated using poly(4‐vinyl pyridine) (P4VP) and surfactants capable of forming hydrogen bonds of different strength with the basic nitrogen of P4VP. Depending on the tail length, the hydrogen bonding strength, the amount of surfactant and the temperature, four different regimes have been identified: I. Micro‐phase separated state, II. Homogeneous state exhibiting a distinct Small Angle X‐ray Scattering (SAXS) peak, III. Homogeneous state without a SAXS peak and, IV. Macro‐phase separated state. Time‐resolved SAXS / W(ide) A(angle) X(ray) S(cattering) / D(ifferential) S(canning) C(alorimetry) as well as rheological measurements are used to identify the different regimes. A simplified model description together with preliminary computer simulation results are presented.
PVC photo‐oxidative degradation: Identification of volatiles
Authors: Krzymien Marek E. 
Published: March 2011

AbstractVolatile products present in poly(vinyl chloride), PVC, after outdoor weathering have been compared with volatiles from laboratory, UV exposed PVC surfaces. Compounds both present in the photo‐degraded polymer surface layer and directly emitted from the polymer were measured in the laboratory experiments. The hydrocarbons, oxygenated compounds and chloro‐organic species were measured and identified by capillary gas chromatography with a mass spectrometer detector.
Highlights in chemistry and physics of polymer stabilization
Authors: Pospíšil Jan , Nešpůrek Stanislav 
Published: March 2011

AbstractDeactivation of free radicals, hydroperoxides and harmful solar radiation are the principal mechanisms increasing stability of commodity and engineering polymers. The stabilization process is accompanied by transformations of individual additives. New compounds influence specifically the integral protecting mechanism. Products contributing to the stability are most beneficial. Mechanistic data are used for optimisation of the inherent chemical efficiency and physical persistence and for explanation of deactivation of stabilizers.
Charge transfer states in the photophysics and photochemistry of polyimides and related phthalimides
Authors: Creed David , Hoyle Charles E. , Jordan John W. , Pandey Chandra A. , Nagarajan Rajamani , Pankasem Surapol , Peeler Alline M. , Subramanian Petharnan 
Published: March 2011

AbstractPolyimides such as 6F‐6F and 6F‐ODA and model N‐arylphthalimides are stabilized against photooxidative degradation by their electron donor (D) – acceptor (A) character. We have investigated the precise origin(s) of this effect using D and A substituents on the N‐aryl groups of these compounds. The lowest excited singlet state (S1) of N‐arylphthalimides is an intramolecular charge transfer (ICT) state. A nominally twisted compound, N‐(2‐t‐butylphenyl)phthalimide, shows greatly diminished CT absorption and blue‐shifted fluorescence with reduced quantum yield when compared to the 4‐t‐butyl isomer with an identical N‐aryl donor group. It therefore seems unnecessary to claim that the ICT state of phthalimides is a so‐called TICT state. Quantum yield and fluorescence lifetime measurements lead to the conclusion that enhanced internal conversion from the ICT state (S1) to the ground state makes a significant contribution to photostabilization of these compounds by suppressing formation of the reactive triplet state. Further stabilization of polymer films may be afforded by triplet state self‐quenching which is enhanced for 6F‐ODA in increasingly poor solvents. N‐alkylarylphthalimides in which the aryl and phthalimide groups are not formally conjugated but, rather, joined by flexible methylene ‘spacers’, exhibit a different kind of fluorescent intramolecular CT singlet state whose formation can also stabilize these compounds by suppressing triplet state formation.
Nematic and smectic liquid single crystal elastomers: Influence of external stress parallel and perpendicular to the director
Authors: Kundler Isabel , Nishikawa Etsushi , Finkelmann Heino 
Published: March 2011

AbstractThe influence of uniaxial mechanical stress applied parallel or perpendicular to the director axis (optical axis) of nematic and smectic‐A elastomers having a permanent macroscopically ordered monodomain structure is investigated. Due to the different phase structures applying an external mechanical stress leads to completely different responses with respect to the young moduli and reorientation processes of the director. Nematic elastomers exhibit a weak anisotropy of the moduli parallel (μ11and perpendicular (μ) to the optical axis with μ11/ μ = 1.5. The moduli are mainly determined by the rubber elasticity of the poly(siloxane) network. Applying the mechanical stress perpendicular to the initial director axis causes a rotation of the director axis that is connected with a periodic pattern formation and a ‘soft elastic’ response. For smectic‐A elastomers μ11/μ is in the order of 102. While μ reflects a rubber elastic response similar to that of the nematic system, μ11indicates an enthalpy‐elastic behaviour of the one‐dimensional long range order of the smectic layers. In this direction reorientation of the phase structure with a deformation of the smectic layers occurs above a threshold elongation. In contrast to the nematic networks, a deformation perpendicular to the optical axis causes no director reorientation, displaying the liquid‐like properties within the smectic layers.
Photo‐controlled diffusion in reacting liquid crystals: A new tool for the creation of complex molecular architectures
Authors: Broer D.J. , Lub J. , Mol G.N. 
Published: March 2011

AbstractDiffusion enforced photo‐assembling during polymerization of a chiralnematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross‐section of the film. The polarization selective reflection band of cholesterics can be made much wider than those of single pitch materials and may expand over the whole visible wavelength. The paper discusses the photo‐controlled diffusion process in thin films, the important process parameters and some of the properties of the molecular architectures obtained.
Ellipsoidal core‐shell cylindrical microphases in PS‐b‐PB‐b‐PCL triblock copolymers with a crystallizable matrix
Authors: Balsamo Vittoria , Stadler Reimund 
Published: March 2011

AbstractPolystyrene‐block‐polybutadiene‐block‐poly(ϵ‐caprolactone) SBC triblock copolymers with a PCL matrix exhibit microphase separation into three different phases within the spherulitic superstructures. Mixing of the PS‐block can occur upon melting of the PCL‐block if the molecular weight is low enough. Even though the crystallization takes place well below the PS‐glass transition, a deformation of the amorphous microphases into ellipsoidal core‐shell cylindrical microdomains is observed by TEM. These copolymers have mechanical properties which are dominated by the PCL (poly(ϵ‐caprolactone)) matrix with an influence of the amorphous blocks.
Microphase separation in block CO‐ and terpolymers of novel macromolecular architectures
Authors: Sioula Stella , Tselikas Yiannis , Hadjichristidis Nikos 
Published: March 2011

AbstractThe synthesis of model miktoarm stars of the A2B, A3B, (AB)2(BA)2 and ABC (A:polyisoprene, B: polystyrene C: poly (methyl methacrylate)) was achieved by using anionic polymerization techniques and controlled chlorosilane chemistry. The microphase separation was studied by TEM, SAXS and image simulation. In the case of A2B and A3B miktoarm star copolymers, the morphology results are in agreement with the newly and after the experimental results developed theory of Milner. One of the symmetric in composition inverse block copolymers ((AB)2(BA)2) shows the OBDD morphology due to the special spatial arrangements of the arms. The first morphological results of ABC miktoarm star terpolymer show interesting future.
Mineralization of gold in block copolymer micelles
Authors: Möller Martin , Spatz Joachim P. , Roescher Arno , Mößmer Stefan , Selvan S. Tamil , Klok Harm‐Anton 
Published: March 2011

AbstractUltrasmall gold particles have been prepared inside the micelles of polystyrene‐block‐poly(ethylene oxide) and polystyrene‐block‐poly(2‐vinylpyridine) in toluene. Starting point was the formation of a thermodynamically stable dispersion of HAuCl4 or LiAuCl4 in the inverse micelles of the block copolymer which were treated with hydrazine or pyrrole. Analysis of the effect of the reduction agent on the stability of the micelles yielded a simple model for the transformation process involving coagulation of the swelling micelles. Kinetic control of the different steps, i.e., reduction, mineralization, coagulation, film formation, allowed to prepare thin films in which highly uniform gold particles were arranged in yet unknown order. When pyrrole was employed for the reduction, the gold monocrystals got embedded in a shell of polypyrrole.
Design of new macromolecular architectures by using quasi‐equivalent monodendrons as building blocks
Authors: Percec Virgil , Ahn Cheol‐Hee , Cho Wook‐Dong , Johansson Gary , Schlueter Douglas 
Published: March 2011

AbstractQuasi‐equivalent building blocks are chemically identical subunits which self‐control their shape by switching between different conformational states. Classic biological examples are the flat‐tapered and conical protein coats which jacket nucleic acids during the self‐assembly of rod‐like and icosahedral viruses, respectively. This paper advances the hypothesis that monodendrons can act as synthetic quasi‐equivalent building blocks. The rational design of flat‐tapered and cone shaped quasi‐equivalent monodendrons and their use in the construction of three dimensional supramolecular and macromolecular rod‐like and spherical systems demonstrates the above hypothesis. Mechanisms which interconvert the spherical systems into rod‐like ones by using the same monodendron building blocks, thus demonstrating their quasi‐equivalence, will be exemplified.
Progress in the syndiotactic polymerization of styrene with metallocene/mao catalysts
Authors: Kaminsky Walter , Lenk Stephan 
Published: March 2011

AbstractMetallocene/MAO catalysts are useful for the production of syndiotactic polystyrene ‐ a new class of high performance polymers. The melting point of the obtained syndiotactic polystyrene depends on the metallocene used and can reach up to 275 °C. In the past, the most active catalysts in polymerization have been half‐sandwich titanocenes such as CpTiCl3 and Cp*TiCl3. If the chlorinated compounds are changed into the fluorinated compounds as CpTiF3 and Cp*TiF3, the activity increases by a factor of 5 to 100. The fluorinated titanocenes are more stable at higher temperatures and need a lower MAO excess in order to obtain optimal activities.Polymers obtained with the unsubstituted CpTiF3 show melting points which are 17 °C lower than those synthesized by pentamethylcyclopentadienyltitaniumtrifluoride. Especially Cp*TiF3 shows a much higher activity and, compared with the chlorinated compound, gives polymers with a higher molecular weight. Substituted cyclopentadienyltitanocenes have even higher activities. Ethene/styrene copolymers can be obtained by catalysis with zirconocene compounds.
Structures and properties of block copolymers in solution
Authors: Chu Benjamin , Liu Tianbo , Wu Chunhung , Zhou Zukang , Mark Nace V. 
Published: March 2011

AbstractStructures and properties of block copolymers in solution depend on the total block length, the block length ratio, the block sequence and the solvent quality. The supramolecular structures formed by core/shell or flower‐like micelles in the concentrated solution region are examined by dynamic light scattering to ascertain some of the conditions which can enhance the formation of open associated structures using a triblock copolymer in a selective solvent for the middle block.
Toughened carbon fiber composites with morphology gradient
Authors: Kim Yu Seung , Kim Sung Chul 
Published: March 2011

AbstractThe morphology and fracture behavior of polyimide modified carbon fiber/dicyanate composites were analyzed. Composites having morphology gradient were prepared by inserting a polyimide film between prepregs of carbon fabric impregnated by dicyanate alone, and controlling the relative rate of dissolution of polyimide and the polymerization of dicyanate by adding zinc stearate catalyst. The composites having morphology gradient showed Gic and Giic values of 2.2 kJ/m2 and 1.4 kJ/m2 respectively, which showed 3–5 times of those values of unmodified carbon fiber/dicyanate composites.
Membrane microfiltration of oily water
Authors: Kim Jae‐Jin , Chinen A. , Ohya H. 
Published: March 2011

AbstractSeparation of oil in water emulsion was carried out by crossflow microfiltration using 3 types of microporous glass tubular membrane with different pore size of 0.27, 0.75, and 1.47 μm. The effect of pore size on permeate flux and oil rejection was investigated and the filtration mechanisms were analyzed based on various types of filtration models.
Measurement of anisotropic refractive indices of free‐standing polymer film
Authors: Lee Seung Won , Kwon Seon Young , Lee Hoosung 
Published: March 2011

AbstractA new technique has been developed to measure the optical refractive indices in the parallel and perpendicular directions to the film surfaces and applied to measure the refractive indices of free‐standing polymer films. The refractive indices were obtained by measuring the reflectivity as a function of the incident angle. The angle dependence of the reflectivity which results from the interference of the light beam reflected from the front and rear interfaces of the film was analysed by means of the Fresnel equation. This technique can be used to measure the refractive indices in three major axes, i.e. one out‐of plane axis and two in‐plane axes of the sample. This technique gives values for the refractive indices and the thickness simultaneously with an accuracy comparable to that measured by optical wave‐guide technique. The validity of the technique has been tested with polymer films of known refractive indices such as poly(methyl methacrylate) and polyimide (PMDA‐ODA).
Thermosensitive hydrogel coatings: Synthesis and heparin release
Authors: Gutowska Anna , Kim Sung Wan 
Published: March 2011

AbstractThe synthesis and drug release properties of crosslinked N‐isopropylacrylamide (NiPAAm) copolymer coatings on the surface of a hydrophobic poly(ester‐urethane) tubing were examined. A method was designed to coat hydrophobic polymer surface with a thermosensitive gel layer. Crosslinked NiPAAm copolymer coatings were synthesized using UV‐initiated polymerization. The feasibility of using NiPAAm based gels as heparin releasing thermosensitive coatings was investigated. Heparin, a high molecular weight hydrophilic solute, was loaded into hydrogels using a simple solution sorption technique. The release of heparin from NiPAAm copolymer gel coatings was compared to that of crosslinked NiPAAm copolymers. The gel coatings demonstrated a more gradual and prolonged heparin release as compared to gel disks of the same composition.
Morphology and degradation behavior of aliphatic/aromatic copolyesters
Authors: Yoo Eui Sang , Im Seung Soon , Yoo Youngtai 
Published: March 2011

AbstractRandom and segmented block copolymers of Poly(tetramethylene succinate) (PTMS) and Poly(tetramethylene terephthalate) (PTMT) were synthesized and characterized regarding sequence distribution and crystalline parameters. Biodegradation behaviors of the copolyesters were examined in activated sludge and enzyme solution in terms of CO2 evolution. It was found that the initial degradation was strongly dependent on the crystallinity in the random copolymer. However, the chemical compositions become a dominant factor at the later stage of degradation. In the case of block copolymers, the biodegradation rate was most significantly affected by size and degree of perfectness of PTMS crystallites.
Applications of two‐dimensional correlation spectroscopy in depth‐profiling photoacoustic spectroscopy, near‐infrared dynamic rheo‐optics, and spectroscopic imaging microscopy
Authors: Noda Isao , Story Gloria M. , Dowrey Anthony E. , Reeder Robert C. , Marcott Curtis 
Published: March 2011

AbstractTwo‐dimensional infrared (2D IR) correlation spectroscopy has found diverse applications in characterizing polymers. The versatility of this powerful technique is demonstrated in the study of a polymeric laminate film by using depth‐profiling photoacoustic spectroscopy, mid‐ and near‐IR dynamic rheo‐optical measurements, and spectroscopic imaging microscopy. Spatial and temporal variations of near‐IR spectra are effectively analyzed by the 2D correlation technique. Step‐scanning FT‐IR spectrometers provide a unique opportunity to obtain desired spectral information often difficult to access by the conventional rapid‐scanning approach.
Synthesis of sulfated alkyl oligosaccharides with potent anti‐HIV activity
Authors: Uryu Toshiyuki , Katsuraya Kaname , Nakashima Hideki 
Published: March 2011

AbstractSulfated alkyl malto‐ and laminari‐oligosaccharides with potent anti‐human immunodeficiency virus (HIV) activities were synthesized. Present work focusses on the syntheses of high anti‐HIV active compounds from low molecular weight carbohydrates which will react selectively with AIDS virus protein only. A surface‐active agent type compound consisting of both hydrophilic sulfated oligosaccharide and hydrophobic alkyl group portion was prepared. Individual pure malto‐oligosaccharides from malto‐tetraose to ‐heptaose and laminarioligosaccharides from laminari‐pentaose to ‐nonaose were used as the starting carbohydrates. Synthesis of peracetylated alkyl oligosaccharide was carried out with β‐peracetylated oligosaccharides and corresponding alcohols by using Lewis acid catalysts. Sulfation was performed with sulfur trioxide‐pyridine complex. The anti‐HIV activity was assayed by means of MT‐4 cells and HIV‐1 or HIV‐2 viruses. Almost all sulfated alkyl oligosaccharides exhibited potent inhibitory effects on HIV infection. Sulfated alkyl laminari‐oligosaccharides which have various kind of aklyl portion such as fluoro alkyl, chiral alkyl, cyclic alkyl, and phenyl alkyl were also examined. In addition, this study also provides an assessment of activity levels of sulfated alkyl oligosaccharides in small mammals.
Microstructural analysis of microfibrils of bacterial cellulose
Authors: Horii Fumitaka , Hirai Asako , Yamamoto Hiroyuki 
Published: March 2011

AbstractThis paper reviews mainly our recent investigations of two allomorphs of native cellulose, celluloses Iα and Iβ, carried out based on the composite crystal model by high resolution solid state 13C NMR and electron microscopy. First the distribution of the two allomorphs in nature is described together with some deviations from the simple composite crystal model. Secondly, the influences of polymer additives on the crystallization of the two allomorphs are described in the bacterial system somewhat in detail. On the basis of these results, the mechanism of the crystallization of the two allomorphs is finally discussed also in the bacterial cellulose system.
Investigation of the supramolecular structure of never dried bacterial cellulose
Authors: Fink Hans‐Peter , Purz Hans Joachim , Bohn Andreas , Kunze Jürgen 
Published: March 2011

AbstractSupramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X‐ray scattering including synchrotron radiation, transmission electron microscopy, and 13C‐CP/MAS‐NMR‐spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consisting of 5 to 12 waterfree Iα‐crystalline subunits with a cross‐section of about 7 nm × 13 nm and of water solvating the subunits. Lateral aggregation of these crystalline units was found along the smaller (110)‐lattice planes with a layer of water between adjacent crystallites. The NMR‐spectrum of wet bacterial cellulose exhibits an additional C‐1 line component indicating cellulose‐water interactions. During drying lateral dimensions of the microfibrillar ribbons, crystallite sizes, as well as the overall crystalline order decrease, whereas the Iα/Iβ‐ratio of about 80/20 remains approximately unchanged. Conclusions were drawn with regard to the early states of structure formation of bacterial cellulose.
Hypolipidemic effects of hydrolyzed xyloglucan
Authors: Yamatoya Kazuhiko , Shirakawa Mayumi , Kuwano Kazutami , Suzuki Junko , Baba Osamu 
Published: March 2011

AbstractXyloglucan is found in the primary cell walls of higher plants, where it plays important biological roles. It also exists in certain seeds, for example tamarind, as a reserve polysaccharide. Some xyloglucan oligosaccharides possess plant growth promotion activity.We prepared hydrolyzed xyloglucan from the tamarind seed xyloglucan using endo‐(1 → 4)‐ β ‐glucanase and examined its effects on lipid metabolism in rats fed a high fat diet. Among the plasma lipids, total lipid, cholesterol, triglyceride and β ‐ lipoprotein were each reduced 14 ‐ 17% by hydrolyzed xyloglucan. Hydrolyzed xyloglucan significantly reduced both adipose tissue weight and plasma GOT. Among the hepatic lipids, total lipid, cholesterol, triglyceride and phospholipid were significantly reduced by hydrolyzed xyloglucan.These hypolipidemic effects may be important for the treatment and prevention of geriatric diseases, including diabetes and cardiac disorders.