bluuebunny/crossref_metadata_2025_split huggingface dataset:
The preparation and characterization of surface‐grafted plastic materials designed for the evaluation of their tissue and blood compatibility
Authors: Fischer J. Paul , Becker Udo , Von Halasz Sigmar‐Peter , Mück Karl‐Friedrich , Püschner Hubert , Rösinger Sigurd , Schmidt Anne , Suhr Hans H. 
Published: June 2010

AbstractWith the objective to develop both characterization methods and test systems for blood and tissue compatibility, some polymers, e.g., polyethylene (PE), polypropylene (PP), and ethylene/propylene/diene‐ter‐polymer (EPDM) of different shapes, e.g., beads, films, tubes, fibers, tubings, and microtome slices, were grafted with a variety of 15 monomers in order to introduce hydrophobic, hydrophilic, and ionizable groups. The grafted surface was characterized morphologically by the surface area (Brunauer‐Emmett‐Teller: BET value), by scanning electron microscopy (SEM), and by profilographic measurements. Surface grafting was controlled by frustrated multiple internal reflexion (FMIR)–ir measurements, by determination of the critical surface tension, and by energy‐dispersive x‐ray analysis (EDXA) combined with SEM. The EDXA–SEM method was found to be a helpful tool to characterize the homogeneity and penetration profile of surface grafting. The tissue compatibility was tested by implanting test samples under the skin of rats. Blood compatibility was determined via in vitro test systems based on the determination of single clotting factors.
Mechanism of stereoselective polymerization of oxirane
Authors: Tsuruta Teiji 
Published: June 2010

AbstractThe reaction mechanism of the stereoselective polymerization of methyloxirane is satisfactorily explained in terms of the enantiomorphic catalyst sites model, in which the symmetrical distribution of d*, and l*, catalyst sites is assumed. d*, Sites would accept D‐methyloxirane in preference to the L‐isomer, resulting in the formation of … DDDD … isotactic sequences, and vice versa. This paper is concerned with a mechanistic study on the origin of d* and l* nature of the catalyst by using a complex, [Zn(OMe)2‐(EtZnOMe)6] (I), the molecular structure of which was elucidated by x‐ray analysis. A possible mechanism for the stereoselective polymerization of methyloxirane is presented on the basis of results obtained from NMR analysis of the polymerization system catalyzed by (I) and GPC analysis of poly(methyloxirane) formed in the reaction system.
Recent results in the radiation synthesis and modification of polymers for special applications
Authors: Hummel D. O. 
Published: June 2010

AbstractThe cost for a mole of radicals from different sources is under the assumptions used, as follows: $0.85 using dibenzoylperoxide, $5.60 with 60Co, and $5.60 using a small 0.2‐MeV accelerator. Fluorine‐containing monomers and monomer mixtures belong to the most interesting class of systems for the radiation‐initiated synthesis of polymers with good thermal, mechanical, and chemical properties. Recently, the vinylfluoride‐vinylidenefluoride system was investigated in detail. The polymers were afterwards grafted with hydrophilic monomers.Films from, for example, polyethylene, polypropylene, polyvinylfluoride, or polytetrafluoroethylene were grafted from the gas phase with butadiene, vinylchloride, and styrene. Usually, homopolymerization in the gas phase can be kept low. A highly interesting system both from a theoretical perspective and for practical reasons is polyethylene‐hexafluoroacetone. The grafting follows a chain mechanism, and the “branches” consist of only one monomer unit each. Cationic grafting was observed during the irradiation of α‐methylstyrene, vinylbutylether, or isobutene in the presence of polyethylene, polytetrafluoroethylene, or PVC. A tremendous amount of work has been done in the field of radiation grafting of fibers and fabrics. In recent years, the following fiber/monomer systems, among others, have been investigated: cellulose with styrene, vinylfluoride. ethylacrylate, or acrylamide; wool with styrene; polypropylene with vinylchloride and vinylidenechloride; poly‐(ethylene terephthalate) with styrene, acrylic and methacrylic acid, acrylic acid plus acrylonitrile, and N‐vinylpyrrolidone.Special applications including radiation synthesis and modification of membranes and hydrogels, biocompatible materials, ion‐exchange membranes and resins, and, finally, the radiation‐grafting of enzymes have found considerable interest.
Radiation‐induced gas‐phase grafted polymerization as a method for producing macromolecular carries for active catalytic sites
Authors: Kritskaya D. A. , Ponomarev A. N. , Pomogailo A. D. , Dyachkovskii F. S. 
Published: June 2010

AbstractTo obtain polymer supports with different functional coverage, the kinetic peculiarities of radiation‐induced gas‐phase grafting of allyl (allyl alcohol, ally and diallyl amines) and vinyl (acryl and methacryl acids, their methyl ethers, methylvinylketone, 2‐ and 4‐vinylpyridine, acrylonitrile) monomers to polymer powder (polyethylene, polypropylene, polystyrene, and copolymer of ethylene with propylene) were studied. The degrees and radiation yields of grafting were measured and evidence of the grafting occurrence is given. The radiation yield of allyl monomers grafting to polyethylene was found to be 10–20 molecules/10 eV of absorbed energy and was found to keep constant on a change of the dose rate from 3 × 10−3to 6.5 Mrad/min. That testifies to the absence of second‐order chain termination and provides wide possibilities for effective use of various radiation sources. By grafting some monomers containing radioactive isotopes (14C,3H) and analyzing the grafted product after extraction, the ungrafted homopolymer content was shown to be less than 10%. The appearance of some additional absorption bands from fragments of the grafted monomers in the IR spectrum of the treated polymer was considered as evidence of grafting. Some polymer‐analogous reactions of the grafted polymer (reduction, saponification, hydrolysis, formation of Schiff bases) are given as illustrations of the validity of the method proposed for producing polyfunctional coverage of the macromolecular carries for active catalytic sites.
Comparative study of homogeneous and heterogenized cobalt systems by macromolecular supports in diene monomer polymerization
Authors: Golubeva N. D. , Pomogailo A. D. , Kuzaev A. I. , Ponomarev A. N. , Dyachkovskii F. S. 
Published: June 2010

AbstractIsoprene and butadiene polymerization has been studied in the presence of homogeneous and heterogenized, polymer‐supported, “cobalt” catalytic systems. Donor‐acceptor or covalent heterogenization Co(II) compounds resulted in retardation of initiation and deactivation reactions in catalytic systems, in increasing molecular masses, and in an integral yield of polymers. It was concluded from analysis of growth‐rate constants, as well as from the structures of the polymers formed, that the active sites were the same in both types of catalysts. The heterogenized systems were postulated to inhibit yielding cobalt compounds in a reduced state.
Synthesis and catalytic properties of transition‐metal complexes immobilized on macromolecular supports in polymerization processes
Authors: Dyachkovskii F. S. , Pomogailo A. D. 
Published: June 2010

AbstractFunctional groups of polymers and copolymers have been considered as the reaction sites for immobilization of transition‐metal complexes. A new type of polymer support has been described, i.e., carbon‐chain polymers with a surface modification due to graft polymerization of monomers with functional groups. Methods have been proposed for investigating the composition and structure of immobilized catalysts. Immobilization of transition metals on polymer supports has been shown to increase their catalytic activity considerably as compared to homogeneous and pseudo‐homogeneous analogs in polymerization processes.
Use of the gel spheron in the study and analysis of polymerous nucleic acids and their components
Authors: Boháček J. , Blažíček G. 
Published: June 2010

AbstractRapid separation of polymerous deoxyribonucleic acid (DNA) from ethanol, acetone, or phenol was performed on Spheron P 1000 gel using a 210‐mm glass column of 4‐mm internal diam. for the purpose of determination of these current contaminations in DNA preparations. Complete separation of polymerous DNA from its components, adenine, guanine, cytosine, and thymine was achieved in the same column isocratically eluted with 2M (NH4)2SO4 in 20‐mM potassium phosphate buffer at pH 7. The procedure was found also to be useful for the evaluation of enzymatic degradation of the DNA. Products of deoxyribonuclease‐I digestion were clearly separated from those of untreated polymerous DNA within a 10‐min period. The mechanism responsible for the separation of polymerous DNA of various origin from its low‐molecular constitutents is based on the combined effects of molecular sieving and the specific sorption properties of the Spheron matrix used.
Adsorption chromatography of proteins on controlled‐pore glass
Authors: Mizutani Takaharu , Mizutani Akira 
Published: June 2010

AbstractAdsorption chromatography on controlled‐pore glass was investigated by a pH‐gradient elution system in glycine buffer using standard proteins and rabbit serum. The pattern on the glass was similar to those on carboxymethylcellulose but there were some differences which might be derived from a cooperative aggregative force between glass and proteins.
Some aspects of organic polymer sorbents and their evaluation
Authors: Millar J. R. 
Published: June 2010

AbstractThe preparation and characterization of macroporous polymeric adsorbents are discussed. Problems arising in the characterization of macropore systems via surface‐area or pore‐size distribution and their relation to the adsorbent behavior of the product are described, and the significance of parameters such as “effective mean pore diameter” or the “inherent dipole moment” of functional groups are considered. An example of the development of a sorbent for a particular commercial process is given to illustrate the points discussed, and the application of novel carbonaceous materials to halocarbon removal is noted. Some pessimism is expressed concerning the practicability of determining the ideal sorbent for a given application by measurement of functionally related parameters.
Calibration of spreading function in GPC using statistical moments
Authors: Vozka S. , Kubín M. , Samay G. 
Published: June 2010

AbstractA new method is proposed for determining the spreading factor h(v) in the Tung integral equation, based on moment analysis of original (uncorrected) and corrected, normal‐flow chromatograms of calibration standards. The reliability of the new procedure has been verified on model and computer‐generated chromatograms, and tested experimentally on standard GPC columns as well as on microcolumns used in high‐speed gel‐permeation chromatography; its accuracy has been compared with that of known methods. The proposed method is particularly suited to fast gel‐permeation chromatography where, by trading the speed of analysis for efficiency, one can dispense with the knowledge of the molecular‐weight averages of calibration standards. If a well‐characterized sample having a broad molecular‐weight distribution is available, the shape of the function h(v) can be determined with sufficient accuracy from a single chromatogram.
Gel chromatography of carbohydrates on polysaccharide gel
Authors: Eltekov Yu. A. , Strakhova N. M. , Kàlal J. , Peška J. , Štamberg J. 
Published: June 2010

AbstractLiquid chromatographies of high and low‐molecular carbohydrates and polyethyleneglycols of different molecular masses were studied on porous microspherical cellulose. Dependence of the distribution coefficients of polymer molecules on molecular mass was determined. It was revealed that the distribution coefficient depends on the hydrodynamic diameters of the polymer molecules. The possibility of using macroporous polysaccharide gels in the liquid chromatography of polymers, in order to study carbohydrates and other water soluble polymer, was discussed.
Phase separation phenomena in solutions of cellulose acetate. I. Differential scanning calorimetry of cellulose acetate in mixtures of dioxane and water
Authors: Altena F. W. , Smolders C. A. 
Published: June 2010

AbstractThe nature and kinetics of phase separation processes of solutions of cellulose acetate (degree of substitution, 2.5) in mixtures of dioxane and water are studied by differential scanning calorimetry (DSC). The thermograms on heating show small endothermic effects, detectable only after prolonged aging below the phase separation temperature. Experiments in two regions of the ternary diagram are of interest for the description of the formation mechanism of asymmetric membranes viz., (1) at high polymer and high concentrations and low concentrations of nonsolvent (gelation); (2) at lower polymer concentrations of nonsolvent (liquid–liquid separation followed by gelation). Endothermic effects after prolonged aging are found at high polymer concentrations (≥40%). These results demonstrate that gelation is very slow in these systems. At lower concentrations of polymer and high concentrations of nonsolvent (up to 40%) a more rapid type of phase separation can be observed visually on cooling. The temperature where turbidity sets in (the cloud point) is independent of the rate of cooling. In DSC experiments no exothermic effect is found on cooling. Again, after aging an endothermic effect is present. The endothermic peak, which is situated below the cloud point, is probably a result of melting of the gelled concentrated phase.
Thermal properties of intact nucleoproteides
Authors: Monaselidze J. R. , Chanchalashvili Z. I. , Mgeladze G. N. , Madjagaladze G. V. , Chitadze G. Sh. 
Published: June 2010

AbstractIt is established that the process of chromatin melting in tissues proceeds in one stage with the following transition parameters: T = 82°C, Δ T = 7°C, and Q = 24 cal/g DNA. The difference between the heats of melting for chromatin and DNA is 12 cal/g and corresponds to the melting of the secondary and tertiary structure of chromatin.
Thermodynamics of protonation of polymeric bases whose repeating units behave independently
Authors: Barbucci Rolando , Barone Vincenzo , Ferruti Paolo , Oliva Leone 
Published: June 2010

AbstractThe protonation of some poly(amido amine)s has been studied in aqueous solution by potentiometric, calorimetric, and 13C‐NMR methods. Only “apparent” constants were usually found in polymeric acids and bases; on the other hand, “sharp” basicity constants could be determined for the poly(amido amine)s studied. The log K values determined from 13C‐NMR shifts versus pH agree well with those determined by potentiometric titrations. Also, the protonation enthalpies do not depend on the dissociation degree of polymeric bases, and this is a further proof of the peculiarity of this class of polymers. The trends of ΔH's and the conformations of polymers in solution are analyzed on the basis of theoretical computations.
Mixing enthalpies of polymers with mesomorphic properties and mesogenic plasticizers
Authors: Cser F. , Nyitrai K. , Hardy G. , Menczel J. , Varga J. 
Published: June 2010

AbstractMixtures of polymers of mesomorphic properties with mesogenic plasticizers were investigated by differential scanning calorimetry (DSC). The nature of the mesomorphic structure of the polymers could be identified by studying the concentration dependence of such thermal processes as glass transition, mutual solution of the phases and formation of eutectic melts. Mixtures of polymers with a supposed nematic structure such as poly(phenyl‐p‐acryloyloxy‐benzoate) (pPAB), poly(p‐butoxy‐phenyl‐p‐acryloyloxy‐benzoate) (pBPAB), poly(p‐methoxy‐phenyl‐p‐methacryloyloxy‐ethoxy‐benzoate) (pMPMEB), and one copolymer of p‐methyl‐p'‐acryloyloxy‐azoxy‐benzene (MAAB) and cholesteryl‐vinyl‐succinate (CVS) and of nematogenic materials as terephthal‐bis‐butyl‐aniline (TBBA), p‐butoxy‐phenyl‐p‐propionyloxy‐benzoate (BPPB) and the monomers of the copolymer were investigated. None of the systems was found fully miscible with nematic structure. The enthalpies of melting at the clearing points were found proportional to the polymer content of the mixtures. The mixing enthalpies in the liquid state are too small to be measured by DSC. The mixing enthalpies of the solid components resulting in solid plasticized polymer are found proportional to the melting enthalpies of the plasticizers and to their saturation concentration in the polymer. The anisotropy of the bulk polymer originated from the anisometric geometrical shape of the macromolecules themselves, which is in good agreement with the structural concept introduced earlier.
The thermal properties of polypropylene
Authors: Grebowicz Janusz , Lau S.‐F. , Wunderlich Bernhard 
Published: June 2010

AbstractThe thermodynamic properties of isotactic polypropylene in the fully crystalline, glassy, and molten state are established from 0 to 500 K based on data bank heat capacities and the vibrational frequency spectrum. The seven skeletal vibrations are described by θ3 and θ1 of 91 and 714 K for crystalline polypropylene. For the calculation of Cp − Cv, a Lindemann A0 value of 1.5 × 10−3 K mol/J was found. Calculated and experimental heat capacity data show agreement within an average error of −0.3 ± 1.6%. Glassy polypropylene was similarly treated up to the glass transition temperature at 260 K (θ3 = 78 K, θ1 = 633 K, average heat capacity error −0.6 ± 2.8%). The residual 0 K entropy of glassy polypropylene is 1.9 J/K mol. Partially crystalline polypropylene is shown through high‐sensitivity DSC measurements to have a glass transition range from 260 to 380 K. Similarly, high‐sensitivity DSC has been used to characterize the condis phase of polypropylene (conformationally disordered polypropylene) which was prior called “smectic mesophase” or “paracrystalline.” Its heat of transformation to the stable crystal phase is 600 J/mol.
Some rheological properties of solutions and blends of hydrogenated polybutadiene
Authors: Graessley W. W. , Raju V. R. 
Published: June 2010

AbstractThis article describes work with model polymers to explore the effects of long branches on polyethylene melt rheology. Dynamic moduli were measured at two or more temperatures on melts, blends, and solutions of linear (L) and star (B) hydrogenated polybutadiene (HPB). Enhancement factor Γ and temperature coefficient (flow activation energy Ea) were determined from viscosity data and correlated with arm molecular weight Mb and volume fraction of the star component Φ. As in other species, Γ for a given branch point functionality is roughly an exponential function of Φ11/6Mb in entangled melts and solutions. In contrast with other species, however, (Ea)B and (Ea)L are different; (Ea)B – (Ea)L is directly proportional to ΦMb, and the degree of thermorheological complexity varies primarily with (Ea)B – (Ea)L. In blends with linear HPB of comparable viscosity, Γ for the star component remains essentially constant, and (Ea)B – (Ea)L is directly proportional to the volume fraction of the star component.
Conformational properties of perfluoroalkane chains. VI. Intrinsic viscosity and unperturbed dimensions of poly(decamethylene perfluorosebacate)
Authors: Matsuo Keizo , Stockmayer W. H. , Needham G. F. 
Published: June 2010

AbstractLight‐scattering and viscosity measurements are reported for fractions of poly(decamethylene perfluorosebacate). Intrinsic viscosity (dL/g) relationships at 25°C are [η] = 1.55 × 10−4Mv0.70 in chloroform and (η) = 8.8 × 10−4Mv0.50 in s‐tetrachloroethane. From these data the characteristic ratio is found to be Cθ = 6.3 ± 0.5, indicating that the perfluoroalkane chain is not much more extended than an alkane chain. The solid semicrystalline polymer melts at 45°C, and its x‐ray powder pattern suggests a structure different from that of poly(decamethylene sebacate).
Miscible blends of a vinylidene chloride/vinyl chloride copolymer with polymethacrylates
Authors: Woo E. M. , Barlow J. W. , Paul D. R. 
Published: June 2010

AbstractA copolymer of vinylidene chloride and vinyl chloride containing 13.5% of the latter has been found to form completely miscible blends with atactic and isotactic poly(methyl methacrylate). poly(ethyl methacrylate), poly(n‐propyl methacrylate), and poly(cyclohexyl methacrylate). All but the latter of these blends were shown to exhibit lower critical solution temperature behavior at temperatures below that at which the copolymer rapidly degrades. The copolymer was found to be only partially miscible with poly(isopropyl methacrylate), while no detectable level of miscibility was observed with poly(methyl acrylate), poly(ethyl acrylate), poly(vinyl acetate), poly(vinyl methyl ether), or poly(vinyl methyl ketone). Information about interactions between components in the miscible blends was estimated from melting point data and is discussed.
Reaction kinetics of polymeric reagents
Authors: Morawetz H. 
Published: June 2010

AbstractKinetic studies of reactions in systems containing polymers have led to the following observations: (1) In dilute solution the thermal and the photochemical isomerization of azobenzene residues is not impeded by their incorporation into a polymer backbone. In the glassy state, the kinetics of the isomerization of azobenzene residues in polymer side chains or backbones reflect the distribution of free volume and volume relaxation. (2) Reactions of polymers with low molecular weight reagents may be affected by neighboring group effects and by the contribution of the polymer backbone to the polarity of its microenvironment. (3) Attack of an enzyme on a polymer side chain depends sharply on the spacing of the susceptible bond from the chain backbone. (4) The expected “kinetic excluded volume effect” in reactions between two flexible chain molecules was not observed. (5) Reactions involving groups attached to a swollen crosslinked gel may reflect spatial variations of the local polarity. (6) Attack of water‐soluble reagents on latex particles may be restricted to the surface of the particle. (7) The presence of a polyion exerts various effects on reactions involving two small ionic species.
Syndiotactic polypropylene
Authors: Elias Hans‐G. , Ogawa Toshio , Kim Young‐Ha 
Published: June 2010

AbstractPropylene is the only monomer which can be polymerized both isospecifically and syndiospecifically with the same family of catalysts, i.e., organometallic compounds of the Ziegler–Natta type. Whereas isotactic poly(propylene) can be manufactured by reasonable polymerization conditions to highly valued thermoplastics, the corresponding syndiotactic polypropylene has remained a laboratory product. However, theoretical considerations show that syndiotactic polypropylene may possess some ultimate properties which surpass those of isotactic polypropylene. Propylene was thus polymerized with various catalyst systems and the resulting polymers characterized by carbon‐13 nuclear magnetic resonance, infrared spectroscopy, X‐ray diffraction, gel permeation chromatography, differential scanning calorimetry, and stress/strain measurements [1,2]. Several polymers were fractionated. The combined evidence points toward stereoblocks in syndiotactic polypropylenes [1]. The highest syndiotacticities achieved are, however, still too low to permit the ultradrawing to highly oriented polymers, which would allow approaching the ultimate properties. This result is probably due to a stereostatistic peculiar to the catalyst system, i.e., a symmetric Markov statistic of the first order [3]. This statistic predicts the experimentally found linear dependence of triad fractions on diad fractions [4], a characteristic restricted diad range, and an unusual dependence of the heterotacticity index on the diad contents. The same formalism also describes the features of the so‐called heterotactic polymerizations.