bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some problems concerning the degradation of linear vinyl polymers and copolymers in nonisothermal conditions
Authors: Schneider I. A. 
Published: June 2010

AbstractA critical review of the experimental results concerning the thermal degradation of linear vinylic polymers in dynamic conditions shows that generally the use of a single thermogravimetric curve may lead to ambiguous conclusions concerning both the steps and the mechanism of the thermal degradation, as well as the corresponding evaluated kinetic parameters. The ultimate values depend not only on the transformation degree, but also on the heating rate used, so that extrapolations may be recommended. However, the significance of the extrapolated kinetic parameters is still arguable, so that to compare thermogravimetric results, standard working conditions must be used. In such conditions the relative thermal stability of the polymers and the influence of comonomer units on the thermal behavior of copolymers may be appreciated.
Considerations of some copolymers obtained by radical mechanisms
Authors: Simionescu Cristofor I. 
Published: June 2010

AbstractThe modification of the chemical character of certain macromolecular products by radical copolymerization and grafting reactions with the object of improving some properties, constitutes a field of continuous and current debate about the correlation between synthesis, outcoming structure, and resulting properties of the final products. In this respect some results have been briefly presented, referring to this dependence in the case of multicomponent copolymers (comprising three to four components) and of grafted copolymers; in the same respect the behavior of some biocopolymers (of the alginate type) has been correlated with their structure deduced by the application of certain principles of classical copolymerization to the natural products under study.
Thermoplastic urethane chemical crosslinking effects
Authors: Schollenberger C. S. , Dinbergs K. 
Published: June 2010

AbstractThis paper reviews the chemical structures and attendant polymer morphology that have been advanced to explain the virtual crosslink (VC) phenomenon in segmented polyurethane elastomers. The different chemical methods employed to produce useful vulcanizates from the classical polyurethane elastomer use‐forms (castable liquid, millable gum) through covalent crosslinks (CC) are discussed. And finally, the nature of the polymer property changes occurring when a CC network is superposed on the VC network of a representative thermoplastic poly(ester‐urethane) elastomer composition through the use of a free radical curing agent (organic peroxide) is described. The CC‐VC network polymer of the subject polyurethane composition proved to have greater resistance to: solvation and its effects, stress relaxation, heat distortion, and compression set, and showed much higher modulus values than the VC network polymer. But the CC‐VC network polyurethane also showed less extensibility, tear strength, low temperature flexibility, and flex life. The degrees of these changes are discussed and molecular explanations proposed in some cases.
Rheology of concentrated solutions of poly(γ‐benzyl‐glutamate)
Authors: Kiss Gabor , Porter Roger S. 
Published: June 2010

AbstractSteady shear viscosity, dynamic viscosity, dynamic modulus, and normal force were measured via rotational rheometry for concentrated solutions of racemic mixtures of poly(benzyl‐L‐glutamate) and poly(benzyl‐D‐glutamate) in m‐cresol. A transition from the isotropic state to liquid–crystalline order with increase in concentration was indicated by optical anisotropy and maxima in all four material functions. This occurred at a critical concentration higher than the Flory prediction. Over a well‐defined range of concentrations and shear stresses, some of the liquid–crystalline solutions exhibited negative first normal‐stress differences that were not due to inertial effects.
Reactive copolymers of N‐(2‐hydroxypropyl) methacrylamide with N‐methacryloylated derivatives of l‐leucine and l‐phenylalanine. II. Reaction with the polymeric amine and stability of cross‐links towards chymotrypsin in vitro
Authors: Kopeček J. , Rejmanová P. 
Published: June 2010

AbstractPolymeric amine (Ia) was prepared by reacting a copolymer of N‐(2‐hydroxypropyl) methacrylamide (HPMA) and N‐methacryloyl ρ‐aminocaproyl L‐leucine p‐nitrophenyl ester with 1,6‐diaminohexane in excess. The rate of reaction of (Ia) with reactive copolymers of HPMA and p‐nitrophenyl esters of methacryloylated amino acids was investigated. The results indicate that interpenetration of polymeric coils occurs in dimethylsulfoxide solution!
.A study of the stability of cross‐links towards chymotrypsin in vitro showed that in addition to steric factors, subsite interactions between substrate and chymotrypsin must also be borne in mind. An aimed synthesis of crosslinks allowing such interactions leads to an increase in the enzymatic degradability of the polymers studied.
Preparation of polymerizable derivatives of N‐(4‐aminobenzenesulfonyl)‐n′‐butylurea
Authors: Obereigner B. , Burešová M. , Vrána A. , Kopeček J. 
Published: June 2010

AbstractPolymerizable derivatives of an antidiabetic N‐(4‐aminobenzenesulfonyl)‐N′‐butylurea were prepared. Hypoglycemic effects of sodium salts of the starting drug, the monomers, and their copolymers with N‐(2‐hydroxypropyl) methacrylamide were investigated.
The specificity of polymer degradation in the living body
Authors: Moiseev Yu. V. , Daurova T. T. , Voronkova O. S. , Gumargalieva K. Z. , Privalova L. G. 
Published: June 2010

AbstractThis paper is concerned with studying the macrokinetic specificities of biodegradation in vivo of some polymer materials (polyesters, polycaproamid) usually used in the medical practice. We observed the change of the structure, mechanical properties, and mass with respect to implantation time. The equations relating the change of these parameters with time have also been found.
Physicochemical aspects of the blood compatibility of polymeric surfaces
Authors: Bruck Stephen D. 
Published: June 2010

AbstractThe hypothesis is advanced that electrical conduction and semiconduction properties of some natural biopolymers and synthetic polymers may have a relationship to blood compatibility. Newly developed impervious, thin carbon coatings perform best biologically when deposited on smooth polymeric and nonpolymeric surfaces. The biological performance of grafted polyacrylamide hydrogels is influenced by both substrate and hydrodynamic effects which may be more dominant in blood compatibility than surface energy forces. Although the latter are undoubtedly involved in bioadhesion, their contributions do not correlate well with the overall biological performance of synthetic materials. Species‐related hematological differences of experimental animals, particularly calves, dogs, and primates, significantly influence the biological performance of materials which must be considered in the human application of medical devices in which biomaterials are in contact with blood.
Adsorbed layers of albumin and fibrinogen on polystyrene, probed by contact angle measurements
Authors: Van Der Scheer A. , Bargeman D. , Koetsier H. G. , Smolders C. A. 
Published: June 2010

AbstractEarlier measurements of paraffin oil (PO)–water contact angles on protein layers [human serum albumin (HSA) or human fibrinogen (HFb)] adsorbed on polystyrene (PS) showed that HSA could be transferred from the PS/water to the PO/water interface by a passing PO–water front, while HFb could not. Interfacial association of adsorbed HFb molecules was adopted as an explanation for the irreversible localization of HFb at the PS surface. In the present work it is shown that aggregation by a heat treatment of adsorbed HSA molecules also causes an irreversible localization of the HSA at the PS surface. It is shown that advancing and receding PO–water contact angles on HSA‐coated PS substrates have practically the same value. Variation of pH and NaCl concentration hardly shows any effect on these contact angles, indicating that in all cases the HSA coating behaves the same. The advancing and receding PO–water contact angles on HFb‐coated substrates differ greatly. In analogy with El‐Shimi and Goddard we conclude that the natural HFb coating is able to adopt and retain a configuration compatible with the immediate environment.
Radiation‐induced modification of polyurethane‐elastomers with hydroxyethyl methacrylate
Authors: Jansen B. , Ellinghorst G. 
Published: June 2010

AbstractThe hydrophilic grafting of a special polyurethane, Tuftane 410 (B.F. Goodrich), with hydroxyethyl methacrylate (HEMA) using 60 Co γ irradiation was described. The grafting was performed by the preswelling technique. The influence of swelling degree in HEMA and irradiation time at constant dose on the grafting yield was investigated. Viscosity and gel fraction of the grafted samples were determined. The swelling of the modified films in water was followed. The penetration depth of the poly‐HEMA graft into the Tuftane matrix was investigated by using sorption kinetics and studies on dyed microtome cuts. From these results a model for the grafting process was derived.
The nature of active centers and mechanism of cyclo‐olefin polymerization and olefin metathesis
Authors: Dolgoplosk B. A. 
Published: June 2010

AbstractExperimental data have been obtained evidencing the chain character of cyclo‐olefin ring‐opening polymerization and the carbene nature of the active centers in this reaction. The formation of metal–carbene complexes via the decomposition of organometallic derivatives of tungsten, molybdenum, and tantalum has been investigated. The mechanism of the chain propagation in cycloolefin polymerization and olefin metathesis as well as the mechanism of cyclodestruction of unsaturated polymers are discussed. The possibility of the inhibition of the chain metathesis process by carbene complexes more stable than active centers of the growing chain is shown.
Vinyl polymerization. CCCLXXVIII. Radical polymerization of methyl methacrylate with starch in aqueous solution of CU(II) ion
Authors: Imoto M. , Morita E. , Ouchi T. 
Published: June 2010

AbstractThe polymerization of methyl methacrylate(MMA) initiated with starch dissolved in water was carried out in the presence of Cu(II) ion. It was concluded that the polymerization proceeded in the water phase, particularly in the hydrophobic areas (or micelles) formed by the starch. The initiation mechanism was discussed. The formation of a complex of Cu(II) ion with starch and water was confirmed by the measurements of electric conductance and difference spectrum of the starch solution in the presence of CuCl2.
Affinity chromatography of human lymphocytes on spheron‐immunoadsorbent columns
Authors: Tlaskalová‐Hogenová H. , Čoupek J. , Pospíšil M. , Tučková L. , Kamínková J. , Mančal P. 
Published: June 2010

AbstractThe hydroxyethyl‐methacrylate Spheron‐gel activated by cyanogen bromide was used for the binding of anti‐immunoglobulin antibody. Anti‐immunoglobulin columns were used for separation of human T and B cells. Depletion of surface immunoglobulin‐positive B lymphocytes from human peripheral blood or tonsils by filtration through anti‐immunoglobulin‐Spheron column was very effective; the purity of obtained T cells being more than 90%, i.e., slightly higher than those of the nylon‐wool‐column purified lymphocytes.
Liquid chromatography of aromatic compounds on monolayers of polyethylene glycol
Authors: Chuduk N. A. , Eltekov Yu. A. 
Published: June 2010

AbstractLiquid chromatography of anisol and benzaldehyde on macroporous silica (Silochrom C80) with an hydroxylated surface (SC) and a surface covered with polyethylene glycol (SCP) is studied. The influence of the chemical properties of the adsorbent surface in the process of adsorption from solutions and of the parameters of liquid adsorption chromatography on the peak shape, retention time, and separation efficiency are shown. Adsorption isotherms calculated from the liquid chromatographic data are compared with the static adsorption data. These isotherms coincide for anisol interacting with either SC or SCP surface: in the case of interaction of benzaldehyde with the SC surface, the chromatographic adsorption values are lower than those estimated from the static data, probably as a result of a slow adsorption kinetics.
TLC experiments elucidating conformation of macromolecules under conditions of adsorption chromatography
Authors: Glöckner G. 
Published: June 2010

AbstractSeveral different polymers were chromatographed with binary developers on silica. The solvent strength of compositions leading to Rf ≈ 0.7 agrees fairly well with conclusions from adsorption theory. It is assumed that, in adsorption chromatography, migration of polymers depends on a definite balance of adsorption power. Macromolecules migrating in adsorption TLC are attached to the adsorbent by a few groups only. The conformation is not changed to such an extent as in the case of static adsorption.
Influence of zncl2 on the bulk polymerization of methyl acrylate, methyl methacrylate, and methyl‐2‐chloroacrylate studied by differential scanning calorimetry
Authors: Malavašič T. , Vizovišek I. , Osredkar U. , Anžur I. 
Published: June 2010

AbstractCourse and kinetics of the isothermal bulk polymerization of methyl acrylate, methyl methacrylate, and methyl‐2‐chloroacrylate at different temperatures were studied by differential scanning calorimetry. The initiator used was 2,2′‐azoisobutyronitrile. The polymerization was investigated without or in the presence of ZnCl2. The course of reactions, the heat of polymerization, the specific constants of polymerization rate, and the activation energy were determined.
Studies on adsorption of poly(vinyl butyral) and dispersibility of γ‐fe2o3 in magnetic paints
Authors: Nakamae Katsuhiko , Sumiya Kenji , Taii Toshiaki , Matsumoto Tsunetaka 
Published: June 2010

AbstractThe adsorption of poly(vinyl butyral) (PVB) at the γ‐Fe2O3–benzene interface and the air–water interface was investigated by means of the adsorbance on γ‐Fe2O3 and surface pressure (π)–area (A) curves. The adsorption isotherms of PVB on γ‐Fe2O3 from the various solvents are of the Langmuir type and can be explained by competitive adsorption between PVB and the solvents. From the π–A curves of monolayers and the adsorbance on γ‐Fe2O3, it was confirmed that the adsorbed PVB on γ‐Fe2O3 is in a train‐loop conformation with the hydroxyl groups and the butyral segments directed toward the solution phase. The packing density of γ‐Fe2O3, particles in the magnetic coatings preferentially depends on the conformation of polymers on the particle surface. The PVB–solvent system which gives the most compact train‐loop conformation gives the highest dispersion and packing of γ‐Fe2O3 in the magnetic coatings.
The transitions and melting behavior of thermally crystallized poly(ethylene terephthalate) and their correlations with ftir and density measurements
Authors: Lin Shaow‐Burn , Koenig Jack L. 
Published: June 2010

AbstractThe transitions and melting behavior of thermally crystallized poly(ethylene terephthalate) (PET) are studied using a computerized differential scanning calorimeter (DSC). A transition occurs from a structural stage characterized by a strong glass transition and an exothermic crystallization peak to a stage with a barely perceptible glass transition and an endothermic low melting (LM) peak in the DSC thermograms. This transition corresponds to the change from the primary to secondary crystallization process of PET. The exothermic crystallization peak is only observed within the primary crystallization stage. The maximum temperature of the LM peak is a function of annealing temperature and time, and depends on the microstructure of the imperfectly formed crystallites. The high melting peak is the melting of crystallites of higher perfection and is influenced by the recrystallization process of the sample during the scan.
Stereoselective hydrolysis of amino acid esters by modified polyethylenimines: Effects of quaternization of polymer and of added surfactants
Authors: Kimura Yoshiharu , Nango Mamoru , Kuroki Nobuhiko , Ihara Yasuji , Klotz Irving M. 
Published: June 2010

AbstractQuaternized polyethylenimines exhibit viscosity behavior very similar to that of linear flexible polyelectrolytes and thus evidently swell in dilute salt solutions. This swelling is manifested also in the rate constants for the hydrolysis of chiral or achiral nitrophenyl esters catalyzed by these polymers. Stereoselective preference is exhibited in hydrolyses catalyzed by the quaternized polymers containing covalently linked l‐histidine moieties. Maximum stereoselectivity is manifested at polymer concentrations corresponding to nonswollen conformations. With added cetyltrimethylammonium bromide, the stereoselective preference of the catalyzing polymer can be reversed. A comparison of the effects of added anionic, nonionic, and cationic detergents shows decreases in rate for the first, no significant effect for the second, and substantial changes for the third, depending on the polymer and detergent concentrations. Cationic detergents of different chain lengths and structures show different effects reflecting largely their extent of binding by the polymer.
Estimating reactivity in free radical copolymerizations
Authors: Laurier G. C. , O'Driscoll K. F. , Reilly P. M. 
Published: June 2010

AbstractGiven good reactivity ratio data for free radical vinyl copolymerizations, the use of the Alfrey—Price Q—e scheme permits the assignment of reactivity parameter values for individual monomers and the prediction of unknown reactivity ratios. A new, statistically based method has been developed and tested on a set of 11 monomers to estimate Q–e values for those monomers. The results of these estimates suggest that if care is exercised in the selection of monomer pairs for use in Q–e determinations, the Q–e scheme is quite reliable for reactivity ratio prediction on many monomer pairs.
Polycondensation of carboxylic acids and carbinols in aqueous emulsion
Authors: Baile Madhu , Chou Yungnien J. , Saam John C. 
Published: June 2010

AbstractWater‐insoluble diols and dicarboxylic acids condense to polyesters in aqueous emulsion under relatively mild conditions in the presence of sulfonic acids. Azelaic acid and 1,10‐decanediol give conversions to polymer of 50% and 75%. Molecular weights range between 1500 and 3000. The best catalysts are sulfuric acid or the sulfonic acid surfactants. Water soluble monomers give little or no increase in molecular weight. Estimates based on equilibrium constants for a typical esterification, and the observed molecular weights indicate that only minute amounts of water can be present at the site of reaction. It is suggested that the process might be related at least in some aspects to the condensation polymerization of silanol‐ended polydimethylsiloxane oligomers in emulsion [1].
Turner alfrey and hollow‐fiber membrane technology
Authors: Davis T. E. , Heitz R. G. 
Published: June 2010

AbstractMembranes in the form of hollow fibers are increasingly being used for processes such as desalination, hemodialysis, and recovery of various gases. Turner Alfrey played a crucial role in the birth of this new technology: (1) He selected and taught the necessary fundamentals of polymer science to the researchers trying to make this new idea work. (2) He actively encouraged the researchers and their financial supporters by his clear understanding of the soundness and the potential of this new engineering tool. (3) He even demonstated how to tailor the properties of a polymer to the task at hand by his own elegant laboratory experiments.
Mechanism of emulsion polymerization
Authors: Vanderhoff John W. 
Published: June 2010

AbstractBoth conventional and inverse emulsion polymerization comprise the emulsification of an immiscible monomer in a continuous medium followed by polymerization with a free radical initiator to give a colloidal sol of polymer particles. Both processes give “emulsion polymerization kinetics,” i.e., a proportionality of both the polymerization rate and polymer molecular weight to the number of particles instead of the inverse relationship between rate and molecular weight observed for mass, solution, and suspension polymerization. The emulsion polymerization process can be divided into particle nucleation and particle growth stages and can be carried out using batch, semicontinuous, or continuous processes. Seeded emulsion polymerization can be used to avoid the particle nucleation stage in all three processes. The many mechanisms proposed for the initiation of emulsion polymerization can be divided into four categories according to the locus of particle initiation: (i) monomer‐swollen micelles; (ii) adsorbed emulsifier layer; (iii) aqueous phase; (iv) monomer droplets. These general principles are applied to: (i) the preparation of monodisperse latexes by seeded emulsion polymerization; (ii) the locus of particle initiation for various monomers and initiators; (iii) emulsion copolymerization; (iv) core‐shell emulsion copolymerization; (v) polymerization in fine monomer droplets; (vi) inverse emulsion polymerization.
Preparation and application of monodisperse polymer particles
Authors: Ugelstad J. , Mfutakamba H. R. , Mørk P. C. , Ellingsen T. , Berge A. , Schmid R. , Holm L. , Jørgedal A. , Hansen F. K. , Nustad K. 
Published: June 2010

AbstractThe swelling capacity of aqueous dispersions of particles (or droplets) containing a relatively low molecular weight, highly water‐insoluble compound (Y) may be more than a thousand times higher than that of particles consisting of polymer only. The rate, and also the degree of swelling, may furthermore be increased by having the swelling substance, which usually is a low molecular weight, slightly water soluble substance, present in a finely dispersed form. A two‐step swelling process has been described. In a first step, relatively small monodisperse polymer particles are swollen with a component Y and then with monomer or monomer mixtures, followed by polymerization. The method allows preparation of highly monodisperse particles of more than 50 μm diameter with a standard deviation of less than 2%. The particles may be prepared as core and shell particles of different density and with various surface layers, or as macroporous particles. The new particles have found application as standards in immunoassays and, most important up to now, in liquid chromatography. An extension of the process allows the production of monodisperse magnetizable particles which have found application in cell separation of cancer cells from normal cells.
Dynamics of conformational transitions in polymers
Authors: Helfand Eugene 
Published: June 2010

AbstractA review is presented of research on several aspects of the dynamics of conformational transitions in polymers. Brownian dynamics computer simulations of polymer chains show that transitions occur frequently in a correlated fashion involving cranklike counterrotation of two parallel bonds. Theoretical analysis brings out the importance of such counterrotations in creating a localized mode by which the transition can proceed without excessive motion of the whole molecule. The correlated motions are reflected in time correlation functions, which take on a character reflecting diffusion of the information about the initial state. Finally, several experiments are cited that can be explained on the basis of this picture of the mechanism of con formation a! transitions.