bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrodynamic properties of complexes of polymethacrylic acid‐polyvinylpyrroli‐done in solutions
Authors: Bimendina L. A. , Roganov V. V. , Bekturov E. A. 
Published: June 2010

AbstractThe intrinsic viscosities and sedimentation constants of polymethacrylic acid‐poly‐vinylpyrrolidone (PMAA‐PVP) mixtures have been measured in water and dimethylsulf‐oxide. By conductometric method it has been shown that the composition of those complexes is stoichiometric.The value of intrinsic viscosity of the complexes in water is about 0.10 dl/g which is close to the viscosity of globular proteins. This value seems to be almost independent of the concentration and molecular weight of the macromolecular components of the complex (both PMAA and PVP have been used as an oligomer and as an matrix), and in the case of high molecular weight of both the components as well.In an organic solvent a sharp increase of intrinsic viscosity is observed. This is probably connected with the weakening of hydrophobic bonds stabilizing the compact structure of complex in water. In dimethylsulfoxide reduced viscosity depends on concentration and intrinsic viscosity on the molecular weight of the matrix (PMAA). The values of hydrodynamic‐average molecular weights of complexes establish the intermolecular association of complexes particles in water, and the degree of association depending on the molecular weight of the matrix. In dimethylsulfoxide probably not only the weakening of hydrophobic interactions but the destruction of hydrogen bonds occurs, following which the dissolution of the complexes takes places. In water‐dimethylsulfoxide mixtures a gradual destruction of the complex is observed at the transition from water to organic solvent.
The mechanism of formation of polymer particles during turbidimetric titration of polymer solutions
Authors: Klenin V. J. , Shchyogolev S. Yu. , Fein E. G. 
Published: June 2010

AbstractStages of formation in the structure of precipitated polymer phase have been found by the method of spectroturbidimetric titration (STT) during precipitation titration of a number of polymer systems. In the first stages of formation of polymer particles, a sharp decrease was observed in the particle size, rCλ, which may be related to a fall in large fluctuations in the postcritical region if the transition of the system through the binodal curve were to be identified with phase transition of the second kind. In the second stage, rλ remains constant at the minimal level, rλ = rλ(γ) = rλ 0 const. The extension of plateau rλ 0 in terms of γ depends on the polymer‐solvent‐precipitant system(P‐S‐P) and conditions of titration. The value of rλ 0 differs insignificantly for different systems, rλ 0 = 0.2–0.3 μm, which is possibly related to the existence of an optimum of particle size in colloid systems of this type. The third stage is determined by the process of particle coagulation, here the kinetics are subject to the equation of Smolukhowskii and the rate depends on the P‐S‐P system. A value of v was determined which appears to be antibate to the effectiveness of attractive forces produced between polymer particles and defines the coagulation process in a specific P‐S‐P system. General conditions for the preservation of particle size during titration were established. Under these conditions, however, an effective separation of fractions with respect to molecular weights can not be attained from the point of view of relaxation thermodynamics. These contradictions are minimized by the use of the STT method. It is shown that the coagulation of particles during turbidimetric titration by the conventional approach leads either to fallacious underestimation or overestimation of the polymolecularity of a polymer depending on the time of beginning of such coagulation, before or after complete precipitation of the polymer.
Temperature dependence of polystyrene Raman depolarization in cyclohexane, methyl ethyl ketone, and deuterobenzene solutions
Authors: Speak R. , Shepherd I. W. 
Published: June 2010

AbstractThe depolarization ratio ρ of the 1002 cm−1 band in polystyrene has been measured as a function of temperature (20 < T < 60°CC) in the solvents cyclohexane, methyl ethyl ketone, and deuterobenzene. The largest changes in ρ were observed in the poorest solvent, cyclohexane and no changes were detectable in benzene. The ratio, 〈r2〉/n/2, measured in the same solvents over the same temperature range by conventional light scattering, is compared with the ρ data. The corresponding changes in rotational isomer population are calculated and the dependence of ρ on these populations is demonstrated.
Electric birefringence, conformation, and rigidity of the molecules of cellulose esters in solutions
Authors: Lavrenko P. N. , Rjumtsev E. I. , Shtennikova I. N. , Andreeva L. N. , Pogodina N. V. , Tsvetkov V. N. 
Published: June 2010

AbstractElectro‐optical properties of solutions of several cellulose esters in dioxane have been investigated. It was shown that macromolecules of these esters are characterized by high equilibrium and kinetic chain rigidity. The coincidence in signs of the Kerr and Maxwell effects in solutions of the samples reveals general relationships exhibited by all rigid‐chain polymers for which the longitudinal geometric axis of the molecule (direction of the greater geometric length) is also the symmetry axis of its polar and optical properties.Experimentally found dependences of hydrodynamic and electro‐optical properties of solutions of cellulose carbanilate (CC) on molecular weight (Mw) show that with the increase in Mw the conformation of the CC molecules varies from a faintly curved rod to a rigid Gaussian coil. A study on the dependence of the equilibrium constant of the Kerr effect on Mw leads to the same conclusion. Besides, in Gaussian region (high Mw) the Kerr effect depends on the longitudinal (with respect to the chain) component of the dipole moment formed by the C‐O bonds making a part of the glucoside ring. At low M the transverse components of the monomer dipoles begin to play an important part in birefringence.
The effect of copolymers of 4(5)‐vinylimidazole and quaternary imidazolium salts on the hydrolysis rates of charged and neutral esters. I
Authors: Overberger C. G. , Pacansky T. J. 
Published: June 2010

AbstractCooperative and electrostatic effects were investigated for the hydrolysis of charged and neutral substrates catalyzed by a copolymer containing pendant nucleophiles (imidazole groups) and permanent positive charges (quaternary imidazolium halides). Limited evidence was also presented for apolar bonding in the hydrolysis of long chain anionic substrates catalyzed by a copolymer of 4 (5)‐vinylimidazole and 2, 3‐dimethyl‐1‐vinylimidazolium iodide (plm + C1+I−).
Polymerization of vinylpyridinium salts. VII. Formation of high molecular weight polyvinylpyridinium salts by spontaneous polymerization
Authors: Salamone J. C. , Ellis E. J. , Bardoliwalla D. F. 
Published: June 2010

AbstractIn this work are discussed the reactions of 2‐vinylpyridine and 2‐methyl‐5‐vinylpyridine with dilute and concentrated acid solutions. In reactions with dilute acid, the concept of pyridyl‐ethylation leading to initiation of polymerization was studied for both monomers. Although this reaction was applicable for 2‐vinylpyridinium salts, it apparently did not occur with 2‐methyl‐5‐vinylpyridinium salts. In reactions with concentrated acid, both monomers have been found to polymerize spontaneously to high molecular weight polymers. In addition, an analysis of the neutralized polymers by gel permeation chromatography (GPC) has shown them to be of narrow molecular weight distribution. An investigation of the effect of air or oxygen on these reactions has shown that they do not significantly alter the resulting molecular weights or molecular weight distributions that can be obtained. From a study of the percent conversion versus time, the data obtained indicated that these spontaneous polymerization reactions are chain‐growth processes.
Viscoelastic behavior of styrene/n‐butyl‐methacrylate/potassium methacrylate polymers
Authors: Erhardt Peter F. , O'Reilly James M. , Richards W. Conrad , Williams Meurig W. 
Published: June 2010

AbstractThis study concerns the ion containing terpolymers of styrene, n‐butylmethacrylate, and potassium methacrylate (S/n‐BMA/K+MA−) produced by the partial hydrolysis of random S/n‐BMA copolymers. The extent of hydrolysis resulted in terpolymers having 1 to 5 mol % potassium ions. The introduction of ionic sites produces labile crosslinks in these low‐molecular weight amorphous polymers which are reflected in many of the physical properties. The effects of temperature, shear rate, and shear stress on steady state and dynamic rheological properties are examined as functions of molecular parameters (ion content, S/n‐BMA composition, and molecular weight). The dependence of viscosity on composition and molecular weight are complicated by the occurrence of molecular entanglements at lower molecular weights as the proportion of n‐BMA is increased. It is found that the Newtonian viscosity, at constant T‐Tg, varies exponentially with the molar ion content. The rate of log viscosity increase with molar ion content varies as the inverse molecular weight of the S/n‐BMA copolymers in the region of molecular weights studied. At ion contents above about 4 mol % potassium ions, the system is rheologically complex. The viscosity exhibits different shear dependence in steady state and in oscillatory response, and the temperature dependence of the shift factor log aT changes abruptly. These have generally been taken to indicate some degree of ion clustering, although no direct evidence for the existence of clusters by low angle x‐ray studies has so far been observed in these materials.
Crystallization of poly‐(ethylene coacrylic acids) and poly(ethylene comethacrylic acids) and their salts
Authors: Macknight W. J. , Taggart W. P. , McKenna L. 
Published: June 2010

AbstractA study of the crystallization behavior of poly(ethylene coacrylic acids) and poly‐(ethylene comethacrylic acids) and their lithium, sodium, calcium, and cesium salts has been made utilizing the techniques of X‐ray diffraction, differential scanning calorimetry, and infrared spectroscopy. The acid substituent content ranged from 2.1 to 6.3 mol %. The results indicate that the acid substituents do not incorporate into the polyethylene crystal lattice and that these substituents have large effects on the kinetics of crystallization, especially in the case of the salts. The results are interpreted on the basis of a three‐phase model consisting of a polyethylene crystal phase, a mixed amorphous phase, and a micro‐phase‐separated ionic cluster phase.
Modulus of tightly crosslinked polymers related to concentration and length of chains
Authors: Smith Thor L. 
Published: June 2010

AbstractThe equilibrium shear modulus G of network polymers increases rapidly with the chain concentration ν when ν ≳ 10−3 mol/cm3. This behavior is accounted for by the equation G=ΦnνRTΓ(1/λm) where Φn(=r̄t2/r̄00) may depend on n̄, the mean number of backbone bonds per chain, and Γ(1/λm) is a function of 1/λm, the mean fractional extension of chains in the isotropic (undeformed) network. In turn, 1/λm=(ΦnC̄n/q2n̄)1/2, where C̄n is a characteristic ratio (= r̄02/n/2) which, for short chains, depends on n̄, and q is a constant determined by bond angles and lengths. An expression for Γ, suggested by a well known equation for a regular cubic network of freely jointed volumeless chains, is derived and then shown to be approximated closely by Γapp=5λ/(5λ‐6) for 1/λm < 0.88. The moduli of some 26 ethyl acrylate‐dimethacrylate networks, for which 5 < n̄ < 23 and 2 × 107 < G < 5 × 109 dyn/cm2, were represented by the equation through use of effective parameters, Φef and Cef, which are independent of n̄. When C̄n is allowed to vary realistically with n̄, the equation also represents G. It then is found that Φn = 0.50 ± 0.05 when n̄ > 9.6, but that Φn increases twofold with decreasing n̄ when n̄ < 9.6. This variation is consistent with the assumption that the volume pervaded by the chains joined at a junction cannot be occupied by other chains.
Isothermal transitions of a thermosetting system
Authors: Gillham J. K. , Benci J. A. , Noshay A. 
Published: June 2010

AbstractA study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures. These are Tg∞ (the maximum glass transition temperature of the thermoset system) and Tgg (the glass transition temperature of the material at its gel point). Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur: if Tcure > Tg∞, only gelation is observed; if Tg∞ > Tcure > Tgg, both gelation and vitrification are observed; if Tcure < Tgg, only vitrification is observed. Tgg corresponds to the isothermal cure temperature at which gelation and vitrification occur simultaneously. Methods for determining the time to gel and the time to vitrify, and also Tg∞ and Tgg, have been developed. The time to gel obeyed the Arrhenius relationship; the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of Tg∞ and Tgg.
Preparation of poly (4‐vinylpyridine borane) and its action as polymeric reducing reagent
Authors: Hallensleben Manfred L. 
Published: June 2010

AbstractLinear and cross‐linked copolymers of 4‐vinylpyridine borane (4VP·BH3) with 4‐vinyl‐pyridine (4VP) and with styrene were prepared and used as polymeric reducing reagents towards various aldehydes and ketones. The monomer 4VP·BH3 could only be obtained in a mixture with 4VP, from which the IR data are submitted.
Synthesis properties and matrix binding of fe‐porphyrins containing isocyanate side‐chains
Authors: Kühn M. , Pommerening K. , Müller H. G. , Mohr P. 
Published: June 2010

AbstractFixation of the prosthetic groups of hemoproteids on synthetic macromolecular carriers is important from the viewpoint of biocatalytic investigations.Fe‐porphyrins which contained isocyanate sidechains have been prepared by two methods. This isocyanate reacted in pyridine as the solvent at room temperature with cross‐linked poly(2‐hydroxyethylmethacrylate) and with Sephadex LH 20, a hydroxypropyl group containing a carrier.The identity of the new Fe‐porphyrin derivatives and coupling products with synthetic carriers could be ascertained by elementary analysis and by absorption spectroscopy in the visible and infrared region.The properties of mesohemin IX are retained after covalent binding to the carriers. At near neutral pH, a spectrum typical of alkaline hematin (parahematin) occurred. At pH 1.6, the spectrum of acidic hematin appears. The ligand binding ability to CN− and imidazole has been retained. The reduction of the Fe(III) with sodium dithionite is possible. The coupling products show peroxidatic activity.
Ion exchangers. XIX. Some properties of the carboxylic cation exchangers obtained by intermesh polymerization of methacrylic acid into styrene and divinylbenzene porous copolymers
Authors: Kolarz Bozena N. 
Published: June 2010

AbstractModification parameters of porous styrene and divinylbenzene (DVB) copolymers modified with methacrylic acid have been investigated using nonlinear optimization techniques. As the basic criterion of the investigation, the exchange capacity of carboxylic cation exchangers has been taken. The impregnation ratio of modifying mixture (1.4 cm3/g of the copolymer) was kept constant. Optimum parameters were found to be as follows: DVB concentration—1.5 % by weight (related to monomers); inert diluent (n‐heptane) concentration—13.3% by volume; temperature—95°C; time—90min, and benzoyl peroxide—2 g/100g of the modifying mixture.Porous copolymers of styrene with the varying amount of DVB (x = 3–17.4%) were modified under these optimal conditions. A constant degree of modification of about 120% was obtained by keeping the constant independent of the swelling of the copolymer, by impregnation, and, thus a similar exchange capacity of the cation exchangers of about 6 meq/g of resin has been reached.Some characteristic properties of six carboxlic cation exchangers as a function of the degree of cross‐linking in the starting porous copolymers were investigated: fractional attainment of equilibium of the exchange H+/Na+ and Na+/MB (methylene blue); exchange half‐time; internal diffusion coefficient; apparent equivalent volume; separation factor of the exchange Na+/Cu2+; porosity; and distribution pore volume.The following suggestions on the mechanism of modification of porous copolymers can be proposed. The modified copolymers which have a high and medium degree of cross‐linking and little swelling have undergone a filling of pores, while a decrease in cross‐linking and an increase in the swelling ability results in two parallel tendencies. The first is filling of pores connected with a simultaneous penetration into the net. In this way, porous (double porous or hybrid) cation exchangers have been produced.
Determination of chemical inhomogeneity of transformation products of poly(vinyl chloride) by extraction of film from aluminium foil
Authors: Hace D. , Vurdelja V. 
Published: June 2010

AbstractThe chemical transformation of poly (vinyl chloride) with toluene in 1, 2‐dichloro‐ethane as solvent has been carried out in the presence of aluminium bromide. A series of copolymer products of certain degrees of transformation has been prepared. The chemical and molecular inhomogeneity has been qualitatively investigated.The products have been fractionated by the Fuchs extraction method and refractionated by successive precipitation methods. The selective solvent systems have been predetermined. The benzene/methanol mixture is selective for the separation of aromatic fractions in copolymer products with low transformation degree. The fractions with noncyclisized aromatic units are separated with a methyl ethyl ketone/methanol mixture. Chloroform/methanol successfully selects aromatic fractions without vinyl chloride units in copolymer products of greater degree of transformation. The ratio of solvent/nonsolvent has been examined.The following fractions have been isolated: the fraction of unreacted homopolymer PVC, the fraction with p‐methylstyrene units in chain, and the fraction of random copolymer with differences in the ratio of vinyl chloride, p‐methylstyrene, and 5‐methyl‐1, 3‐dimethyleneindan units. Characterization of the products and their fractions has been done on the basis of IR spectra, chlorine content, intrinsic viscosity, and x‐ray diffraction results. Analysis of IR spectra for PVC of low transformation degree in th region of C‐Cl stretching vibrations indicates the presence of changes. The inclusion of coloured crystalline complexes of C6H5CH3‐Al2Br6‐HCl intermediate from the reaction, which is incorporated into the copolymer, has been noticed.
Effect of the polymer matrix structure of reticular poly(vinylpyridines) on their electron‐donor properties
Authors: Saldadze K. M. , Kopzlova V. D. , Kargman V. A. , Gali‐Tskaya N. B. 
Published: June 2010

AbstractThe effect of the polymeric matrix structure on the acidic‐base, coordination, and kinetic properties of reticular poly (vinylpyridines) (RPVPs) obtained by copolymerization of 4‐vinylpyridine (AH‐40) and 2‐methyl‐5‐vinylpyridine (AH‐25) with divinyl aromatic compounds has been investigated by potentiometric as well as by IR and EPR spectroscopic methods.The increase in the content of the crosslinking agent results in a lower pKa of RPVP and in reduced stability constants of their complexes with transient metal ions; therefore, the defectiveness of the coordination centers is increased.The nature of the crosslinking agent determines the flexibility of the polymeric matrix and the availability of electron‐donor groups in them affects the structure of the average statistical coordination center, thus bringing about a change in the RPVP electron‐donor properties and in the stability constant of the polymeric complex.
Thermodynamic and hydrodynamic properties of polyelectrolytes
Authors: Nagasawa Mitsuru 
Published: June 2010

AbstractAn outline of thermodynamic and hydrodynamic properties of polyelectrolytes in solution is given. It is pointed out that proper models should be adopted to explain those properties. A polyion is often assumed to be a rigid rod having smeared charges on its surface for analyzing thermodynamic properties. The electrostatic potential distribution around rod‐like polyions, which may be calculated from the Poisson‐Boltzmann equation, can be tested by comparison with potentiometric titration data of poly(weak acids). Features of the counterion‐binding concept in analyzing thermodynamic properties are explained.It is pointed out that the radius of gyration is important for analyzing hydrodynamic properties. Features of sedimentation, diffusion, and electrophoresis are explained and compared with each other. Discussion on the expansion factor of the polyion in the presence of added salt is also given in comparison with the theories published. Finally, a characteristic polymer concentration dependence of reduced viscosity, diffusion coefficient, and osmotic pressure coefficient of polyelectrolytes in pure aqueous solutions is explained.
Gel chromatography studies of gelatin
Authors: Coopes I. H. 
Published: June 2010

AbstractGel chromatography studies of a series of gelatins and dextrans on Sepharose 4B substrates are described. The intrinsic viscosities and weight average molecular weights of the gelatin samples are also measured. A plot of mean partition coefficients versus log (M>W[η]) is found to be linear for the dextrans, but not for the gelatins, in 0.1 M urea. In 0.1 M urea/0.1 M NaCl solution, the gelatins behaved more reproducibly.The molecular weight distributions of the various gelatins, as delineated by the gel chromatography data, are considered in relation to manufacturing processes and physical properties.
Applications of thermal analysis to polymers
Authors: Loft B. C. 
Published: June 2010

AbstractThe term “thermal analysis” now refers to a set of techniques which measure the response of a specimen to a linearly varying temperature. They are versatile techniques with particular value for polymer science. The applications of the various thermoanalytical methods to the study of fusion, crystallization, glass transition, thermal degradation, oxidation, and crosslinking reactions and the use of the results in polymer science and technology are discussed.
Polymerization kinetics of N–vinyl pyrrolidone
Authors: Senogles E. , Thomas R. 
Published: June 2010

AbstractPolymerization rates of N‐vinyl pyrrolidone and corresponding activation energies depend on the nature of the polymerization solvent. This is mainly due to the influence of solvent polarity on the propagation reaction. The dependence of the termination rate on the viscosity of the polymerization medium has a relatively minor effect.