bluuebunny/crossref_metadata_2025 huggingface dataset:
The gaussian chain in the theory of rubber elasticity
Authors: Staverman A. J.
Published: June 2010

The importance of the conception of the kinetic theory of rubber elasticity is comparable to that of the kinetic theory of gases. In the theory of rubber elasticity the concept of the Gaussian chain is comparable to that of the Maxwell distribution in a gas. However, whereas the theory of gases has been refined in successive approximations to a coherent set of equations relating meaurable macroscopic properties to the field of force between the molecules and thus allowing the collection of detailed information on molecular forces, no similar progress has been made in the theory of rubber elasticity since its conception 40 years ago. The molecular forces appear in the theory of the Gaussian chain in the quantity r02, the mean square end‐to‐end distance of the “free” chain. In a bulk rubber and also in a swollen rubber this quantity depends on intra‐ and intermolecular forces. If the definition of a Gaussian chain is a chain in which magnified image is independent of r (F(r) being the free energy of the chain with fixed end‐to‐end distance r), then the observation of the Rivlin‐Mooney term in measurements of rubber elasticity appears to be incompatible with the assumption of Gaussian chains. Starting from James's theory of networks of Gaussian chains, it is shown that the Rivlin‐Mooney term can be explained by assuming that the chains are indeed Gaussian, but that r02 depends on the internal pressure pi. However, in order to explain what was observed, the effect of pi on r02 should be much larger than one expected, and hence additional effects are needed to explain the behavior. The additional effects can consist of higher terms in the development of r02 with respect to pi and also in anisotropic terms giving rise to differences between the 3 components of r02 in a nonisotropic stress field. In order to answer the question whether Gaussian chains exist at all in rubber much more experimental information on deformation under different pressures and stress tensors should be available. By ignoring the effect of pressure on r02 one can derive equations between measurable quantities from which r02 is eliminated. These equations should be considered unfounded since already a small effect of pressure in r02 will invalidate them. In the introduction it is shown, in accordance with an earlier conclusion of Lodge, that James's theory of networks of Gaussian chains predicts isotropic elastic behavior of the network, irrespective of any anisotropy of the topology of the network. It is also shown that the expression for the elastic free energy is insensitive to the choice of the junctions and of the chains between junctions.
Recent advances in man‐made fibers
Authors: Magat E. E. , Morrison R. E.
Published: June 2010

Advances in man‐made fiber technology are reviewed. The two main topics are second‐generation fibers and specialty fibers. Chemical or physical modification of polymers or fibers through additives or alteration of polymer backbone has led to a variety of second‐generation fibers. Incorporation of dye sites, antioxidants, antistatic and flameproof modifiers into fibers are discussed. Specialty fibers engineered to meet specific market needs are described. These include heat‐ and flame‐resistant fibers, reinforcing fibers and low‐density pneumatic‐cellular fibers. Energy consumption in the preparation and use of polyester garments is compared to that of corresponding cotton garments. The outlook for continued growth and advances in man‐made fibers continues to be highly promising.
Anionic polymerization mechanism of n‐carboxy‐α‐amino acid anhydrides
Authors: Sekiguchi Hikaru , Froyerd̊ Gerard
Published: June 2010

The anionic polymerization mechanism of N‐carboxy‐α‐amino acid anhydrides (NCAs) is studied. Polymerization of α‐aminoisobutyric acid NCA in the presence of triethylamine as catalyst is fairly accelerated by addition of ring amide compounds, namely 2‐oxazolidone and 3‐methyl hydantoin. Similar effects are noted when N‐acetyl derivatives of such compounds are used. This observation corroborates the usual hypothesis which presumes a N‐acylated NCA ring structure for the growing chain end.

By comparing this polymerization with that of lactams, one reveals some common features as well as differences between these two reactions. Theoretical considerations supported by some experimental data lead us to assume two hypotheses in interpreting the anionic polymerization of NCAs: first, the 2‐carbonyl group is the most electrophilic of the three carbonyls present at the active site of chain growth, and second, the NCA anion has a pronounced oxanionic character.

Thus, the anionic polymerization mechanism of NCAs we propose, involves attack of the 2‐carbonyl group of the terminal ring unit by NCA oxanion. In the resulting reaction intermediate, the attacking unit then swings to the 5‐carbonyl through a series of electron transfers by mesomerism, helped by the release of carbon dioxide after the neutralization of the ionic charge of the polymer chain.

This mechanism is an improved version of the “activated monomer” mechanism, and is based on the same principle as the latter. Thus, not only can our own results be explained without difficulty by this mechanism, but also the experimental facts presented in support of the conventional mechanism in the literature agree with it.
Etude De La Reticulation Thermoreversible De Copolymeres Porteurs De Fonctions Anhydride
Authors: Decroix J. C. , Bouvier J. M. , Roussel R. , Nicco A. , Bruneau C. M.
Published: June 2010

Cette étude sur des copolymères ethylène‐anhydride maléique (EAM) modifiés par des réactifs polyalcools ou aminoalcools met en évidence par deux méthodes leur possibilité de réticulation par formation de liaisons ester: une méthode indirecte, par la variation de l'indice de fluidité en fonction de la température; et une méthode quantitative, par spectroscopie IR, permettant la détermination des paramètres thermodynamiques de l'équilibre de la réaction entre fonctions anhydride et fonctions alcool.
The role of microparacrystallites in polymer network
Authors: Hosemann R. , Loboda‐Čačkovič J.
Published: June 2010

A two‐dimensional analysis of the wide‐ and small‐angle x‐ray scattering (WAXS, SAXS) of well‐oriented polymers allows us to calculate some of the gik parameters of the paracrystalline superlattice that are built up by the centers of the microparacrystallites, which comprose the “crystalline phase.” The dependence of gik upon mechanical deformation, heat treatment, and graft copolymerization of the sample is explained by a three‐dimensional network of chain segments, which not only connect the “crystalline lamellae” of the two‐phase model, but also run through lateral grain boundaries of neighbored microparacrystallites within one “crystalline lamella.” These microparacrystals act, therefore, as special knots of the network. They generally have a much larger volume than the chemical crosslinks and instead of having one strong chemical bond there is a series of much weaker physical bonds, creating the single microparacrystallite. The importance of this model for “amorphous” polymers is also pointed out.
Collagen low angle diffraction patterns and crosslinking reactions
Authors: Bieńkiewicz K. J. , Bukowska‐Strzyźewska M.
Published: June 2010

Crosslinking reactions exert some influence on low‐angle diffractograms. In samples crosslinked with Cr (III) salts a significant shortening of the identity period was observed, as well as some changes in the intensity of particular reflexes. A similar, although less expressed change, was observed in the samples crosslinked with formaldehyde. This phenomenon is supposedly due to the easier penetration of the crosslinking agents into the nonpolar regions. The change in the intensity of the reflexes may be explained in the same way. A “fan effect” in the reflexes is due to the isolating effect of acetone in the course of dehydration. Identity subperiods are proposed, probably connected with charge distribution along the molecule.
Temperature dependence of elastic constants of rubbers
Authors: Shumskaya A. G. , Priss L. S. , Popov V. F.
Published: June 2010

On the specially designed dynamometer with automatic control of λ = constant condition at temperature alteration (λ is the extension ratio), there were studied the temperature dependence of stress, f, in uniaxial tension tests of butyl and butadiene‐acrylonitrile vulcanisates at various λ. Temperature coefficients of C2 constant in the Mooney‐Rivlin equation, calculated from these data, are represented reasonably well by the semiempirical formula (β is the bulk thermal expansion coefficient, T is the absolute temperature, To is the constant temperature), derived using molecular theory which revealed the origin of the C2 term and the empirical generalization of the dependence of C2 on swelling degree.

The published data on the temperature dependence of C2 and the methods of further experimental examination of conception suggested are discussed.
Photoelastic behavior of poly(methacrylamide) and poly(methacrylamide‐co‐2‐hydroxyethyl methacrylate) gels
Authors: Ilavský M. , Dušek K.
Published: June 2010

The photoelastic behavior of swollen gels prepared by the crosslinking copolymerization of methacrylamide (MA), or of MA and 2‐hydroxyethyl methacrylate (HEMA), with methylene bisacrylamide as the crosslinking agent was investigated in water and in aqueous solutions of urea and magnesium perchlorate. Stress and birefringence could be separated into a time‐ and deformation‐dependent part; in all cases the stress‐optical coefficient,Ce, was independent of time and deformation. The characteristic features of the photoelastic behavior may be summarized as follows: (1) Time dependences of stress and birefringence at constant deformation increase with increasing MA content in the copolymer and are not reduced to any considerable degree even by compounds which break the water structure; (2) The equilibrium modulus related to the dry stateGedincreases with increasing MA content owing to an increase in the Mooney–Rivlin constantC2; the increase in swelling due to an addition of urea or Mg(ClO4)2does not affectGedfor MA‐rich gels; (3)Cedecreases with increasing content of MA, increasing content of the crosslinking agent, and decreasing dilution during the polymerization; (4) Mg(ClO4)2and urea have only a small effect on the optical anisotropy of the statistical segment δα. The above results are interpreted by a decrease in the importance of correlation structures originating in hydrophobic interactions, and by the increase in the role of hydrogen bonds in the transition from poly‐HEMA to poly‐MA.
The dependence of dielectric properties on crosslinking density of rubbers
Authors: Bakule R. , Havránek A.
Published: June 2010

The dielectric properties of natural rubber, synthetic polyisoprene, and polybutadiene samples crosslinked with sulfur and of natural rubber samples crosslinked simultaneously with sulfur and dicumyl peroxide were studied. In the investigated systems, the number of polar groups in unit volume and the crosslinking density may be changed independently in relatively wide ranges. The measurements were performed in the frequency range from 101 to 105 Hz at various temperatures, and macroscopic parameters describing the dielectric properties of the samples were evaluated. The position and intensity of the dielectric dispersion peak in the main transition zone is only slightly dependent on the crosslinking density of the samples. These two values are mainly influenced by the amount of combined sulfur, or more generally, by the number and the dipole moments of polar groups in the sample. The influence of crosslinking density on the width of the absorption curve is very strong; the width increases with increasing crosslinking density. The possibility of explaining this effect in terms of the dependence of the free volume distribution function on crosslinking density is discussed.
Retardation spectra of various cross‐linked rubber systems
Authors: Havránek A. , Bakule R.
Published: June 2010

Retardation spectra of crosslinked natural rubber samples were obtained from creep measurements performed in the time range 10−2‐103 sec and in the temperature range 200–360°K. The samples were crosslinked only with sulfur, with sulfur in the presence of antioxidant and accelerators, and simultaneously, with sulfur and dicumyl peroxide. Thus, we have a set of samples with a wide range of crosslinking densities (v = 0.1 – 7 × 10−4 mole/cm3) in which the same crosslinking density may be obtained for samples with different sulfur content. The results of our measurements are as follows: The friction coefficient, standard reference temperature Ts and time position of the spectrum depend on sulfur content, and not on crosslinking density in the system natural rubber‐sulfur‐dicumyl peroxide. The addition of accelerators diminish the friction coefficients, decrease Ts temperatures, and shift the spectrum maxima to shorter times. The spectrum width depends on crosslinking density and not on sulfur content in the measured set of samples. The spectra of more crosslinked samples are narrower. These results are compared with the results of dielectric measurements performed on an analogous set of samples.
Kinetics of heat precipitation of proteins
Authors: Macritchie F.
Published: June 2010

The precipitation of lysozyme at 60°C in pH 9.2 buffer solution followed first‐order kinetics. The first‐order rate constants varied with initial protein concentration possibly due to nonpurity. Heat precipitation of bovine serum albumin (BSA) in pure water did not follow any simple rate law but in pH 5.8 buffer obeyed first‐order kinetics in the initial stages.

The extent of aggregation of BSA in the precipitate was followed by dissolving the precipitate in acid solution with subsequent characterization by gel‐permeation chromatography. Addition of small amounts of the sulfhydryl blocking agent, iodoacetamide (twelve times the concentration of protein on a molar basis), reduced the aggregation. Heat precipitation of proteins appears to be governed by the favorable entropy change when interactions between water molecules and nonpolar groups of the protein are decreased.
Polymer photostabilization by surface grafting
Authors: Burchill P. J. , Pinkerton D. M.
Published: June 2010

Various means by which photostabilization of polymers can be achieved are described, and work on a method of photostabilization by surface screening on a substrate polymer is presented. The surface screen is obtained by graft copolymerization of a polymerizable hydroxybenzophenone ultraviolet absorber. The results show that the application of this method to polypropylene and poly(vinyl chloride) is an effective stabilization treatment.
Photooxidation of polystyrene–the role of impurities as prodegradants
Authors: George G. A. , Hodgeman D. K. C.
Published: June 2010

The role of in‐chain peroxides and phenyl alkyl ketone end groups in the initiation of photooxidation of polystyrene is discussed. Using quantitative phosphorescence spectroscopy and viscometric methods, the photolysis and thermolysis of small amounts of in‐chain peroxides present in polystyrene prepared under different oxygen concentrations was investigated. It was shown that in‐chain peroxides are unlikely initiators of photooxidation in polystyrene prepared in high‐temperature commercial syntheses, but will act as the precursor of the photoinitiator, the phenyl alkyl ketone end group.
Radiation‐induced polymerization of vinyl and diene monomers in deoxycholic acid inclusion compounds
Authors: Miyata Mikiji , Takemoto Kiichi
Published: June 2010

A series of deoxycholic acid inclusion compounds with vinyl and diene monomers were prepared, and their radiation‐induced polymerization was studied. In the case of 2,3‐dimethyl‐and 2,3‐dichlorobutadienes, highly 1,4‐trans tactic polymers were obtained, while in the case of acrylonitrile, an atactic polymer resulted. Stability of the deoxycholic acid adducts as well as polymerization characteristics are described.
Novel sequential copolymers by elucidating the mechanism of initiation and termination of carbocationic polymerizations
Authors: Kennedy Joseph P.
Published: June 2010

Elucidation and understanding of the fundamentals of the initiation and termination of cationic olefin polymerization led to the control of these elementary events and in turn to the synthesis of novel sequential (block and graft) copolymers exhibiting unique physical properties. Most recent research concerns olefin polymerizations with BCl3 coinitiator. For example, the polymerization of isobutylene with the H2O/BCl3 initiator system produces macromolecules with tertiary chlorine termini. These end groups, in conjunction with certain alkylaluminum compounds, can be used to initiate the polymerization of a second olefin and thus can lead to new block copolymers. The synthesis of poly(isobutylene‐b‐styrene) by this technique will be discussed.
Study of the thermal oxidation of polyolefins. IV. Formation, characterization, and decomposition of polyethylene hydroperoxide
Authors: Iring M. , Kelen T. , Tüdös F. , László‐Hedvig S.
Published: June 2010

A study was made on the structure and decomposition rate of polyethylene hydroperoxide obtained by the initiated oxidation of low density polyethylene. It was established that the decomposition is not a simple unimolecular process. The rate was found to be dependent on the amount of carbonyl groups formed during the synthesis.
Activation energy and critical concentration of peroxy radicals in low‐temperature oxidation of natural rubber and 1,4 cis‐polyisoprene
Authors: Tkáč A.
Published: June 2010

A method is presented for studying the mechanism of carbonyl group formation in the low‐temperature oxidation of natural rubber and 1,4 cis‐polyisoprene, which does not require the investment of activation energy for the thermal or light scission of the polymer chain. Precise concentrations of t‐butyl peroxy radicals stabilized by coordination on Co (III), are used for initiation of the primary polymer radicals ˜Ṙ˜ after abstraction of an α‐methylene‐hydrogen. The “critical” threshold levels of peroxy radicals before and during the course of the oxidative degradation is discussed. The sensitivity for radical attack increases with the number of aliphatic double bonds; this is demonstrated using polypropylene and paraffin oil.
Recent advances in mechanisms for the stabilization of polyolefins
Authors: Hawkins W. L.
Published: June 2010

Over the past several decades, there has developed a comprehensive mechanism for the stabilization of polyolefins. Degradation can be inhibited at the propagation stage through the use of chain terminators and in the chain‐branching stage with peroxide decomposers. Combinations of chain terminators with peroxide decomposers result in synergism, and mechanisms have been proposed to account for this phenomenon. Recently it has been demonstrated that the catalytic effect of transition metals in promoting oxidation of polyolefins at a polymer‐metal interface is initiated at the metal surface. Metal deactivators, which react by chelating active metal species, also function first at the interface, although in subsequent stages of oxidation, soluble metal salts may penetrate into the matrix and catalysis then may be inhibited in the bulk polymer.

Reexamination of the role of carbon black in the stabilization of polyethylene against photo‐oxidation has shown that in the presence of this light screen, reactions of degradation and stabilization more closely resemble those found in thermal oxidation.
Time controlled stabilization of polyolefins
Authors: Scott Gerald
Published: June 2010

Hydroperoxides are key initiators in both thermal and UV initiated oxidation processes in polymers. The control of hydroperoxide concentration and hence the rate of the oxidation process can be achieved either directly by means of antioxidants which destroy hydroperoxides in nonradical generating reactions (preventive antioxidants) or indirectly by means of compounds which trap free radicals (chain‐breaking antioxidants) leading to a slower rate of hydroperoxide buildup.

Transition metal ions which catalyze the breakdown of hydroperoxides to free radicals lead to the rapid achievement of a stationary hydroperoxide concentration and a rapid and initially linear rate of thermal oxidation. Some metal complexing agents delay the achievement of this linear rate.

The effect of UV light in photooxidation of polymers has a similar effect to metal ions in thermal oxidation and the combined effect of both transition metal ions and UV irradiation can be catastrophic in polyolefins. However, certain metal ion complexing agents behave both as thermal oxidative stabilizers and as UV stabilizers due to a combination of different kinds of activity in the same molecule. These include metal deactivation, UV absorption, peroxide decomposition, and radical trapping. The photolytic stability of these complexes ultimately determines the length of the induction period which precedes polymer degradation. In general, nickel and cobalt complexes are UV stable and behave as long term stabilizers, whereas iron complexes are photolytically unstable and although they give rise to a period of initial stabilization which is related to their concentration, they photolyze to become effective photoinitiators.
Uni‐ and biaxial orientation of polymer films and sheets
Authors: de Vries A. J. , Bonnebat C. , Beautemps J.
Published: June 2010

Uni‐ and biaxial stretching of various polymer films has been studied under well‐defined conditions of temperature and elongational strain rate in order to determine the relationship between stress and recoverable strain for both modes of deformation. The extent of molecular orientation has been investigated with the aid of stress optical methods: In amorphous polymers birefringence was found to be directly proportional to the frozen‐in internal entropic stress irrespective of the latter's relationship with recoverable strain. In a first approximation, molecular orientation can be understood in terms of deformation of a rubberlike network with temporary junction points. The total internal stress in an oriented glassy polymer may be significantly larger than the entropic stress. Experimental methods based on retractive force measurements, able to distinguish between internal stresses of different nature, are described.

In uni‐ and biaxially drawn films of polyethylene terephtalate preferred planar orientation of (100) planes has been studied by means of X‐ray diffraction and measurement of the three principal refractive indices. The intrinsic birefringence of completely oriented PET films has been estimated from these measurements with the aid of the Lorentz‐Lorenz theory. The effect of draw ratio and temperature on the rate of crystallization and its consequences (increase of stretching stress and density, decrease of shrinkage) has also been studied.

Finally, the effect of molecular orientation on various mechanical properties: modulus, tensile strength, impact resistance, creep compliance, is discussed for both amorphous and semicrystalline polymers, with special emphasis on the predominant influence of amorphous phase orientation.
Direct observation of structure in high‐modulus aromatic fibers
Authors: Dobb M. G. , Johnson D. J. , Saville B. P.
Published: June 2010

A detailed structural characterization of three aromatic polyamide (PPT) fibers has been carried out by means of direct electron microscope observations and X‐ray and electron diffraction analysis. Data obtained by the diffraction techniques are supplemented by high‐resolution images recorded from fragmented specimens, which provide both a qualitative assessment and quantitative information in terms of crystallite perfection and the distribution of crystallite size. Dark‐field images suggest major differences between the macrostructures of various PPT fibers; indeed some specimens are composed of long‐range axially periodic assemblies, while others appear to be homogeneous. Such differences in organization may well account for variations in tensile behavior.
Small‐angle light scattering from polymer films with rod‐like superstructure—effects of volume fraction and orientation
Authors: Chu W. H. , Yoon D. Y.
Published: June 2010

The light scattering patterns from anisotropic rods have been calculated as a function of the degree of volume filling by these rods, and also as functions of their orientation distribution and the resulting birefringence effect in biaxially oriented polymer films. The resultant theoretical calculations compare well with available experimental results and, thus, demonstrate their applicability to the study of the course of crystallization and the structural characterization of biaxially oriented polymer films.
Computer analysis of light scattering data. II. Critical assessment of molecular parameters
Authors: Roberts Kenneth R. , Torkington John A. , Gordon Manfred , Ross‐Murphy Simon B.
Published: June 2010

Three different Fortran computer programs based upon different regression models have been applied to the computer analysis of light scattering data by variously weighted linear and nonlinear least‐squares methods to calculate the molecular parameters, viz., (MW)w,z. etc. for standard polystyrene samples in good solvents (benzene and toluene). Comparison of the results from the computer programs provides greater insight into the theoretical validity of these parameters, and leads to the conclusion that standardization of the data processing is an essential part of any “Round Robin” experiment to evaluate the molecular weight of standard polymer samples in different laboratories.
Anisotropic light scattering by solutions of large macromolecules oriented in the intense electric fields of laser beams
Authors: Dȩbska‐Kotłowska M. , Kielich S.
Published: June 2010

Light scattering by monodisperse solutions of rigid anisotropic rod‐like macromolecules of lengthl, of the same order as the wavelength λ, reoriented in the strong electric field of linearly polarized laser light is discussed. This discussion is based on numerical calculations of the relative variations in intensity δH, δHδV, δVof the light scattering components, induced by a laser beam of high intensityIpolarized horizontally or vertically to the plane of observation. Calculations are made for various values of q(ωL) = [(a–a)/a)I/2kT] (the reorientation parameter of the optical polarizability ellipsoid with principal polarizabilitiesa,afor the laser frequency ωL) and for the three valuesl/δ = 0.5, 1, and 2.
Thermodynamics of polymer mixtures
Authors: Koningsveld R. , Kleintjens L. A.
Published: June 2010

The compatibility of mixtures of homopolymers, mixtures of the same polymer differing in chain length, and mixtures of random copolymers is discussed from a thermodynamic standpoint. Small deviations from the Flory–Huggins combinatory entropy of mixing reveal themselves markedly in phase diagrams and second virial coefficients. Suitable experimental methods such as Pulse Induced Critical Scattering, neutron scattering, and low‐speed analytical centrifugation are discussed briefly. The molecular origins of phenomena discussed can at present best be traced for mixtures of homopolymers. The mutual influence the constituents exert on each other's chain flexibility seems to manifest itself in the shape of the miscibility gap. The other types of mixture allow less well developed theoretical description, due to lack of experimental data.
Hydrodynamics of block copolymers
Authors: Price Fraser P.
Published: June 2010

In order to gain insight into the viscosity behavior of linear block copolymers, formulas have been developed for the calculation of radii of gyration of block copolymers whose blocks deviate from the theta condition by any given degree. In the course of this study the radii of gyration of sets of centrosymmetric arrays have been studied and the mean separation between the center of mass and the end of a random chain has been calculated. The results show that for AB block copolymers of fixed degree of polymerization (DP), the intrinsic viscosity varies in a monotonic, sigmoidal fashion when the composition is varied from homopolymer A to homopolymer B. The magnitude of the effect depends upon the relative stiffness of the A and B segments and upon the total DP. In ABA copolymers, on the other hand, at constant DP, varying the composition from all A to all B usually leads to a composition‐intrinsic viscosity relationship containing maxima and minima. As A becomes increasingly stiff compared to B, this relationship tends towards a monotonic one. This behavior is surprising and should be checked experimentally.
The search for spinodal decomposition in binary systems of high molecular weight polymers
Authors: Price Fraser P.
Published: June 2010

Phase transformations associated with spinoidal decompositions are reviewed. Such phenomena associated with inorganic glasses are considered for the case of amorphous binary systems of organic high polymers. The thermodynamic and experimental considerations are projected and sample systems selected and tested. Results are presented for poly 1, 4(2, 6 dimethylphenylene oxide) plus a copolymer of styrene and orthochlorostyrene and also for this plasticized binary system.
Blends of poly(ϵ‐Caprolactone) with poly(vinyl chloride). II. Crystallization kinetics
Authors: Ong C. J. , Price F. P.
Published: June 2010

Crystallization kinetics of poly(e‐caprolactone) from the blends of poly(e‐caprolactone (PCL) and poly(vinyl chloride) (PVC) were investigated. The isothermal spherulitic growth rates were measured with an optical microscope. Linear growth rates were obtained for all samples at temperatures between 20° and 35°C. The introduction of PVC into PCL resulted in a reduction in spherulitic growth rate. The overall crystallization rates were measured with a density gradient column. The Avrami equation was employed to analyze the isothermal crystallization kinetics. It was found that the value of Avrami constant k decreases markedly with increasing PVC concentration. However, the Avrami constant n has a value in the neighborhood of 3, almost independent of the composition. In light of these results, it is suggested that, for these blends, the crystallization proceeds by heterogeneous nucleation, followed by a three‐dimensional growth.
Mean chain length distributions in finite polycondensing systems
Authors: Donoghue Edward , Gibbs Julian H.
Published: June 2010

The current expressions for the molecular size distributions in certain polycondensing systems of linear or branched‐chain polymers were derived by Flory and by Stockmayer in the limit of infinitely large systems. These expressions are experimentally verified in the sol. But the expressions for the distributions of nonlinear polymers, although manifesting the observed gel point, do not describe a gel phase. With a view towards ultimately deriving expressions that do describe the gel, a probabilistic theory of condensation polymerization in finite systems is introduced here. The theory is based on Stockmayer's statistical weight factor, ω, and, as presented, applies to the elementary system composed of chemically identical structural units, each bearing two or more chemically identical functional groups. The probability density function for molecular size distributions is constructed from ω, and expressions for the mean number of k‐mers and the variance about this mean are derived from it. A generating function formalism for evaluating these expressions exactly is exhibited in the elementary case of linear polymers. Asymptotic expansions of the exact expressions for the means and variances are then obtained in the large system limit. The expansion for the means shows that the Flory‐Stockmayer expression represents the distribution of linear polymers accurately—in finite systems—only at low molecular weights. The expansion for the variances justifies—at low molecular weights—the expectation that observed distributions differ negligibly from the mean distribution, but shows that populations of higher molecular weight polymers deviate markedly from their means.
Inorganic fragments in graft and block copolymers: A review of solved and unsolved problems
Authors: Haiduc Ionel
Published: June 2010

In the first part of the paper some problems related to the formation of inorganic chains in polymeric backbones are discussed and the difficulties in the use of polymerization reactions in inorganic polymer chemistry are reviewed: the lack of suitable inorganic monomers; the tendency of inorganic ring formation; and the tendency of structure unit redistribution. In the second part several possibilities of introducing inorganic fragments in block and graft copolymers are reviewed.
Some problems concerning the degradation of linear vinyl polymers and copolymers in nonisothermal conditions
Authors: Schneider I. A.
Published: June 2010

A 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

The 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

This 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

Steady 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

Polymeric 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

Polymerizable 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

This 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

The 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

Earlier 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

The 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

Experimental 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

The 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

The 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

Liquid 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

Several 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.
Wall effect in cylindrical pores and the shape of GPC calibration curve
Authors: Kubín M. , Vozka S.
Published: June 2010

A simple model of spherical molecules in cylindrical pores has been used to show that the shape of GPC calibration curve is quite insensitive to the width of the pore‐size distribution of the porous packing.
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

Course 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.
A new approach to polymer chemistry: Organometallic and bioactive phosphazenes
Authors: Allcock Harry R.
Published: June 2010

Polyphosphazenes are prepared by a substitutive process that involves nucleophilic displacement reactions on poly(dihalophosphazenes). A variety of strategies are described for the utilization of this approach for the preparation of polymeric drugs and polymer‐bound transition metal systems.
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

The 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.