bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of supermolecular order in aqueous solutions of poly(vinyl alcohol) in a turbulent flow
Authors: Kolnibolotchuk N. K. , Klenin V. J. , Frenkel S. Ya. 
Published: June 2010

AbstractThe process of formation of the supermolecular order (SMO) in aqueous solutions of poly(vinyl alcohol) (PVA) has been studied by the method of turbidity spectrum in a turbulent flow produced by a blade stirrer rotating at a rate of 1,500 rpm.The kinetics of SMO formation has been investigated depending upon the polymer molecular weight (Mw) and concentration (C) and temperature (T) of the solution. The rate of formation of SMO was characterized in the first stage of the process by a relative increment in τ at 540 nm per hr. The concentration dependence, K = K(C), is extremal in character having its maximum at C = 0.5–1 g/dl. When T was increased from 20 to 50°CC, K decreased, whereas average equivalent size of supermolecular particles, rλ, remained unchanged. The colloid disperse phase of supermolecular particles (SMP) appears to be in a quasi‐equilibrium with the molecular‐disperse solution, since, after removal of SMP, the process of formation of SMO is resumed at the same rate. To a greater extent the character of SMO formation depends on the chemical structure of PVA (K drops off to zero with increasing content of the acetate groups up to 7.6%) and physical prehistory of the PVA sample (an increase in K after thermal treatment of the polymer in the condensed state). PVA films cast from stirred solutions revealed (by IR spectra) a greater degree of crystallinity then those cast from unstirred solutions. All other conditions being equal, K in a turbulent flow is higher by one to two orders of magnitude than K under static conditions. The data obtained have been explained from the point of view of crystallization of PVA when intensified by the turbulent regime of solution stirring.
Structure changes in glassy hydrophilic polymers under the stress of water sorption
Authors: Spencer H. Garth , Beyerlein Anne , Honeycutt S. C. 
Published: June 2010

AbstractThe sorption of water vapor by poly (vinyl alcohol) films at moderate vapor activities was followed by mass regain and electrical conductance. A slow rearrangement of polymer structure in the swollen state is indicated by the observed sorption overshoot.
Electrooptical investigations on organized structures of spherical polymers in solutions
Authors: Sokerov S. , Vorobeva T. , Stoylov S. 
Published: June 2010

AbstractUnder the action of an electric field at a frequency of 1000 Hz, an interaction occurs between spherical latex particles in aqueous solution. These spheres arrange themselves in linear aggregates along the lines of the force field. The formation of these aggregates is studied by the electric light scattering method. The case is investigated where the aggregates disintegrate after the electric field is switched off. Some preliminary theoretical ideas are presented concerning the electrooptics of the phenomenon. The constant of coagulation and the electric polarizability of the spheres are estimated, their radius being constant and known. The investigations carried out could be the beginning of the development of an electrooptical method for the determination of the electric polarizability of spherical particles in solution. In addition this investigation shows that electrooptical effects by solutions of spherical particles are possible.
Specific solvent interactions in the stereo‐regular polymerization of methacrylic acid
Authors: Lando J. B. , Litt M. , Kumar N. G. , Shimko T. M. 
Published: June 2010

AbstractA study has been made of the marked effect of solvent on the stereoregularity of poly (methacrylic acid) prepared by the radical polymerization of methacrylic acid initiated by Co60 gamma radiation. The specific interaction of the solvent with the monomer and the growing polymer chains, leading to particular structures at the growing chain end, leads to the observed effect on the stereoregularity of the polymer. It is apparent that solvents of intermediate hydrogen bonding strength and bulkiness lead to highly syndiotactic polymer. Thus poly (methacrylic acid) prepared at −78°CC in a 20% by volume solution of methacrylic acid in 2‐propanol contains 95% syndiotactic triads. The effect of the steric hindrance of the solvent is amply demonstrated by the fact that polymerization in 2‐methylcyclohexanol results in the highest degree of syndiotacticity at 0°CC (82% syndiotactic triads) but yields polymer having only 69% syndiotactic triads at −78°CC. This is in contrast to the usual effect on stereoregularity upon lowering the temperature of radical polymerization. The detailed mechanism of this polymerization and its relation to the polymerization of other monomers capable of hydrogen bonding to solvents will be discussed with specific reference to the particular structures that may give rise to the observed effects.
A model for the structure of ionomers
Authors: Macknight W. J. , Taggart W. P. , Stein R. S. 
Published: June 2010

AbstractThe nature of the distribution of ionic groups in cesium salts of ethylene‐methacrylic acid and ethylene‐acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small‐angle and wide‐angle x‐ray scattering techniques. The low‐angle data containing a maximum characteristic of these materials were analyzed according to principles of small‐angle scattering theory. The radial distribution functions for a typical salt and unionized copolymer were derived from the combined small‐ and wide‐angle data. The results of these two approaches indicate the presence of ionic clusters of the order of 10–20 Å in size. There is evidence that these clusters are of spherical geometry. The low‐angle maximum is interpreted as an interference resulting from short range ordering of ionic groups around ionic clusters.
Mechanics of elastomeric adhesion
Authors: Andrews E. H. , Kinloch A. J. 
Published: June 2010

AbstractThe mechanics of adhesion have been investigated both theoretically and experimentally, using model adhesive joints consisting of a crosslinked amorphous rubber bonded to a variety of rigid polymeric substrates.An adhesive failure energy, θ, is defined which is characteristic of the bond but independent of test‐piece geometry. Both theory and experiment show that θ has the form, θ=θ0f(R) where θ0 is the “intrinsic adhesive failure energy” which depends only on the physical and chemical nature of the adhesive‐substrate interface, and f is a function of R, the “reduced” rate of failure propagation obtained from rate and temperature data using the WLF equation.θ0 is the work of bond fracture across the interface and, for clean interfacial failure, is equal to the thermodynamic work of adhesion wA. Where failure is not purely interfacial, θ0 can be expressed as θ0=iI+r𝒯0+sF where i, r, and s are respectively the area fractions of interfacial, cohesive‐in‐rubber and cohesive‐in‐substrate failure, and I, θ0, and F are the intrinsic failure energies for the interface, rubber, and substrate, respectively.It is believed that this work is the first to demonstrate explicitly and quantitatively the separate contributions of interfacial properties and bulk rheological behavior to the strength of adhesive joints.
Dielectric relaxation in solutions of poly (ϵ‐caprolactone)
Authors: Jones A. A. , Brehm G. A. , Stockmayer W. H. 
Published: June 2010

AbstractDielectric relaxation has been studied for poly (ϵ‐caprolactone) in dioxane solution. As expected from the head‐to‐tail structure [‐(CH2)5COO‐]x, at a given temperature there are two distinct dielectric loss peaks. Radio‐frequency bridge measurements reveal a low‐frequency peak due to a component of the repeat unit dipole parallel to the direction of the chain backbone and amounting to about 0.8 Debye per ester group. The position of this peak on the frequency scale varies with molecular weight as predicted from the longest normal‐mode relaxation time, τ1≅M[η]η0/RTThe second relaxation, which is independent of chain length, is conveniently studied over a wide range of concentrations by the technique of time‐domain reflectometry (TDR). This peak is associated with relaxation by local conformational rearrangement of a component of the dipole moment perpendicular to the chain direction, amounting to about 1.6 Debye per ester group. The extrapolated frequency of maximum loss at infinite dilution is about 3 GHz at 300K, with an apparent activation energy of about 30 kJ mol−1. The dependence of the local relaxation time on concentration can be fitted by a familiar free‐volume equation of the type τ = A exp(B/vf), in which the free volume vf is a linear function of composition.
Epoxy/acrylic simultaneous interpenetrating networks
Authors: Touhsaent R. E. , Thomas D. A. , Sperling L. H. 
Published: June 2010

AbstractSimultaneous interpenetrating networks were prepared by simultaneously synthesizing crosslinked epoxy and poly (n‐butyl acrylate) polymers. A two‐phase morphology emerged, with the dispersed rubber domains being of the order of 0.1–0.2 m̈ in size. The actual dimensions of the dispersed phase, and the extent of molecular mixing between the two networks, depends on the relative rates of polymerization, or the gelation time. The minimum domain size and greatest molecular mixing occurs when the closest approach to simultaneity is attained. Spherical rather than elongated rubber domains yield the greatest toughening of the epoxy when the domains are smaller than optimum.
Enzymes covalently bound to acrylic gel beads. I. Interaction of hydrophilic anionic gel beads with biomacromolecules
Authors: Krämer D. M. , Lehmann K. , Plainer H. , Reisner W. , Sprössler B. G. 
Published: June 2010

AbstractGel beads of excellent mechanical properties are obtained by copolymerization of methacrylic acid anhydride with acrylamide using ethyleneglycoldimethacrylate or N, N′‐methylene‐bis (methacrylamide) as a cross‐linker.When protein is covalently bound to the anhydride groups of the beads, residual anhydride groups are hydrolyzed to form an anionic matrix (AM). The hydrophilic gel beads are stable to 1M NaOH, mechanical stirring, and dehydration by lyophilization or organic solvents. Proteases, nucleases, and amylases bound to AM are efficient catalysts in breaking down high molecular weight substrates.As far as the interaction of AM with biomacromolecules at pH 7.5 in 0.05M phosphate buffer is concerned, polyanions like DNA or tRNA are strictly excluded from the gel volume, whereas cationic polymers like basic proteins are strongly absorbed even at an ionic strength of 0.3. Little or no interaction is observed with neutral biopolymers.
Photochemically initiated maleic anhydride addition on polystyrene sensitized by free and bonded sensittzer
Authors: Hrdlovič Pavol , Lukač Ivan 
Published: June 2010

AbstractMaleic anhydride addition to polystyrene in diluted dioxane solutions initiated by radiation of wavelength longer than 340 nm proceeds only in the presence of sensitizers, such as benzophenone and acetophenone. The degree of addition is, however, about 17 times less than for low‐molecular maleic anhydride addition to cumene under similar conditions. Due to the concentration effect, the efficiency of the bonded sensitizer exceeds that of the freely added one by up to three times in this instance. Quenching experiments showed that maleic anhydride acts as a quencher of poly (vinyl phenyl ketone) photolysis (Ksv = 31.5 1./mole) and copolystyrene/vinyl phenyl ketone (Ksv = 41.5 1./mol), although acting with only one‐half of the efficiency obtained with naphthalene. A comparison of the quenching efficiency of naphthalene with that of maleic anhydride for poly (vinyl phenyl ketone) (1.43) and copolystyrene/vinyl phenyl ketone (1.32) leads to the conclusion that in diluted dioxane solution there is no interaction of maleic anhydride with aromatic nuclei in the copolymer. The sensitized photoaddition is supposed to proceed via an attack by the excited maleic anhydride in the triplet state on the aromatic nucleus and not by the excited state of the charge transfer complex between maleic anhydride and the aromatic nucleus.
Rubber and rubber elasticity: A review
Authors: Gent Alan N. 
Published: June 2010

AbstractThe physical basis of rubber elasticity is reviewed, particular attention being given to the dependence of elastic stresses upon the imposed strains and upon the molecular constitution of the rubber. Applications of this fundamental understanding to a variety of other phenomena, including thixotropic effects shown by rubbers containing particulate fillers, the crystallinity and rigidity of partially crystalline polymers, and the frictional properties of soft solids are also referred to. A brief survey is included of some important but still unsolved problems in rubber elasticity.
The influence of curing systems on the properties of natural rubber
Authors: Chan B. L. , Elliott D. J. , Holley M. , Smith J. F. 
Published: June 2010

AbstractAfter a brief historical introduction the influence of curatives on the chemical structure of vulcanizates is discussed. Emphasis is given to physically important features of network structure such as crosslink density, crosslink type, and various main‐chain modifications. The significance of extra‐network materials such as curative residues and zinc soaps is introduced. Nonsulfur systems are briefly considered.The effects of differences in network structure and in extra‐network materials on aging properties is outlined with special emphasis on the importance of total combined sulfur, conjugated triene groups, and curative residues. The special problem of finding suitable antioxidants and antiozonants for peroxide cured rubber is mentioned. The influence of different curing systems on the crystallization of natural rubber both at low temperatures and at large extensions is described and shown to be a similar function of vulcanizate structure in both cases when compared at constant degrees of crosslinking. Problems in the interpretation of stress‐strain behavior are reviewed.Changes in the C1 term of the Mooney‐Rivlin relation can only be interpreted as changes in crosslink density or as a filler stiffening effect of insoluble extra‐network material. Changes in the C2 term of this relation also take place as the curing system is changed and are correlated with inelastic behavior. Analysis of stress‐strain relations at high strain using the Martin‐Roth‐Stiehler equation indicates significant differences in the strain‐induced crystallization behavior of vulcanizates based on various curing systems, even when compared at similar crosslink densities.The inelastic stress‐strain properties of natural rubber vulcanizates are divided into three main regions: (a) the glass transition region; (b) the chemical transition region, and (c) the intermediate region. The effects of network structure and extra‐network materials in each region are considered separately. In particular, the effects of zinc soap structurization on stress relaxation behavior in the intermediate region is described, including the likely mechanisms by which rubber‐soluble zinc soaps reduce the stress relaxation rate.The influence of curing systems on the strength properties of homogeneous and isotropic natural rubber vulcanizates is described briefly, with particular emphasis on the role of polysulfidic crosslinks and main‐chain modifications.
Theoretical study of the effects of surfactants on seeded polymerization
Authors: Chambers James S. , Smitham James B. , Napper Donald H. 
Published: June 2010

AbstractA simple analytical theory is developed to explore the effects of surfactants, whether ionic or nonionic, on the rate of polymerization of seeded systems. It is assumed that the average number of free radicals per particle is small (n < 1), that termination is rapid, and that free radicals may exit from the particle.Some consequences of the variation of the kinetic parameters are explored numerically. It is shown that the radical capture efficiency decreases in the order electrostatic, steric, then electrostatic plus steric for these three different types of stabilization. The radical capture efficiency is shown to be very low (1 free radical captured in 103 – 104) despite the absence of new nucleation. Possible reasons for the low efficiency are discussed.
Mechanism of peroxidation of solid polymers as derived from the kinetics of the induced graft copolymerization
Authors: Chapiro A. 
Published: June 2010

AbstractGrafting of acrylonitrile onto various radiation peroxidized polymers was used as a technique to investigate the peroxidation mechanism. It was found that in polymers such as polypropylene, poly(vinyl chloride), and polystyrene, a chain hydroperoxidation process only occurs above the glass transition temperature of the polymer. In the vitreous state, the polymer peroxidizes much more slowly via a single step radical‐radical combination process. In polyethylene and cellulose triacetate, a chain hydroperoxidation reaction is also observed at elevated temperatures, but the chain process is stopped at a critical temperature, which is dependent on the radiation intensity. It is shown that this effect can be interpreted, assuming that radical‐radical combination then efficiently competes with chain propagation. A discussion of the results shows that a polymer is likely to suffer more severe oxidation than a mobile liquid of similar chemical structure, owing to the much slower radical‐radical combination process in the viscous medium of the polymer.
Glassy transitions in semicrystalline polymers
Authors: Boyer Raymond F. 
Published: June 2010

AbstractConsiderable confusion exists in the literature concerning the glass temperature, Tg, of many highly crystalline polymers, in particular, linear polyethylene (PE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(oxymethylene) (POM), and poly(ethylene oxide) (PEO). We attempt to resolve some of this confusion first, by defining the nature of the problem; second, by developing criteria for defining the locations along a relative temperature scale (T/Tg or T/TM) of the key relaxations and transitions, Tg, T < Tg, TM, and Tαc for C‐C and CO backbone polymers free from long alkyl side groups; third, by developing a set of typical mechanical relaxation spectra for amorphous, semicrystalline, and single crystal materials of known Tg; fourth, by defining the concept of a double glass transition with values Tg(L) and Tg(U) and the optimum conditions for observing same. Finally, we apply these concepts and criteria to resolving the value of Tg for PVF and PVDF. Criteria employed include ratios of relaxation temperatures such as (T < Tg)/Tg, Tαc/TM, and Tg/TM, typical activation enthalpies for various relaxation processes, thermal expansion and heat capacity data. Two theoretical subjects are explored: the effect of crystallinity on increasing Tg and the effect of crystallinity on the relative strengths of the Tg and T < Tg processes. We also employ a “comparative anatomy” technique of comparing temperatures and related activation enthalpies of the several relaxations and transitions for a series of closely related polymers such as PE, PVF, PVDF, PTFE, Polytrifluorochloroethylene, and poly(vinyl chloride). We suggest that a new scientific discipline of interpreting the relaxation spectra of crystalline polymers may be emerging through integration of a large body of literature, the refinement of old criteria, and the development of new criteria. Even so, we are not yet able to offer a satisfactory interpretation of the relaxation spectra for POM and PEO.
Analysis of polymers by chemical modification
Authors: Schulz Rolf C. , Aydin Oral 
Published: June 2010

AbstractPart one describes general aspects which must be considered when discussing the chemical analysis of polymers. By means of examples taken from literature, some fundamental procedures are illustrated, for example, color reactions, complex formation, degradation reactions (thermal, oxidative, solvolytic degradation), and polymer‐analogue reactions.Part two describes our own investigations on analysis of different vinyl acetate copolymers having the general formula . The method is based on the elimination of acetic acid by melting the copolymer with p‐toluene‐sulfonic acid. The acetic acid can be determined by potentiometric titration or gas chromatography. The method may be used for soluble and insoluble copolymers (with R:H; OH; phenyl; C2H5COO) and graft copolymers (i.e., poly(vinyl chloride)) containing 0.2 to 100% vinyl ester. With copolymers from vinyl esters and acrylic esters (R; COOR'), alkaline hydrolysis followed by gas chromatographic determination of the acids and alcohols being formed is more advantageous.
Acrylonitrile copolymerization. VII Solvents effects in styrene copolymerization
Authors: Pichot C. , Zaganiaris E. , Guyot A. 
Published: June 2010

AbstractThe styrene‐acrylonitrile radical copolymerization kinetics have been studied for polymerizations carried out in two different solvents, toluene and dimethylformamide (DMF), in the whole range of monomer mixture compositions and at various dilutions. The copolymer prepared in toluene solutions are poorer in acrylonitrile than those prepared in bulk. The reverse situation is observed in DMF solution, where the polymerization rate is the highest. In the latter case, also for acrylonitrile rich mixtures, the relative polymerization rate of styrene tends to increase with conversion; this effect is attributed to preferential solvation of styrene. Possible explanation of these facts are briefly discussed.
Polymer crosslinking by a bimolecular peroxide decomposition
Authors: Chodák I. , Rado R. 
Published: June 2010

AbstractThe present paper examines the possibility of the utilization of the bimolecular cumyl hydroperoxide redox decomposition, catalyzed by Co11 naphthenate for the polymer crosslinking. The study of the mechanism and the kinetics of this reaction was performed both in a model medium heptane and polymer or polymer solution. In the case of redox initiation, the value of the crosslinking efficiency was found to be about 0.4, and its decrease can be attributed mainly to the formation of ions and, partly, to recombination of peroxy radicals producing dialkyl peroxide. On the basis of data obtained concerning the efficiency and rate of the process, conclusions are made on its applicability, especially for the crosslinking below the melting point of a crystalline polymer, as is the case of the crosslinking of polyethylene films.
Negative C2 values of inhomogeneous polymer networks measured in elongation
Authors: Janáček J. , Vojta V. 
Published: June 2010

AbstractIt was found that negative slopes of the Mooney‐Rivlin plot (negative C2 values) can be expected for polymer networks prepared by means of a crosslinking polymerization of respective monomers in the presence of large concentrations of a diluent, or for such systems having macroscopic porosity. Some examples are given for swollen poly (2‐hydroxyethyl methacrylate) networks prepared in the presence of high concentrations of water (porous systems), and/or ethylene glycol (nonporous systems), and also for a network of partially hydrolyzed polyacrylonitrile prepared in a similar way. Negative C2 parameters are probably connected with inhomogenous deformations of supramolecular domains in the stressed cross section of the systems studied.