bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and glass transition behavior of ionomers from styrene/n‐butyl methacrylate
Authors: Williams M. W. 
Published: June 2010

AbstractStyrene/n‐butyl methacrylate/potassium methacrylate ionomers have been prepared by partial alkaline hydrolysis of the copolymers. Ion contents were determined by atomic absorption and neutron activation analyses. Glass transition temperatures (by DSC) increase with ion content but reach limiting values at 1–2 mol % ions. The limiting values are 5–20° higher than those of the starting polymers—depending on the molecular weight–and increase linearly with styrene content. These relationships are approximately described by Tg = Tgx ‐ (K/M + 4)e−x where x is the molar ion content, Tg∞ is the limiting Tg value and M the molecular weight. Data are provided to indicate that the Tg increase due to introduction of ions can be balanced by aqueous plasticization at ambient relative humidity, but the sharp shoulders in the Tg variations suggest the presence of a more fundamental mechanism in addition to this. Onset of domain formation or transition from growth of number of domains to growth of the size of these domains are possible mechanisms. Hydrolysis of polyacrylates can be accompanied by intramolecular catalysis leading to less random distribution of ions in the chains. Comparative studies were made with an alternating styrene/n‐butyl methacrylate copolymer in which this effect cannot occur. Hydrolysis rate was comparable to that of the random copolymers suggesting the absence of this effect under our conditions. Ionomers prepared from the alternating copolymer showed the characteristic Tg shoulder, indicating that this is not a consequence of block ion formation.
Surface activity of oligomeric surfactants as function of their composition
Authors: White W. W. , Jung H. 
Published: June 2010

AbstractA series of ten oligomeric surfactants of general formula RS (CH2CHCN)a(CH2COOK)bH were prepared and tested for surface activity. The R groups (corresponding to the lipophile of a conventional surfactant) studied were n‐butyl, n‐octyl, and n‐dodecyl. Surface activity increased with size of R. Molar amounts (a+b) of acrylonitrile and acrylic acid were 8 or 16 with b/(a+b) varied from 0.25 to 1.00. Increased b/(a+b) gave increased surface activity.Oligomers prepared with octyl mercaptan all exhibited two critical micelle concentrations (CMC) with the second occurring at concentrations greater than ten times those at the first CMC. The In CMC were found to increase linearly with increased acid content. Surface excesses at the air water interface determined by the Gibbs relationship were similar on a molar basis but over four times greater on a weight basis than conventional surfactants. Results of adsorption studies at latex particle surface were consistent with results from the Gibbs relationship confirming the unique long range ionic stabilization inherent with the oligomeric surfactants.
Time‐temperature superposition of the fundamental relaxation processes of polyethylene
Authors: Stein R. S. , Finkelstein R. S. , Yoon D. Y. , Chang C. 
Published: June 2010

AbstractThe application of Tobolsky's time‐temperature superposition principle for the stress‐relaxation behavior of amorphous polymers is reviewed, and its extension to crystalline polymers and the employment of X‐ray and optical methods is discussed. The desirability of applying the superposition principle to time‐dependent crystal orientation functions is described. The use of those techniques for the study of the relaxation of a low‐density polyethylene sample is illustrated. Spherulite orientation theory is used for analysis of the results.
Kinetic behavior of gel entrapped enzymes
Authors: O'Driscoll K. F. , Hinberg I. , Korus R. , Kapoulas A. 
Published: June 2010

AbstractA variety of enzymes have been successfully immobilized in our laboratory by entrapping them in hydrogels. The entrapment procedure consists of dissolving an enzyme in a polymerization reaction mixture which typically consists of about 50% water, a water‐soluble polymer such as poly(vinylpyrrolidone), a monomer such as 2‐hydroxyethylmeth‐acrylate, a crosslinking monomer and a low‐temperature, free radical initiating species.After immobilization, the enzymatic activity of the gel was measured against a suitable substrate, usually chosen for the ease of following its reaction. The gel itself is dried, crushed to a fine powder, sieved, and rehydrated before the enzymatic activity is measured.We have experimentally studied the activity of gels containing trypsin, glucose oxidase, β‐galactosidase, and other enzymes. Details of this work and applications of these immobilized enzymes are discussed.
Criteria for random degradation of linear polymers
Authors: Scott Kenneth W. 
Published: June 2010

AbstractVarious criteria for random degradation of linear polymers were evaluated. Some preference is given for a criterion that compares the relative decreases in weight‐ and number‐average molecular weights with those expected from theory because it utilizes the maximum information available and essentially includes the other useful criteria. Several examples of data from the literature were examined in this way.
A comparison of various cross‐linked polystyrenes as diluting media in reactions of ester enolates
Authors: Kraus Menahem A. , Patchornik Abraham 
Published: June 2010

AbstractVarious forms of cross‐linked polystyrene were compared as to their effectiveness as carriers‐diluents in reactions of carboxylic ester enolates. The polymers compared were microporous (2 % divinylbenzene), “popcorn,” and macroporous polystyrenes. In the acylation by acyl halides of polymer ester enolates, higher yields were obtained and less self‐condensation occured with the popcorn polymer as carrier than with the microporous polystyrene. Popcorn and microporous polymers gave similar results in the alkylation of polymer ester enolates. The macroporous polymers (both commercial and synthetized) gave much poorer results in this latter reaction (low yields and more self‐condensation). Popcorn and microporous polystyrenes gave equally good results in the mixed ester condensation of two esters attached to a common polymer backbone. When polymer esters were treated with base without subsequent addition of electrophile, 10‐15% of intrapolymeric self‐condensation occurred with all three types of polymer, when ester concentration was 0.1‐0.15 mmole/ g. Under similar conditions, the analogous soluble ester self‐condensed to the extent of 67 %. It is concluded that under the proper conditions, all of the cross‐linked polystyrenes are capable of inhibiting mutual interactions of attached molecules. These conditions are low concentration and low molecular weight of attached molecules, and short reaction times.
Spectroscopic study on the elementary reactions of oxidative polymerization
Authors: Tsuchida Eishun , Nishide Hiroyuki , Nishikawa Hiroshi 
Published: June 2010

AbstractThe catalytic cycle of the Cu‐pyridine complex catalyzed polymerization of 2,6‐xylenol was divided into four elementary processes: the coordination of the substrate, the electron transfer from the substrate to the cupric ion, the dissociation of the activated substrate, and the reoxidation of the catalyst. Rate constants of each elementary reaction, k1, ke, kd, and ko, were determined spectroscopically by the stopped‐flow method. The approximate magnitudes of each rate constant were k1: 10 (1·mole−1·minp−1), ke :10−2 (min−1), and ko, 102 (min−1), respectively. Thus, it was considered that the ke or the kd process was the rate‐determining step, but the latter could not be measured in this procedure. The rate constants were affected by the species of the solvent. With a few exceptions of the solvent which had coordinating ability, k1 and ke increased and ko decreased with the polarity of the solvent. The effects of the polymer‐ligand on each elementary reaction were also studied in the polymerization catalyzed by the Cu‐partially‐quaternized poly(vinylpyridine) complex. k1 and ko were smaller and ke was larger than those of the monomeric analog. It was interpreted that the ke step was accelerated by the electrostatic field of the polymer‐ligand.
Investigation of the ionogenic group distribution in ion‐exchange resins
Authors: Saldadze G. K. , Varentsov V. K. 
Published: June 2010

AbstractThis paper deals with the experimental establishment of the heterogeneity of gel‐type ion‐exchange resins by x‐ray diffraction local analysis using an electronic probe. The relationship between the cross‐linking agent content and the microstructure of ion‐exchange resins is shown.
Macronet isoporous ion‐exchange resins
Authors: Tsyurupa M. P. , Davankov V. A. , Rogozhin S. V. 
Published: June 2010

AbstractMacronet isoporous polystyrene structures are obtained by cross‐linking of dissolved polystyrene by means of bischloromethylated benzene or biphenyl. Macronet isoporous cation exchangers, irrespective of the type and amount of cross‐linking agents, can be completely saturated with the tetrabutylammonium ions. The swelling capacity of resins containing a sufficient amount of cross‐linking bridges is independent of the type of the counter‐ions and of the ionic strength of the outer electrolyte solution. These resins can be used in nonaqueous solvents.
Dependence of the sorption of aliphatic amines on the number and distribution of sulphonic acid groups of styrene‐divinyl‐benzene ion exchangers
Authors: Prokop Z. , Setinek K. 
Published: June 2010

AbstractThe sorption of methylamine and trimethylamine on partially neutralized and incompletely sulphonated ion exchangers was carried out by the dynamic pulse method. The results revealed that with macroporous samples, where a considerable part of functional groups is directly accessible from the gaseous phase, the sorption capacity (S) is linearly dependent on the titration exchange capacity. The sort of neutralizing alkaline metal ion and sulphonation procedure does not exert any effect. With samples of standard ion exchangers, the external surface of which is negligible and the functional groups are accessible only via penetration of sorbate to gel, the sorption capacity was not linearly dependent upon the titration exchange capacity and it increased with an increasing radius of the neutralizing ion. With incompletely sulphonated samples, the capacity increased in those cases where the sulphonation procedure produced ion exchangers with functional groups located near the external surface of the gel.
Changes of cellulose accessibility to reactions in alkaline medium by activation with ammonia
Authors: Schleicher Harry , Daniels Carola , Philipp Burkart 
Published: June 2010

AbstractThe effect of activation of cellulose by ammonia is surveyed with regard to an increase of accessibility of different cellulose structures to subsequent reactions proceeding in an alkaline medium, causing considerable swelling by itself. Special subjects were the reactions of xanthogenation, carboxymethylation, and cyanoethylation. In all these heterogeneous reactions a considerable increase in the reaction rate and degree of conversion was found.Using the emulsion xanthogenation with a stepwise enlargement of NaOH concentration as a method of accessibility measurement, considerable changes of the accessibility spectrum of different cellulose structures were found after activation with liquid ammonia or aqueous solutions of ammonia at high concentration. In all the cases investigated, the activation brings about a considerable broadening of the accessibility distribution.
The complexeng of Ca(II), Co(II), and Zn(II) by polymethacrylic and polyacrylic acid
Authors: Travers C. , Marinsky J. A. 
Published: June 2010

AbstractAn experimental method proposed for the accurate estimate of the nonideal behavior of metal ions in the course of their complexation by polyacids has been shown to be valid. This nonideal behavior, due to the large and variable electrical field at the surface of the polyelectrolyte in the polyion domain, is ascertained from direct examination of the nonideality of mobile hydrogen ions during potentiometric examination of the competing polyacid dissociation reaction. As a consequence of this approach, it has been possible to show that the dominant complex species in Ca(II)‐, CO(II)‐, and Zn(II)‐polymethacrylic (PMA) and polyacrylic (PAA) acids is an ion pair. The respective formation constants of the ion‐pair species have been determined as well.
Studies of alcoholysis of poly (vinyl acetate) to poly (vinyl alcohol)
Authors: Bravar M. , Rolich J. , Ban N. , Gnjatovic V. 
Published: June 2010

AbstractThe effect of degradation on poly (vinyl acetate) (PVAc) during hydrolysis to poly (vinyl alcohol) is significantly greater with higher molecular weight PVAc than with that of lower molecular weight.There is no data, in literature however, of comparative studies of alcoholysis on commercial samples of PVAc. Two commercial polymers, poly (vinyl acetate) A and B, prepared by the suspension polymerization method to high conversions and having different molecular weights, were fractionated using ethyl acetate as solvent and petroleum ether as precipitant. The weight percent versus intrinsic viscosity [η] distribution curves are given. Both polymers were fully alcoholized and reacetylated. Again the distribution curves are given. The shifting of the distribution curves to lower intrinsic viscosity values as well as their narrowing is discussed.The course of the process (mild alcoholysis) was followed and the extent of alcoholysis in both polymers of fractions of various molecular weights noted.
A possibility of influence of the degree of coiling of macromolecules in solution on the kinetics of side‐groups reactions
Authors: Turska E. , Jantas R. 
Published: June 2010

AbstractPapers published earlier have shown that the accessibility of the end‐groups, in conjunction with the degree of coiling of the macromolecules, undoubtedly affects the kinetics of reactions in solutions.Our work was carried out in order to investigate the possibility of an analogous phenomenon in the case of reactions involving side‐groups. We considered the factors which have been supposed, until now, to influence these reactions. We suggested that together with other factors the degree of coiling could influence the course of the reaction. To check the validity of this suggestion, a number of kinetic measurements were made of the hydrolysis of poly (vinyl acetate) and specially chosen model compounds in selected mixed solvents. Low‐molecular weight substances, as well as partially hydrolized poly (vinyl acetate), were investigated as model compounds. The experimental data obtained were considered in various apsects, taking into account both our suggestions and those by other authors. It was found that not all the observed phenomena could be explained without using our theory.
Elasticity of uncrosslinked rubbers
Authors: Djiauw L. K. , Gent A. N. 
Published: June 2010

AbstractRelaxation of stress at constant elongation, instantaneous recovery, delayed recovery, and permanent set, have been measured for four simple rubbery polymers over a wide range of time, temperature, and amount of elongation. The extent of instantaneous recovery is shown to be in satisfactory accord with a two‐network calculation based on the hypothesis that the preceding stress relaxation is due to progressive rearrangement of a constant number of molecular entanglements. Delayed recovery R was found in all cases to follow a simple empirical time function
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where ts is the period of prior deformation. This relationship was obeyed for times t and ts varying from 1 to 106 sec, temperatures between 4 and 80°C, and imposed extensions ranging from 30 to 200%. It was also found to hold in some preliminary measurements on carbon black filled rubbers. Thus, it appears to have wide applicability, although this particular time function is not readily accounted for in terms of a theoretical model. Permanent set was found to be in reasonable accord with Newtonian flow behavior under the observed stress history.
Hysteresis in rubber vulcanizates
Authors: Payne A. R. 
Published: June 2010

AbstractThis paper reviews the studies of the author and colleagues into the mechanisms of hysteresis in polymers. The subjects discussed include low strain amplitude dependence of modulus and hysteresis, stress‐softening effects, the energetics at rupture over a wide temperature range and rate of straining, energy failure envelopes, as well as proposing a physical interpretation of the phenomenon of reinforcement by small particles.
The random coil dimensions of methylated polypeptides
Authors: Burgess Antony W. , Paterson Yvonne , Leach Sydney J. 
Published: June 2010

AbstractThe random coil dimensions of polysarcosine and poly‐α‐aminoisobutyric acid have been evaluated using both theoretical and experimental methods. Theoretical values for characteristic ratios were derived from the (ϕ, Ψ) potential energy maps for the cis and trans isomers of Nα‐acetylsarcosine N,N‐dimethylamide and for Nα‐acetyl‐α‐aminoisobutyryl N‐methylamide. Experimental values were derived from viscosity data in various solvents. For polysarcosine in glacial acetic acid, the experimentally derived characteristic ratio agreed with the theoretically derived value for the trans isomer. From the lower ratios observed using water and particularly chloroform, these solvents are presumed to admit the cis isomer. Theoretical calculations (derived from energy maps) of poly‐α‐aminoisobutyric acid gave an unusually low characteristic ratio (<1) which was not in agreement with that from viscosity measurements in heptafluorobutyric acid. Reasons for the discrepancy are discussed in terms of the ease of propagation of helical regions in the polypeptide chain.
New developments in polysaccharide chemistry
Authors: Whistler Roy L. 
Published: June 2010

AbstractWater soluble polysaccharides are used broadly and in large amounts by food and nonfood industries. These polymers are plant exodates, seaweed extracts, plant extracts, seed endosperms, modified starches and cellulose, and biosynthetics. They may be neutral or anionic through their content of carboxyl or sulfate half‐ester groups. They may be linear or branched but their usefulness depends upon their causing large rheological or other physical effects at low concentrations. They are used mainly to improve viscosity, suspension stability, emulsification, flocculation or emolliency. Their use is increasing each year and the trend is toward use of agricultural or biosynthetic gums or starch and cellulose derivatives.
Environmental effects on low temperature crazing of crystalline polymers
Authors: Peterlin A. , Olf H. G. 
Published: June 2010

AbstractThe ductile behavior of crystalline polymers between liquid nitrogen and room temperatures is primarily due to enhancement of crazing by the presence of gases (N2, A2, O2, CO2) of high thermodynamic activity, i.e., close to their condensation point. Without the presence of such a gas, at temperatures sufficiently above its condensation point so that its activity has dropped to a few percent, the crystalline material is rather brittle although some very limited crazing can be detected. As expected, the ductility and the amount of crazing are very nearly the same in helium as under vacuum. The crazes in smectic PP are extremely long, often traversing the entire width (0.5 cm) of the sample, and generally very similar to crazes in glassy amorphous polymers. They are thin and become thicker at higher temperatures. In monoclinic PP with well developed spherulitic structure, crazing occurs along spherulite diameters that are perpendicular to the stress direction but not along the boundaries between spherulites. In general, the length of a craze equals the spherulite diameter. At low temperatures all crazes originate on the outer surface of the sample which is in direct contact with the gas.The action of the gas is due to two mechanisms. First, the adsorbed gas reduces the surface energy of the polymer, facilitating the creation of a new surface in the holes and voids of the craze. Second, the gas becomes highly absorbed at the tip of an incidental flaw or of an existing craze, since these are regions of high dilatant stress. The locally absorbed gas acts as a plasticizer easing the flow involved in the nucleation and growth of the craze, i.e., in the formation of fibrillar material of the craze.
Dielectric relaxation in polymers with particular reference to two‐phase systems
Authors: North Alastair M. 
Published: June 2010

AbstractDielectric relaxation is introduced as the response of charged species to a change in the electric field applied to a sample. In the case of polymeric materials two important processes are orientation of segment dipoles and limited migration of charge carriers.Two areas where new advances of technical importance are being made are discussed: dielectric processes at very high frequencies which might be encountered when plastic materials are used in communication and dielectric waveguides, and interfacial polarizations encountered in two phase systems. These latter may be used to create devices of high permittivity and are also responsible for deterioration in the performance of many electrical‐grade laminates.
Light scattering as a tool in the study of multicomponent polymer systems
Authors: Kratochvíl Pavel 
Published: June 2010

AbstractThe importance of the refractive index increment measured after the establishment of dialysis equilibrium between the polymer solution and the mixed solvent for the evaluation of light scattering measurements from polymer solutions in multicomponent solvents is stressed. The feasibility of determination of heterogeneity in copolymer composition by light scattering can often be considerably extended by using mixed solvents. Light scattering measurements from solutions of binary polymer mixtures yield correct molecular weights of the components and parameters characterizing the thermodynamic interaction of unlike polymer molecules. In all the types of measurements discussed, information is obtained from ratios or differences of rather close values. In order to get physically meaningful data a higher experimental accuracy is required than in conventional light scattering measurements.
Two‐component polymer systems: Physical properties as related to compatibility and interaction
Authors: Rånby B. G. 
Published: June 2010

AbstractThe physical properties of mechanical blends of poly (vinyl chloride) (PVC) with ethylene‐vinyl acetate copolymers (EVA) and with acrylonitrile‐butadiene copolymers (NBR) have been studied using light scattering. gas permeability, density, and dynamic‐mechanical (loss tangent) measurements for thin films. The data show that the PVC/EVA blends are not compatible at 45% VAc content in EVA. A “phase inversion” is indicated at 5‐7 wt‐% EVA. EVA containing 65% VAc interacts more with the PVC component and shows no indication of phase inversion. A mixed phase of PVC/EVA‐65 is formed with higher measured density than calculated, assuming additivity. NBR containing increasing amounts of AN (21.7, 29.6, and 41.6 wt‐%) shows increasing compatibility with PVC due to interaction. For 50:50 blends of PVC/NBR the measured densities are 0.033, 0.050, and 0.053 g/ml higher than the calculated values for the three NBR samples. There are some indications of a phase inversion at NBR contents of 5‐7 wt‐%.