bluuebunny/crossref_metadata_2025 huggingface dataset:
Polypeptides at the air‐water interface and in solution
Authors: Birdi K. S. , Fasman Gerald D.
Published: June 2010

Monomolecular films of various polypeptides spread at the air‐water interface have been investigated. The conformation in the solid state (e.g., a‐helical or β‐structure) was known for all the polymers studied. In the surface pressure‐area isotherms the a‐helical polymers gave a distinct flat plateau, whereas the β‐form polymers showed only an inflexion. A correlation between the collapse pressure and the stability in solution for β‐form polymers was found, while no similar relationship was observed for the a‐helical polymers. Surface entropy and enthalpy were determined for each polymer and these results indicated that the polypeptides retained the same conformation in the monolayer as in the solid state, i.e., a‐helical or β‐structure. For a‐form polymers a correlation exists between the intermolecular forces in solution and the cohesive forces at the interface. The lack of such a correlation for a‐helical polypeptides thus provides a means of determining the conformation of polypeptides and proteins at the interface.
Thermodynamic properties of liquids, including solutions. VIII. Comparison of properties of several polymer and solvent systems
Authors: Huggins Maurice L.
Published: June 2010

The writer's new theory of solutions has, so far, been applied in detail to experimental data from four types of polymer solutions: rubber plus benzene, polyisobutylene plus benzene, polyisobutylene plus cyclohexane, and poly(propylene oxide) plus carbon tetrachloride. The parameters deduced for these systems are here compared and interpreted in terms of molecular and intermolecular properties. The effects of these parameters on the magnitudes and concentration dependence of the related thermodynamic properties (especially the interaction coefficient χ and its enthalpy and entropy components) are discussed and illustrated.
Precipitation of polymers from solution in the presence of an electrical field
Authors: Krozer S. , Cantow H‐J.
Published: June 2010

Some polymers and copolymers were precipitated from solutions by nonsolvent addition with and without stirring as well as by temperature lowering. It turned out that the precipitate is charged in all these cases. Stirring yields an increase of the charge quantity. The charging of the precipitate in experiments without stirring being a result of electron transfer between the solvent and polymer rich precipitate phase is probably due to the density fluctuations. The precipitation by stirring was used for preparative purposes to remove the precipitated drops from solution by fractionation. Deviation in composition observed in different fractions of copolymers could influence the molecular weight and molecular weight distribution measurements.
Kinetics of destruction of stressed polymers
Authors: Korsukov V. E. , Vettegren V. I. , Novak I. I.
Published: June 2010

The infrared spectroscopy technique (IRS) was used for the investigation of polymer film destruction under the action of tensile stress and temperature.

The structure and concentration of the stable chemical compounds has been found. The regularities of their accumulation as a function of time, temperature, and the magnitude of the applied load has been studied.

These compounds are assumed to be formed due to the decay of free radicals arising from the breakage of the polymer macromolecules under the action of mechanical stresses and thermal agitation. It has been shown that both at room and at elevated temperatures the kinetics of the accumulation is controlled by the rate of breakage of the macromolecules, but not by that of the occurrence of subsequent reactions.

The activation energy of formation of new stable products has been found.
The hydrolytic degradation of polyurethanes
Authors: Cohen J. L. , Van Aartsen J. J.
Published: June 2010

The hydrolytic degradation of poly(ester)‐urethanes (PUR) has been studied by viscometry of solutions of films that were treated for various times with water of fixed temperature.

On the basis of some simplifying assumptions a general expression was derived relating the decay of the limiting viscosity number (LVN) upon hydrolysis to the reaction rate constant of the hydrolysis reaction.

For a homologous series of polymers, with decreasing molecular weight that eventually resulted from the measurements of the hydrolysis, the relation mechanical property versus molecular weight was obtained for four mechanical properties. These relations were interpreted in terms as described previously by Flory and many others.

The mechanical properties of hydrolyzed films and those of redissolved and recast hydrolyzed films were compared and showed some interesting features.
Some aspects of γ‐radiolysis of polyisoprene in the form of natural rubber latex
Authors: Ambroź Hanna
Published: June 2010

The most important radiation‐induced reactions of polyisoprene in the form of natural rubber latex are cross‐linking and dislinking. They have been tested in the system with six methane halides at 77, 195, 273, and 328°K. Chlorides are sensitizers of the cross‐linking process within the whole range of temperatures studied. Bromine and iodine derivatives exhibit different features depending on temperature and composition. The activation energies of the cross‐linking process in sensitized and unsensitized systems have been evaluated within the range of high and low temperatures. The dislinking of polyisoprene estimated on the basis of the Charlesby‐Pinner theory varies from 0.3 to 5% of cross‐links, depending on experimental conditions.

The role of oxygen in polyisoprene radiolysis and aging resistance of cross‐linked latex films has been also examined.
Oxidation of cellulose by acid‐sodium nitrite systems
Authors: Arendt J. H. , Carrière J. P. , Bouchez P. , Sachetto J. P.
Published: June 2010

Investigations on the oxidation of cellulose by phosphoric acid‐sodium nitrite systems have shown that the specificity of the reaction depends on the concentration of the acid. Supporting evidence has been given by chemical analysis, x‐ray diagrams, and identification of degradation products. The suggestion of a mechanism of oxidation by the nitrosonium ion instead of nitrous acid is supported by experimental results.
Concentration and size effect of microgel particles of acetylcellulose spinning solutions on physicomechanical properties of fibers
Authors: Klenin V. J. , Denisova G. P. , Lyutaya E. N. , Milevskaya R. A. , Kosimtseva L. V.
Published: June 2010

The correlation between physicomechanical properties of fibers and parameters (average size and concentration) of raicrogel particles (MGP) of acetylcellulose (AC) spinning solution has been studied.

The average size λ and numerical concentration N (the number of particles in 1 cm3 of solution) of MGPs have been measured by the method of the turbidity spectrum. Fibers and solutions of specially selected industry batches of AC and their mixtures have been studied.

The selection of AC batches has been done in the following manner. A chosen pair of batches has approximately equal molecular parameters (molecular weight, polymolecularity, degree of substitution) with different MGP parameters (the turbidity of equiconcentrated AC solutions is extremely varied). Mixtures of different compositions were prepared from batches thus chosen.

Thus there was a number of AC samples with size and concentration of MGPs varying in their solutions while the molecular parameters remained constant. Several pairs of AC batches have been chosen. These pairs may vary between each other in their molecular characteristics.

Physicomechanical properties of fibers were compared with MGP parameters in AC solutions within each number of samples which had either the same concentration and different sizes of MGPs (one series of comparison) or the same size MGPs but different concentrations (second series).

Dependence of physicomechanical properties upon MGP parameters shows that the MGPs form the imperfect regions in fiber structure. This is why an increase of MGP size decreases both strength and breaking elongation of fibers.
The thermal breakdown mechanism of polybenzoxazoles and polybenzothiazoles
Authors: Ehlers G. F. L. , Fisch K. R. , Powell W. R.
Published: June 2010

Polybenzoxazoles, when heated up to 660°C in vacuum, lose most of their oxygen as carbon monoxide and carbon dioxide and possibly form Schiff base‐type structures. The carbon required for the formation of carbon monoxide is predominantly supplied by the benzene rings. About one out of every six CN linkages is eliminated as hydrogen cyanide, and some free nitrogen from this group is reduced to ammonia. The elimination of about 1 hydrogen atom per polymer unit (in the form of free hydrogen, hydrogen cyanide, ammonia, and methane) results in free radical formation and crosslinking.

Carbon monoxide and carbon dioxide are also some of the major decomposition products of the benzoxazole in poly‐2,2′‐(1,8‐perfluorooctane)‐6,6′‐bibenzoxazole. In addition, fluorine from the perfluoroalkyl chain combines with ring hydrogen to form hydrogen fluoride, which in turn attacks the quartz of the crucible and reaction vessel to form silicon tetrafluoride.

A polybenzothiazole, on heating to 625°C, crosslinks with elimination of some hydrogen. One out of every ten sulfur atoms is removed, essentially as hydrogen sulfide, leaving a Schiff‐base linkage; very few of the CN‐groups are eliminated as hydrogen cyanide. Two less stable polybenzothiazole systems, heated to 660 and 670°C, lose about 50% of their sulfur, mainly as hydrogen sulfide, and 20% of their nitrogen as hydrogen cyanide.

Flash pyrolysis of model benzoxazoles and benzothiazoles was tried as a means to provide supporting data.
The structural characterization of oxidized celluloses by thermogravimetric analysis
Authors: Pataky B. , Perczel S. , Sachetto J.‐P.
Published: June 2010

The oxidation of cellulose may lead to polymers of more or less complex structure according to the type of oxidizing agent used. No practical methods are available for a quick structural characterization of these compounds. The only reliable method is chemical in nature and very time‐consuming.

The object of this paper is to present some results obtained by the thermogravimetric analysis of oxidized celluloses used as a means of characterization for these compounds.
Gel permeation chromatography: Efficiency and operational variables
Authors: Chuang Jau‐Yi , Cooper Anthony R. , Johnson Julian F.
Published: June 2010

A variety of expressions for measuring efficiency and resolution in gel permeation chromatography have been used. These are compared and evaluated. In general, there are large differences for all of these methods as a function of molecular weight. Further, at the same molecular weights the various equations do not always rank columns in the same order. This complicates the problem of selecting the optimum operational variables. The various expressions are compared as a function of flow rate and temperature.
A method for characterization of long–chain branched polymers by GPC and intrinsic viscosity
Authors: Kraus Gerard , Stacy C. J.
Published: June 2010

The authors previously reported a method for molecular weight and long‐chain branching distributions using GPC and intrinsic viscosity measurements on whole polymer and fractions [1]. The method does not require prior knowledge of the functional relationship between branching frequency and molecular weight. Applications included “randomly” branched polymers, prepared by free radical initiation, and anionically polymerized macromolecules branched by various techniques leading to specific distributions of branches. Additional examples are given in the present report. The technique has been applied both without and with GPC band spreading correction. The effect of this correction on the resulting estimate of the long‐chain branching distribution is insignificant.

When the method is applied to whole polymer only (without preparative fractionation), an average branching factor is obtained, which serves as a useful partial characterization of long‐chain branching. Use of this alternative is discussed and illustrated with examples of low and high density polyethylene, branched styrene‐butadiene block copolymers, star‐branched polybutadiene and others. For the special case of statistically random branching, the average branching factor may be converted to a branching frequency by a straightforward computer program, leading to a description of branching similar to that of Drott and Mendelson [2].
Supramolecular structural transitions in polypeptide solutions: An NMR study
Authors: Hines William A. , Samulski Edward T.
Published: June 2010

Proton NMR spin‐lattice relaxation times are reported for the solvent in the two component lyotropic liquid crystal, dichloromethane plus poly(γ‐benzyl‐L‐glutamate). The relaxation times become Larmor frequency dependent on passing from the isotropic solution to the liquid crystal. A simple model based on the supramolecular structure in the liquid crystal exhibits orientational fluctuations in the radio frequency region suggesting that spin‐lattice relaxation of the polypeptide protons should also show frequency dependence.
Structure of poly (n‐alkylacrylates) gels
Authors: Tal'Roze R. V. , Shibaev V. P. , Platé N. A.
Published: June 2010

The crystallization of polymers with long side chains proceeds in the form of hexagonal crystal lattice, regardless of the configuration of the backbone chain. For these polymers the ordered structure in the crystalline state as well as in the melt is typical. The tendency to form an ordered structure takes place in the solutions of branched polymers. At polymer critical concentration about 0.5 wt % the gelation process occurred.

The structure and properties of gels of acrylic polymers (i.e., polycetylacrylate) in n‐aliphatic alcohols (C7H15OH–C12H25OH) and hydrocarbons (C10H22–C16H34) were studied. The x‐ray patterns show that all the gels have the same interplanar spacings at the wide angles which correspond to the hexagonal cell. The phase transitions and thermodynamic parameters of gel‐solution transition were studied by means of x‐ray and differential thermal analysis. The structure of gels in alcohols and hydrocarbons was found to be different. This difference was explained in terms of specific polymer‐solvent interactions.

The kinetics of supermolecular structure formation in gels was investigated using small‐angle light scattering (SMAL) method. Rather good correlation between SMAL and electron microscopic data was found.

Some conclusions about the character of the supermolecular structure‐forming process were made and the model of gel structure was proposed.
Studies on swelling and liquid‐induced crystallization of polycarbonates
Authors: Turska E. , Benecki W.
Published: June 2010

Rate of the diffusion front displacement, rate of sorption and rate of turbidity for the system of bisphenol A polycarbonate foil‐methylisobutylketone were determinated. The influence of the temperature on the observed phenomena was investigated. An attempt at apreliminary interpretation was done.
Principles regulating the morphology of crystallization nuclei in concentrated polymer solutions
Authors: Zurabian R. S. , Baranov V. G. , Frenkel S.
Published: June 2010

General expressions are obtained for the nucleation rate taking into account explicitly the contribution of the free energy change when nucleation follows two different mechanisms, both monomolecular and multimoleuclar, i.e., with folded and extended chains.

Nucleation with folded chains is the more probable for flexible random coiled macromolecules. However, upon decreasing the degree of coiling without affecting the origin of the uncoiling, the probability of the formation of multimolecular nuclei increases while that of the formation of monomolecular nuclei decreases. At some critical degree of uncoiling a reverse situation as compared to the initial probabilities is attained.

A general thermodynamic and thermokinetic interpretation is given of the influence of the equilibrium or induced rigidity on the morphology of crystallization of polymers from solutions and melts.
Angular dependence of the light scattering of polymer solutions at moderate concentrations especially near the consolute point
Authors: Vrij A.
Published: June 2010

The light scattering equation ℋ︁c2(1 + cos2 θ)/Rθ = dΠ/RTdc2 + (16 π2 〈r2〉/3λ2)M2−1 sin2θ/2 for moderately concentrated polymer solutions derived previously from a gradient dependent free energy will here be rederived with the help of the so‐called direct correlation function, C(s), first introduced by Ornstein and Zernike.

The equation will be used to calculate 〈r2〉/M2 for polystyrene in cyclohexane near the consolute (or critical) point from light scattering measurements of Debye, Coll, and Woermann in combination with those of Scholte We found [〈r2〉/M2]1/2 = 3.5 (± 0.1) nm mol1/2 g−1/2 for M2 ranging from 8 × 104→ 106 g mol−1.
Polymerization in preoriented media: Polymerization rate of p‐styrene sulfonic acid on poly(cationic) backbones
Authors: Blumstein A. , Kakivaya S. R. , Shah K. R. , Wilkins D. J.
Published: June 2010

Many important naturally occurring biochemical reactions such as synthesis of nucleic acids, proteins, and polysaccharides proceed through template polymerization. Such reactions are very complex, and the study of simpler systems is of great interest.

A radical initiated polymerization of p‐styrene sulfonic acid anion attached to a poly(quaternary ammonium) backbone (ionene) was studied. The polycationic matrix was prepared from 1–4 diazobi‐cyclo (2.2.2.) octane and 1–4 dibromobutane. It was of low molecular weight (5–10 monomeric units), high rigidity, and could be considered to be in a rod‐like conformation in dilute water solutions. The polymerization of the pSSA‐ionene complex was followed by means of ultraviolet spectroscopy. The overall polymerization kinetics was studied as a function of temperature, concentrations of monomer and initiator, and of the “degree of filling” of the matrix at neutral pH. A rate increase of over two orders of magnitude was observed in the presence of the matrix. This effect was maximum for stoichiometric amounts of monomer and matrix and fell off rapidly for lower monomer‐to‐matrix ratios. The kinetic effect is accompanied by a large decrease in the overall activation energy by 6 kcal/mol.
Graft copolymers from cobalt‐60 pre‐irradiated starch and mixtures of acryl‐amide with N,N,N‐trimethylaminoethyl methacrylate methyl sulfate
Authors: Fanta George F. , Burr Robert C. , Doane W. M. , Russell C. R.
Published: June 2010

Starch was preirradiated with cobalt‐60 and then allowed to react with mixtures of acrylamide and N,N,N‐trimethylaminoethyl methacrylate methyl sulfate (TMAEMA·MS) in a water solution. The graft copolymers resulting were purified and characterized, and the influence of a number of irradiation and reaction variables on graft copolymer composition was determined. Although the reaction of irradiated starch with monomers must be carried out with a monomer solution purged with nitrogen to remove dissolved oxygen, a nitrogen atmosphere over the starch sample during irradiation is not necessary to achieve graft polymerization. With monomer mixtures containing 2, 5, 10, 15, and 50 mol% TMAEMA·MS, the mole percentage of TMAEMA·MS in grafted branches was less than that in the initial monomer mixture, whereas ungrafted polymer generally contained a higher percentage of the cationic monomer than was present initially. A tenfold variation in irradiation dose (0.5–5.0 Mrad) caused only small variations in percent add‐on; however, intrinsic viscosities of grafted branches decreased with increasing irradiation dose. Substituting aqueous ethylene glycol for water as the reaction medium produced more frequent grafts of lower molecular weight. Graft polymerization onto partially degraded starches gave graft copolymers with better water solubility.
The solid‐state properties of ionomers, A comparison of ethylene and styrene based materials
Authors: Eisenberg A.
Published: June 2010

A comparative review of properties of ionomers is presented, stressing primarily the similarities and contrasts between ethylene and styrene based materials. In particular, it is shown, that in the concentration region where ion clustering is encountered, the mechanical properties of the two ionomers resemble each other more closely than do those of the styrene ionomers and styrene. The similarity can be seen from a range of experimental results, and several different approaches are described.
Synthesis and glass transition behavior of ionomers from styrene/n‐butyl methacrylate
Authors: Williams M. W.
Published: June 2010

Styrene/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

A 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

The 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

A 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

Various 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

Various 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

The 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

This 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

Macronet 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

The 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

The 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

An 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

The 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

Papers 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

Relaxation 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
magnified image
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

This 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

The 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

Water 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

The 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

Dielectric 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.
Superposition in rheology
Authors: Markovitz Hershel
Published: June 2010

The uses of superposition in linear viscoelasticity and steady‐state shearing flow are treated from the point of view of phenomenological theory. Special attention is paid to exact and approximate relations concerning superposition of various rheological properties. Shift factors are related to the viscoelastic constants.
Light scattering as a tool in the study of multicomponent polymer systems
Authors: Kratochvíl Pavel
Published: June 2010

The 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

The 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‐%.
Optical activity as a tool in the investigation of the conformational equilibria of poly‐α‐olefins in solution
Authors: Pino P. , Neuenschwander P.
Published: June 2010

An attempt has been made to evaluate the contribution derived from the investigation of optically active poly‐α‐olefins to our knowledge of the conformational equilibria of isotactic vinyl polymers in solution. The data obtained from the measurement of optical rotation and its temperature coefficent, as well as of optical rotatory dispersion, in solution, leaves little doubt about the existence, for the most stereoregular poly‐α‐olefin, in solution, of main chain sections spiralized in both screw senses with one of the two screw senses prevailing. For a given degree of stereoregularity the length and the prevalence of the chain sections spiralized in the more favored screw sense depend on the structure of the lateral chains; the type of screw sense prevailing depends on the absolute configuration of the asymmetric carbon atoms contained in the monomers. This qualitative model has been confirmed by a series of experiments, including measurements of chiroptical properties in the solid state and determination of the end‐to‐end distance and copolymerization of chiral with nonchiral monomers. The possibility of extending the above model to include polymers containing functional groups for which no suitable method exists to relate optical activity to conformation and the consequences of ordered conformations for the isotactic vinyl polymers in solution are briefly discussed.
Polyisoprene and polybutadiene derivatives of potential biomedical interest. Part II
Authors: Pinazzi C. P. , Menil A. , Rabadeux J. C. , Pleurdeau A.
Published: June 2010

Some polyalkadienes (polyisoprenes and polybutadienes) have been modified along the macromolecular backbone by hydroboration‐hydroxylation followed by reaction with phosgene. These polyalcohols and new polychloroformates in reaction with pharmaceuticals such as quinine, cholesterol, and testosterone, lead to new polycarbonates of potential biomedical interest.
Substitutions Electrophiles Sur Le Polyphenylsiloxane
Authors: Conan Jean , Llauro Marie‐France , Bartholin Michel , Guyot Alain
Published: June 2010

On étudie le comportement du polyphenylsiloxane, polymère en échelle de formule brute (Ø ‐ SiO3/2)n, vis à vis des réactions de substitution des noyaux phényles pendants: nitration et chlorométhylation. Le caractère hautement électroattracteur du groupement SiO3/2 désactive le noyau aromatique, mais confère au polymère sa remarquable tenue en milieu acide. La réaction de dégradation qui accompagne le chloromethylation et forme des structures cycliques, a des conséquences limitées du fait de la structure en échelle du polyphenylsiloxane; le polymère ainsi modifié perd sa rigidité.
Synthèse D'Alcools Terpéniques par Oligomerisation Anionique en Phase Hétérogene
Authors: Rupprecht Robert , Brossas Jean
Published: June 2010

Terpenic alcohols have been synthetized by anionic dimerization of isoprene in the heterogeneous phase and oxidation of carbanions. Metallic lithium is used as initiator. A small number of isomers have been obtained and characterized.
Kinetic study of the anionic polymerization of propylene sulfide. VI. Influence of the solvent and of several cryptating agents
Authors: Hemery P. , Boileau S. , Sigwalt P.
Published: June 2010

Solvent effect upon the reactivity of ion pairs has been examined for the cesium salt of polypropylene sulfide. k± increases with the dielectric constant of solutions. The size effect of the counterion upon the propagation rate constants has been studied in tetrahydrofuran (THF) at −30°C. Values of the dissociation constant KD and of the interionic distance parameter a have been deduced from conductivity measurements made on seeds of living polypropylene sulfide with the cryptate Na+∥222∥ as counterion. k± and k− were determined for several cryptated counterions. Cryptated ion pairs are more reactive than free ions.