bluuebunny/crossref_metadata_2025 huggingface dataset:
The supermolecular structure of viscose fibers and its dependence on spinning conditions
Authors: Nikonovich C. V. , Kerimova N. G. , Burchanova N. D. , Usmanov Kh. U.
Published: June 2010

The supermolecular structure of viscose fibers (VF) has been studied by electron microscopy and some other physical methods. Experimental and industrial VF samples were selected at different spinning stages and served as the objects of investigation.

Coagulation conditions (bath composition) were shown to affect significantly VF surface structure. Besides, the latter essentially depends on VF swelling and shrinkage in the course of spinning. In the case of tire cord fibers the surface reveals no significant changes after bath stretching; on the contrary, the structure of the surface and inner regions of the VF, spun according to the Lilienfeldt process (in concentrated sulfuric acid) shows noticeable changes after bath stretching.

Electron micrographs of isotropic VF reveal a loose fibrillar network with pore dimensions and homogeneity depending on the coagulation bath composition and its component ratio (H2SO4/ZnSO4). While increasing the ZnSO4 content in the coagulation bath, some decrease of the network pore diameter was observed to take place.

Stretching leads to the orientation of VF structural elements in the direction of the fiber axis, followed by formation of lamellar structures.

Investigations of crystallites isolated by hydrolysis and estimation of their dimensions allow to come to conclusions on changes in the fine structure of microfibrils in the course of spinning.

Electron microscopy data and some other VF structural characteristics are shown to be in good agreement.
Hardness as a rapid, reliable measure of polymer crystallization
Authors: Wilkes Charles E. , Walters Maxie R.
Published: June 2010

Since polymer crystallization rate is such a universal measure of backbone stereo structure, side chain structure, crosslinking, and the effect of additives, we have developed a routine, easily used method for its measurement. Normalized plots of the time‐honored measurement of hardness vs time compare well with results obtained by dilatometry, x‐ray diffraction, and light absorption (or optical birefringence). Sample preparation, surface roughness (especially important in the case of “nervy” rubbers), shortcuts to round‐the‐clock testing, temperature control and fine points of hardness measurements are discussed.
Differential scanning calorimetry of polypentenamers: Correlation of thermal properties with cis/trans content
Authors: Wilkes Charles E. , Pekló Mária J. P. , Minchak Robert J.
Published: June 2010

First and second order thermal transitions have been characterized for a number of cis/trans‐polypentenamer copolymers, for blends of high cis and high trans polymers, and for high trans polypentenamer containing oil and carbon black. The extrapolated value of Tg for 100% trans polypentenamer is −91°C at a heating rate of 10°C/min. At the same heating rate the maximum, equilibrium melting point is estimated to be 44°C. Correcting for the thermal lag in the experiment (i.e., extrapolating to infinitely slow heating rate), the above value is 40°C. The heat of fusion of trans‐polypentenamer is 1.93 ± 0.11 K cal/mole. The presence of crystalline polypentenamer slightly raises the glass transition temperature of the amorphous phase. This effect becomes measurable when the trans content is greater than 80%. Once calibrated by infrared or other spectroscopic determination of composition, thermal analysis is a rapid, precise method for measuring cis/trans contents in polypentenamers.
Viscoelastic measurement of polybutenes and low viscosity liquids using ultrasonic strip delay lines
Authors: Knauss Carl J. , Leppo Dale , Myers Raymond R.
Published: June 2010

A new method for measuring the shear mechanical properties of liquids in the 1–20 MHz range is used to obtain data for low‐viscosity liquids at approximately 2 MHz. The results obtained agree with literature data reported for these samples at 40 MHz. The technique involves the propagation of a pulsed, shear wave in a thin strip of metal, and measurements of the phase shift and increased attenuation of the wave by a sample at the metal‐liquid interface. The method is then extended to measuring the properties of polybutenes, whose average molecular weights range from 250–920. The relationship between average molecular weight and the dynamic viscosity and elasticity is studied for these polymers.
A role of internal viscosity in the intrinsic hydrodynamic and rheooptical properties of polymer solutions
Authors: Peterlin A.
Published: June 2010

Exact treatment of intrinsic viscosity and streaming birefringence is possible for the limiting case of zero gradient where the coil dimensions are not yet perturbed by the flow. Experimental data on streaming birefringence in solvents of low viscosity suggested an internal viscosity characteristic for the polymer and independent of the viscosity of the solvent. More recent data on frequency dependence of viscosity in very viscous solvents unequivocally demand an internal viscosity proportional to the viscosity of the solvent. By reconsiderations of the possible origins of internal viscosity one indeed finds two contributions one prevailing at low and the other one at high solvent viscosity in good agreement with experimental data. The former is the original Kuhn‐Cerf term based on energy barriers opposing rapid conformational changes. The latter is caused by the coupling of lateral and longitudinal displacement of chain elements as a consequence of conformational limitations by valency angles and bond orientation (g,g′,t).
Large scale preparative gel permeation chromatography
Authors: Montague P. G. , Peaker F. W.
Published: June 2010

The design and construction of a large‐scale gel permeation chromatographic unit is described, and it is a tenfold scale‐up of the usual analytical instrument. Important aspects of the column packing procedure are given. Fractions prepared using this apparatus were isolated and reinjected into an analytical instrument. In this way the efficiency of preparative fractionation was investigated using several polystyrene samples covering a wide range of molecular weights and distributions. Generally the highest molecular weight fraction isolated from a sample had the narrowest molecular weight distribution.
Structurization in the poly (m‐phenylene isophthalamide)–dimethylacetamide system
Authors: Klenin V. J. , Prozorov L. V. , Prozorova M. Yu. , Zhizdyuk B. I.
Published: June 2010

The methods of turbidity spectrum and viscometry have been used to investigate structurization in the concentrated solutions of poly (m‐phenylene isophthalamide) (Pm‐PIPA) in dimethylacetamide (DMA). The kinetics of formation of the supermolecular order (SMO) were studied under isothermal conditions within the temperature and concentration range of 30 to 150°CC and 5 to 25 g/dl, respectively. Two stages of formation of SMO were observed, viz., a comparatively slow stage and after that a very fast increase in the SMO level. In the first stage, the average particle radius, rλ, decreases, which probably is related to the continuous formation of nuclei. In the second stage, rλ and the turbidity, τ, of solution increase steeply. In the same stage, an increase in the viscosity of solution was also observed. A diagram of the properties of the system was constructed, which is analogous to the phase diagram. The temperature limit of the stability, Tbi, fulfills the requirement of Vτ = 0, where Vτ (the rate of increasing turbidity), was determined. Tbi determines the binodal curve depending on the polymer concentration. The temperature limit of absolute instability, Tsp, fulfilling the requirement of Vτ→∞, was determined. Depending on the concentration of solution, Tsp was identified with a spinodal curve. The property diagrams obtained are characteristic of the curves of amorphous separation with the lower critical solution temperature. With increasing molecular weight, Mζ, Tc decreases. Additions of a third component cause a deformation of the binodal curve and shift it to higher (lithium and calcium chlorides) or lower (water) temperatures. The time, ts, of reaching a certain level of SMO during thermostabilization at T = 80°CC was taken as a measure of stability of technological solutions.
Viscoelastic relaxation times of a homogeneous block copolymer
Authors: Shen Mitchel , Hansen David R.
Published: June 2010

The molecular theory of viscoelasticity has been modified in a previous publication for homogeneous block copolymers; the theory predicts that the maximum relaxation time of the block copolymer can be computed with the knowledge of submolecular sizes and monomeric friction coefficients. Stress‐relaxation experiments were carried out for two samples of styrene‐(α‐methyl styrene)‐styrene triblock copolymers. Maximum relaxation times were determined from the viscoelastic master curve through the use of procedure X developed by Tobolksy and Murakami. Experimental results were found to be in reasonable agreement with theoretical predictions. The theory also predicts the existence of a singularity in the distribution of relaxation times at very short relaxation times, but as is discussed, this prediction cannot be verified by existing experimental techniques.
Correlation between molecular structure and some bulk properties of highly crosslinked polysiloxanes
Authors: Katz D. , Zewi I. G.
Published: June 2010

Little consideration has until now been given to the effect of microphase separation in crosslinked polymers. This work deals with the correlation between the network chain length and some bulk properties of a series of seven highly crosslinked polymers prepared from dimethylsiloxane diacrylate oligomers with different lengths between their acrylic terminal groups. The occurrence of multiple transitions in the shear modulus versus temperature behavior, probably due to microphase separation, and the dependence of the transition regions and shear moduli on the siloxane network chain length were studied. The findings are compared with those of a similar work reported by us earlier, in which carboxyl‐terminated poly(dimethylsiloxanes) of similar chain lengths of the prepolymers were condensed with a trifunctional imine and yielded polymers exhibiting multiple transitions.

Multiple transitions were observed in some of the crosslinked polymers, but this phenomenon disappeared with an increase in the amount of siloxane groups in the prepolymers. It seems that the reason for this suppression of microphase separation, as compared with the crosslinked carboxyl‐terminated oligosiloxanes, derives from the absence of sufficiently long organic sequences, from their limited number in the network chains, and from internal plasticization by the side chains formed as a result of inefficient crosslinking. The nature of the crosslinking site and the mechanism of crosslinking have a decisive influence on the structure and properties of the polymers including the occurrence of multiple transitions, even when the prepolymers are almost identical between their functional end groups.
Production of high‐molecular amphoteric compounds by means of polymer‐analogous conversions
Authors: Pashkov A. B. , Vakulenko V. A. , Samborsky I. V. , Makarov M. K.
Published: June 2010

Polymer‐analogous transformations of styrene and divinylbenzene (DVB) copolymers permit us to obtain sulfonic cation‐ and anion‐exchange resins of a different basicity. In the last few years, new methods for the production of complex‐forming resins for nonferrous metals have been intensively developed. This paper is also devoted to this problem. Among the series of complexing resins, those derived from the ion‐exchange resins are the best known; they contain aminocarboxylic groups obtained by thermal treatment of an ion‐exchange resin with monohaloacetic acid in a low‐alkaline medium:
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For the improvement of the complexing ability, the presence of iminodiacetic acid groups is desirable. In our opinion, the simplest among many possible variants is oxidation of the ion‐exchange resin with diethanol amine groups. An acid solution of sodium dichromate may be applied as the oxidant. Other oxidizing agents tested do not give the desired results. The oxidation process requires great skill; otherwise, the resulting product could not be completely or excessively oxidized. An amphoteric ion exchanger of this type has been successfully used for the copper pulp process:
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The 2,5 methyl vinyl pyridine (MVP) and DVB copolymer can be transformed by two‐stage synthesis into an amphoteric ion exchanger containing an α‐picolinic acid group:
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The degree of transformation in the oxymethylation stage amounts to 85%; that in the oxidation stage ranges from 92 to 100%. To obtain a better complexing ability of the result‐ ing amphoteric ion‐exchange resin, it is necessary to use a macroporous modilkation.

Anion‐exchange resins containing secondary amino groups can be converted into ion exchangers with dithiocarbamate groups if processed by carbon disulfide:
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In this case, the capactiy of the exchanger with respect to silver, mercury, and molybdenum greatly increases.

Interaction of the high‐molecular hydrocarbon compound with chlorosulfonic acid and subsequent treatment of the resulting polysulfochloride with aliphatic diamines or poly‐ amines yielded compounds with cation‐ and anion‐exchange amino groups:
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Uber den einflub der chemischen struktur von phosphorsauren kationenaustauschern auf deren thermischen stabilitat in wasser
Authors: Polyanskii N. G. , Nikitina A. I. , Polyanskaja N. L. , Isaeva G. Ja. , Slabkaja L. D.
Published: June 2010

Thermal stability of different phosphorus‐containing cation exchangers in water has been studied. It has been shown that at heating to temperatures of 80–180°C the phosphorus content decreases on account of (1) thermal hydrolysis leading to phosphoric acid formation and (2) matrix splitting leading to phosphorus‐containing soluble organic compounds. Therefore for precise percentage loss determination [so‐called dephosphorilation degree (DD)] it is necessary to mineralize the organic compounds. A comparative study of the following cation exchangers has been carried out: KF‐I—nonporous styrene‐divinyl‐benzene phosphorylated copolymer (A); KF‐II—the same, but macroporous (B); KFP—macroporous exchanger with styrene‐divinylbenzene matrix containing methylene‐phosphoric acid groups (C); KF‐7—nonporous exchanger prepared by copolymerization of β‐β‐dichlorethyl‐phosphoric acid ester, vinylacetate, and divinylbenzene (D). The most stable are the macroporous exchangers with styrene‐divinylbenzene matrix B and C. The nonporous exchanger A having the same chemical structure as B is less stable. With increasing temperature the phosphorus splitting increases, though the Arrhenius equation is not fulfilled. The DD values at 80°C and a heating duration of 1 to 20 days are not more than 5%. At 180°C DD is as high as 6 to 50%, depending on resin structure and heating duration.
Chemical transformation of polymers. XVII. Amination of poly(oxy(2,2‐bis‐chloromethyl‐trimethylene)) (penton)
Authors: Kahovec J. , Štamberg J.
Published: June 2010

Poly(oxy(2,2‐bis‐chloromethyl‐trimethylene)) reacts with methylamine, dimethylamine, and ethylenediamine in N‐methylpyrrolidone at 115–190°C forming corresponding amino derivatives; trimethylamine does not react under these conditions. The aminations are accompanied by a decrease in molecular weight. The dimethylamino derivative was quaternized with methyl iodide in dimethylformamide, and from the iodide the corresponding quaternary ammonium polybase was prepared using a strongly basic anion exchanger. This base, in an approximately 10% aqueous solution, was thermally degraded at 120°C for 70 hr. Under these conditions, the quaternary ammonium base was completely degraded, viz., about 63 %, to the polymeric dimethylamino derivative and methanol and about 37 % to the polymeric alcohol and trimethylamine. The unexpected splitting off of trimethylamine during the degradation is explained by the proximity of the ammonium groups in geminal CH2N+(CH3)3OK−.
Chemical transformations of polymers. XVI. Preparation and splitting of poly (methacryloyloxyethyltrimethyl‐ammonium hydroxide)
Authors: Holata J. , Ševčík S. , Štamberg J.
Published: June 2010

Poly (methacryloyloxyethyltrimethylammonium hydroxide) was obtained by polymer analogous transformations or polymerization and transformations from poly (2‐hydroxyethyl methacrylate), chloroethyl methacrylate, or methacryloyloxyethyltrimethylammonium salts. The preparation from these latter compounds by polymerization and anion exchange was the most advantageous.

At elevated temperature (60‐120°C) in aqueous solutions, the poly (methacryloyloxyethyltrimethylammonium hydroxide) split only hydrolytically; no Hofmann's degradation of quaternary ammonium hydroxides appeared. Kinetic measurements performed both on the polymer and on the low‐molecular weight model compounds (2‐hydroxyethyl pivalate and pivaloyloxyethyltrimethylammonium hydroxide) showed that the introduction of a quaternary ammonium group into the structure of an aliphatic ester considerably accelerates its alkaline hydrolysis.
Methods for forensic comparison and characterization of commercial polymer‐based materials
Authors: West J. C.
Published: June 2010

The methods used to examine forensic samples of commercial materials containing polymeric substances are summarized. The materials most commonly encountered are paint, textile fibers, fabrics, plastics, wire insulation, adhesives, adhesive tapes, and buttons. These materials are basically organic polymers which are filled to various extents with inorganic stabilizers, pigments, and/or extenders. The materials are therefore examined for both organic and inorganic constituents.

Techniques used to examine organic constituents include infra‐red, pyrolysis and infra‐red, pyrolysis gas chromatography, and chemical modification such as hydrolysis, followed by derivatization and gas chromatographic analysis of the derivatives.

Techniques used to examine inorganic constituents include spectrography, x‐ray fluorescence spectrometry, infra‐red, and scanning electron microscopy when coupled to an x‐ray analyzer.
Analogies and discrepancies between cationic and anionic polymerizations
Authors: Pepper D. C.
Published: June 2010

Results are reviewed on cationic polymerizations initiated by γ‐rays, by carbocation salts, and by strong acids, especially HClO4, with the conclusion that in no case are all criteria for true living polymerization satisfied.

Detailed information is presented on bimodal molecular weight distributions found in polystyrenes initiated by HClO4 in CH2Cl2 between 0 and −97°C, showing that at all temperatures, polymerization can take place via both pseudo‐cationic and true ionic species, with the former in numerical preponderance. Transfer reactions prevent these species from being in simple ionization/recombination equilibria with each other, hence precluding a true living polymerization situation.

The chief reason for these kinetic complexities is concluded to be a strong monomer‐complexation of the HClO4 initiator and of propagating species. Indications of similar complexation in styrene/H2SO4 and Ph3CClO4, and between HClO4 and five other monomers suggests it may be a fairly widespread feature in cationic polymerizations.
Copolymerization and the hot radical theory
Authors: Tüdöds F. , Kelen T. , Berezhnikh T. Földes
Published: June 2010

A new improved linear graphic method allowing simple and reliable determination of the reactivity ratios and estimation of the adequacy of the composition equation (i.e., of the mechanism of copolymerization) is presented.

After a brief description of the basic principles of the hot radical theory, a complete treatment of the binary copolymerization, with the aid of this theory, is given. A kinetic analysis shows that for the complete characterization of the copolymerization, 13 parameters are required. According to this theory, four parameters of the classical theory depend on concentration and dilution, and only one value is a real constant. The requirements of experimentation and computation for the real estimation of all 13 parameters are elaborated.
Chemical transformations of cyclo and related polymers
Authors: Butler George B.
Published: June 2010

The 1:2 regularly alternating copolymer of divinyl ether and maleic anhydride produced via the cyclocopolymerization mechanism has been converted to a number of derivatives, and certain of these derivatives have been found useful as antitumor agents. Citraconic anhydride was substituted for maleic anhydride in the above cyclocopolymerization and its derivatives also exhibited antitumor properties, as did the derivatives of the copolymers of furan with maleic anhydride and with itaconic anhydride, respectively. The divinyl ether‐maleic anhydride copolymer reacts with dimethylformamide to yield a copolymer possessing polyelectrolyte character. The completely methylated copolymer was found to be useful in determining the molecular weight distribution of the original copolymer by gel permeation chromatography.

A second series of reactive polymers were prepared by cationic initiation of o‐, m‐, and p‐(2‐vinyloxy)ethoxy‐β‐nitrostyrenes, propagation occurring only through the vinyloxy group. The polymer of the p‐isomer was crosslinked through anionic initiation on the nitrovinyl group. The m‐ and p‐isomers were converted to linear polymers through the nitrovinyl group via anionic initiation which underwent crosslinking through the vinyloxy group upon standing in air. The o‐isomer was not converted to polymer via anionic initiation. This unusual “ortho effect” appears to be a steric effect, as the only ortho derivative of β‐nitrostyrene which has been polymerized by anionic initiation is o‐fluoro‐β‐nitrostyrene. Poly‐m‐β‐dinitrostyrene was converted to the polyanion by sodium methoxide.

A third series of reactive polymers were synthesized via anionic initiation on the o‐, m‐, and p‐(2‐vinyloxy)ethoxystyrenes. Propagation occurred through the styrene double bond leaving the vinyloxy group pendant. Hydrolysis of this vinyl ether was accomplished in all cases to yield the poly‐2‐hydroxyethylstyrenes. Further reactions of these polymers with acrylonitrile, phenyl isocyanate, and diisocyanates led to new polymeric systems. Hydrolysis of the vinyloxy group of the original styrenes followed by esterification with acrylyl chlorides led to monomers that were cyclopolymerized by a radical mechanism to polymers containing ten‐membered rings.
The paracrystalline state of synthetic polymers
Authors: Hosemann R.
Published: June 2010

The combined analysis of x‐ray small‐ and wide‐angle scattering (SAXS and WAXS) or oriented synthetic polymers provides much information about their molecular and supermolecular structures. Special liquid‐like distortions exist as a consequence of chain conformations, typical to polymers. They can be described quantitatively by paracrystalline distorted microdomains. Their size is determined by the concentration of these distortions. The microparacrystallites are interconnected by segments of chains, both in lateral and chain directions. This three‐dimensional network is the reason for a rubber‐like elasticity of all polymers, whatever their degree of crystallinity. The microparacrystallites are the knots of the network, which can also be described by a paracrystalline superlattice with nematic‐ and smectic‐like properties dependent on the mechanical and heat prehistory. On the basis of this very general concept, stretching and annealing phenomena can be described quantitatively, as well as structural changes by graft copolymerization of polyethylene with styrene under 60Co‐irradiation. The insufficiency of the two phase model is pointed out.
Organization of macromolecules in the solid state: A personal approach
Authors: Keller A.
Published: June 2010

The purpose of the article is to highlight the existence of large‐scale regular organizations in high polymers in order to provide a contrast with the more traditional conceptions based on randomness in the solid polymeric state. The selection adopted in this article is highly personal. Not unnaturally the author's own material forms the backbone of the survey; other material featured is quoted selectively to fit into the spirit of the narrative. It is hoped nevertheless that the overall impression given will be a balanced view, particularly in the more controversial aspects of the subject, emphasizing the complementary part played by order and disorder in a solid polymer. The material selected ranges from “historical” items to most recent developments, some still unpublished, which perhaps in retrospect are not as far apart as it may appear at first sight.

Most of the material quoted is concerned with crystallization. The main items featured are macroscopic single crystals obtained by solid‐state polymerization, spherulites, chain‐folded lamellae with current issues relating to the nature of the fold surface, fibrous crystals, and the range of validity of the fringed micelle concept. In the course of this the nature of disorder in all these systems is also outlined and an appreciation is given of the usual technological material. The final section is devoted to some examples of remarkably regular organizations in twophase amorphous block copolymers.
Some photochemical reactions in solid polymer systems
Authors: Smets G. J. , Thoen J. , Aerts A.
Published: June 2010

The influence of the polymeric matrix on photochemical reactions proceeding in solid polymers has been examined in the case of a free radical photosensitive svstem and in the case photochromic polymers. The free radical photosensitive system is composed of polyvinylcarbazol matrix (PNVC) containing carbon tetra‐bromide as activator and di‐β‐naphthospiropyran as dye‐precursor in an average ratio 5/0.1.1. The latent image formation results from the photolysis of the charge‐transfer complex between PNVC and CBr4 (γ = 405 nm); hydrobromic acid is produced and reacts with the dye‐precursor with formation of a pyrylium salt. This pyrylium salt (latent image) and its CBr4 complex act as photosensitizers (Λ = 600–700 nm) for further HBr formation; the optical development results thus from the dve accumulation at the sites of primary irradiation. Quantum yields of photolysis of CBr4 and coloration efficiencies have been measured under different experimental conditions. With respect to photochromic polymers, the influence of the molecular size of indoleninobenzopirans on the thermal decoloration reaction has been examined. It was found that bisphotochromes oligomers dissolved in a poly(ethylene terephthalate). poly(ethylene isophthalate) (50/50) or in polystyrene and irradiated above 60°C show only a very limited fading in a first phase. and then are stabilized. On the contrary, low molecular photochromes or photochromic dimers present a rapid initial fading followed by a slow first‐order decoloration reaction.
Telomerization of styrene initiated by the system magnesium‐isopropanol‐carbon tetrachloride
Authors: Bormann Patrick , Franta Emile , Rempp Paul
Published: June 2010

Telomerization of styrene and of some other vinyl monomers is achieved by means of an initiating mixture made of a metal with a single positive degree of oxidation, a transfer agent, a solvent, and a monomer. The four constituents have to be present at the beginning of the reaction.

The yield and the molecular weights of the polymers produced have been studied as a function of temperature and concentration of reactants.

Propagation and termination steps proceed via a radical mechanism. The initiation reaction shows a surprisingly low activation energy.
Relative reactivities in cationic polymerization of styrene, acenaphthylene, 4‐vinyl biphenyl and 2‐vinyl fluorene influence of experimental parameters
Authors: Cohen Sylvain , Marechal Ernest
Published: June 2010

The relative reactivities of the following monomers: acenaphthylene, 4‐vinyl biphenyl, and 2‐vinyl fluorene are determined both experimentally and through quantum chemistry methods. Styrene is the reference monomer. The influence of experimental conditions: solvent, temperature, nature of the initiator are studied and the activation enthalpy and entropy differences determined. The comparison of these values with the 1/r2 (index 2 is relative to styrene) shows that, in a general way, the activation entropy is the determining reactivity factor. The stabilization energies are calculated both by Hückel's and Pople's methods and the values so obtained are in close agreement with experimental results. The discrepancy observed for acenaphthylene, between Hückel on the one hand, and Pople and experimental determinations on the other hand, is due to the strain of the pentagonal ring.
Infrared spectroscopic study of the conformations assumed, in solution, by β‐diamides considered as model compounds for the repeating unit in poly amides synthesized from β‐amino and β‐imino acids
Authors: Marraud M. , Neel J.
Published: June 2010

In order to get a closer understanding of the conformational features displayed by poly‐amides obtained from different β‐amino and β‐imino acids, a systematic investigation was carried out with three sets of model β‐diamides.
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Very dilute solutions in carbon tetrachloride were studied by infrared spectroscopy in the 3200‐3500 cm−1 frequency range which includes the vNH stretching absorption bands.

Depending on the substitution of the middle aliphatic sequence, molecules I (R, R') mainly assume either a stretched form (when R = H in β‐alanine derivatives) or a folded six‐membered ring conformation (when R = Me in the compounds synthesized from β‐aminobutyric acid). This latter conformer is stabilized by an intramolecular hydrogen bonding.

A similar behavior was evidenced with N‐dimethylated species III(R). The β‐alanine derivative III(H) was found to be in an open form, whereas, the β‐aminobutyric analogous diamide III(Me) assumed a folded structure. In this latter case, however, it was shown that the folding is mainly governed by a NH…π interaction between the NH group and the π orbital of the tertiary amide function.

On the other hand, the N‐methylation of the acetylamino group in models II(R) produces preferentially an eight‐membered ring chelate which is stabilized by an intramolecular hydrogen bonding involving the NH of the C‐terminal amide function and the highly nucleophilic CO in the N‐methylated acetylamino group.

Each of the evidenced conformers is described by a set of three rotational angles and is experimentally characterized by its specific spectroscopic features.
Postgelation relationships for number fraction distribution after polyfunctional polymerization
Authors: Luby P.
Published: June 2010

Correlations between weight and number fraction distributions of a reaction mixture obtained by polyfunctional homopolymerization of a single kind of repeat unit under postgelation conditions are derived by virtue of an inter‐ and intramolecular bonds balance. An expression for the number average degree of polymerization was derived by means of the probability generating function of the first generation. Number fractions of a specific group of topologically distinguishable structures corresponding to a certain class of molecular trees defined by a vector u may be calculated in this way. Relations were established in terms of the link distribution function which allows for a substitution effect. Gelation phenomenon is shown to cause the number distribution mathematical relations to take two different forms while the weight fraction distribution equations remain valid throughout the whole conversion range.
Spin labeling studies on constituents of wood. II. Correlation times of spin probes and rigidity of network structure in isolated lignin
Authors: Lindberg J. Johan , Bulla Ivan , Tö;rmälä Pertti
Published: June 2010

The correlation times, T, of stable pyrroline nitroxyl radicals were determined in solutions of thioglycolic acid lignin from birch pulp dissolved in dioxane, pyridine, or dimethyl sulfoxide‐water at 298 and 325 K. It was found that T decreases continously with temperature, but increases with increasing lignin concentration. In pyridine and dimethyl sulfoxide‐water, the lignin seems to behave as a nearly compact sphere, whereas in dioxane a more loose structure occurs in accordance with the correlation time data. However, the rigidity of the lignin network is evident in all cases investigated.
Polymerization of trans‐7‐oxabicyclo[4.3.0]nonane
Authors: Kops J. , Larsen E. , Spanggaard H.
Published: June 2010

The polymerization of trans‐7‐oxabicyclo[4.3.0]nonane in bulk has been investigated in connection with PF5 initiation. Complete reversability of the polymerization of this system has been demonstrated. The ceiling temperature is around 12°C, and thermodynamic parameters have been calculated from the temperature dependence of the equilibrium composition. The rate of polymerization decreases rapidly with temperature and becomes very slow below −30°C, particularly at higher degrees of conversion where a glassy state is approached. The molecular weights increase as expected with decreasing temperature, and products with molecular weights above 100,000 are obtained. In the upper range of polymerization temperatures, an appreciable oligomer fraction is formed which has been analyzed. The chain propagation occurs by predominant breakage of the O‐C8 bond, leading to an all‐trans configuration as shown by NMR. Polymerization may also be carried out in solution in toluene; however, the presence of solvent lowers both conversion and molecular weight. The polymers are elastomeric solids at room temperature (Tg ∼ 0°C).
Synthesis, hydrolytic reactivity, and polymerization of 2,6‐ and 2,7‐dioxabicyclo[2.2.1]‐heptanes
Authors: Hall H. K. , Deblauwe F. , Carr L. J. , Rao V. S. , Reddy G. S.
Published: June 2010

2,6‐Dioxabicyclo[2.2.1]heptane (3), the parent of a new ring system, has been synthesized by acid‐catalyzed bicyclization of 1,1‐diethoxy‐3‐hydroxymethyl‐4‐butanol. Conditions which were crucial to success included working in dilute dioctyl phthalate under high vacuum with vigorous stirring and distilling 3 as formed.

2,7‐Dioxabicyclo[2.2.1]heptane (4) was synthesized by similar acid‐catalyzed cyclization of either 5‐hydroxy‐2‐methoxytetrahydropyran or 1,1‐diethoxy‐4,5‐pentanediol.

In acid‐catalyzed hydrolysis, 3 was almost one million times as reactive as dimethyl acetal, and 4 was only slightly less. General acid catalysis was observed for both during studies of hydrolysis in presence of buffers.

Polymerization of 3 occurred very readily with a variety of cationic initiators. Protonic acids gave high conversion to soluble polymer which was of moderate molecular weight (ζinh = 0.35), liquid (rubber), and consisted of a 60:40 mixture of isomers (probably trans:cis) detected by NMR.

Cationic polymerization of 4 also occurred readily. Again, high conversions to moderate molecular weight liquid polymer were obtained. At −78°C, the polymer contained exclusively tetrahydrofuran links; at a higher temperature, several initiators gave significant amounts of tetrahydropyran links.
The oxidative thermal degradation of polypropylene containing various 2,6‐di‐t ert‐butyl‐4‐alkylphenols
Authors: Holčík J. , Košík M.
Published: June 2010

The oxidative thermal stability of isotactic polypropylene stabilized by a series of 2,6‐di‐tert‐butyl‐4‐alkyl (aralkyl, cycloalkyl)phenols by means of a thermoanalytical technique was investigated. The inhibition and the course of the oxidative thermal reaction was determined. The influence of the structure of antioxidants on active thermal decomposition in an oxygen atmosphere was compared. The effect of substituents in the applied type of antioxidants on the oxidative thermal reaction and the active thermal decomposition is discussed in detail.
Solvent effect on decomposition of hydroperoxides with dithiophosphates
Authors: Ivanov S. K. , Kateva J. D.
Published: June 2010

Decomposition of tetralin hydroperoxide in the presence of zinc diisopropyldithiophosphate and N‐phenyl‐β‐naphthylamine has been performed in solvents such as n‐decane, decalin, tetralin, cumene, anisole, acetophenone, nitrobenzene, chlorobenzene, and quinoline. The decomposition of hydroperoxide to molecular products and free radicals has been studied by means of the inhibitor method. The effect of solvent on the rate of oxidation of cumene and on the rate and course of decomposition of hydroperoxide is discussed.
Hypersound propagation in oriented polymethylmethacrylate
Authors: Lindsay S. M. , Shepherd I. W.
Published: June 2010

The hypersonic elastic properties of oriented polymethylmethacrylate (PMMA) have been studied using high contrast (>108) multipass Fabry‐Perot techniques. Four samples of different degrees of orientation (birefringence Δn = −4, −9, −15, −24 × 10−4) were prepared by drawing at 130°C. Measurements of longitudinal sound velocity, VL, as a function of ϕ, the angle between the draw and propagation directions, show an anisotropy which scales with Δ and amounts to 6% in the sample having Δn = 24 × 10−4. At ϕ = 0, VL = 2.80 kilometers per second, (KMS−1), the same as the value in an isotropic sample. The elastic constants C11 and C33 are measured as a function of Δn. Data as a function of sound wavelength, Λ, show dispersive effects in both VL and attenuation αΛ, for Λ > 0.7 μ. Over the range 0.7 μ < Λ < 1.3 μ, αΛ increases from 0.1 to 0.5 and VL increases by 8%. Attenuation is consistently higher for ϕ = 0. The data are interpreted in terms of densification (up to 15%) accompanied by void formation on orientation, the structure having characteristic dimensions of approximately 1.5 μ. The structure may be asymmetric with the longer dimension perpendicular to the draw direction. Additional Brillouin peaks may result from sound propagation in the voids (VL = 5.8 KMS−1) in which case the density is approximately 0.3 g cm−3. Measurements of the Landau‐Placzek ratio support these ideas, but evidence from electron micrographs is inconclusive. Dispersion measurements should in principle help determine details of the structure shape.
Melt‐spun polypropylene fibers with helical orientation. I. Morphology and mechanical properties characterization
Authors: Pakułl T. , Morawiec J. , Swiȩtosławski J. , Kryszewski M.
Published: June 2010

A new method of melt‐spinning of fibers with a twist is presented. The analysis of the dynamics of the spinning process shows differences in the distributions of rotational and longitudinal velocity gradients along the distance from the spinneret. The morphology of polypropylene fibers spun with the twist was examined by various techniques. It was shown that the applied method of spinning produces the distinct helical orientation inside the fibers. The overall and crystalline orientation was observed by birefringence and X‐ray diffraction techniques. The light diffraction patterns have shown the periodic helical unhomogenities inside the fibers. Measurements of mechanical properties have shown the dependence of the stress‐strain behavior of fibers on the twist rate. It was established that the fibers spun with intermediate rotational speed have the maximal tensile and sonic modulus and the ultimate strength.
A comparison of the supermolecular structure of wholly‐aromatic and aliphatic polymer fibers
Authors: Slutsker L. I. , Utevskii L. E. , Yu. Chereiskii Z. , Perepelkin K. E.
Published: June 2010

This paper considers specific features of the supermolecular structure of wholly‐aromatic polymer (WAP) fibers as compared with that of aliphatic polymer (AP) fibers revealed by small‐ and wide‐angle X‐ray diffraction and acoustic methods. Long periods of 150‐230 Å in size were observed in many WAP fibers. Special studies showed these periods to consist of crystalline and intercrystalline amorphous regions alternating along the fiber axis. These intercrystallite regions represent, just as in AP fibers, “weak” spots in the structure with respect to deformation and are responsible for the sorption properties. Acoustic measurements permitted the evaluation of the fraction of load‐holding chains in intercrystallite regions from the number of chains in the crystallite per the same section. It can reach 60‐80% for WAP, while only 10‐15% for the strongest AP fibers. Besides, in WAP fibers all tie molecules in intercrystallite regions are load‐holding, while only a small fraction of them hold the load in AP fibers. A study of poly‐p‐benzamide fibers showed their structures to be close to homogeneous. This accounts for the unusually high elastic modulus of this fiber (16,000–17,000 kg/mm2) which is close to that of crystallites (18,600 kg/mm2) and to the theoretical modulus of the molecule. Such a homogeneous supermolecular structure of oriented polymers is observed for the first time.
Properties of oriented block copolymers
Authors: Skoulios A.
Published: June 2010

In this paper, we shall be concerned with single crystals of block copolymers. As we shall have occasion to note later, these are highly oriented specimens of block copolymers in the mesomorphic state. The present condensed review of the subject is based mainly on published evidence worked out conjointly at Bristol and Genoa; it also refers, however, to unpublished work carried on in Strasbourg at Ecole d'Application des Hauts Polymères and at Centre de Recherches sur les Macromolécules. It is proper to specify immediately that the only copolymers found so far to produce “single crystals” are formed of polystyrene and polydiene blocks.
Styrene‐diene triblock copolymers: Orientation conditions and mechanical properties of the oriented materials
Authors: Weill A. , Pixa R.
Published: June 2010

The organization of the hexagonal structure of some block copolymers has been obtained directly from the melt. We have pointed out the temperature and shear conditions which give a well‐organized and oriented structure. In order to represent the viscous and elastic behavior of the melt, we have drawn flow curves and have measured the die swell ratio. A flow mechanism, corresponding to grain structure, is proposed. The results obtained enabled us to build a molding device. Fracture tests under tension on ABA poly(styrene‐b‐isoprene) samples exhibiting hexagonal structure showed a highly anisotropic behavior: If the crack propagates in a plane perpendicular to the isoprene cylinder axes or parallel with it, the fracture is either brittle or ductile accordingly. In the latter case, branching also occurs on both sides of the main crack. By using optical and scanning electron microscopy, the corresponding fracture surface morphologies have been studied. The brittle fracture surface shows a pattern of alternating rough and smooth bands which is characteristic of pure polystyrene. On the other hand, the ductile fracture surface is composed of an array of elongated “chips.” They are disposed practically parallel to the fracture propagation direction. Moreover, indentations made with a spherical steel penetrator led to residual ellipsoidal impressions. By measuring their dimensions, the anisotropy of the mechanical properties was displayed.
Bundle‐like nucleation and longitudinal growth of fibrillar polymer crystals from flowing solutions
Authors: Pennings A. J.
Published: June 2010

This paper gives a brief account of the areas in which fibrillar crystals have been encountered and provides a mechanism for the formation of bundle‐like nuclei and the longitudinal growth of fibrillar polymer crystals from flowing solutions.
Molecular motion, thermal expansion, and phase transitions in paraffins: A model for polymers
Authors: Strobl G. R.
Published: June 2010

Owing to their simple chemical structure paraffins are generally regarded as representing a system which is especially suitable for a model study of the thermal behavior of oligomeric and polymeric solids. Extensive investigations on the properties of n‐tritriacontane (C33H68) provide an example. For this system an identification of several types of motional mechanisms become possible. Their presence leads to peculiarities in the thermal expansion and to the occurrence of solid‐solid phase transitions.

Paraffins and polyethylene exhibit a marked anisotropy in the lateral thermal expansion. An analysis of the molecular background can be based on a modified Grüneisen theory which connects expansion coefficients with elastic constants and Grüneisen constants. The Grüneisen constants describe anharmonic properties of the lattice vibrations and can be derived from a temperature dependent measurement of the frequencies of a number of Raman active lattice modes. The analysis shows that the observed anisotropy is mainly a consequence of the uniaxial orientation of the strong thermal pressure originating from the rotational and torsional oscillations of the chains.

In the case of C33H68, the transition from the well ordered crystalline state to the melt occurs in several consecutive steps. Three solid‐solid phase transitions occur before melting and each one leads to a steplike decrease in the degree of order. Applying a combination of x‐ray and spectroscopic techniques it was possible to follow on a molecular level the changes in the state of order by specifying the defect structure. It is found that coupled 180°‐jumps, flip‐flop screw jumps, and defect diffusion along a chain set in successively, the onset of each mechanism of motion being accompanied by a phase transition.

The measured melting entropy is indicative for a coiled chain conformation in the melt with slight deviations from a random coil owing to the occurrence of limited short range order. This follows from theoretical considerations.
State conditions of polymer and monomer with liquid crystalline phases
Authors: Cser F. , Nyitrai K. , Hardy Gy.
Published: June 2010

Results are presented for studies of p‐substituted p'‐acryloyloxy‐azoxy‐benzene, cholesteryl vinyl‐succinate, and cholesteryl vinyl fumarate in systems containing monomers and polymers in different mesomorphic states.
Analysis of exponential clipped photon autocorrelation spectra
Authors: Nieuwenhuysen P. , Clauwaert J.
Published: June 2010

Several fitting procedures were applied to the analysis of experimentally obtained mono‐exponential clipped photon autocorrelation spectra to find out how small distortions of individual measurements can best be taken into account. An iterative method seems unsatisfactory. The interpretation of a plot of the combined results of unweighted and weighted linear least square fits to straight lines and quadratic curves is more successful. This prevents a possible bias caused by using only one kind of fit. A smoothed weighting procedure was compared with the direct use of weighting factors from the raw data.
Spectral broadening of light scattered from alginate gels
Authors: MacKie W. , Sellen D. B. , Sutcliffe J.
Published: June 2010

Light scattering Rayleigh linewidth measurements have been made on calcium alginate gels using the autocorrelation method. The degree of broadening has been found to be small (∼2%) although two relaxation times (∼7 and 50 msec) within the broadened component have been measured. Oscillations were generally found to be superimposed upon the autocorrelation function and these have been positively identified with bulk oscillations of the specimen. By scanning through the gel with the focused laser beam it has been shown that there are long range (tenths of millimeters), long term (tens of minutes), fluctuations in alginate density.

Experiments were also carried out in which the diffusion constants of dextran fractions and globular proteins within the gel were measured by investigating the heterodyne beat spectrum. It was found that the movement of macromolecules with hydrodynamic diameters less than 10 nm was virtually unimpeded by the gel. Diffusion constants fell to about one third of those in aqueous solution for hydrodynamic diameters of ∼30 nm.