bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion‐dipole interactions and chiroptical property changes of an optically active nylon‐type polyamide in CaCl2‐methanol solutions
Authors: Bris Joel Le , Vert Michel , Selegny Eric
Published: June 2010

The chiroptical properties of poly(‐) 1,2‐diaminopropane sebacamide) (I) and of its model molecule: the N, N'‐didecanoyl (‐) 1,2‐diaminopropane (II) in CaCl2‐methanol solutions have been investigated by ORD (optical rotatory dispersion) and CD (circular dichroism) over a wide range of salt/monomeric units or salt/model molar ratios τ. The origin of the observed CD bands is discussed on the basis of the electronic transitions of isolated amide chromophores. The polymer behaves exactly as if the monomeric units were completely independent. The optical activities of (I) and (II) in CaCl2‐methanol solutions are found to depend on two overlapping phenomena: an ion‐dipole complex which prevails at low τ; a solvent‐like effect of the excess salt on the complexed species. A method for calculating the ion‐dipole association constant Kc from the optical rotatory power changes as a function of τ, is described. It is not necessary to know [ϕms] and [mms], the molar specific rotatory powers of the model and polymeric complexed species, which are subsequently deduced using Kc. The structure of the ion‐dipole complex and the nature of the solvent‐like effect are discussed.
Analysis of conformational changes in polystyrene and its derivatives in dilute solution by using the ultraviolet absorption behavior of model compounds
Authors: Van Nguyen‐Luong Bach , Noël Claudine , Monnerie Lucien
Published: June 2010

Study of the variation as a function of temperature of the molar extinction coefficients of dilute solutions of various alkylbenzenes, the configurational isomers of 2, 4‐diphenylpentane and 2, 4, 6‐triphenylheptane, and polystyrene and certain of its halogenated and methylated derivatives, has revealed behavioral anomalies. These have been attributed to changes in the position of the benzene rings whether accompanied or not by rotations of the backbone bonds leading to an overall conformational change.
Polyurethane networks
Authors: Rutkowska M. , Kwiatkowski A.
Published: June 2010

Thermoplastic urethane elastomers are interesting materials, to work with when physical and mechanical properties of plastics are being studied. This is due to the frequently large or sometimes, exclusive participation of the secondary bonding. Measurements were taken in order to establish the size and extent of reaction of the primary and secondary bonds in thermoplastic urethane elastomers obtained from polyethylene adipate, 4,4 diphenylmethane diisocyanate, and the following chain extenders: ethylene glycol, propylene glycol 1,3; propylene glycol 1,2; butylene glycol 1,4. Through a series of simple stress‐strain measurements at different temperatures, and by using the swelling equilibrium method in different solvents, the crosslinking density with primary and secondary bonds was determined; in addition, we have also found the activation energy of secondary bonds in thermoplastic urethane elastomers.
Photoelastic behavior of poly(n‐alkyl acrylate) networks in the rubbery state
Authors: Ilavský M. , Hasa J. , Dušek K.
Published: June 2010

The photoelastic behavior of poly(methyl acrylate), poly(ethyl acrylate), poly(butyl acrylate), and poly (octyl acrylate) networks was investigated in the temperature range 15–95°C. The temperature dependence of unperturbed chain dimensions dIn (r20/dT, and the temperature dependence of the optical anisotropy of the statistical segment, dIn δα /dT, were determined. For all polymers, low positive values of dIn (r20)/dT were found, while the absolute values of dIn δα /dT were high and decreased with the increasing length of the side chain. These results led to the suggestion that correlations exist between side chains of poly(alkyl acrylate) networks, and that the extent of these correlations increases with the increasing length of the side chain. The stress‐optical coefficient of poly(alkyl acrylates) is independent of both time and deformation, but decreases markedly with increasing content of the crosslinking agent, which is explained by disturbances of the local order due to cross‐linking rather than to non‐Gaussian behavior. The experimental values of δα, which were negative in all cases and decreased with increasing length of the side group, were compared with the calculated values of the optical anisotropies of monomeric units for various models of the latter.
Mechanical behavior of lightly cross‐linked polyurethanes
Authors: Dzierźa W. , Janáček J.
Published: June 2010

Stress‐strain and stress‐relaxation behavior, ultimate properties and equilibrium swelling of polyurethane elastomers based on poly (ethylene adipate), poly (ethylene maleate), propylene glycol, and 4,4‐diphenyl methane diisocyanate (MDI) have been studied. The elastomers were crosslinked by an excess of MDI and by tetramethylthiuram disulfide (TMTD); the latter was supposed to form additional crosslinks on the unsaturated bonds. Although no true equilibrium was found during the stress relaxation experiments, samples crosslinked by MDI measured at 25, 50, and 80°C, and samples crosslinked with additional TMTD measured at 50°C gave very good Mooney‐Rivlin plots, from which the elastic parameters C1 and C2 could be determined. The E (10 sec) and E (100 sec) moduli from the stress‐relaxation experiments, the relaxation speed, C1 values, and equilibrium swelling degree v2 were used to estimate the effect of MDI and of additional crosslinks due to TMTD. It was found that if TMTD was added as a second crosslinking agent to MDI systems, the moduli first passed through a minimum. On the other hand, TMTD was found to have a negative effect on the tensile strength σb and strain‐at‐break εb values throughout the whole concentration range used. The results obtained were clarified on the basis of mutually influencing crosslinking reactions in the formation of the resulting networks.
Trends in polymer characterization
Authors: Billmeyer Fred. W.
Published: June 2010

The unique properties of polymers derive chiefly from their long‐chain nature, their high molecular weights, and their molecular weight distribution. The characterization of these properties has developed in steps, each followed by a period of consolidation and application. The most recent of these steps of advancement were the introduction of gel‐permeation or liquid‐exclusion chromatography (GPC), solving the problem of determining molecular weight distributions, and the calculation of the unperturbed dimensions of polymer chains. In the current period of consolidation following these advances, disturbing trends are evident. More use is being made of empirical but rapid techniques such as GPC, but less regard is being paid to the need for the calibration samples required to give them meaning. Absolute methods for molecular weight measurement, providing such samples, are practiced far less than a decade ago, and much special apparatus developed for these techniques is no longer commercially available. These methods are vital, and their continuing development and practice must be encouraged.
Monte carlo simulation of a random‐flight chain in a restricted environment: The polymer‐in‐a‐box problem
Authors: Smitham James B. , Napper Donald H.
Published: June 2010

Computer simulations of polymer chains in restricted environments were carried out by the Monte Carlo technique. The model investigated was that of a random‐flight chain that commenced at an impenetrable barrier. The effect of close packing of contiguous polymer chains and the likely effects of the self‐excluded volume of the segments on the thickness of the adsorbed layer were studied.

The results obtained suggest that the extension normal to the interface of a random‐flight chain with no volume exclusion was seemingly hardly affected by the presence of lateral compressive boundaries, at least at the usual surface coverages studied experimentally. When the effects of volume exclusion were simulated, the extension normal to an impenetrable barrier increased. This implies that the effects of excluded volume are likely to be responsible for the experimentally observed expansion of polymers normal to the interface.
Comparison of different methods of determining the functionality of polyisocyanates
Authors: Guise G. B. , Zoch C. G.
Published: June 2010

Gel‐point methods for the determination of the functionality of some of the most widely used types of industrial polyisocyanate and polyisocyanate derivatives have been investigated. No single method was applicable to all types, and the most suitable method for each type was determined.

With aliphatic polyisocyanates such as N,N′,N‐tris(6‐isocyanatohexyl)biuret I and II b or c (derived from trimethylolpropane and diisocyanates), the most satisfactory method was gel‐point titration with amino‐terminated polyethers. This method was unsuitable for the more reactive aromatic polyisocyanates IIa (from trimethylolpropane and tolylene diisocyanate) or III (poly(methylene phenylene) polyisocyanate), but these could be gelled by reaction with water. Gel‐point condensations with polyamines could be used for the less reactive phenol‐ and ketoxime‐blocked polyisocyanates.

Poly(carbamoyl sulfonate) (VI) could be gelled either by hydrolysis to a polyurea in the presence of excess tertiary amine or by reaction with a diamine in the presence of a slight excess of tertiary amine to neutralize the bisulfite released. In all the gelations studied, the functionalities depended on concentration as a result of intramolecular reactions; this is a possible source of error in functionality determinations, particularly in the titration method.
Hydration of biopolymers
Authors: Watt I. C. , D'Arcy R. L.
Published: June 2010

Water‐vapor sorption by a range of biopolymers is reviewed to demonstrate the general similarities in sorption characteristics. The interaction of water and the protein wool keratin is considered in more detail and further analyzed in terms of a three‐component isotherm equation. Similar analyses have been applied to the water‐vapor absorption isotherms of chemically modified wools and nylon 66. Changes in the secondary structure of wool affect the water content only at high humidities and have little effect below 80% R.H., where specific site absorption is the predominant mechanism. The analyses confirm that both the polar side chains and the peptide groups of the main polypetide chains provide specific sites for association of water molecules. Sorption hysteresis is shown to be dependent on the experimental procedure for determining “equilibrium” water content. By adopting an experimental technique which minimizes conformational changes during desorption of water from wool, sorption hysteresis is reduced and may be eliminated at low humidities. It is apparent that hysteresis water, when present, is not associated with specific sites but results from conformational changes in the substrate.
Persulfate‐initiated reactions of N‐vinylpyrrolidone
Authors: Senogles E. , Thomas R.
Published: June 2010

In the presence of excess water and potassium persulfate, N‐vinylpyrrolidone reacts to form 1,1‐bis(1′‐pyrrolidonyl)ethane. At lower water concentrations, potassium persulfate initiates the cationic polymerization of vinylpyrrolidone.
Pulse radiolysis of N‐vinylpyrrolidone
Authors: Davison A. , Sangster D. F. , Lynn J. E. , Senogles E.
Published: June 2010

The pulse radiolysis of N‐vinylpyrrolidone and poly(vinylpyrrolidone) in aqueous solution has been studied. The absorption spectra of the intermediates produced have been measured and the kinetics of their disappearance studied. Further study is necessary before the precise structure of the intermediates can be described.
Grafting of methyl methacrylate to polypropylene
Authors: Burchill P. J. , Pinkerton D. M. , Stacewicz R. H.
Published: June 2010

The mutual γ‐irradiation method has been employed to graft methyl methacrylate (MMA) to polypropylene (PP) film in solutions open to the air. It was observed that grafting occurs only when the monomer solutions contain water. This effect of water has been related to a reduction in the oxygen solubility in aqueous solutions. There is some evidence that water affects the kinetics of the graft polymerization.
Stopped‐flow studies of cationic polymerizations
Authors: Pepper D. C.
Published: June 2010

This paper summarizes results and conclusions from an extensive study by stopped‐flow methods of the rapid nonstationary phase of the polymerization by HClO4 in CH2Cl2 of styrene and some styrene derivatives. With styrene, this precursor reaction is detectable but unimportant at 0°C, becomes longer‐lasting as the reaction temperature falls, and at –97°C is the only contributor to the polymerization.

Detailed studies at −60 and −80°C, identifying a transient absorption (λmax‐340 nm) as that of the (poly)styryl carbenium ion, lead to the conclusion that the reaction is a composite, with nonionic as well as ionic components. The rates of the polymerization by the two mechanisms can be distinguished only in favorable circumstances (presence of perchlorate salts) but can be interpreted to yield approximate rate constants for propagation by polystyryl carbenium ion‐perchlorate ion‐pairs, viz., kp± ∼ 2000 M−1S−1 at −80°C; 4000–5000 at −60°C. The rate constants of propagation by free ions are estimated as 10–20 times greater.
Kinetics of isobutyl vinyl ether polymerization initiated by trityl salts: A critical reexamination
Authors: Subira F. , Sauvet G. , Vairon J. P. , Sigwalt P.
Published: June 2010

Kinetics of isobutyl vinyl ether polymerization initiated by Ph3C+SbCl6− in CH2Cl2 were reexamined by using adiabatic calorimetry and spectrophotometry as previously applied to p‐methoxystyrene polymerization. Consumptions of monomer and trityl hexachloroantimonate were followed simultaneously in the temperature range −40° to +25°C. Initiation appeared to be slow (incomplete initiator consumption at temperature equal to or lower than 0°C), and significant transfer and termination processes prevent the system to be considered as “living” (active‐centers concentration goes through a maximum during the polymerization). The initiation step was found to be first‐order with respect to monomer and to initiator, and an overall second‐order with respect to monomer was found for the polymerization. Initiation parameters were separately determined, whereas propagation, transfer to monomer, and termination parameters were computed on the basis of a unimolecular termination process, this leads, for example, to the following rate constants at 0°C and to the activation energies of corresponding reactions:

.
Study of thermal oxidation of polyolefins. VI. Change of molecular weight distribution in the thermal oxidation of polyethylene and polypropylene
Authors: Iring M. , László‐Hedvig S. , Kelen T. , Tüdós F. , Füzes L. , Samay G. , Bodor G.
Published: June 2010

In the thermal oxidation of low density polyethylene (PE) in the melt phase and isotactic polypropylene (PP) in the solid phase, the changes in molecular weight distribution (MWD), weight average molecular weights (Mω), and average number of chain scissions have been studied by gel permeation chromatography (GPC).

It has been established that in the case of PP degradation, there is an increase in molecular weight during the induction period both at 80 and 760 torr with simultaneous scission of the macromolecules. In contrast, a similar tendency can be observed in the degradation of PE only at very low (20 torr) pressures, i.e., the degree of molecular weight increases proportional to the length of induction period.

For both polymers at the temperature of investigations, considerable molecular weight decrease can be detected both at reduced and atmospheric pressures at the onset of measurable oxygen absorption.

In the maximum rate oxidation of PE and PP, the increase of temperature, oxygen pressure, and degradation time each causes a shift of the MWD curves towards lower molecular weights.

The average number of chain scissions against the amount of absorbed oxygen was also studied. It has been found that the average number of chain scissions per 1 mole absorbed oxygen is considerably higher for PE than for PP.

Molecular weight studies performed in the kinetic range of thermal oxidation show that under given conditions, Intermolecular combination reactions and chain scissions may occur simultaneously.
A “heterogeneous” model for oscillations of chemiluminescence in nonstationary oxidation of hydrocarbons
Authors: Rychlý J. , Matisová‐Rychlá L. , Lazár M.
Published: June 2010

The oscillations of the chemiluminescence intensity observed after oxygen drop in the system ethylbenzene‐benzene‐Co (naphthenate)2 are interpreted by the formation and decay of dissipative structures in the oxygen solution induced by the change in the direction of the temperature gradient between the sample and thermostatting equipment.
The influence of sample holders on oven aging of polypropylene
Authors: Drake W. O.
Published: June 2010

The effect of various types of glass specimen holders on the observed degradation time of polypropylene samples was investigated. Depending upon the type of holder used, different results could be obtained with the same antioxidants.

In partially enclosed holders, degradation products from samples drastically reduced the long‐term stability of other samples contained in the same holders. No evidence was found to indicate that this influence extended to adjacent sample holders, nor was any evidence found to suggest a positive influence of one sample upon another.

Furthermore, under routine testing conditions, no such adverse effects were found. However, in ovens not having sufficient circulation of air or without adequate exchange of fresh air, such adverse effects are believed possible.
Supermolecular structure and mechanical stress distribution among the chemical bonds in polymers
Authors: Friedland K. J. , Marikhin V. A. , Myasnikova L. P. , Vettegren V. I.
Published: June 2010

Stress distribution among the polymer chain segments and parameters of the supermolecular structure of oriented polypropylene, polyethylene terephthalate and polycaproamide films have been compared. The stresses have been determined by infrared spectroscopy, and the structure has been studied by electron microscopy and small‐angle and wide‐angle X‐ray scattering. The polymers studied are shown to have a microfibrillar structure. The sizes of long periods, the lengths of crystallites and amorphous regions are found. Stress distribution among the polymer chain segments is extremely nonuniform. Most of the segments, i.e., 90–95%, are subjected to stresses close to the applied stress, the rest of the segments, i.e., 5–10%, experience stresses which are at least an order of magnitude higher. Highly overstressed segments lie in the amorphous regions of microfibrils. They bear the major part of the applied load (not less than 80–90%). A model for the amorphous regions' structure of microfibrils in oriented polymers is discussed.
Chain orientation distribution and elastic properties of poly (p‐phenylene terephthalamide), a “rigid rod” polymer
Authors: Northolt M. G. , van Aartsen J. J.
Published: June 2010

On the basis of a single‐phase structural model a theory has been developed, which yields a relation between the fiber compliance and the chain axis distribution. It is shown that this relation, viz.

Is quantitatively fulfilled for poly(p‐phenylene terephthalamide) fibers studied in this investigation.
Lichtstreuung und polydispersität von polymerlösungen. I. Theoretische betrachtungen
Authors: Lechner M. D.
Published: June 2010

The influence of the type of molecular weight distribution function (Gaussian distribution, Schulz‐Flory distribution, log‐normal or Wesslau distribution) and of the distribution function itself on the light‐scattering behavior of polymer solutions is discussed. It is shown that the three types of distribution functions yield characteristic scattering functions Pθ, which permit us to determine the nonuniformity of the polymer and in some cases the type of distribution function.
Light scattering by solutions of tRNA molecules oriented in D.C. magnetic field
Authors: Dobek A. , Patkowski A. , Labuda D.
Published: June 2010

Light scattering measurements of macromolecular reorientation in a d.c. magnetic field, predicted and calculated theoretically by Kielich, were carried out for yeast (unfractionated) transfer ribo‐nucleic acids (tRNA) solutions of concentrations ranging from 0.001 g/cm3 to 0.05 g/cm3. The vertical and horizontal intensity components of light, scattered at 90° to the incident beam, were measured. The d.c. magnetic field parallel to the direction of observation was fixed in the 0‐20 kOe interval. These studies, together with previously performed Rayleigh light scattering measurements, permitted evaluation of the NaCl and nucleic acid concentration range in aqueous solutions in which tRNA molecules occurred in the monomer form. In concentrated salt solutions tRNA molecules associate with the highest probability parallel to their long axes. Light scattering studies in an external d.c. magnetic field showed the anisotropy of optical and magnetic polarizabilities of tRNA molecules to be negative. The conclusion from scattering measurements concerning the conformational changes of tRNA molecules in solutions of different ionic conditions are compared and discussed with data from the literature. The described method is suggested for studies of biological macromolecular complexes in vitro.
Laser light scattering and polydispersity of polymers
Authors: Meyerhoff G. , Hack H. , Raczek J.
Published: June 2010

The application of lasers to light scattering improves the potentials of elastic scattering, especially in the high molecular weight range and enables the technique of inelastic scattering to be used.

For elastic light scattering an experimental arrangement and an evaluation method is described which allows, within appropriate molecular weight ranges, the determination of the ratio Mw/Mn from the experimental scattering function with an accuracy down to 0.02.

The newer technique of inelastic light scattering yields the coefficient of translational diffusion D. Besides D, the friction coefficient f is also directly accessible. The basic equations are reported, as well as an application to mixtures of two nearly monodisperse polymers. Always a z‐average is obtained.
Complete temperature dependence of the far infrared absorption spectrum of linear polyethylene from 14°k to the melting point
Authors: Frank W. , Schmidt H. , Wulff W.
Published: June 2010

In the far infrared, polyethylene shows two absorption bands: a very strong one at 73 cm−1 and a weak one centered at 109 cm−1 which is only observable below 160°K. From the frequency and temperature dependence of the 73 cm−1 band, the maximum frequency shift, the peak height, integrated absorption intensities, and the integral half‐width are determined. The frequency shift with temperature is shown to be a linear function of the related lattice parameter. A comparison with the temperature behavior of the CH2‐rocking vibration at 730 cm−1 is given.
Blends of poly(ϵ‐Caprolactone) with poly(vinyl chloride). I. Morphology
Authors: Ong C. J. , Price F. P.
Published: June 2010

The morphology of blends of poly(ϵ‐caprolactone) (PCL) with poly(vinyl chloride) (PVC) was investigated. The observations made with the optical microscope and electron microscopes indicate that for the blends rich in PCL, the samples are almost completely filled with spherulites composed of lamellas radiating from the spherulite center and twisting regularly. As the concentration of PVC increases, the texture of the spherulites becomes increasingly coarse and open. The results of the elementary analysis, made with an x‐ray spectrometer, indicate a uniform distribution of chlorine atoms in the blends regardless of the composition. X‐Ray diffraction studies reveal that the unit cell dimensions of PCL are not changed by the presence of PVC. It is believed that the PVC molecules were trapped within the spherulites and rejected preferentially into interlamellar regions. The results of differential scanning calorimetry measurement show that the crystallinity of PCL decreases with increasing PVC content. PCL in the blend containing more than 70% PVC exhibits no tendency to crystallize. The blends show a depression of the melting point of PCL. Over a wide range of composition, the blends display a single glass transition intermediate between the transition of the respective components. The glass transition shows a systematic increase with PVC concentration.
Effect of free‐volume fluctuations on polymer relaxation in the glassy state
Authors: Robertson Richard E.
Published: June 2010

As is most clearly seen in the results of A. J. Kovacs on the volumetric relaxation following changes in temperature, the initial relaxation in polymers is surprisingly rapid, considering how slowly relaxation becomes later. We suggest that this rapid initial relaxation is due to relaxing molecular rearrangements in regions of particularly high free volume produced by thermal fluctuations. The magnitude of thermal fluctuations increases as the size of the region decreases, and molecular rearrangements are described that probably contribute to most polymer relaxation and seem to be completely contained in regions as small as 2–3 nm.
Crystal nucleation and the crystalmelt interfacial tension in linear hydrocarbons
Authors: Turnbull David , Spaepen Frans
Published: June 2010

Recent results on the homogeneous nucleation of crystals in n‐alkane (CnH2n+2) melts are used in conjunction with simple nucleation theory to calculate scaled crystal‐melt interfacial tensions, α (n), per CH2 group. α(n) falls off smoothly and, at first, sharply with n increasing to 12–15, where it levels and remains roughly constant at ca. 0.15 to n = 32, at least. We show that these results are accounted for satisfactorily by the Spaepen‐Meyer negentropic model for the crystal‐melt tension, if it is assumed that there is high probability for the occurrence, within the melt, of planar conformations persisting for 14–15 C atoms.
Formation properties of solid‐state extruded high density polyethylene fibers
Authors: Mead W. T. , Porter Roger S.
Published: June 2010

Extrusion rates have been measured for high density polyethylene fibers prepared by solid‐state extrusion through a conical die with maximum draw ratio of 52, using constant pressure and temperatures ranging from 0.12 to 0.49 GPa and 60° to 140°C and molecular weights from 5 × 104 to 6 × 106. The processing variables are reported in terms of an apparent elongational viscosity. The logarithm of the extrusion rate was proportional to the applied pressure. Deviation from the Eyring theory of viscosity was found, since lowering of the extrusion temperature to 60°C produced an anomalous decrease in the extrusion rates. The anomaly was explained by the increased friction between die and polymer, the pressure dependence of the yield stress, and by the pressure dependence of the α‐relaxation mechanism. Apparent activation energies of 60 and 100 kcal/mole were calculated for the solid‐state extrusion in the region 100°–130°C and 80–100°C. Three modes of deformation were observed for each extrusion, consisting of an unsteady state, a second stage of drawing in which the extrusion rate approached a constant value, and a fracture region. The first mode corresponded to orientation and rotation of the crystalline lamellae, as shown by the rapid increase and plateau region of the crystalline and noncrystalline orientation functions. During the second stage of deformation, the apparent elongational viscosity ηE increased linearly with draw ratio, as did the modulus, and this mode was found necessary for the attainment of high modulus fibers. The second mode of deformation was associated with the deformation of the crystalline lamellae and strain hardening in which ηE‐approached that for a glass. Strain hardening readily occurred with decreasing temperature, and increasing draw ratio and molecular weight. Continuous extrusion producing uniform modulus fibers was only possible when the maximum draw ratio of the die was less than the fiber draw ratio, where strain hardening occurred. The third mode of deformation limited the maximum modulus obtainable and consisted of fracture or kink planes oblique to the fiber axis. The relations between the processing variables used in the solid‐state extrusion and the resulting fiber properties are discussed.
Topological model of the crystalline morphology in polyethylene with grafted defects
Authors: Drǎgan Gh.
Published: June 2010

The most important results obtained on polyethylene morphology as a function of thermal, mechanical and chemical treatments are reviewed. Amorphous–crystalline coupling in high density polyethylene with grafted defects by photochlorination is quantitatively studied by differential thermal analysis using six parameters. The model of this coupling is discussed in terms of the topological thermodynamics.
Contributions to vinyl chloride suspension polymerization with constant rate
Authors: Feldman D. , Macoveanu A.
Published: June 2010

In the present paper the authors study the possibility of conducting vinyl chloride suspension polymerization at constant rate using a temperature program, as well as some physical and morphological characteristics of the obtained polymer. The elaboration of the temperature program necessary for conducting vinyl chloride suspension polymerization with constant rate was realized by two different means: empirical, on the basis of experimental data, and theoretical, on the basis of a mathematical model, which describes the kinetics of suspension radical vinyl chloride polymerization. In performing the polymerization with constant rate, the design of caloric exchange surfaces becomes much easier, an optimal using of the reaction space being in the same time ensured during the whole time of the process. The interpretation of experimental data permits us to affirm that by polymerization with constant rate can be obtained a poly(vinyl chloride) similar to the polymer with the same average molecular weight synthesized at a constant temperature with slightly weaker volumetric properties but some better thermal stability.
Liquid–crystalline solutions of polyhydrazides and poly(amide‐ hydrazides) in sulfuric acids
Authors: Morgan P. W.
Published: June 2010

Para‐linked aromatic polyhydrazides and poly(amide‐hydrazides) can be dissolved in sulfuric acid of about 100% concentration to form liquid–crystalline solutions, and if the solutions are not heated excessively, they are reasonably stable and can be spun into strong fibers. Similar results can be obtained in fluorosulfonic acid and its admixtures with sulfuric acid. Polyhydrazides and copolyhydrazides based on oxalyl, terephthaloyl, chloroterephthaloyl, and 2,5‐pyridinedioyl units and poly(amide–hydrazides) based in part on such intermediates as 4‐aminobenzhydrazide and terephthalic dihydrazide were examined for formation of optically anisotropic solutions. Polymers with high proportions of meta‐ and ortho‐linked ring units were highly soluble but did not yield liquid–crystalline solutions.
Synthesis, characterization, rheological, and fiber formation studies of p‐linked aromatic polyamides
Authors: Aoki Hiroshi , Coffin David R. , Hancock Tony A. , Harwood Daniel , Lenk Rudolph S. , Fellers John F. , White James L.
Published: June 2010

Aromatic polyamides are being extensively studied in our laboratories along the lines of synthesis, dilute solution viscosity and light scattering, concentrated solution optical and rheological measurements, and wet spinning of fibers. Several series of polymers have been synthesized, including those starting with chloro‐ and methyl‐substituted p‐phenylene diamine and also those starting with the monomer bisacid A2. Poly(chloro‐p‐phenylene terephthalamide) in dilute solution shows a marked hydrodynamic volume dependence on solvent when studied in DMA–5% LiCl versus H2SO4 At higher concentration, optical characterization shows that liquid crystal formation in the quiescent state corresponds to changes observed in the rheological behavior for Kevlar–H2SO4 solutions; these observations include a yield stress and the inversion of the order ofG/G' = tan 5. Fibers produced by wet spinning and subsequently studied in cross section via SEM have revealed that material continuity is easily attained with Kevlar‐H2SO4 spinning dopes under a variety of processing conditions.
Properties of a phenyl‐substituted polyphenylene in dilute solution
Authors: Work James L. , Berry Guy C. , Casassa Edward F. , Stille John K.
Published: June 2010

Three preparations of a phenyl‐substituted polyphenylene were fractionated and studied in solution by light scattering, osmometry, viscometry, fluorescence depolarization, and exclusion chromatography. Three of the five main‐chain phenylene groups in the repeat unit are linked para, but the other two may be either meta or para, with the latter linkage predominating. The data are consistent with a chain structure characterized by rigid segments about 70–75Å long, on the average, joined with 120° bond angles, about which virtually free rotation is allowed. For chains of up to about 250 backbone phenylene units, the hydrodynamic behavior in tetrahydrofuran, and other solvents, is that of a freely draining coil with intrinsic viscosity proportional to molecular weight. The effect of intramolecular excluded volume on chain conformation is negligible, although intermolecular interactions are reflected by a positive second virial coefficient (in tetrahydrofuran). Study of polymers of higher molecular weight is hampered by formation of what appear to be metastable aggregates resembling randomly branched chains.
Effect of the length and structure of the side chain of soluble copolymers of the methacrylamide type on the mobility of the spin label bonded to the chain end
Authors: Labsky J. , Pilar J. , Kalal J.
Published: June 2010

Results are reported obtained by the ESR study of the mobility of spin labels bonded at the side‐chain ends of copolymers of the polymethacrylamide type. The correlation times, γ, characterizing the mobility of the spin label were determined by analyzing the EPR spectra of 1% methanolic solutions of copolymers. The log γ vs 1/T dependences within the temperature interval 233‐313 K studied are linear and are characterized by the same activation energy, Ea = 3 kcal/mole (12.5 kJ/mole), for both types of the side chains. The mobility of the spin label bonded at the end of the side chain of the oligoglycine type is lower than that of the spin label bonded at the end of the equally long side chain of the methylene type.
Polyaspartamide — a potential drug carrier
Authors: Drobník J. , Saudek V. , Vlasák J. , Kálal J.
Published: June 2010

The molecular weight of polysuccinimide prepared by thermal polycondensation depends mostly on the reaction temperature. Antioxidants have no effect. Proteolytic enzymes do not degrade the main chain of N‐substituted polyaspartamides tested. Bacteria are capable of utilizing about 4% of aspartic acid from the 2‐hydroxyethyl derivative. Side chains are sensitive to enzymes as in the previously studied polyolefinic polymers.
Application of polysaccharides and their derivatives as supporting materials and auxiliary substances in medicine and nutrition
Authors: Philipp B. , Bock W. , Schierbaum F.
Published: June 2010

Given certain peculiarities of polysaccharides in comparison to synthetic polymers, a survey is made of the application of polysaccharides in the field of nutrition for calory‐reduced food, in pharmacy, and as auxiliary products in surgery, stressing to some extent recent results of the authors in cellulose and starch chemistry. In dealing with nutritional uses in calory‐reduced food, the problem of persorption of cellulose powders is discussed as well as properties and uses of recently developed starch products obtained by partial hydrolysis. In reviewing pharmaceutical uses of polysaccharides, we mention the active therapeutic effects of these substances, with detailed emphasis on the application of starch and cellulose products as carrier compounds. A survey of polysaccharide products as surgical auxiliaries is centered on their application as plasma expanders, as internal surgical dressings, and as external aids (glove powders). Finally, the need for further progress in polysaccharide chemistry is stressed as a prerequisite for finding and realizing new applications in restoring human health.
Problems of matrix activation in using the cyanogen bromide method
Authors: Pommerening K. , Jung W. , Kühn M. , Mohr P.
Published: June 2010

The CNBr used to activate carriers for covalent binding of biologically active substances must not contain free cyanide ions. Several carrier materials, such as poly‐2‐hydroxy‐ethyl methacrylate (Spheron) or cellulose, adsorb cyanide ions that cannot be removed by thorough washing. But when these carriers are incubated with substances or ions showing high affinity for cyanide ions, such as methemoglobin or Fe2+, then as a result of complexing, desorption from the carrier and inhibition of the fixed or incubated substances are effected.
The kinetic specificity of polyethylene terephthalate degradation in the living body
Authors: Rudakova T. E. , Zaikov G. E. , Voronkova O. S. , Daurova T. T. , Degtyareva S. M.
Published: June 2010

The kinetic specificity of polyethylene terephthalate (PET) degradation in a living body was investigated. The polyethylene terephthalate net implanted subcutaneously in the backs of rabbits and dogs usually degrades from the surface very slowly. The time of complete degradation of PET fibers in both dogs and humans amounts to 30 ± 7 yr. The time for loss of 50% of the initial filament strength under similar conditions is 10 ± 2 yr. An equation for promotion of changes in the mechanical properties of polyethylene terephthalate fibers in living animals and humans has been derived.
Synthetic polymers with anticoagulant activity
Authors: Van Der Does L. , Beugeling T. , Froehling P. E. , Bantjes A.
Published: June 2010

Polymers with C=C bonds have been modified by reaction with chlorosulfonyl isocyanate (CSI). Addition products were obtained in yields varying from 60% to 75%. Reaction of these products with NaOH yielded polyelectrolytes with sulfamate and carboxylate groups, whereas from the reaction with NH4OH polyelectrolytes with sulfamate and carbonamide groups, were obtained. The polyelectrolytes showed anticoagulant activity depending on the structure and on the presence of both sulfamate and carboxylate groups. These groups are essential for the anticoagulant activity, because N‐S bond cleavage in the sulfamate groups as well as substitution of carboxylate by carbonamide groups resulted in loss of activity. From the recalcification times of bovine plasma, it could be concluded that the most active polyelectrolyte had an activity of 6‐7% compared with heparin. However, determination of the activated clotting time of blood from rabbits showed that this compound had an in vivo activity of 50% in comparison with heparin.
Blood‐compatibility‐water‐content relationships for radiation‐grafted hydrogels
Authors: Ratner B. D. , Hoffman A. S. , Hanson S. R. , Harker L. A. , Whiffen J. D.
Published: June 2010

A series of radiation‐grafted hydrogels with water contents ranging from 10% to 90% have been prepared. When evaluated by the vena cava ring test, increasing amounts of adherent thrombus were found in rings with lower graft water contents. Using a baboon arteriovenous shunt evaluation system, platelet thromboembolic consumption was found to be directly proportional to graft water content. Hydrogels studied by the renal embolus ring test were found to cause numerous infarcts in the kidneys of test animals. Results from these studies do not support “water‐content‐blood‐compatibility” hypotheses which have been suggested for hydrogels. Results obtained with a series of hydrophilic‐hydrophobic copolymers suggest that a balance of polar and apolar sites at a polymer‐surface may be important for blood compatibility. The significance of results from the three evaluation systems used is discussed.
Platelet adhesion from human blood to bare and protein‐coated polymer surfaces
Authors: Neumann A. W. , Moscarello M. A. , Zingg W. , Hum O. S. , Chang S. K.
Published: June 2010

A static platelet adhesion test using whole human blood was employed to assess the affinity of various bare polymer (sulfonated polystyrene, acetal resin, Teflon FEP, polystyrene) surfaces as well as various surfaces of glass and polymers that were coated with plasma proteins. Platelet adhesion to the bare polymer surfaces was found to increase with increasing solid surface tension of the substrate. With protein‐coated glass and polymer surfaces, however, platelet adhesion did not follow the above pattern; more platelets adhered to the fibrinogen‐coated surfaces than to albumin‐coated surfaces. The solid surface tension of the underlying substrate also influenced the adhesion of platelets to the protein‐coated surfaces; platelet adhesion to the proteincoated high‐energy sulfonated polystyrene substrates was found to be greater than to the corresponding protein‐coated lower‐energy substrates of acetal resin and Teflon FEP.
The interaction of polymer surfaces with blood
Authors: Beugeling T.
Published: June 2010

Some general aspects of the interaction of foreign materials with blood are summarized. The role of protein adsorption in this interaction is briefly discussed. In an attempt to produce more stable antithrombogenic surface coatings than the well‐known heparin‐bonded surfaces, a method is described in which a high‐molecular‐weight polyelectrolyte is bound to polymer surfaces. In vitro experiments carried out with freshly drawn human blood show a reduced platelet adhesion on such surfaces.
The role of adsorbed proteins in platelet adhesion onto polymer surfaces
Authors: Kim Sung Wan , Lee Eun Soo
Published: June 2010

Polymer surfaces adsorb plasma proteins upon contact with blood. The nature of this adsorbed layer may determine the extent of platelet adhesion onto these surfaces. It is proposed in this study that incomplete terminal oligosaccharides, galactose, and N‐acetyl‐glucos‐amine in adsorbed fibrinogen and γ‐globulin are mainly responsible for the platelet adhesion, possibly via glycosyl transferase reactions. In order to verify these proposed mechanisms, platelet–protein interactions in the bulk state and platelet aggregation caused by the interactions were studied. The study was further extended into the reactions of platelets with adsorbed proteins. Data on protein adsorption from blood plasma onto model polymers (Teflon FEP, silastic rubber, Avcothane, and Biomer) provide supportive evidence for the proposed mechanism. The results discussed in this paper emphasize the important role of protein adsorption onto polymer surfaces and the possible involvement of specific reactions in platelet adhesion.
The preparation and characterization of surface‐grafted plastic materials designed for the evaluation of their tissue and blood compatibility
Authors: Fischer J. Paul , Becker Udo , Von Halasz Sigmar‐Peter , Mück Karl‐Friedrich , Püschner Hubert , Rösinger Sigurd , Schmidt Anne , Suhr Hans H.
Published: June 2010

With the objective to develop both characterization methods and test systems for blood and tissue compatibility, some polymers, e.g., polyethylene (PE), polypropylene (PP), and ethylene/propylene/diene‐ter‐polymer (EPDM) of different shapes, e.g., beads, films, tubes, fibers, tubings, and microtome slices, were grafted with a variety of 15 monomers in order to introduce hydrophobic, hydrophilic, and ionizable groups. The grafted surface was characterized morphologically by the surface area (Brunauer‐Emmett‐Teller: BET value), by scanning electron microscopy (SEM), and by profilographic measurements. Surface grafting was controlled by frustrated multiple internal reflexion (FMIR)–ir measurements, by determination of the critical surface tension, and by energy‐dispersive x‐ray analysis (EDXA) combined with SEM. The EDXA–SEM method was found to be a helpful tool to characterize the homogeneity and penetration profile of surface grafting. The tissue compatibility was tested by implanting test samples under the skin of rats. Blood compatibility was determined via in vitro test systems based on the determination of single clotting factors.
Mechanism of stereoselective polymerization of oxirane
Authors: Tsuruta Teiji
Published: June 2010

The reaction mechanism of the stereoselective polymerization of methyloxirane is satisfactorily explained in terms of the enantiomorphic catalyst sites model, in which the symmetrical distribution of d*, and l*, catalyst sites is assumed. d*, Sites would accept D‐methyloxirane in preference to the L‐isomer, resulting in the formation of … DDDD … isotactic sequences, and vice versa. This paper is concerned with a mechanistic study on the origin of d* and l* nature of the catalyst by using a complex, [Zn(OMe)2‐(EtZnOMe)6] (I), the molecular structure of which was elucidated by x‐ray analysis. A possible mechanism for the stereoselective polymerization of methyloxirane is presented on the basis of results obtained from NMR analysis of the polymerization system catalyzed by (I) and GPC analysis of poly(methyloxirane) formed in the reaction system.
Recent results in the radiation synthesis and modification of polymers for special applications
Authors: Hummel D. O.
Published: June 2010

The cost for a mole of radicals from different sources is under the assumptions used, as follows: $0.85 using dibenzoylperoxide, $5.60 with 60Co, and $5.60 using a small 0.2‐MeV accelerator. Fluorine‐containing monomers and monomer mixtures belong to the most interesting class of systems for the radiation‐initiated synthesis of polymers with good thermal, mechanical, and chemical properties. Recently, the vinylfluoride‐vinylidenefluoride system was investigated in detail. The polymers were afterwards grafted with hydrophilic monomers.

Films from, for example, polyethylene, polypropylene, polyvinylfluoride, or polytetrafluoroethylene were grafted from the gas phase with butadiene, vinylchloride, and styrene. Usually, homopolymerization in the gas phase can be kept low. A highly interesting system both from a theoretical perspective and for practical reasons is polyethylene‐hexafluoroacetone. The grafting follows a chain mechanism, and the “branches” consist of only one monomer unit each. Cationic grafting was observed during the irradiation of α‐methylstyrene, vinylbutylether, or isobutene in the presence of polyethylene, polytetrafluoroethylene, or PVC. A tremendous amount of work has been done in the field of radiation grafting of fibers and fabrics. In recent years, the following fiber/monomer systems, among others, have been investigated: cellulose with styrene, vinylfluoride. ethylacrylate, or acrylamide; wool with styrene; polypropylene with vinylchloride and vinylidenechloride; poly‐(ethylene terephthalate) with styrene, acrylic and methacrylic acid, acrylic acid plus acrylonitrile, and N‐vinylpyrrolidone.

Special applications including radiation synthesis and modification of membranes and hydrogels, biocompatible materials, ion‐exchange membranes and resins, and, finally, the radiation‐grafting of enzymes have found considerable interest.