bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gel permeation chromatography. II. The nature of the separation
Authors: Moore J. C. , Hendrickson J. G. 
Published: June 2010

AbstractGel permeation chromatography is a special type of liquid‐solid elution chromatography based on the permeation of solute molecules into a rigid gel particle. The large molecules penetrate less into the small void spaces of the gel, and they are eluted first. Ideally, the entire separation is due to the size barriers that exist within the gel. Gel columns were readily calibrated with a series of polymer samples with a narrow molecular weight distribution. Elution curves of single components were found to be symmetrical, fitting closely the normalized probability function. Peak widths divided by their elution volumes correlated well with their heights. Complete resolution of the elution curve of a low polymer was demonstrated with these correlations. Calibration curves for polystyrenes and polyglycols were brought into coincidence by plotting elution volume against chain length on a logarithmic scale. These curves were not affected by column temperature changes or by changes to other good solvents as eluants.
Numerical analysis and kinetic interpretation of molecular weight distribution data
Authors: Goodrich Frank C. , Cantow Manfred J. R. 
Published: June 2010

AbstractA novel numerical method is described for calculating both the distribution moments and the molecular weight distribution curve from fractional on data. The method is based upon Gauss‐Laguerre integration techniques and enables the user to calculate six distribution moments by finite algebraic operations on the cumulative distribution curve. Results obtained by this method on a sample of thermally polymerized polystyrene are described and compared with the theoretical predictions of polymerization kinetics. The data are found to be equally consistent with an initiation mechanism which is either second‐ or third‐order in monomer concentration. The calculated activation energy for second‐order initiation compares favorably with values already reported in the literature, but insufficient data are available to make the same comparison for third‐order initiation.
Transport through polymer films
Authors: Kumins C. A. 
Published: June 2010

AbstractA brief summary of some of the factors influencing the transport of gases, vapors and ions through polymeric films is presented. The activated transition suite theory of diffusion and the application of Fick's law to the movement of molecules are discussed. The part played by the glass transition temperature and its relation to segmental mobility in determining the diffusion coefficients and hence the permeability characteristics of organic films is described. It will also be shown how the degree of crosslinking, hydrogen bonding, plasticization, and polymer adsorption in heterogeneous systems affect the chain mobility with subsequent effects on transport phenomena. In the case of the transport of ionic species through membranes, investigations are discussed which relate the permselectivity characteristics of polymers to their ability to act as barriers.
Ionic conduction in polymer films and related systems
Authors: Barker R. E. , Sharbaugh A. H. 
Published: June 2010

AbstractIn polymer films, electrical conduction by ion transport is a significant process which is potentially capable of revealing various aspects of the film's morphology. In this report, further details and consequences of conduction experiments with ion‐doped cellulose 2.5 acetate will be discussed along with some corroborating evidence for a large number of organic liquids. The most important conclusions are: (1) sorbed moisture provides charge carriers by dissociation to H+ and OH−, and (2) the effective dielectric constant ϵ′ is increased by sorbed moisture to a value above that of the pure polymer, or organic liquid, so that barriers to the dissociation of ionic species are greatly reduced. Furthermore, the theory of weak electrolytes may be applied to “strong electrolytes” within solid polymeric and/or liquid organic systems.
The polymerization of 1,4‐anhydro sugar derivatives
Authors: Kops Jorgen , Schuerch Conrad 
Published: June 2010

Abstract1,4‐Anhydro‐2,3,6‐tri‐O‐methyt‐D‐galactose has been synthesized and positively identified for the first time. 1,4‐Anhydro‐2,3‐di‐O‐methyl‐L‐arabinose was obtained in nearly pure form by an analogous reaction sequence. Both of these compounds undergo addition polymerization under the influence of Lewis acid catalysts to yield amorphous polymers with maximum degrees of polymerization of approximately 90. The chain propagation proceeds in each case with nearly equal amounts of 5‐ and 6‐mernbered ring opening leading to a mixture of furanosidic and pyranosidic unite in the polymer backbone. The resulting configurations at the anomeric centers under various conditions of polymerization, as elucidated mainly by degradation studies, can be explained only by a carbonium ion rather than a trialkyl oxonium ion polymerization mechanism and with the assistance of conformations analysis. The C‐5 substituent in the 1,4‐anhydro‐2,3,6‐tri‐O‐methyl‐D‐gitlactose was found to influence the stereochemistry of the chain propagation.
Mechanical loss mechanisms for polymers at very low temperatures
Authors: Woodward Arthur E. 
Published: June 2010

AbstractResults of dynamic mechanical investigations for various polymers in the temperature region from 4.2–77°K. or above are reviewed, and the mechanisms believed to be responsible for the various loss maxima are discussed. Dynamic mechanical data, obtained at ∼104 cps with a longitudinal vibrational apparatus, are presented for an un‐annealed polypropylene sample, for a commercial poly(methyl methacrylate) specimen, for a sample of purified poly(methyl methacrylate) containing 1% water, for three poly(vinyl toluene) samples (in the 200–300°K. range), and for a 76% styrene‐24% acrylonitrile copolymer.
Dielectric study of the transition temperature regions for poly (vinyl chloride) and some chlorinated poly(vinyl chlorides)
Authors: Reddish W. 
Published: June 2010

AbstractAudio frequency dielectric constant data versus temperature data for poly(vinyl chloride) exhibit a high temperature (glass) transition which becomes steeper and reaches higher values as the frequency is reduced. The same trend is demonstrated for a series of chlorinated poly(vinyl chlorides) although the transition decreases in magnitude and moves to higher temperatures systematically with increasing chlorine content. Corresponding loss data are presented. Dielectric constant values for poly(vinyl chloride), determined in the high temperature transition region from reversible (d.c.) polarization experiments, show that the trend to steeper and larger transitions continues as polarization lime increases. For 10,000 sec. polarization the curve exhibits a sharp peak with lambda point character and twice the highest a.c. value is reached. This dielectric constant peak is interpreted as a cooperative interaction in noncrystalline regions of long‐rod dipoles with moments perpendicular to the chain axes. This model is related to Natta's crystal structure for syndiotactic PVC where the assembly of planar molecules form an antipolar array. For PVC all the chlorines are on the same side of the axis but for chlorinated PVC, dipolar balancing due to 1,2‐dichloro groupings is responsible for the reduced transition magnitude. The high temperature process involves equilibrium of macroscopic volumes, whereas the low temperature transition, which is little affected by chlorination, involves local equilibrium only.
Non‐newtonian intrinsic viscosity and streaming birefringence of polymer solutions
Authors: Peterlin A. 
Published: June 2010

AbstractThe gradient dependence of intrinsic viscosity and streaming birefringence is a function of the orientation and deformation of the randomly coiled macromolecule in the viscous force field of the laminar flow. Orientation decreases the contribution of the coil to the shearing stress and deformation increases it. The anisotropy of hydrodynamic interaction favors orientation and slightly decreases deformation. Free deformation first increases and then decreases the hydrodynamic interaction thus causing the hydrodynamic resistance of the average chain segment and hence the intrinsic viscosity to pass through a minimum point. Finite chain length limits the expansion of coil and introduces saturation effects in viscosity and streaming birefringence. In the former it may eventually completely mask the effect of coil expansion on hydrodynamic interaction so that the minimum in the gradient dependence of viscosity may be observable with very long macromolecules only in good agreement with experimental data. In addition, the finite resistance of molecules to rapid change of coil shape also reduces the deformation and hence suppresses the up‐turn effect. The influence of coil rigidity is larger with low solvent viscosity and may be negligibly small with a very viscous solvent. Indeed, experiments with poly(methyl methacrylate) in Aroclor show effects characteristic for large‐coil deformation, i.e., a minimum in intrinsic viscosity and a subsequent increase with increasing gradient.
Synthesis of Polymers with Charged Heteroatoms in the Chain by the “Onium Polymerization” Method
Authors: Berlin A. A. , Razvodovskii E. F. 
Published: June 2010

AbstractThe method of “onium polymerization” was used for the preparation of conjugated polymers with quaternary nitrogen atoms in the main chain. The polymerization was studied for the case of 4‐chloropyridine, 4‐bromopyridine, and 4‐chloromethylpyridine. Poly‐4‐chloropyridine has increased electroconductivity and contains a considerable number of paramagnetic particles. The introduction of methylene groups between pyridinium nuclei results in the disappearance of this property. Poly‐4‐chloropyridine is soluble only in water, hydrolyzing rapidly to form pyridylpyridone and hydroxypyridine. Under the action of ammonia poly‐4‐chloromethylpyridine is transformed to the polymeric ilide.
Cooperative Interactions of Bound Ions and Sulfhydryl Groups in Hemerythrin
Authors: Keresztes‐Nagy S. , Klotz I. M. 
Published: June 2010

AbstractHemerythrin, the oxygen‐carrying protein of sipunculids, has been known in three forms: deoxy, oxy, met. A characteristic spectrum has been associated with each form. We have now found, from electrophoretic mobilites, that anions are bound to hemerythrin with concomitant large shifts in spectra. All of the ions showing these effects, N3−, HS−, SCN−, CNO−, Cl−, F−, and OH−, are known to form coordination complexes with Fe(III). Association constants have been evaluated for several of these complexes by spectrophotometric titration. The association is stronger with the protein in which the sulfhydryl group has been previously blocked. In a complementary manner, the reaction of hemerythric with mercaptan reagents, such as N‐ethylmaleimide, is very slow in the absence of iron‐coordinating ligands but rapid in the presence of ions such as N3− or SCN−. This cooperative interaction can be accounted for in either of two ways: (I) if under normal conditions hemerythrin is in equilibrium with a very small amount of its subunits (in which mercaptan groups are more accessible), bound ions would shift this equilibrium toward subunits; (Q) bound ions may produce a change of conformation in the macromolecule. Hybridization experiments provide strong evidence that the octamer → monomer equilibrium is the actual mechanism of the cooperative interactions.
Slereospecific copolymers 1,3‐butadiene‐2‐phenylbutadiene
Authors: Marconi W. , Mazzei A. , Lugli G. , Bruzzone M. 
Published: June 2010

AbstractThe results obtained in the stereospecific copolymerization of 1,3‐butadiene with 2‐phenylbutadiene are reported. The copolymers were generally obtained using catalysts prepared from substituted aluminum hydrides, AlI3 and TiCl4. Homopolymerization of 2‐phenylbutadiene with such catalysts gives an amorphous, low M.W. polymer having prevailing 1,4‐cis structure. In the copolymers the 2‐phenylbutadiene units still have a substantially cis structure; also the butadiene units are mainly 1,4‐cis up to 90‐95%. The 1,2 content in the copolymers is always very low. The content of 2‐phenylbutadiene units in the copolymers varies in a broad range from 10 to 80% and the reaction rate and the average molecular weight diminish as the phenylbutadiene increases. The monomer reactivity ratios were calculated and the distribution of sequence lengths in the copolymer chains was made by statistical analysis. The copolymer composition was determined by IR and NMR analysis and the results compared with spectra obtained from mechanical mixtures of the homopolymers. The formation of a true copolymer was confirmed by extractions, fractionations, and glass transition temperature determinations. Mechanical properties of the copolymers are given and compared with those of other polymers, in particular with those of 1,4‐cis polybutadiene.
Large deformation tensile properties of elastomers. I. Temperature dependence of c1 and c2 in the mooney‐rivlin equation
Authors: Smith Thor L. 
Published: June 2010

AbstractTensile stress‐strain data were determined at various extension rates and temperatures on unfilled butyl and silicone vulcanizates and on six hydrofluorocarbon (Viton A‐HV) vulcanizates that contain between 0.90 and 12.2 × 10−5 mole of effective network chains per unit volume of gel rubber. From 1‐min. isochronal data, values of C1 and C2 in the Mooney‐Rivlin equation were derived. For the butyl and silicone vulcanizates from, respectively, −20 to 150°C. and −45 to 200°C., C1 increases with temperature at a rate which is in reasonable agreement with published data from forcetemperature measurements. Because C2 is sensibly temperature independent over these extended temperature ranges, it is concluded that C2 is a finite quantity under equilibrium conditions. Time‐dependent behavior was observed on the Viton A‐HV vulcanizates between −5 and 230°C. For each vulcanizate between about 25 and 230°C., C1273/T is temperature independent, but it increases with decreasing temperature below about 25°C. Except at the lowest temperatures, C2273/T decreases with increasing temperature, the rate of decrease becoming progressively less with an increase in crosslink density. Above 25°C. the ratio C2/C1, which ranges from about 90 to 0.6, decreases with an increase in either temperature or crosslink density. The time‐dependent behavior of C2273/T appears to arise primarily from molecular processes whose relaxation times are considerably longer than the terminal relaxation time of individual chains.
Electrical and mechanical properties of anhydride‐cured epoxy resins
Authors: Shito Nobuhiko , Sato Mikio 
Published: June 2010

AbstractA diglycidyl ether of bisphenol A was crosslinked with several acid anhydrides of different structures, such as the homologs of succinic anhydride and the acid anhydrides with a double bond or a ring structure. Dilatometric, dielectric, and dynamic mechanical measurements were carried out on the cured resins. The glass transition temperature is shown to be influenced by the presence of double bonds or ring structures in the chain backbones. The specific volume at the glass transition temperature can be predicted as a sum of atomic volumes. Two dielectric relaxation processes were observed in all the resins. The temperature dependence of the relaxation time for the α‐process can be represented by the WLF equation. The mechanical retardation time for the α‐process generally agrees with the dielectric relaxation time. The observed dynamic Young's modulus in the glassy state is nearly one‐third of the value calculated from the cohesive heat density. A good correspondence is obtained between the observed dynamic Young's modulus in the rubbery state and the Young's modulus calculated from the crosslinking density, but the deviation increases with decreasing crosslinking density.
A light‐scattering study of degradation of polyisoprenes
Authors: Vavra J. 
Published: June 2010

AbstractThe molecular weights of natural and synthetic polyisoprenes have been measured by the light‐scattering method. The changes of intensity of scattered light caused by heat aging of these rubbers in air have been investigated. During aging of natural rubber considerable depolymerization takes place, with simultaneous formation of new macromolecules with a higher degree of branching, as confirmed by the unusual shapes of Zimm diagrams. The experimental values of the Pθ functions have been compared with theoretical ones calculated from the combined Debye and Mie theories.
New transparent plastics of polyacrylonitrile
Authors: Shavit Nehemia , Konigsbuch Mordechai , Oplatka Avraham 
Published: June 2010

AbstractThe ordinary bulk polymerization of acrylonitrile (AN) yields a powdery precipitate or an aggregated white polyacrylonitrile (PAN). Only one case has been reported, previous to our work (presented in this and in another paper5), in which AgNO3 catalyst yielded a transparent PAN gel containing, however, 50% salt. We have found that conventional initiators can be employed in a bulk polymerization process, carried out under controlled conditions, to yield transparent rigid plastics of pure PAN. The process found involves a phenomenon of spontaneous transformation of the polymerizing system at high conversions from a heterogeneous polymer‐monomer mixture to a homogeneous transparent solid polymer. Processes employing benzoyl peroxide, α,α‐azobisiso‐butyronitrile, p‐toluene sulfinic acid, and mixtures of these, other catalysts, co‐catalysts, and additives are described. The transformation was found to depend on catalyst type and concentration, temperature, volume, and shape of the system as well as on the presence and supply of oxygen above the reaction mixture.
Reactivities of alkyl methacrylates in their radical polymerization
Authors: Otsu T. , Ito T. , Imoto M. , Otsu Takayuki , Ito Toshio , Imoto Minoru 
Published: June 2010

AbstractThe effect of the alkyl group on radical polymerizations of alkyl methacrylates (RMA) has been investigated. From the results on copolymerizations of RMA(M2) with styrene or B‐chloroethyl methacrylate (M1), the relative reactivities (lr1) of RMA toward attack of polymer radicals were plotted by the Taft's equation: log (1/r1) = ρ* σ*+δE8. The plot could correlate with polar substituent constants (σ*), but not steric substituent constants (E8) of the alkyl substituents in RMA. These results might strongly indicate that the radical reactivities of RMA depended on the polar character of the alkyl groups, but not on their steric character. This conclusion is compared with other experimental results and discussed.
The relationship between unpaired spin concentration, structure, and electrical conduction of a pyrolytic aromatic polyimide
Authors: Bruck Stephen D. 
Published: June 2010

AbstractWhen films of poly[N,N′‐(p,p′‐oxydiphenylene)pyromellitimide] are pyrolyzed in vacuum between 575 and 800°C., they are converted into products having electrical conductivities as high as 20 (ohm‐cm.)−1 measured at 25°C. This transformation of the polymer from an insulator into an electroconductor is accompanied by distinct changes in the electron paramagnetic resonance absorption (EPR) vs. time curves, x‐ray diffraction, elemental composition, and density. From the rates of EPR absorption, a tentative activation energy of 25 ± 3 kcal./mole was calculated for this internal transformation. The absence of polarization effects and the fact that repeated thermal cycling does not significantly diminish the observed electrical conduction suggest that it is electronic rather than ionic in character. The development of electrical conduction in the pyrolyzed polymer occurs well below the graphitization temperature and with the retention of considerable quantities of nitrogen and oxygen. Apparently a fused conjugated network with a large pool of π‐electrons and π‐orbital overlap develops and the reduction of interboundary resistance at sufficiently high temperatures causes the appearance of electrical conduction.
Fibers of thermally stable ordered heterocycle–amide copolymers
Authors: Preston J. , Black W. B. 
Published: June 2010

AbstractThermostable fibers were spun from several ordered heterocycle‐amide copolymers. Tenacities up to 8 g./den. at standard conditions were obtained. The polymers were prepared by condensation of arylene diacid chlorides with aromatic diamines containing preformed heterocyclic units of types known to be thermally stable (oxadiazole, thiazole, and bithiazole). Fiber tensile properties were determined at temperatures up to that at which the fiber failed. Each fiber had a zero strength temperature of over 515°C. in nitrogen, and each had appreciable strength at 400°C. In general, the fiber showed excellent retention of tenacity after heat aging for long periods of time at 300°C. in air. An oxadiazole‐amide fiber retained three‐fourths of its original tenacity after 168 hr. under these conditions.
Formation of metal filaments and their characterization
Authors: Ross J. H. 
Published: June 2010

AbstractA technique has been established for the drawing of bundles of sheathed superalloy wires. Reduction of the individual filaments to a final diameter of 0.0005 in. was accomplished for Chromel R and René 41 with as many as 100 filaments per bundle. The problems of sheathing, stress‐relieving, and desheathing were solved. However, the problem of interfilament welding and/or oxide bonding still requires extensive explanation, first, to define more clearly the causes of welding or bonding, second, to develop techniques for separating the welds or bonds, and third, to accomplish this with a minimum of loss in strength and elongation while achieving the flexibility and bending recovery of yarns formed by stranding single‐drawn superalloy fibers. The successful achievement of these goals will yield high strength, flexible superalloy yarns capable of being woven and fabricated, systems requiring the thermal stability provided by super‐alloys.
Influence of the structure of unsaturated imides on their polymerizability and on the polymer properties
Authors: Sheremeteva T. V. , Larina G. N. , Tsvetkov V. N. , Shtennikova I. N. 
Published: June 2010

AbstractOn the basis of the comparison between the polymerization rates, intrinsic viscosities and molecular weights of the polymers of N‐substituted maleimides and citraconimides a conclusion is drawn that the methyl group in citraconimide causes a decrease in the reactivity of its double bond. Fractions of poly‐N‐isobutylmaleimide (P‐N‐IBMI) were investigated by the methods of translational diffusion, sedimentation, and flow birefringence. In the range of molecular weights from 0.19 × 106 to 3.6 × 106 relationships are obtained between the molecular weight M of the fractions investigated, their intrinsic viscosity [η], diffusion coefficient D, and sedimentation coefficient S. The hydrodynamic data obtained indicate that macromolecules of P‐N‐IBMI exhibit high rigidity due to the presence of cycles in their main chain. A marked optical anisotropy of the P‐N‐IBMI molecules is positive and indicates that molecular chains of P‐N‐IBMI in solution have a trans conformation.
Reaction of nickel carbonyl on halogenated olefins obtention of polymers
Authors: Asfazadourian M. , Prillieux M. 
Published: June 2010

AbstractThe reaction of nonsaturated dihalogenated hydrocarbons (halogen atoms in the a position of the double bond) with nickel carbonyl. 1,4‐dichlorobutene‐2 and nickel carbonyl magnified image gives almost quantitatively a powdered, colored solid, insoluble in all common solvents. Physical studies showed this solid to be a new polymeric complex, Ni 2+ bound to a hydrocarbon skeleton. Derivatives from dichloroparaxylene were also prepared and studied. The complexes are decomposed by water and methanol, giving polymers and a nickel halogenide solution. The polymers obtained are described. They are insoluble in all common solvents and of good thermal stability up to 350°C.