bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of chlorinated poly(vinyl chloride). II. Distribution of Cl atoms in the polymer chain
Authors: Doskočilová D. , Schneider B. , Drahorádová E. , Štokr J. , Kolínský M.
Published: April 2003

The distribution of chlorine atoms in the chain of solution‐chlorinated PVC (CPVC) composed of CH2CHCl (1), CHClCHCl (2), and CCl2CHCl (3) monomeric units is described by first‐order Markoffian statistics based on the assumption that the chlorination mechanism is independent of tacticity. In this case, all the statistical parameters can be obtained from experimentally determined concentrations of CH2, CHCl and CCl2 units. Populations of the sequences (11) and (111) calculated from the statistical parameters agree with experimental values determined from infrared and 220 MHz NMR spectra. From infrared spectra, suspension‐chlorinated CPVC contains blocks of intact PVC.
Synthesis and characterization of poly‐β‐hydroxybutyrate. II. Synthesis of D‐poly‐β‐hydroxybutyrate and the mechanism of ring‐opening polymerization of β‐butyrolactone
Authors: Shelton J. Reid , Agostini D. E. , Lando J. B.
Published: April 2003

Synthesis of the naturally occurring polyester, D‐poly‐β‐hydroxybutyrate (PHB) was accomplished by using an optically active monomer. Polymerization of D‐(+)‐β‐butyrolactone (β‐BL) of 73% optical purity with a catalyst system of Et3Al–H2O produced a polymer with a similar optical activity and essentially identical to the natural polymer as isolated from bacterial cells. This paper describes the synthesis and characterization of this optically active polyester along with a suggested mechanism to account for the observed stereospecific polymerization of β‐BL with this catalyst system.
Permeability of membranes containing ionogenic groups
Authors: Kopeček J. , Vacík J. , Lím D.
Published: April 2003

The present paper deals with the transport properties of membranes made of hydrophilic gels containing ionogenic groups. Introduction of ionogenic groups into a gel based on 2‐hydroxyethyl methacrylate will affect the permeability of the investigated membranes for sodium chloride by an order or more. Dependences of the permeability on the content of ionogenic groups, three‐dimensional network density, and pH were established. The permeability for NaCl was compared for that for bivalent salt (MgSO4). It is shown, on the basis of independently determined distribution coefficients, that an increase in the permeability of ampholytic membranes in comparison with the neutral ones is primarily due to an increase in the diffusivity of the salt in the membranes with modified structure. It can also be concluded that an approximation of the free volume from the volume of the solvent in the membrane cannot be applied to the poly(2‐hydroxyethyl methacrylate) gel.
Acid‐catalyzed polymerization of 1,6‐anhydro‐β‐D‐glucopyranose
Authors: Wollwage Paul C. , Seib Paul A.
Published: April 2003

A number of 1,6‐anhydrides were polymerized in the melt at 115°C by use of monochloroacetic acid as catalyst. In the early stages of polymerization (up to 40–50% monomer consumed), each monomer was found to disappear by a first‐order rate process. The 1,6‐anhydrides investigated and their relative rates of polymerization were: 1,6‐anhydro‐2‐O‐methyl‐β‐D‐glucopyranose, 1.0; 1,6‐anhydro‐3,4‐di‐O‐methyl‐β‐D‐glucopyranose, 1.4; 1,6‐anhydro‐2‐O‐methyl‐β‐D‐galactopyranose, 2.3; 1,6‐anhydro‐3‐O‐methyl‐β‐D‐glucopyranose, 2.6; 1,6‐anhydro‐4‐O‐methyl‐β‐D‐glucopyranose, 6.3; 1,6‐anhydro‐4‐O‐(β‐D‐glucopyranosyl) β‐D‐glucopyranose, 9.0; 1,6‐anhydro‐β‐D‐galactopyranose, 17; 1,6‐anhydro‐β‐D‐glucopyranose, 37; 1,6‐anhydro‐β‐D‐mannopyranose, 91; and 1,6‐anhydro‐2‐deoxy‐β‐D‐arabino‐hexopyranose, 240. The effect of substitution on the rate of polymerization suggests this reaction is mechanistically related to the acid hydrolysis of pyranosides. The results suggest that polymerization proceeds in two stages: (1) an initial build‐up of dimer followed by (2) a slower growth to higher molecular weight material.
Cationic polymerization of cyclic dienes. X. Cationic polymerization of 1‐vinylcyclohexene and 3‐methyl‐1,3‐pentadiene
Authors: Hara Kazuo , Imanishi Yukio , Higashimura Toshinobu , Kamachi Mikiharu
Published: April 2003

1‐Vinylcyclohexene (VCH), which has one of the double bonds in the ring and the other outside the ring, was synthesized and polymerized by cationic catalysts. The reactivity of VCH was very large in the polymerizations catalyzed by boron trifluoride etherate (BF3OEt2) and stannic chloride–trichloroacetic acid complex. Similar to other cyclic dienes, the polymerization of VCH was a nonstationary reaction having a very fast initiation step. The polymerization proceeded by either a 1,2‐ or a 1,4‐propagation mode in which vinyl group was always involved. Particularly when BF3OEt2 was used as a catalyst, an intramolecular proton or an intramolecular hydride ion transfer reaction took place, resulting in the formation of methyl groups in the polymer. The degree of polymerization of polymer formed was about 10. This indicates the preponderance of monomer transfer reaction. To investigate the reason for the high reactivity of cyclic dienes, cationic copolymerizations of VCH and 3‐methyl‐cis/trans‐1,3‐pentadiene (cis/trans‐MPD) was carried out. The relative reactivity of monomers decreased in the order VCH > trans‐MPD > cis‐MPD. On the other hand, the resonance stabilization of monomers decreased in the order VCH > trans‐MPD > cis‐MPD. Therefore, it could be considered that the monomer reactivity is mainly determined by the stability of carbonium ion intermediate. The relative stability of carbonium ion must be VCH > trans‐MPD > cis‐MPD. Thus the influence of the conformation of ion on its stability was clearly demonstrated.
Effects of temperature on styrene–methacrylonitrile copolymerization
Authors: Rudin A. , Yule R. G.
Published: April 2003

The free‐radical copolymerization of styrene and methacrylonitrile was studied in toluene solution at 60, 90, and 120°C. Copolymer composition was estimated from gas‐chromatographic measurement of unreacted monomer concentrations. Reactions were carried to about 20% conversion to minimize analytical errors. Reactivity ratios were calculated by using an integrated form of the Mayo‐Lewis simple copolymerization equation. Reactivity ratios were not sensitive to reaction temperature. The values at 90°C are r1 = 0.41 (methacrylonitrile) and r2 = 0.37 (styrene). The r1 values are higher than those reported by other workers, presumably because of advantages in the present analytical technique and calculation method. The negligible temperature dependence of reactivity ratios is in accord with theory. If monomer pairs exhibit pronounced dependence of reactivity ratios on polymerization temperature, this may indicate a change in mode of placement of units in the polymer chain.
Inorganic coordination polymers. XI. A new family of chromium(III) bis(phosphinate) polymers, [Cr(OH)(OPRR′O)2]x
Authors: Nannelli Piero , Gillman H. D. , Block B. P.
Published: April 2003

Heating hydroxyaquochromium(III) bis(phosphinates) at temperatures up to 200°C under vacuum yields the corresponding anhydrous polymers [Cr(OH)(OPRR'O)2]x. The infrared and visible spectra and solution properties lead to the following conclusions. When R and R′ are phenyl groups, the hydroxyl groups appear to bridge between adjacent chromium atoms in the chain together with the phosphinate ligands to yield a linear, triple‐bridged polymer. When at least one substituent on the phosphorus is an alkyl group, some of the hydroxyl groups crosslink between chains to yield less soluble polymers. Comparison of the properties of these new polymers with the parent polymers suggests that the latter should be formulated [Cr(H2O)n(OH)(OPRR′O)2]x·pH2O and that they contain more than one kind of monomer unit. The parent polymers can be readily prepared by a new method which involves reaction of a soluble chromium(III) salt with alkali metal phosphinates or of chromium(III) hydroxide with phosphinic acids in a water–tetrahydrofuran mixture.
Cationic polymerization of 2‐vinyl‐1,3‐dioxane
Authors: Sumitomo Hiroshi , Okada Masahiko , Ito Hiroshi
Published: April 2003

The cationic polymerization of 2‐vinyl‐1,3‐dioxane initiated with triethyloxonium tetrafluoroborate was studied with particular emphasis on elucidation of the structure of the polymer. The polymer was a light yellow powdery material with a molecular weight of several thousands which was soluble in most organic solvents. The infrared and NMR investigations on the polymer, together with chemical analyses, showed that the polymer consisted of the three structural units I, II, and III, the contents of which were estimated to be 5–10%, 20–25%, and 65–70%, respectively.
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The formation of the structural units I and II was discussed in detail.
Photochemical and thermal isomerization in polymer matrices: Azo compounds in polystyrene
Authors: Priest W. J. , Sifain M. M.
Published: April 2003

Photochemical and thermal geometrical isomerizations of monoazo compounds have been studied in polystyrene–n‐butylbenzene compositions. Cis–trans isomer ratios established by light absorption were found to depend on matrix viscosity. Where the compositions were above their respective glass temperatures, all thermal isomerizations conformed to first‐order kinetics. Where compositions were below their respective glass temperatures, the initial isomerization rates were abnormally fast, decaying to normal first‐order processes after substantial amounts of reaction had taken place. These effects have been interpreted in terms of the vitreous properties of polystyrene.
Titration curves of p‐aminobenzoic acid–formaldehyde polymer in relation to its structure
Authors: Chatterjee S. K. , Agrawal V. B.
Published: April 2003

p‐Aminobenzoic acid and formaldehyde were condensed in the presence of acid catalyst. The linear condensation polymer thus obtained was then separated into four fractions by a fractional precipitation method. Conductometric titrations were carried out on these four polymer fractions and the conglomerate in nonaqueous solvents with acid as well as base. The titration curves indicated a large number of additional breaks before the complete neutralization of COOH or NH2 groups. These observations have been interpreted in terms of degree of polymerization and the structure of the polymer.
Synthesis and characterization of some trithiols
Authors: Overberger C. G. , Scheinfeld I.
Published: April 2003

The preparation of 1,3,5‐pentanetrithiol is described to provide model systems for poly(vinyl mercaptan). In addition, the preparation and identification of the three stereoisomers of 2,4,6‐heptanetriol are reported as models for isotactic, syndiotactic, and heterotactic poly(vinyl mercaptan).
Rotational mobility of nitroxyl radicals in polyesters
Authors: Gross Susan C.
Published: April 2003

Rotational mobility of nitroxyl radicals in polyester films was investigated at temperatures from −180 to +240°C by ESR spin‐probe techniques. Evidence obtained indicated that mobility of radicals was related to polymer structure and reflected increased volume made available to the probe molecule by the polymer matrix. A single correlation time, which followed the form τC = τ0 exp {Ea/RT}, was calculated for the temperature range of rapid reorientation (∼109 Hz) of nitroxyl radicals. Ea ranged from 5 to 25 kcal/mole for various systems. Uniaxially oriented semicrystalline polymer matrix restricted radical mobility to a greater extent than a semicrystalline biaxially oriented sample. Effective local viscosity encountered by a nitroxyl radical in several polymers was calculated as 9–13 poise.
Radiation‐induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether
Authors: Tabata Y. , Du Plessis T. A.
Published: April 2003

The radiation‐induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether was investigated in the liquid phase at 20 and −78°C over a wide range of monomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over the entire range of monomer compositions investigated. Both the rate of copolymerization and the intrinsic viscosity of the resulting copolymer were found to depend strongly on the initial monomer composition, both reaching a maximum value at an equimolar concentration of the monomers. The monomer reactivity ratios were determined and correspond well with calculated values. A decrease in the irradiation temperature was accompanied by a marked decrease in the rate of copolymerization and the intrinsic viscosity of the copolymer.
Kinetics of heterogeneous free‐radical polymerization of vinylidene chloride
Authors: Wessling Ritchie A. , Harrison I. R.
Published: April 2003

Poly(vinylidene chloride) precipitates as a crystalline phase during the polymerization reaction. Under the conditions studied, this phase is made up of complex particles with a lamellar substructure. The detailed morphology is very sensitive to reaction medium. The morphology developed by particles formed during polymerization of vinylidene chloride in dioxane suggests a mechanism of polymerization followed by crystallization. The morphology observed in mass polymerization suggests that both processes occurs simultaneously. Kinetic data, however, suggest a solid‐phase reaction mechanism for both cases. The results are analyzed by comparison with a model that takes into account the solid‐phase morphology. The theoretical analysis is consistent with experimental results if it is assumed that polymerization occurs on the edges of the lamellar crystals.
Estimation of parameters of the scattering particles in elastoidin by low‐angle X‐ray methods
Authors: Ratho T. , Misra T.
Published: April 2003

Low‐angle x‐ray scattering methods have been used to evaluate some parameters like specific inner surface of the dispersed phase, transverse lengths, the length of in homogeneity, the length of coherence, and the air‐fraction of the scattering particles in Elastoidin. The low‐angle Kratky camera of the latest design was used for the experimental measurements. Since the sample under investigation is a densely packed solid polymer, the theories of Kratky and Kratky and Porod have been used to evaluate these parameters.
Preparation and properties of some water‐soluble cobalt (III)–poly‐4‐vinylpyridine complexes
Authors: Kurimura Yoshimi , Tsuchida Eishun , Kaneko Masao
Published: April 2003

Water‐soluble cobalt(III) chelates having a polymeric ligand such as cis‐[Co(en)2‐PVPCl]Cl2 and cis‐[Co‐(trien)PVPCl]Cl2 (PVP = poly‐4‐vinylpyridine) were prepared by substitution reactions between cobalt(III) chelate and PVP in water–alcohol solution. PVP of different degrees of polymerization was used as the ligand in preparation of these complexes. The PVP complexes were identified and their properties ascertained by microanalysis and by a study of the infrared, ultraviolet, visible, and PMR spectra. Most of the characteristic properties of these complexes may be ascribed to the polymeric structure of the PVP ligand.
Imidization reaction in polyvinylamides
Authors: Haas Howard C. , Macdonald Ruby L.
Published: April 2003

Depending on their method of preparation, polyvinylamides can have nitrogen contents which vary from the theoretical value to considerably lower values. Cyanamer P‐250, a polyacrylamide, manufactured by American Cyanamid Corporation, had a nitrogen content of 17.67% compared to the theoretical value of 19.7%. A polyacrylamide prepared in dioxane at 60°C and initiated by benzoyl peroxide, had a nitrogen content of only 15.5%. These low values are ascribed to loss of ammonia via intramolecular imide formation. We have found that when the intramolecular imidization reaction in poly acrylamide and in polymethacrylamide is driven to completion by heating the polymers in dilute solution, very close to 33% of the amide groups remain unreacted. Thus, unlike poly(methyl vinyl ketone) and poly(vinyl chloride), the poly‐vinylamides do not obey Flory's statistical calculation for the random reaction of 1,3 groups in a head‐to‐tail polymer which predicts isolation of only 13.53% of the vinyl residues. Of the various possible explanations, the hypothesis of larger ring formation seems the most plausible, since specific interactions have been shown to exist between widely spaced amide groups in low molecular weight diamides. The infrared spectra of polyacrylimide and polymethacrylimide are presented and compared with those of the corresponding polyvinylamides. When the nitrogen content of polyacrylamide falls to the 14.9–15.4% N range due to imide formation, the polymer becomes water‐insoluble. Because imidization stiffens the polymer chain and introduces weakly acidic groups, the imide content of a polyvinylamide should affect its compatibility with other polymeric systems.
Studies of the polymerization of diallyl compounds. XII. Cyclocopolymerization of dimethallyl phthalate with vinyl acetate
Authors: Matsumoto Akira , Oiwa Masayoshi
Published: April 2003

Dimethallyl phthalate was copolymerized with vinyl acetate at 60°C with the use of benzoyl peroxide as an initiator. The rate and degree of copolymerization increased with an increase in the mole fraction of vinyl acetate. The residual unsaturation of the copolymer was nearly constant, regardless of the feed molar ratio. The monomer reactivity ratios (MRR) were obtained on the basis of the copolymer composition equation in which the intramolecular cyclization reaction was considered: γ1 = 1.08 (MRR of the uncyclized radical), γ2 = 0.99 (MRR of vinyl acetate radical), γc = 0.73 (MRR of the cyclized radical). The difference between γ1 and γc is discussed.
Synthesis and properties of anthracene‐containing polybenzyls
Authors: Montaudo G. , Finocchiaro P. , Caccamese S.
Published: April 2003

A number of alternating copolymers containing anthryl and aryl units in the polymer chain have been prepared by Friedel‐Crafts arylation of the anthracene (polymer type B) or by condensation of 9,10‐bis(chloromethyl) anthracene with opportune aromatic substrates (polymer type A). Polymers of type A were all found to contain 9,10‐disubstituted anthracene units, but polymers of type B were found to contain 1,4‐disubstituted anthracene units. Structure of the polymers were established through their NMR and ultraviolet spectra, and through analogy with appropriate model compounds. It has been found that the inclusion of anthracene units in the polymer chain yields higher melting and more soluble materials with respect to polybenzyls containing only aryl units. Anthracene units introduce, also, some interesting fluorescence characteristics in the polymers, which show intense emission at about 440 mμ.
Radiation‐induced polymerization of 1,2‐cyclohexene oxide in the plastic crystalline state
Authors: Hiramoto Tetsuo , Nishii Masanobu , Hayashi Koichiro , Okamura Seizo
Published: April 2003

Radiation‐induced solid state polymerization of 1,2‐cyclohexene oxide has been investigated. By the differential thermal analysis and x‐ray diffraction analysis, it was found that this compound has a phase transition point at −81°C and behaves as a plastic crystal in the temperature range from −81°C to −36°C (melting point). The in‐source polymerization proceeded not only in the plastic crystalline state but also in the ordinary crystalline state at temperatures below the phase transition point. The overall rate of polymerization and the rate of chain transfer to monomer in the plastic crystalline state were larger than those in the ordinary crystalline state by a factor of about forty, but the kinetic mechanisms were identical, i.e., the termination mechanisms were unimolecular in both solid states. In contrast, the kinetic mechanisms in the plastic crystalline state and in the liquid state were different. From these observations, the effects of molecular motion and molecular arrangement on the polymerizations of 1,2‐cyclohexene oxide in the three phases were discussed.
Synthesis of titanium polyesters
Authors: Carraher Charles E.
Published: April 2003

Titanium polyesters of the form
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where Cp denotes cyclopentadiene, have been synthesized by utilizing both the interfacial and solution techniques. Polymer yield increases with reaction time. The reactive titanium reactant in the solution polycondensations is believed to be the Cp2Ti+2 cation.
Orientation in nylon 6 films as determined by the three‐dimensional polarized infrared technique
Authors: Sibilia John P.
Published: April 2003

A three‐dimensional polarized infrared technique was used to obtain information about molecular orientation in both uniaxially and biaxially drawn nylon 6 films. The 835 and 930 cm−1 bands were used to describe the orientation of the A (extended chain) conformation while absorptions at 1175 cm−1, and 1120 cm−1 and 1075 cm−1 were used to give some information about orientation of the B (twisted chain) conformation. On the basis of the 835 and 930 cm−1 bands, it was shown that the hydrogen‐bonded sheets made up of chains in the A conformation are parallel to the film surface in the biaxially drawn film. Uniaxially drawn films obtained by drawing both at 100 and 150°C showed a high degree of chain alignment in the draw direction for the A conformation at draw ratios greater than 2.5. Some planar orientation was also observed in these uniaxially drawn films for both the A and B conformations at high draw ratios.
Plastic deformation of polyethylene II. Change of mechanical properties during drawing
Authors: Meinel G. , Peterlin A.
Published: April 2003

The crystallinity, elastic modulus, and tensile strength of samples of various draw ratios together with the true stress—strain curves of high‐density polyethylene were determined to establish correlations with morphological changes occurring during deformation. Changes of crystallinity at draw ratios below 5, i.e., constancy during drawing of quenched film and a decrease during drawing of annealed film, are explained by the formation of microfibrils with crystallinity independent of the thermal history of the film. The microfibrils slide past each other at higher draw ratios, generating an increasing number of interfibrillar tie molecules, which is reflected in the increasing number of interfibrillar tie molecules, which is reflected in the increase of crystallinity, elastic modulus, and tensile strength. From the true stress—strain curves, the differential work density for the deformation of the volume element was calculated as a function of the draw ratio. It contains two components which reflect two different mechanisms of deformation. The first component, decreasing with increasing draw ratio, can be associated with the destruction of the original microspherulitic structure; the second one, increasing with increasing draw ratio, can be associated with the deformation of the new fiber structure, i.e., with the sliding motion of the microfibrils formed during the first deformation step.
Correlation between the temperature dependence of apparent specific volume and the conformation of oligomeric propylene glycols in aqueous solution
Authors: Sandell L. S. , Goring D. A. I.
Published: April 2003

The apparent specific volumes, ϕ2, of a series of poly(propylene glycol) and poly(ethyleneglycol) oligomers in aqueous solution were determined as a function of temperature from 4 to 25°C. The slope, dϕ2/dT, was taken as a measure of the extent of interaction between the hydrophobic portions of the oligomer and water, higher values of dϕ2/dT representing diminished hydrophobic interaction. It is suggested that the observed increase in dϕ2/dT with chain length for the poly(propylene glycol) oligomers can be attributed to the previously proposed disk coiled conformation of the chain which reduces the degree of contact between the side‐chain methyl groups and water as the chain length increases. This interpretation is supported by (1) the direct relationship between the difference in the thermal expansion behavior of the two oligomer series and the accessibility of the methyl groups in the poly(propylene glycol) disk‐coil, and (2) the agreement between the calculated volume changes on mixing for the methyl groups and the values predicted for the disk‐coil model from the Némethy and Scheraga theory.
Ethylene‐propylene copolymers: Degree of crystallinity and composition
Authors: Ver Strate G. , Wilchinsky Z. W.
Published: April 2003

X‐ray, differential scanning calorimeter, and density measurements of the degree of crystallinity have been made on ethylene—propylene copolymers which range in composition from 60 to 100 mole‐% ethylene. At 23°C the degree of crystallinity was found to vary from zero to approximately 75 wt‐% in a regular manner with composition. A systematic difference exists between the x‐ray and heat of fusion measurements if a simple two‐phase model is assumed in order to calculate the per cent crystallinity from heats of fusion. The apparent heat of fusion of the crystalline fraction detected by the x‐ray method is as low as 30 cal/g. This discrepancy increases with comonomer content. It is suggested that large surface or defect energies are present. The broad melting behavior of the samples is also consistent with such a description of the system.
γ–α transformation in isotactic polypropylene
Authors: Newman B. A. , Song S.
Published: April 2003

A γ‐phase to α‐phase transformation in a specimen of isotactic polypropylene crystallized under conditions of high pressure was induced by drawing at 100°C. X‐ray studies showed that the unoriented component remained in the γ‐phase, and that the oriented component was found only in the α‐phase. This evidence supports a previous suggestion that the phase transformation is martensitic in character. The consequences of such an assumption are discussed. The role of dislocations in polymeric systems is generally believed to be not too significant, but since martensitic reactions involve cooperative movements of atoms, an exception in this case is suggested. A possible mechanism for the phase transformation is suggested.
Viscoelastic behavior of low molecular weight polystyrene
Authors: Plazek Donald J. , O'Rourke V. Michael
Published: April 2003

The shear creep and creep recovery behavior of narrow molecular weight distribution polystyrene samples of low molecular weight, 1.1 × 103, 3.4 × 103, and 1.57 × 104 are reported as a function of temperature, near and above the glass temperature. Time‐temperature equivalence for the total creep compliance is found to be nonapplicable, and in fact the steady‐state recoverable compliance, Je, is a strong function of temperature. The time‐scale shift factors for the recoverable compliance are analyzed in the light of free volume theory. Viscosity data are presented for samples with molecular weights between 1.1 × 103 and 6.0 × 105. The temperature dependence of the characteristic time constant ηJe can be explained in terms of free volume concepts whereas that of viscosity η cannot. Effects of residual molecular weight heterogeneity are demonstrated.
Light scattering by cellulose. III. Morphology of wood
Authors: Borch Jens , Sundararajan P. R. , Marchessault R. H.
Published: April 2003

Radial, tangential and cross cuts of Eastern spruce are examined by a solid‐state light‐scattering method which allows study of light scattering due to fluctuations in density and fluctuations in anisotropy. All of the samples investigated show well‐defined scattering maxima which are related to their anisotropic texture with limited contributions from random density fluctuations. The radial cuts give rise to scattering similar to that by a grating with orthogonal characteristic spacings. The gratinglike character is due mainly to the pit structure and their periodic spacings, which can be deduced from the “unit‐cell” dimensions of the scattering pattern. The scattered intensity is maximum when the fiber direction is at 45° to the polarization direction; when it is either horizontal or vertical, a distinct “spherulitic” scattering is observed from which size and asymmetry of the pits can be deduced.
Crystallization of polyethylene at elevated pressures
Authors: Rees D. V. , Bassett D. C.
Published: April 2003

The crystallization from the melt of three sharp polyethylene fractions has been studied at 5 kbar. It has been shown that the thickness of so‐called extended‐chain lamellae is a function of time, temperature, and molecular weight. There is by no means just the fully extended molecular configuration present. Crystallization is qualitatively similar to that of chain‐folded crystals at 1 bar, giving an optimum lamellar thickness which increases with time and decreasing supercooling. Fractional crystallization is widespread and is a major cause of disparate lamellar thickness. Isothermal thickening of lamellae during crystallization has been established directly. Morphological detail suggests further that layers can increase their thickness tenfold over their initial size.
Long‐chain branching in low‐density polyethylene
Authors: Cote J. A. , Shida M.
Published: April 2003

A method is given for the analysis of long‐chain branching in polymers by using combined GPC and intrinsic viscosity measurements. A computer program was written to evaluate branching indices by a tabular, iterative method. The method was applied to the evaluation of long‐chain branching in low‐density polyethylene.
Liquid‐induced reversible long‐spacing changes in polyethylene single crystals and their implications for the fold‐surface problem
Authors: Udagawa Y. , Keller A.
Published: April 2003

The long spacing of single‐crystal mats of polyethylene was found to increase reversibly on addition of liquids which normally act as swelling agents. The magnitude of the increase follows the sequence of the solvent power which these liquid exhibit at higher temperatures. The increase in long spacing depends to a minor extent on crystallization conditions, such as concentration and crystallization temperature, but increases very markedly with the molecular weight of the polymer. Heat treatment reduces the amount of swelling, even in the range of low treatment temperatures which do not produce a foldlength increase, implying a reorganization of the fold surface. It is inferred that there is a layer along the fold surface which expands by swelling which in turn implies a disordered amorphous component. Nevertheless, such disordered material need not be an intrinsic consequence of chain folding, as its amount can be reduced to insignificant proportions, e.g., by taking molecules which are short but still fold. Thus both, the presence of amorphous disorder and the nonunique nature of such a disorder along the surface is demonstrated. Further implications for the fold‐surface problem are discussed.
Fox‐Flory constant K obtained by viscometric measurements for poly(ethyl methacrylate) and poly(methyl methacrylate) systems
Authors: Vasudevan Padma , Santappa M.
Published: April 2003

Poly(ethyl methacrylate) and poly(methyl methacrylate) prepared by benzoyl peroxide‐catalyzed polymerization were fractionated. The Fox‐Flory constant K was determined for these polymers by viscometry in several good and bad solvents. Application of some empirical methods for evaluation of K are also briefly discussed in relation to our results.
Some probability relations in multicomponent copolymers
Authors: Pyun Chong Wha
Published: April 2003

It was previously shown that for a stationary random copolymer of A, B, and C, we have in general p(AB) + p(AC) = p(BA) + p(CA), etc., in place of p(AB) = p(BA) which is valid for a stationary binary copolymer. Here, p(AB) for example, is the probability that a randomly picked pair of consecutive comonomers in the polymer consists of an A followed by a B. For a stationary ternary copolymer produced by a first‐order Markovian addition mechanism, we show that PABPBCPCA/PACPCBPBA = k, where k is a constant characteristic of a particular set of three monomers but independent of its composition. Here, PAB is the conditional probability of finding a monomer of B given that its immediate predecessor is an A. We further show that if the individual rate constants of the monomer additions involved take a special form such as used in the Alfrey‐Price Q–e scheme, then we have k = 1 irrespective of the kinds of monomers, and in addition we have p(AB) = p(BA), p(AC) = p(CA), etc. Thus, although these latter results were previously proposed by Ham as an alternative basis to supplant the Q–e scheme, they may rather be regarded as mathematical consequences of special assumptions adopted for the form of the individual rate constants. For a stationary random copolymer of four components A, B, C, and D, we have p(AB) + p(AC) + p(AD) = p(BA) + p(CA) + p(DA), etc., in general. For a first‐order Markovian four‐component copolymer, we show that there are seven different combinations of the conditional probabilities that are constants (k1, k2,…, k1) independent of the monomer composition. Again, if we assume the same special form for the rate constants involved, we find that all the seven constants k1, k2, …, k7 reduce to unity and p(XY) = p(YX) for X,Y, = A, B, C, D.
Effects of a static electric field upon dielectric properties of poly(vinylidene fluoride) and poly(vinyl fluoride)
Authors: Osaki Shigeyoshi , Uemura Shinsaku , Ishida Yōichi
Published: April 2003

Dielectric measurements on poly(vinylidene fluoride) at higher temperatures result in anomalously large values of ε′ and ε″ at lower frequencies. When a static field is applied, a drastic decrease of ε′ and ε″ occurs. The effects of a static field can be summarized as follows: (1) the field effect upon ε′and ε″ is more significant at lower frequencies; (2) with increasing field strength, the rate of decrease of ε′and ε″ with time becomes greater and the ultimate values are smaller; (3) when the field is removed, ε′and ε″ recover but the ultimate recovery is incomplete; (4) the field effect depends strongly on temperature. Such behavior seems to be attributable to the displacement of ionic impurities and to their electrolysis. These results provided a method to remove the contribution of ionic impurities to ε′and ε″ and to measure the relaxation process due only to dipoles of a polymer. The application of this method revealed the dielectric high temperature absorption which had been masked by the ionic conduction in poly(vinyl fluoride).
Measurement of the stress‐relaxation modulus in the primary transition region
Authors: Kelchner R. E. , Aklonis J. J.
Published: April 2003

Difficulties have been encountered in experimentally measuring the stress‐relaxation modulus for systems with steep slopes in the primary transition region. The usually applied “factor‐of‐ten” rule is shown to apply in these cases as well as in cases where the relaxation is slower; with the steep slope, however, the rule offers little help, since the decay in the modulus is so fast that stresses are usually very small at times when direct modulus calculations may be made. A technique is suggested which allows calculation of the modulus in this difficult region. A slow constant strain‐rate deformation is followed by a constant strain period. Modulus values for times during the constant strain rate period are calculated using well known relationships. Long‐time values are calculated from the definition of the modulus (the factor‐of‐ten rule being employed) and a recursion relation is developed which is used for modulus calculations during the constant strain period at relatively short times where effects of strain rate are important. Starting values for the recursion relation are long‐time moduli which can be calculated directly.
Kinetic study of dissolution of poly(vinyl chloride) in cyclohexanone
Authors: Lapc̆ík Lubomír , Valko Ladislav
Published: April 2003

The kinetics of dissolution of five fractions of commercial poly(vinyl chloride) in cyclohexanone was studied at temperatures from 20 to 70°C. Good agreement was observed between the experimental results and equations expressing the dependence of the induction periods and the rates of dissolution on temperature and molecular weight. It was found that the apparent activation energy for the swelling process lies in the range 9–14 kcal/mole and the apparent activation energy for the dissolution diffusion process in the range 8–12 kcal/mole. The apparent dependence of activation energies on number‐average molecular weight indicates that the chain ends are more important in determining the dissolution rate than the centers of the polymer chains.
Thermodynamic and conformational properties of polystyrene. III. Dilute solution studies on branched polymers
Authors: Berry G. C.
Published: April 2003

Light‐scattering and viscometric measurements on dilute solutions of five branched polystyrene polymers are reported. The data include studies in decalin as a function of temperature, including the theta temperature, and in toluene. The results for the radius of gyration and the second virial coefficient are not in accord with the two parameter random‐flight model. Possible causes of this descrepancy are considered. It is shown that the intrinsic viscosity of branched chains is not uniquely determined by the radius of gyration.
Generalizations of the diffusion equation
Authors: Lesse P. F.
Published: April 2003

The mass flux entering the Fick's diffusion equation is considered as an arbitrary analytical function of concentration, concentration gradient, and of the gradient of concentration gradient. The restrictions imposed on the flux by the principle of material objectivity are stated and briefly discussed.
Optical anisotropy of polymer chains and Markov processes. I. Polyethylene
Authors: Lemaire Bernard , Fourche Georges
Published: April 2003

A study of the average molecular optical anisotropy 〈γ2〉 of tetrahedral lattice polyethylene chains of any length has been carried out by using Markov processes. The results of this treatment include simplified models of polymer chains, as well as more elaborate models, which are in current use.
Structural phenomena in polymers arising at low temperatures and by the action of high forces
Authors: Kargin V. A. , Andrianova G. P. , Tsarevskaya I. Yu. , Goldanskii V. I. , Yampolskii P. A.
Published: April 2003

New structural phenomena which can be produced in polymers at low temperatures or by the action of high forces are described and discussed. Experimental evidence supports the argument that the deformation of polymers can develop not only as a result of conformational changes of the macromolecules proper but also by transformation of more complex structural formations. The consequence of this phenomenon is the possibility of large deformations far below the glass‐transition temperature in a crystalline polymer with well‐developed supermolecular structure. This type of deformation takes place without molecular orientation. Another phenomenon discussed is the sharp change of supermolecular structure in crystalline polymers caused by the action of a shock wave. These effects ought to be connected with an energetic rather than entropic deformation mechanism because the transformations occur at a supermolecular level. Thus, there can be two extreme types of deformation processes: the well‐known conformation changes that occur at a molecular level, and the deformation of supermolecular structures. Examples of the pure form of the latter type of mechanism obtained under extreme conditions are given.
Low‐temperature mechanical relaxations in polymers containing aromatic groups
Authors: Chung C. I. , Sauer J. A.
Published: April 2003

Studies have been made of the secondary relaxation processes in the solid state of a number of polymers containing aromatic groups in the polymer chain. The polymers investigated include one, polystyrene, with the aromatic group in side‐chain positions, and six high polymers in which phenylene rings lie in the main backbone chain. In polystyrene, wagging and torsional motions of the side chain phenyl rings give rise to a low‐temperature δ‐relaxation which is centered at 33°K (1.7 Hz) and which has an activation energy of about 2.3 kcal/mol. Most of the polymers with phenylene rings in the main chain exhibit a low‐temperature relaxation in the temperature region from 100°–200°K. This relaxation process is centered at 159°K (0.54 Hz) in poly‐p‐xylylene, at 162°K (0.67 Hz) in polysulfone, and at 165°K (1.24 Hz) in poly(diancarbonate). In poly(2,6‐dimethyl‐p‐phenylene oxide), two overlapping low‐temperature relaxations are found, one in the range 125–140°K and the other near 277°K (ca. 1 Hz). The low‐temperature secondary relaxation process in all of these polymers is believed to be associated with local reorientational motion of the phenylene, or substituted phenylene, rings or with combined motion of the phenylene rings and nearby chain units. For these low temperature relaxation processes, the activation energy is about 10 kcal/‐mole. The temperature location of the relaxation appears to depend on the specific units to which the phenylene rings are attached and on steric and polar effects caused by substituents on the ring. In the poly‐p‐xylylenes the relaxation is shifted to much higher temperatures by a single Cl substitution on the ring but remains at essentially the same temperature position when dichlorosubstitution is made. The effects of water on the magnitude and temperature location of the observed low temperature relaxations, as well as the implications of the study for other polymers containing aromatic groups in their backbone chains, are discussed.
Properties of ethylene–propylene–vinyl chloride graft copolymers. II. Viscoelasticity and composition of graft copolymer and composite
Authors: Bares J. , Pegoraro M.
Published: April 2003

The viscoelasticity and volume expansion of the raw polymerizate of ethylene–propylene copolymer with vinyl chloride grafts, and of the individual components has been studied. The raw polymerizate (composite) and the pure ethylene–propylene–vinyl chloride graft copolymer were found to consist of two phases. The pure graft copolymer has an ethylene–propylene matrix containing some fraction of poly(vinyl chloride) (PVC) grafts and a microphase with the remainder of the PVC grafts. The raw polymerizate consists of a PVC matrix plasticized with ethylene–propylene chains and a microphase of the ethylene–propylene copolymer. An attempt has been made to calculate the participation of components in microphases and the minimum dimension of the PVC microphase aggregates.
ESR single‐crystal study of radical and radical‐pair formation in some γ‐irradiated vinyl monomers
Authors: Gillbro T. , Kinell P.‐O. , Lund A.
Published: April 2003

Single crystals of methyl methacrylate (MMA), methyl acrylate (MA), and acrolein (A) have been prepared by a low‐temperature technique. After irradiation with γ‐rays at 77°K the paramagnetic species were identified by ESR spectroscopy. MMA gave a seven‐line single spectrum from radicals formed by hydrogen addition. The hyperfine coupling constants are slightly anisotropic with a mean value of 22 G. Radical pairs were observed as ΔMs = 1 and ΔMs = 2 transitions; the hyperfine coupling was 11 G. From the strongly anisotropic dipolar interaction, upper limits for the distances between the pair components were calculated to be 5.45 Å and 6.3 Å. MA gave a five‐line main spectrum with the same hyperfine coupling values and two radical pairs, one with a distance 5.9 Å between the components. In a there was also a strongly anisotropic interaction. The hyperfine coupling of the ΔMs = 2 transition was 9.8 G. The number of radical pairs compared to the total number of radicals increases only slightly with the radiation dose. This makes it likely that pair formation occurs in the spurs and blobs formed by the γ‐radiation. At an increased temperature the radical pairs disappeared; the spectrum of MMA changed to that characteristic of propagating polymer radicals.
Salt rejection by polymer membranes in reverse osmosis. II. Ionic polymers
Authors: Yasuda H. , Lamaze C. E. , Schindler A.
Published: April 2003

The water permeability K1 [which is related to water flux J1 per unit membrane area by J1 = K1(Δp − ΔII)/ΔX, where Δp is the pressure difference, ΔII is the osmotic pressure of feed solution, and ΔX is the membrane thickness] of homogeneous ionic polymer membranes in reverse osmosis and their salt rejection Rs [which is given by Rs ≡ 1 − (C2″/C2′), where C2′ is the concentration of the salt in feed solution, and C2″ is the concentration of salt in effluent] were examined with cationic and anionic membranes of block and graft copolymers. For ionic membranes, Rs and K1 are related by K1 = A exp { − BRs}, where A and B are constants. This equation was found to be independent of the ion charge, the chemical nature of the polymer, and film morphology. The principle of salt rejection by ionic membranes was explained by the difference in the transport volumes (volume elements available for transport) for mobile co‐ions and water. The electric repulsive force between a fixed ion and a mobile co‐ion decreases the transport volume of the latter, thus creating a transport depletion of salt flux relative to water transport. This transport depletion is governed by the amount of water sorbed by a fixed ionic site, which also determines the water flux. Consequently, Rs and K1 for ionically charged membranes are related as described above. This relation significantly differs from that found between Rs and K1 for nonionic polymer membranes, where the size and the solubility of ions in the membrane are mainly responsible for the transport depletion. The decline of Rs with increasing K1 is much less in ionic membranes than in nonionic ones; however, in the high Rs region, K1 for both ionic and nonionic membranes become similar as the dominant mode of water transport changes from flow to diffusion.
Characterization of moisture‐cured polyurethane films
Authors: Hassan A. M. , Ray L. N.
Published: April 2003

A series of polyurethanes (PU) prepolymers with NCO/OH ratios of 2.1:1 and 1.9:1 were prepared by reacting hydrogenated methylene di‐p‐phenyl diisocyanate (HMDI) with triol mixtures of TP740 (molecular weight 740) and TP1540 (molecular weight 1540). Stress–strain (S/S) and swelling equilibrium measurements were performed using thin‐film samples prepared by moisture‐curing the prepolymer at room temperature. The swollen PU networks gave an S/S curve which is fully described by rubber elasticity theory. The Mooney‐Rivlin constant C1 (swollen) was found to increase directly while the molecular weight between crosslinks Mc decreases as the number of branches per cubic centimeter is increased. The solvent—polymer interaction parameter χ determined in benzene was 0.077 + 0.97vr, where vr is the volume fraction of rubber in the swollen network. The crosslink density v′, and Mc were calculated from the relations v′ = pNB and Mc = 0.667 B−1, where B denotes moles of branches per gram, and were found to be in good agreement with v′ and Mc established from S/S and swelling‐equilibrium measurements. In calculating v′ and Mc, the water‐PU crosslinking reaction at room temperature was assumed to occur mainly through the formation of a urea linkage.