bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocurrents in simple polymer systems. II
Authors: McGibbon G. , Rostron A. J. , Sharples A.
Published: April 2003

Large photocurrents have been observed in films of some simple polymers (containing no π‐orbitals), of which poly(vinyl fluoride) is a typical example. Not only are the currents large (up to 10−5 A/cm2) but also they are capable of being excited by light in the visible wavelength region where absorption by the polymer is too low to be detectable. The results indicate that the effects are electronic, rather than ionic, in nature.
Analysis of small‐angle x‐ray diffraction from polymers
Authors: Buchanan D. R.
Published: April 2003

The Fourier transform method of Vonk and Kortleve for the analysis of small‐angle x‐ray diffraction (SAXRD) from semicrystalline polymers has been compared with a modified direct method, originally due to Tsvankin. SAXRD data for three melt‐crystallized polyethylene samples have been analyzed in terms of the mean true periodicity, mean crystal length, and mean length of amorphous segments. The two methods of analysis yield substantially equivalent results for all three samples. Calibration curves for the Tsvankin analysis are tabulated, and the relative merits of the two methods of analysis are discussed. With either method, information about the diffracting structure may be deduced that is not available from a simple measurement of the position of the SAXRD maximum. In fact, direct application of the Bragg law to any but the sharpest maximum yields a spacing (the long period) that lacks direct physical significance.
Relationship between compressive yield and tensile behavior in glassy thermoplastics
Authors: Haward R. N. , Murphy B. M. , White E. F. T.
Published: April 2003

The effect of temperature and strain rate on the compressive yield behavior of polystyrene is compared with the effect of the same variables on crazing in tension. The results support the conclusion of other, more extensive work, which shows that crazing involves the same types of molecular processes as those which occur during deformation under compression and shear. An improved method of measuring compressive stress–strain curves is then described, and the compressive yield stress is also compared with an extrapolated tensile yield stress. The difference between the two is in line with concepts which assume a dependence of yield stress on the state of hydrostatic tension (or compression). It can be adequately described by the Mohr‐Coulomb yield criterion. Application of this criterion also enables a theoretical stress strain curve in tension to be derived from other results in compression. Comparison of the tensile stress–strain curve so obtained with those which can be directly measured with other plastics, supports the hypothesis that crazing is favored by a marked decline in engineering stress during tensile elongation (plastic instability).
Effect of water sorption on the dielectric behavior of calcium chondroitin‐4‐sulfate
Authors: Kaufman Leslie J. , Bettelheim F. A.
Published: April 2003

The dielectric properties of calcium chondroitin‐4‐sulfate were studied as a function of frequency, temperature, and water content. The dielectric constant changes very little with water content below “monolayer” coverage, and after that the dielectric constant follows the shape of the adsorption isotherm. The dielectric behavior is discussed as affected by interfacial polarization and by the increase in the rotational freedom of the polymer side chains.
Optical anisotropy of polymer chains and Markov processes. II. Polyoxyethylene
Authors: Lemaire Bernard , Fourche Georges
Published: April 2003

A comparative study of the average molecular optical anisotropy 〈γ2〉 of the polyoxyethylene chain, \documentclass{article}\pagestyle{empty}\begin{document}${\rm R} \hbox{---} {\rm O}\rlap{--} ({\rm CH}_2 {\rm CH}_2 {\rm O}\rlap{--} )_n {\rm R}$\end{document} where R = CH3, H and n is the degree of polymerization of the molecule, was carried out for the different internal rotational models considered in Part I of this series. In particular, the results obtained show that the condition of interdependence between internal rotational angles of nearest‐neighboring bonds increases the average molecular optical anisotropy by about 4% (n ≫ 1), compared with the case of independent rotations. This increase is much weaker than in polyethylene chains, for which it is about 20% under analogous conditions.
Orientation effects in biaxially stretched linear polyethylene
Authors: Adams G. C.
Published: April 2003

The literature on polymer morphology contains many studies of structural and orientation changes occurring upon uniaxial stretching of films and fibers, but it has only an occasional reference to such studies on biaxially stretched film. This paper presents data on a structural change due to simultaneous biaxial stretching up to 6 × 6 stretch ratio of quenched linear polyethylene slightly below the melting temperature. At low stretch ratios the b axis of the orthorhombic unit cell orients predominantly in the biaxial plane of stretching or film plane. At higher than 4 × 4 stretch ratio, a second crystal orientation appears which is a (110) orientation in the film plane. Differential scanning calorimetry scans show two melting peaks occurring concurrently with diffraction effects of two crystal orientations. The evidence for two populations of crystals differing in orientation are discussed in the light of current concepts of folded‐chain lamellae and their fragmentation with elongation.
Surface tension of polymer solutions. III. Effect of molecular weight distribution
Authors: Gaines George L.
Published: April 2003

The lattice‐theory equations for the surface tension of polymer solutions based on the parallel‐layer model have been extended to include more than two components. The surface tensions of tetrachloroethylene solutions of some blended polydimethylsiloxane fluids have been measured at room temperature. The results are in nearly quantitative agreement with the theoretical calculations.
Structural origin of the cryogenic relaxations in poly(ethylene terephthalate)
Authors: Armeniades C. D. , Baer Eric
Published: April 2003

The effect of molecular organization (crystallinity, orientation) on the internal friction of poly(ethylene terephthalate) was studied by means of dynamic mechanical measurements at temperatures from 300 to 4.2°K, with a free‐oscillating torsion pendulum at 1 Hz. It was found that crystallinity decreases the intensity of the composite γ relaxation at 210°K and gives rise to an additional loss maximum ε at 26°K. Uniaxial orientation broadens the γ relaxation and gives rise to an additional loss peak δ, at 46°K. The δ and ε losses are dependent on molecular organization, occurring only in samples containing aligned, taut chain segments and crystalline structures, respectively. They have a common activation energy of 4 kcal/mole. All three low‐temperature relaxations in oriented specimens show pronounced directional anisotropy, which, in the γ loss, may be due to the preferred orientation of noncrystalline chain segments, while in the δ and ε losses, may be associated with the direction of defect structures. On the basis of the observed behavior of the δ and ε relaxations it is suggested that they may involve motions of defect structures and may thus participate in stress‐transfer mechanisms at large deformations.
Thermodynamic parameters of polymer‐solvent systems from light‐scattering measurements below the theta temperature
Authors: Scholte Th. G.
Published: April 2003

As is well known, the chemical potentials of polymer and solvent in solution and, hence, the Flory‐Huggins interaction parameter χ can be determined from scattered light intensities from dilute and concentrated solutions of the polymer in the solvent concerned. Preferably, measurements should be performed at temperatures as low as possible, provided the temperature exceeds the cloudpoint for the concentration used. It is shown that the lower the temperature and, consequently the higher the scattered light intensity, the better is the accuracy of the parameters obtained. At each temperature the scattered light intensity shows a maximum at some concentration. Below the theta temperature the ratio of scattered light intensity and concentrations also shows a maximum at some concentration. The values and the concentrations of these maxima for various temperatures enable the maximum of the spinodal to be determined. The spinodal itself can be determined by an extrapolation procedure of the reciprocal scattered light intensities. Measurements have been performed with three narrow‐distribution polystyrene samples in cyclohexane. On the basis of the results, χ, and its dependence on concentration, temperature, and molecular weight can be determined to high accuracy.
Morphology of polyethylene crystallized under the simultaneous influence of pressure and orientation in a capillary viscometer
Authors: Crystal Richard G. , Southern John H.
Published: April 2003

The morphology of high‐density polyethylene crystallized under simultaneous pressure and shear in an Instron capillary viscometer has been examined by scanning electron microscopy, electron microscopy, and selected‐area electron diffraction. Two distinct fibrous morphologies were observed in these unusually transparent strands. The outer sheath was composed of fibers, 3000 Å in diameter, aligned parallel to the extrusion direction and apparently interconnected by a lamellar cross texture. A highly crystalline ribbon texture composed of fine fibers, 200–250 Å in diameter, dominated the inner core. Sharp‐spot electron diffraction patterns obtained from these central ribbons indicated a high degree of c‐axis orientation parallel to the fibers and an extended‐chain crystal structure. The melting behavior of both irradiated and unirradiated strands examined by differential scanning calorimetry was consistent with the formation of two distinct crystalline morphological units.
Glass transition in nylons
Authors: Gordon Gerald A.
Published: April 2003

Differential thermal analysis (DTA) of some commercial nylons has disclosed some anomalous phenomena with respect to the glass transition, generally considered to occur at 40–50°C. On the first heat cycle the transition occurs normally. On cooling, however, no corresponding transition occurs, and on an immediate rerun the transition has disappeared. If another DTA thermogram is made after a few hours, the transition begins to reappear, but at a temperature lower by a few degrees. After about five days rest, the transition is again normal in size and temperature. On annealing at 75°C, the 43°C transition is pushed up to about 92°C. On resting after annealing, transitions appear at both 40 and 92°C. These phenomena are explained in terms of the slow formation of a hydrogen‐bonded network in the amorphous regions of the polymer. It is the disruption of this network that is normally considered to be the glass transition in nylons. The network is slow in re‐forming because of problems involved in matching up potential hydrogen‐bonding sites, which are, of course, distributed at intervals along the polymer chain. The temperature at which the network is disrupted is apparently dependent not so much on the ratio of bonding to nonbonding sites, as on the temperature at which it was formed.
Radiation chemistry of poly(propylene oxide)
Authors: Roberts G. P. , Budzol M. , Dole Malcolm
Published: April 2003

Atactic, isotactic, and optically active poly(propylene oxides), PPOx, were irradiated with both γ‐rays and electron beams. Up to a dose of 37 Mrad no change could be detected in the optical activity. G values for hydrogen evolution decreased as compared to polypropylene in about the same ratio as G(H2) of polyoxymethylene decreased as compared to polyethylene. G values for crosslinking and scission, estimated by means of gelation theories of Saito and Inokuti, were found to be greater for isotactic than for atactic PPOx. The behavior of transient infrared and ultraviolet absorption bands is discussed. Intrinsic viscosity data indicate a rapid initial chain degradation whereas CO gas and OH group production is linear with dose. Evidence for the conversion of one type of free radical to another on heating an irradiated sample from 77°K to room temperature is based on the behavior of transient infrared and ultraviolet absorption bands.
Fold surface of polyethylene single crystals as assessed by selective degradation studies. II. Refinements of the nitric acid degradation method
Authors: Keller A. , Udagawa Y.
Published: April 2003

Detailed critical examinations of three aspects of nitric acid treatment of polyethylene are reported. (1) The endgroups introduced by the nitric acid are examined. It is concluded that in samples degraded to a single‐crystal traverse stage, carboxyl features only as endgroup, and conversely each chain‐end is terminated by such a group. Consequently, the carboxyl content can be used for quantitative characterization of the cut chain length. The function and position of the nitro group remains unexplained. (2) The morphological selectivity of the nitric acid‐induced degradation is scrutinized. It is concluded that the crystal core is attacked and thinned by the acid; the slowing down of the reaction is principally due to accumulation of reaction products. Accordingly, the usual distinction between a vulnerable amorphous layer and a resistant crystal core is not justified on the basis of such degradation experiments. It follows that meaningful structural information is obtained only when the relevant crystal properties are studied as a function of chain cutting, assessed from the molecular weight distribution (GPC), as opposed to that of degradation time alone. (3) The role of sample consistency and reagent strength has been examined. It is demonstrated that for the reaction to be sufficiently uniform throughout the sample for the results to be meaningful, the reaction rate has to be slow compared to the rate at which the reagent diffuses into the specimen. To realize these conditions, finely dispersed samples and weak reagents were found to be favorable
NMR observations of drawn polymers. VIII. Doubly oriented nylon 66
Authors: Olf Heinz G.
Published: April 2003

A wide‐line NMR study of chain segmental motion in nylon 66 has been made on a rolled sheet having “double orientation.” In this sheet the crystallite c axis, i.e., the molecular chain axis, is oriented preferentially along the roll direction, and the crystallographic (010) plane lies predominantly parallel to the roll plane, or the plane of the sheet. The direction of the applied magnetic field with respect to the sheet is characterized by two angles, the polar angle γ subtended by the roll direction and the magnetic field, and an azimuthal angle ϕ. NMR spectra were taken at various values of the angles γ and ϕ and at three temperatures −196°C, 20°C, and 180°C. The second moments of the absorption spectra taken at 180°C were compared with theoretical predictions of second moments based on two models for the high‐temperature segmental motion (called the αc process) in crystalline regions of nylon 66. One model consists of rotational oscillation with amplitudes δ of segments around their axies. The second model is denoted 60° flip‐flop motion and consists of rotational 60°C jumps of the segments around their axes between two equilibrium sites with the possibility that the segments also oscillate with a general amplitudes δ around each site. The experimental results are consistent with fairly large amplitudes δ, in which case both models approach the limiting case of full segment rotation. For this reason the experiments do not allow a distinction between the two models. From the second moments at −196°C and 20°C the decrease in second moment due to the low temperature segmental motion, the γ process, is obtained. This motion occurs in noncrystalline regions of nylon 66 and is found to cause a decrease in second moment which is strongly dependent on the two angles γ and ϕ, implying double orientation of the noncrystalline segments. It is suggested that at low temperatures the noncrystalline segments become immobilized in sites dictated by the crystallite orientation through the extensive hydrogen bonding known to exist in nylon 66.
Self‐oscillation mechanism of necking on extension of polymers
Authors: Andrianova G. P. , Kechekyan A. S. , Kargin V. A.
Published: April 2003

A new phenomenon in necking of some polymers, including poly(ethylene terephthalate) (PETP) was detected. It was found that extension of PETP films under certain conditions results in periodic stress oscillations and a periodic change in appearance of the sample. The conditions at which self‐oscillations appear have been determined, and the principal regularities of this regime of deformation are described. The following factors are critical for the appearance of self‐oscillation: speed of straining and compliance of the sample. The self‐oscillation of stress and formation of the periodic transverse bands is attributed to heat dissipation during necking corresponding to local temperature jumps and periodic strong variation of elasticity modulus due to poor heat conductivity of the polymer. Changing the external conditions of heat transfer influences the possibility and development of the effect. The phenomenon is common for various crystallizing polymers, being dependent on physical properties of the polymer and conditions of deformation.
Crystallinity and conformational changes in poly(β‐benzyl L‐aspartate)
Authors: Obata Hiroko , Kanetsuna Hisaaki
Published: April 2003

The crystallinity of poly(β‐benzyl L‐aspartate) is highly variable, in a series of specimens prepared under various conditions: films cast from chloroform solutions at various evaporation rates, films cast comparatively slowly from chloroform–trifluoroacetic acid solutions, films prepared from dichloroacetic acid solution by treatment with ethyl alcohol, precipitates formed from trifluoroacetic acid solution by addition of ether. Film cast slowly from chloroform is in the highly crystalline ω form. In contrast, the conformation of the benzene rings in the ω helix obtained from the α helix by heating is distorted to some extent in comparison with the structure of the highly crystalline ω form. Crystallization and conformational changes from the α to the ω form, and from the ω to the β form upon heating, are correlated with the dispositions of the side chains, the packing of the benzene rings, and the motion of the side chains. The main chain of the α helix is distorted into the ω form when its side chains are in a favorable conformation. The α helix is stable in the disordered conformation, and it is distorted to some extent at high temperature.
NMR observations of drawn polymers. IX. Chain mobilization and water mobility in nylon 66
Authors: Olf H. G. , Peterlin A.
Published: April 2003

Wide‐line NMR spectra of nylon 66 fibers have been obtained at different alignment angles between the fiber axis and the magnetic field, at varying water contents (H2O and D2O), and at different temperatures. At 28°C the spectrum of the dry fibers consists of a nearly structureless broad line. At water regains of 1.4% by weight (dry basis) and higher a sharp line appears which originates from highly mobile water molecules. The width of this line decreases with increasing water content, implying an increase of water mobility. Moreover, the width is a function of the alignment angle; this shows that the water is not reorienting isotropically owing to specific water‐polymer interaction. The amount of mobile water is always smaller than the amount of water absorbed. At water contents close to saturation, a mobile polymer line appears with a width intermediate between the broad line (immobile polymer) and the sharp water line. This line, most clearly observed at an alignment angle of 0°, is due to a shift of the αa process to lower temperatures in the presence of water. A similar line is observed in the dry fibers at 120°C. It is shown that the αa process decreases the NMR second moment only slightly. The shift of the high temperature drop in second moment to lower temperatures in the presence of water is therefore interpreted as due to a shift of the αc process, and not of the αa process, to lower temperatures.
Growth and morphology of single crystals of linear aliphatic polyesters
Authors: Kanamoto T. , Tanaka K. , Nagai H.
Published: April 2003

In order to elucidate the relations between morphological habits and chemical structure of polymers, poly(ethylene sebacate), poly(hexamethylene sebacate) and poly(decamethylene 1,16‐hexadecanedicarboxylate) were crystallized from dilute solutions in n‐hexanol, isoamyl acetate etc., and were studied with the electron microscopy and x‐ray diffraction. The crystal structure of these polyesters are tentatively determined. Morphological “regularity” and “simplicity” of the single crystals are correlated with the chemical structure of the polymers. The crystallization conditions under which “regular” and “simple” single crystals are obtained are relaxed with increase of methylene sequence length in chemical repeat unit. The Bragg extinction bands in the single crystals of poly(hexamethylene sebacate) and poly(decamethylene 1,16‐hexadecanedicarboxylate) suggest nonplanar nature of these crystals. The molecular chains in the poly(ethylene sebacate) single crystals are inclined from the normal of the basal plane; the fold surface corresponds to the (001) plane.
Fractionation of linear polyethylene during bulk crystallization under high pressure
Authors: Kardos J. L. , Li H.‐M. , Huckshold K. A.
Published: April 2003

Two linear polyethylene fractions (Mη, 11,260 and 100,000) and mixtures of these fractions have been isothermally crystallized from the melt under pressures up to 3000 atm. Characterization of individually crystallized fractions with transmission electron microscopy indicates that pressure can be used to produce a crystallite whose thickness is a measure of the chain length within it. Although the high molecular weight fraction yields spherulites containing individually varying lamellae thicknesses, the maximum thickness of each lamella is a measure of the chain length within it. Both electron micrographs and differential thermal analysis results show that crystallization of homogeneous mixtures of the high and low molecular weight fractions under high pressure results in a distinct fractionation and segregation according to molecular weight.
Statistical thermodynamics of networks at large deformations
Authors: Smith K. J.
Published: April 2003

A general theory of non‐Gaussian elasticity is presented for real polymeric chains having fixed bond angles and restricted internal rotations. The theory contains the displacement‐vector distribution given by Nagai, and the Flory‐Wall‐Hermans procedure is used for the calculation of network properties. Whereas the treatment is valid for all types of polymer chains, it is not totally satisfactory from a practical standpoint because of a slow series convergence if the chains are stiff. It is best utilized for flexible polymers under conditions of light crosslinking. Detailed network behavior is investigated only for polyethylene type chains having uncorrelated internal rotations. In this instance the fractional contribution fe/f of the internal energy of the total force f is found to be a function of elongation at high degress of stretching. It may decrease, or increase, depending upon the sign of fe/f at low elongations. Furthermore, the variation of fe/f with elongation is independent of the fixed bond angle of the chain backbone. Stress–strain behavior and energy–strain behavior are in opposition, i.e., when the non‐Gaussian contribution to the stress is greatest, it is the least for the ratio fe/f, and vice versa. The presence of correlated internal rotations would not be expected to greatly alter these general conclusions.
Oxidation of polypropylene in benzene solution
Authors: Van Sickle Dale E.
Published: April 2003

The oxidation of both amorphous and crystalline polypropylene in benzene solution was studied at 100–130°C. tert‐Butyl peroxide was used as an initiator. The kinetic behavior of the amorphous and crystalline forms differs slightly; the oxidation rate of the amorphous type is slower for a given polymer and initiator concentration. The oxidation rate of solutions of the crystalline form can be simply described by the expression: R0 = 1.87 × 1013 exp {−29,000/RT} [t‐Bu2O2]0.58[polypropylene]0.73, mole/l.‐min. Product analyses of the oxidized solutions are incomplete, but the results do show that only ∼40% of the absorbed oxygen is present as hydroperoxide. Further, much of the hydroperoxide is present in low molecular weight polar fragments which are acetone‐soluble. These results show that oxidized polypropylene cannot be regarded simply as “polypropylene hydroperoxide” with repeating hydroperoxide groups attached to the polymer chain in 1,3,5… (tertiary) positions.
Polymerization of complexed monomers. II. Alternating copolymers of indene with methyl acrylate and methyl methacrylate
Authors: Hecht Jeffrey K. , Dix Don T.
Published: April 2003

Indene has been copolymerized with polar monomers in the presence of ethylaluminum sesquichloride. The polymers have molecular weights in the 7,000–10,000 range and soften at temperatures above 150°C. The NMR spectra of the copolymers are discussed with reference to polymer structures and chain conformations. Indene is comparable to cyclopentene in reactivity in copolymerizations with methyl acrylate but is much more reactive than cyclopentene toward methyl methacrylate.
Photodegradation of urethane model systems
Authors: Beachell H. C. , Chang I. L.
Published: April 2003

The photo‐oxidation products of ethyl N‐phenyl‐carbamate (EPC) were identified as ethyl o‐aminobenzoate, ethyl p‐aminobenzoate, aniline, water, carbon dioxide, azo compounds, and other colored material. The ethylaminobenzoates, formed by intramolecular rearrangement of EPC, were precursors of the azo and colored products. Diethyl 4,4′‐azobenzenedicarboxylate was produced by the ultraviolet irradiation of the precursor, ethyl p‐aminobenzoate, in the presence of oxygen. Benzophenone and anthraquinone, as the triplet donors, sensitized the photo‐oxidation of EPC. Quantum yields of photolysis of EPC were measured. The photorearrangement reaction was inhibited by the polar solvent (ethanol). The presence of metal ions and phenyl isocyanate in EPC showed no effect on the oxygen consumption rate.
Effect of chelation on the polycondensation of monomers having an active ester group
Authors: Ogata N. , Sanui K. , Ikari T. , Okouchi K.
Published: April 2003

Various amino acid esters and dicarboxylic acid esters having a β‐thioether group have been synthesized and their polycondensation with diamine was found to occur at room temperature to form polyamide thioether. The effect of solvents or chelating agents on their polycondensation reaction was investigated. Metal acetylacetonates or inorganic salts had a great influence on the rate of the polycondensation reaction, and the catalytic activity of metal acetylacetonates M(AcAc)n or inorganic salts decreased in the following order: Mg(AcAc)2≫Th(AcAc)4>Cu(AcAc)2>Li(AcAc)>None>Zr(AcAc)4, MgCl2·6H2O>CuCl2·.2H2O>ZnCl2>MgCl2>None. It was also found that the amount of polyamide thioether was dependent on solvents or the presence of chelating agents because the polycondensation rate and the apparent equilibrium between ring and chain structures were both greatly influenced by solvents or chelating agents.

These effects of solvents or chelating agent on the polycondensation may be attributable to formation of a complex with the thioether group which enhances the reactivity of ester.
Electron paramagnetic resonance study of thermal‐oxidative degradation of nylon 6
Authors: Chiang T. C. , Sibilia J. P.
Published: April 2003

Electron paramagnetic resonance studies were conducted on thermally degraded nylon 6 polymers. A nitroxide radical was observed from nonterminated and amineterminated nylon 6 samples heat‐treated in the persence of air. The nitroxide concentration in the latter was about twice that of the former under the same conditions. The nitroxide radical was not observed in acid‐terminated nylon 6 samples. A mechanism of nitroxide radical formation was proposed based on the oxidation of secondary amines. A one‐line EPR signal was also observed from nonterminated, amine‐terminated, and acid‐terminated nylon 6 samples heated in the presence of air. This singlet signal was attributed to conjugated systems with unpaired electrons.
Theoretical reaction kinetics of reversible polymerization
Authors: Huang Ching‐Rong , Wang Huei‐Hsiung
Published: April 2003

The kinetics of reversible polymerization of a polymer system without transfer and termination reactions is investigated theoretically. An analytic solution is obtained that enables one to predict the variation of monomer concentration with respect to time in a closed system. When the polymer system reaches equilibrium, three different relationships are derived between the equilibrium monomer concentration and the ceiling temperature under different conditions. The classical relationship by Dainton and Ivin is a special case of the three derived cases.
Degradation of chlorinated polyethylene. I. Effect of antimony oxide on the rate of dehydrochlorination
Authors: Abu‐Isa Ismat A.
Published: April 2003

The degradation of two chlorinated polyethylene compounds CPE 25 (45% chlorine) and CPE 16 (36% chlorine) was studied by following their rates of dehydrochlorination at two temperatures, 150°C and 180°C in pure nitrogen and pure oxygen atmospheres. Studies on the powdered polymers showed that the dehydrochlorination rate of CPE 25 is about fourteen times faster than that of CPE 16 in nitrogen atmospheres and only three to four times faster in oxygen. The molded polymers gave a lower rate of dehydrochlorination than when in the powdered form. This effect is attributed to diffusion factors. The antimony oxide brought about an induction period in the dehydrochlorination reaction during which only a small amount of HCl is evolved, followed by a very fast rate of dehydrochlorination both in oxygen and nitrogen atmospheres. The duration of the induction period increases with increase in the Sb2O3 concentration, but is followed by an accelerated HCl loss which is faster when Sb2O3 concentration is higher. This work provides supporting evidence that SbCl3 was formed and lost during degradation. Mechanisms of dehydrochlorination are suggested for the reaction in the case of pure chlorinated polyethylene and for the polymer containing antimony oxide.
Synthesis of some vinyl‐substituted pyrylium salts and their intermediates
Authors: Petropoulos Constantine C.
Published: April 2003

The preparation of vinyl‐substituted pyrylium salts and their intermediates is described. These monomers and intermediates have been derived from syntheses based onp‐2‐hydroxyethoxybenzaldehyde and 4‐methoxypyrylium salts. Treatment of the hydroxybenzaldehyde with acetophenone gives a hydroxypyrylium intermediate which, when methacrylated, gives a pyrylium methacrylate. Methacrylation of the hydroxy‐benzyldehyde followed by condensation with methylpyrylium salts gives styryl‐pyrylium methacrylates. Displacement of the methoxy group in methoxypyrylium salts with ethanolamine derivatives followed by methacrylation yields a series of aminopyrylium methacrylates. The preparation of a divinylpyrylium urethane and a pyrylium‐type copolymer is also described.
Radical polymerization of methyl methacrylate in the presence of isotactic poly(methyl methacrylate)
Authors: Buter R. , Tan Y. Y. , Challa G.
Published: April 2003

Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed isotactic PMMA (iMA) with about 90% isotactic triads and different M̄v's, viz., iMA‐1: 7.2 × 105; iMA‐2, 5.0 × 105; iMA‐3, 3.5 × 105; iMA‐4, 1.25 × 105; and iMA‐5, 1.15 × 105. The MMA:iMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. It is found that the M̄v of the polymer formed ran parallel to the M̄v of iMA. In all cases syndiotactic PMMA (s‐PMMA) was produced which associated with the isotactic substrate to form acetone‐insoluble stereocomplexes. The syndiotactic polymers probably consist of long syndiotactic and heterotactic sequences. The syndiotacticity decreased with conversion and was generally highest in the presence of iMA‐1. With iMA‐1 even the formation of some additional i‐PMMA (in the acetone‐insolubles) was indicated, especially in the later stages of the polymerization. Characterization of the acetone‐soluble fractions indicated that i,s‐stereoblock polymers were also produced, of which the persistence ratios ρ increased with the M̄v of iMA. From these results it is concluded that this reaction differs from the conventional radical polymerization and can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i‐ and s‐PMMA to associate. The formation of i,s‐stereoblock polymers and additional i‐PMMA indicates that s‐PMMA in its turn can also act as a polymer matrix.
Synthesis of polyimides by photoaddition of bismaleimides to alkylbenzenes
Authors: Kardush Nabil , Stevens Malcolm P.
Published: April 2003

Bismaleimides undergo successive 2 + 2 and 2 + 4 cycloadditions to alkylbenzenes to form polyimides. For the series toluene, ethylbenzene, cumene, tert‐butylbenzene, highest yields of polymer are obtained with toluene and tert‐butylbenzene with three different bismaleimides. This is explained in terms of inductive and steric effects of the alkyl substituents.
Polymerization of vinyl monomers with chlorosilane compounds and metal halides
Authors: Minoura Yuji , Toshima Hiroyuki
Published: April 2003

It was found that styrene was polymerized with chlorosilane compounds and metal halides in 1,2‐dichloroethane. The rate of polymerization of styrene was proportional to the concentration of styrene, trimethylchlorosilane, and mercuric chloride. The overall activation energy of polymerization was −2.9 kcal/mole. The polymer yield decreased markedly on addition of ether into the polymerization system, and the infrared spectrum showed evidence of silicone fragments in the polymer. From the results, it was considered that the polymerization was initiated by a siliconium cation. The formation of a complex between trimethylchlorosilane and metal halides (i.e., ferric chloride) was confirmed by the continuous variation method of ultraviolet and visible absorption spectra.
Equilibrium anionic polymerization of the isopropenyl monomers containing aromatic heterocycles
Authors: Yagi Kohji , Miyazaki Tatsuru , Okitsu Hiroyuki , Toda Fujio , Iwakura Yoshio
Published: April 2003

The anionic polymerization of three monomers, 2‐isopropenyl‐4,5‐dimethyloxazole(I), 2‐isopropenylthiazole(II), and 2‐isopropenylpyridine(III), was studied in THF. These monomers produced red‐colored living polymers on addition of sodium naphthalene or living α‐methylstyrene tetramer as an initiator. It was observed that a considerable amount of monomer remained in the respective living polymer–monomer system, indicating that an equilibrium between the polymer and the monomer existed as in the case of α‐methylstyrene. At lower temperatures, the conversion of the monomer to the polymer increased. The equilibrium monomer concentrations [Me] were determined at different temperatures, and the heats (ΔH) and the entropies (ΔS°) of polymerization were obtained by plotting In(1/[Me]) against 1/T as ΔH = −9.4, −6.8, and −6.2 kcal/mole, ΔS°S = −22.9, −16.5, and −16.6, eu for I, II, and III, respectively.
Synthesis of polysulfonates and polysulfonamides from 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene‐5,9‐disulfonyl chloride
Authors: Wilson John C. , Hamb F. Lynn
Published: April 2003

Treatment of 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene with chlorosulfonic acid leads to the formation of the mono‐, di‐ and tetrasulfonyl chloride derivatives. The 5 and 9 positions of 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene were found to be most active toward electrophilic sulfonation. Polysufonates and polysulfonamides prepared from 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene‐5,9‐disulfonyl chloride exhibit glass transition temperatures above 200°C and show little weight loss at temperatures to 350°C.
Asymmetric selective copolymerization of propylene oxide with d‐camphoric acid anhydride
Authors: Yamaguchi Hidemasa , Nagasawa Masayuki , Minoura Yuji
Published: April 2003

The ring‐opening copolymerization of propylene oxide with d‐camphoric acid anhydride [α]D −3.4° was carried out with diethylzinc and triethylamine as catalysts. It was found that the products were alternating copolymers which were optically active. The optical rotatory dispersion curves were found to fit a simple Drude equation having a λc value of 201 mμ. The specific rotation increased with increasing intrinsic viscosity of the product. The propylene oxide recovered from the polymerization system was optically active. Its specific rotation increased with increasing polymerization time. It is thought that the asymmetric selective copolymerization of propylene oxide is caused by the influence of the optically active camphoryl group of the polymer end.
Hydrogen‐transfer polymerization of acrylamide and methacrylamide with optically active basic catalysts
Authors: Yamaguchi Koichi , Minoura Yuji
Published: April 2003

Hydrogen‐transfer polymerization of acrylamide and Methacrylamide with an optically active amyl alcoholate or n‐amyl alcoholate (sodium, calcium, magnesium, barium, and aluminum) was investigated to 100°C in toluene. The initiation ability of the metal ion of the initiator increased in the order, sodium > barium > calcium > magnesium > aluminum. The optically active polymer was obtained by the polymerization of methacrylamide with an optically active alcoholate (barium or calcium), but was not obtained by the other alcoholates and by the polymerization of acrylamide with the optically active alcoholate. The specific rotation of the optically active polymer obtained was about +1.1° ∼ +1.3°. The hydrolyzed product of the optically active polymer was α‐methyl β‐alanine having optical activity (+1.0°). The initiation mechanisms of the polymerization were thought to be the dehydrogenation of the monomer of the negative ion and the Michael addition reaction with the monomer of the negative ion and the catalyst, and it was confirmed that the optically active polymer was prepared by intermolecular hydrogen transfer mechanism. In the polymerization of MMA with menthol barium and borneol barium as the optically active catalyst, the optically active polymer was obtained.
Branching of anionic poly(methyl methacrylate)
Authors: Trekoval J. , Kratochvíl P.
Published: April 2003

A viscometric determination of the degree of branching γ, of poly(methyl methacrylate) obtained by anionic polymerization proved the reaction of the growing center of poly(methyl methacrylate) with the ester group of another polymer molecule, accompanied by the formation of a trifunctional branch point. This reaction occurs if the solution polymerization of methyl methacrylate is initiated: (1) with butyllithium at −78°C only on attaining 100% conversion and after a long time or at +20°C immediately after the polymerization has set in; (2) with lithium tert‐butoxide at +20°C after a long time. The degree of branching of poly(methyl methacrylates) obtained under similar conditions in the presence of tetrahydrofuran reaches higher values than for polymers prepared in toluene. The tacticity of polymers does not affect the experimentally determined γ values.
Anionic polymerization of caprolactam. XLIII. Relationship between osmometric molecular weight, viscosity, and endgroups of a polymer
Authors: Goebel C. V. , Čefelín P. , Stehlíček J. , Šebenda J.
Published: April 2003

For unfractionated anionic polymers, the following relationship between the osmometric molecular weight and intrinsic viscosity is valid: M̄n = 13200[η]1.115 (cresol), or M̄n = 13000[η]1.021 (93.8% H2SO4). A comparison of the osmometric and viscometric data with the number of endgroups of a polymer confirmed the finding that under certain conditions, moderately branched molecules can be formed; the above parameters depend on the type of the activator used.
Polybenzodipyrroloquinoxalines
Authors: Janović Z. , Higgins Jerry
Published: April 2003

Three polymers have been prepared by the condensation of benzo[1,2‐b;5,4‐b ′]‐dipyrrolo‐2,3,4,5‐tetraone (I) with 1,2,4,5‐tetraaminobenzene (II), 3,3 ′‐diaminobenzidine (III), and 3,3 ′,4,4 ′‐tetraaminodiphenyl ether (IV) in polyphosphoric acid (PPA) solution. The polymer structures were substantiated by comparison of their infrared and ultraviolet spectra with spectra of the model compounds and elemental analysis. The polymers had inherent viscosities of 0.86‐0.90 (H2SO4) and thermal stabilities of 460°C and up to 700°C in air and nitrogen atmospheres, respectively.
Fluorine‐containing poly(vinyl alcohol): A helix or a random coil
Authors: Haas Howard C. , MacDonald Ruby L.
Published: April 2003

Substitution of several mole per cent of the hydroxyl groups of poly(vinyl alcohol) by fluorine results in marked changes in polymer properties. These fluoro poly(vinyl alcohols) (PVAF) form thermally reversible gels in water at low polymer concentrations. In solution, a helical conformation or a random coil containing helical sequences is more in accord with the experimental observations than the random coil structure of poly(vinyl alcohol). This helical hypothesis is supported by high heats of crosslinking of the aqueous thermally reversible gels, the difficult solubility of PVAF in H2O, the insolubility of the PVAF–iodine complex under conditions where the PVA–iodine complex remains soluble, the temperature‐independent high value for the Huggins k ′ slope constant, the greater stability of the PVAF–iodine complex, the shear dependence of the solution viscosity and our inability to form thermally reversible gels by the introduction of fluorine into other water‐soluble polymers which are capable of hydrogen bond formation. Infrared dichroism and deuteration measurements do not differentiate between PVA and PVAF. If this conclusion is correct, PVAF is the first vinyl polymer of which we are aware that maintains a helical conformation in solution.
Relation between free radicals and ultraviolet absorption in poly(methyl methacrylate)
Authors: Bosch J. J. Ten , Verhelst W. F. , Chadwick K. H.
Published: April 2003

A correlation between the radiation‐induced nine‐line electron spin resonance signal and the unstable component of the optical absorption in the near ultraviolet in poly(methyl methacrylate) is made on the basis of the radiation dose relationship, the dependence of production on irradiation temperature at a constant radiation dose, and on the fading of both signals on oxygen diffusion into the poly(methyl methacrylate) after irradiation. It is concluded that this correlation is applicable only immediately after irradiation and the stability of the initial radical is discussed with respect to the fading results. A process of radical decay and conversion is suggested to account for differences found in the fading characteristics of the two signals.
Thermal degradation of poly‐p‐oxybenzoate under vacuum
Authors: Jellinek H. H. G. , Fujiwara H.
Published: April 2003

The thermal degradation of poly‐p‐oxybenzoate in vacuo as function of temperature has been studied. The energy of activation of the process up to about 30% volatile formation is 59.6 kcal/mole. The degradation is preceded by induction periods, which have been shown to be due to poor heat conductivity of the polymer powder. CO, CO2, phenol, and an unknown compound of molecular weight larger than 200 are the main degradation products found by chromatographic analysis. Infrared spectra of the original polymer, the polymer residue after degradation and of a degradation product solid at room temperature are presented. The possible reactions taking place have been indicated. The heat stability of the polymer in vacuo lies between those of polytetra‐fluoroethylene and polyethylene.
Study of some silver‐thiol complexes and polymers: Stoichiometry and optical effects
Authors: Andersson Lars‐Olov
Published: April 2003

The silver complexes of various thiols of low molecular weight have been studied by amperometric and spectrophotometric titrations. Cysteine and cysteamine form complexes with silver containing up to 1.5 Ag+/—SH. The ligands participating in the binding of silver are the —SH and amino groups.

Under some conditions it was found that 1:1 thiol‐silver polymers were formed. These polymers probably have the general structure AgS(R)AgS(R). Some of them were prepared in pure form and subjected to various studies. Molecular weight determinations of the cysteine‐silver and glutathione‐silver polymers yielded values of 4000–7000 daltons. Studies on the UV absorption characteristics revealed that all of the polymers showed some type of regular band pattern. The cysteamine‐silver polymer is able to sensitize photographic emulsions.
ESR study on the photosensitized decomposition of polyethylene
Authors: Takeshita Takuo , Tsuji Kozo , Seiki Toshifumi
Published: April 2003

Several aromatic compounds were added to low‐density polyethylene to determine their effects on the photodegradation of polyethylene. It was shown that some aromatic compounds indeed sensitize the hydrogen abstraction of the allylic hydrogen of unsaturated groups contained in polyethylene as an improper bond. The mechanism of photosensitization was investigated by an ESR method. It was found that the higher photoexcited triplet state of an aromatic molecule produced by the biphotonic ultraviolet light absorption transfers its excess energy to the unsaturated bond to excite it, and the excited unsaturated group releases its allylic hydrogen atom, giving an allylic radical.
Reaction profiles for kinetic studies of inhomogeneous reactions within solid organic films
Authors: Webb J. R.
Published: April 2003

A technique is described whereby an assessment of the extent of reaction at any time and at any selected depth beneath the surface of a solid film is obtained from infrared spectrophotometric data. The resultant reaction profiles can be used to investigate the kinetics in planes normal to the surface. Group concentration–time curves can be constructed for planes at selected depths parallel to the surface and used to assess the kinetics in such planes. As a result it is possible to study realistically reactions which do not occur homogeneously throughout a solid, e.g., those effected by oxidation, irradiation, plasma treatment, etc.
Kinetics of donor–acceptor complex polymerization. III. Assessment of some approximations in the kinetics
Authors: Rybicky J. , Tanner J. , Funt B. L.
Published: April 2003

The mathematical solution of the equations derived from a kinetic scheme previously developed for donor–acceptor complex polymerization was based on steady‐state conditions and the applicability of initial concentration conditions over a range of conversion. These assumptions are scrutinized and tested by computer simulation and by the exact differential equations utilizing Runge‐Kutta method. The analysis shows that for case I conditions of low concentration of complexing‐agent, the degree of conversion is not critical and that the previous approximate solutions are valid. The steady‐state and non‐steady‐state conditions are compared, and the range of validity of the assumptions is established. The approximate solutions are found inapplicable in the instances of non‐steady‐state conditions coupled with a low concentration of either monomer.