bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct rotating‐sector studies of the systems: Styrene–methyl methacrylate and styrene–methyl acrylate
Authors: Marano J. P. , Shendalman L. H. , Walker C. A.
Published: April 2003

The rotating‐sector technique was applied directly in a study of two copolymerization systems: styrene–methyl methacrylate and styrene–methyl acrylate. The two coupled rate expressions which describe the change in radical concentrations for two‐component polymerizations degenerate into a single expression identical in form to the radical expression for a homopolymerization when the ratio of the radical concentrations under intermittent illumination is assumed constant and equal to the ratio under steady illumination. Numerical solutions of the complete rate expression by use of constants from the literature confirm that this assumption is valid for a rotating‐sector experiment. The overall lifetimes of these two‐component systems were defined and measured experimentally as a function of monomer composition and then compared with lifetimes calculated by using literature rate constants. The agreement was satisfactory. The direct application of the technique to the two‐component system provides an independent experiment which for some systems seems to be more sensitive to the value of the cross‐termination constant than the usual steady‐state method.
Dependence of the catalytic activity of organoaluminum compounds and some of their complexes on their composition
Authors: Mateva R. , Konstantinov Ch. , Kabaivanov V.
Published: April 2003

The influence of the acidity of organoaluminum compounds and their complexes on the catalytic activity in polymerization of trioxane has been studied. It is found that the catalytic activity of organoaluminum compounds of the type RnALX3−n depends on n as well as the nature of R or X. Catalytic activity of the complexes also depends on the type of cocatalyst used. The change of electroconductivity in the course of formation of some initiator complexes has been studied and an attempt has been made to determine the relation between conductivity and polymerization activity.
Temperature variation of piezoelectric moduli in oriented poly(γ‐methyl L‐glutamate)
Authors: Date Munehiro , Takashita Saburo , Fukada Eiichi
Published: April 2003

The real and imaginary components of the complex piezoelectric strain constant, which relates the polarization to the applied stress, have been determined for elongated films of poly(γ‐methyl L‐glutamate) over the temperature range −170°C to +170°C at a frequency of 20 Hz. The variation of the piezoelectric constant with temperature is similar for both α‐helical and β‐form molecular conformations. The sign of piezoelectric polarization is opposite for L and D polymers. A simple model, representing the piezoelectric crystallites as embedded in nonpiezoelectric amorphous regions, is proposed to account for the piezoelectric temperature dispersion curves.
Effect of molecular structure on polyethylene melt rheology. I. Low‐shear behavior
Authors: Mendelson R. A. , Bowles W. A. , Finger F. L.
Published: April 2003

The melt rheological properties of both linear and branched polyethylene were investigated by use of narrow molecular weight distribution fractions and experimentally polymerized samples. Studies carried out in steady shear and in oscillatory shear yielded information concerning both the melt viscosity and the melt elasticity as a function of molecular structure, where the latter was characterized by various solution property techniques. The 3.4–3.5 power dependence of the low shear limiting viscosity on molecular weight was confirmed for linear polyethylene. The effect of long‐chain branching on rheological properties was defined both at constant molecular weight and at constant molecular weight distribution and coupled with variation of molecular weight.
Dynamic and steady‐shear melt rheology of and ethylene‐methacrylic acid copolymer and its salts
Authors: Sakamoto Kunisuke , MacKnight William J. , Porter Roger S.
Published: April 2003

Studies have been made on the dynamic and steady‐shear melt rheology of an ethylene–methacrylic acid copolymer and two of its salts obtained by partial neutralization with sodium and with calcium bases. Measurements were made with a Weissenberg rheogoniometer over a broad range of shear rates and frequency in the temperature interval mainly from 100 to 160°C. The temperature coefficients of dynamic and steady shear viscosity are evaluated at both constant shear rate and constant stress. Likewise, complex dynamic viscosities and apparent high steady‐flow viscosities and intercompared at equivalent frequencies and shear rates. The un‐ionized acid copolymer shows good correlation between the frequency dependence of the complex viscosity and the shear rate dependence of the apparent viscosity. This is not true for either the sodium salt or the calcium salt. These results are consistent with the two‐phase structural model for these materials, i.e., a matrix of hydrocarbon in which are embedded ionic domains.
Transitions of the hydrogen bond in epoxy–diamine networks
Authors: Williams J. G. , Delatycki O.
Published: April 2003

The variation of the fundamental hydroxyl stretching frequency in the infrared spectrum of a number of epoxy–diamine networks has been determined as a function of temperature. Short‐range hydrogen bonds appear to be formed in all the epoxy networks examined. For polymers formed by using short‐chain α,ω‐diamines, it appears that a hydroxyl–hydroxyl bond is dominant. For longer chain lenghts, a hydroxylamine bond becomes important. The hydroxyl–hydroxyl bond breaks at the glass transition temperature, whereas the hydroxyl–amine bond breaks at a higher temperature. At the highest temperatures studied, all hydroxyl groups form weak short‐range bonds to the alkyl‐aryl ether function. The absorption frequency for the hydroxyl group in all types of hydrogen bonds formed shows a strong dependence on temperature and absorption moves to a higher wavenumber with increase in temperature.
Normal stress and shear stress in a viscoelastic liquid under oscillatory shear flow
Authors: Endo Hiroshi , Nagasawa Mitsuru
Published: April 2003

Normal stress and shear stress of concentrated polystyrene solutions in a chlorinated diphenyl were measured under steady flow and oscillatory shear flow in a Weissenberg rheogoniometer. The normal stress difference was observed to oscillate at double the frequency of the applied shear strain with amplitude proportional to the square of the applied amplitude, while the shear stress was found to oscillate at the same frequency with amplitude proportional to the applied amplitude. A theoretical relation between the displacement of the oscillatory normal stress difference from zero level and the dynamic modulus derived by Lodge and other investigators was confirmed experimentally, and the theoretical predictions of Coleman and Markovitz concerning the relation among steady‐flow normal stress difference and dynamic modulus were also confirmed. However, the theoretical predictions of Lodge, of Spriggs, Huppler and Bird, and of Williams on the relation between the amplitude and phase of oscillatory normal stress and those of oscillatory shear stress did not agree with experimental results.
ESR study of the initial reaction of the photodegradation of nylon 6
Authors: Heuvel H. M. , Lind K. C. J. B.
Published: April 2003

The free radicals formed on irradiation of nylon 6 have been studied by means of electron spin resonance (ESR). The irradiation was performed at liquid nitrogen temperature with wavelengths in the region of solar radiation. The spectrum so obtained could best be fitted by assuming CH2ĊHCH2 and CH2ĊO to be the trapped radicals. The assignment of the spectrum supports the idea that the first step in photodegradation is the breaking of the amide bond. The splitting constant of the α proton of the alkyl radical has been found to be nearly the same for drawn and undrawn yarn. This strongly suggests that the low‐energy radiation is capable of breaking bonds only in the unoriented amorphous regions.
Structure of a typical amine‐cured epoxy resin
Authors: Bell James P.
Published: April 2003

A technique for estimating Mc, the molecular weight between crosslinks, of amine‐cured epoxy resins is described. The technique is based upon the stoichiometry of the curing reaction and the amount of primary amino and epoxy groups remaining in the polymer at a given time. The Mc values so calculated are shown to be consistent with Mc results obtained from separate measurements of swelling and the polymer–solvent interaction parameter χ1 for the range of polymer concentration in which both measurements could be obtained. A means of estimating the relative reaction rates of the primary and secondary amino groups with the epoxy groups is given. Under proper curing conditions the amine–epoxy reaction goes very nearly to completion. The presence or absence of an exotherm has no noticeable effect on the course of the reaction between bisphenol A‐epichlorohydrin (Epon 828) and methylene dianiline.
ESR studies on gamma‐irradiated (KPO3)n crystals
Authors: Hukuda Kenzi , Nakahara Motohiro , Kusumoto Naoshi
Published: April 2003

Two types of (KPO3)n crystals have been obtained: transparent crystals and semitransparent crystals that grew in the neighborhood of the wall of the crucible. In the latter type of crystals, four kinds of radicals, denoted B, C, D, and E, are observed by ESR measurements at 77°K on crystals irradiated with γ‐rays at the same temperature. The probable structure of B, C, and D radicals is concluded to be OPO̊2O from their g values and hyperfine constants (the superscript circle indicates a hole trapped in the radical). When these crystals are heated to room temperature, the ESR spectra of B, C, and D radicals disappear and the spectrum of another radical appears. This radical, designated A, has the possible structure OṖO2. The assumption that B radicals thermally decompose into A radicals is confirmed by experiment. With the transparent crystals, C, D, and E radicals are observed at low temperature, but only E radicals are stable at room temperature. The structure of the E radical is thought to be\documentclass{article}\pagestyle{empty}\begin{document}${\rm \hbox{---}O \hbox{---}PO}_2{{_\circ} \atop ^{\hbox{---}}} {\rm PO}_2 {\rm \hbox{---}O\hbox{---}} $\end{document}, but more detailed studies are required.
Viscoelastic properties of branched polyethylene melts
Authors: Chartoff Richard P. , Maxwell Bryce
Published: April 2003

The dynamic mechanical properties of branched polyethylenes in the molten state were determined in the frequency range 10−3–10 radians/sec. The materials tested have remarkably similar rheological properties even though they vary greatly in molecular weight and molecular weight distribution. The similarity in properties is attributed to the influence of long chain branching on the relaxation spectra. A mechanistic argument is proposed to relate the observed behavior to molecular entanglement coupling. The concept of entanglement coupling involving long‐chain branching leads to the expectation that the quasi‐Newtonian and non‐Newtonian viscosities of branched polymers may be either greater or less than those of linear polymers of the same species, which have comparable molecular weights. This is borne out by experiment.
Effect of birefringence on light scattering from deformed spherulitic polymer films
Authors: Motegi Masahiko , Moritani Masahiko , Kawai Hiromichi
Published: April 2003

Light scattering from oriented samples of crystalline polymers is affected by the birefringence of the sample. An extension of the theory for scattering from uniaxially deformed two‐dimensional and three‐dimensional spherulites is made so as to include the retardation of the incident and scattered beams in passing through the birefringent sample. Strain influences scattering, in that it changes the birefringence of the sample and it also changes the anisotropy and shape of the spherulites. Scattering intensities are calculated for both crossed and parallel polarizers as a function of Ω, χ, and Φ, where Ω is the angle between the stretching direction of the sample and the horizontal direction, and χ and Φ are the angles between the stretching direction and the polarization directions of the polarizer and analyzer, respectively. It is shown that for crossed polarizers with Φ = 45° and χ = 45° birefringence changes largely influence the results but that for the polarizers parallel at Φ = 0° and χ = 0° or crossed at Φ = 90° and χ = 0° the birefringence effect is minimized. The intensity distributions for crossed polarizers at Φ = 45° and χ = 45° from polyethylene films stretched to give retardations up to several wavelengths, are found to be in good agreement with the calculated results.
Photocurrents in simple polymer systems
Authors: Binks A. E. , Campbell A. G. , Sharples A.
Published: April 2003

Photocurrents have been detected in a wide range of simple polymer systems at irradiation wavelengths as high as 365 mμ. These photocurrents are shown to be due to phtoemission from the electrode system. Pulsed photoconductivity experiments show that at least two stages of charge transport are involved. In the first stage photoemitted electrons travel a short distance into the polymer before being trapped. This is followed by a slower process of trap‐dominated charge transport.
Thermal expansion, free volume, and molecular mobility in a carbon black‐filled elastomer
Authors: Kraus Gerard , Gruver J. T.
Published: April 2003

The thermal expansion of a butadiene–styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated. The glass transition was unaffected by MT and was raised only 0.2°C for every 10 parts per hundred by weight of polymer of HAF black added. The coefficient of expansion of the polymer component of the composite in the rubbery region was substantially unaffected by either carbon black, but decreased markedly with increasing black loading in the glassy state. These results suggest that free volume is not altered appreciably by the presence of the filler in the rubbery state, but expands with decreasing temperature below Tg. The latter effect is explained by dilatation due to stresses set up around filler particles, arising from differences in the expansion coefficients of filler and polymer, which are not relieved in the glassy state. The near invariability of Tg and of the rubbery fected by adsorption of polymer segments on the carbon black surface. A conservative rough estimate indicates that restriction of segmental motion is confined to a 30 Å layer around the particles in which Tg is elevated by only 10°C.
Fracture surface of polystyrene: Mackerel pattern
Authors: Murray J. , Hull D.
Published: April 2003

Characteristic markings of concentric bands are formed on the fracture surface of tensile specimens under certain loading conditions. The marking form in the fast crack growth region of the mirror area of fracture. Optical and electron optical microscope techniques have been used to study the morphology of the markings. It is shown that in this region the crack propagates along the interface between the craze, in which the crack nucleated, and the bulk material. The mackerel pattern is caused by the crack jumping from one craze–matrix interface to the other.
Effect of bending and stretching of polyethylene strips on the adsorption of surface‐active substances
Authors: Seimiya T. , Yamamoto H. , Sasaki T.
Published: April 2003

The adsorption of tritium‐labeled sodium stearate and 35S‐labeled sodium dodecylsulfate from aqueous solution on bent and on stretched polyethylene strips was directly measured. The amount of adsorption increased from 2.5 to 4.5 times on surfaces of various polyethylene samples stretched from 5.2 to 5.3 times the original length. For one sample, adsorption increased 8 and 2.5 times, respectively, on the convex and concave surfaces of a bent strip. Autoradiographs of the strips taken after adsorption revealed the appearance of both homogeneous and heterogeneous adsorption on the stretched surface of the polyethylene. The electron micrographs of the strips showed that many small fissures, about 1–5μ in length, formed on their surfaces after the strips were bent or stretched. Enhanced adsorption of the surface‐active substance along these fissures was suggested. On the basis of these observations, it is proposed that in stretching or bending, fissures increase adsorption of the detergent, and the adsorption in turn promotes further development of fissures. Thus, bending and adsorption mutually promote the growth of fissures which finally result in failure of the polyethylene.
A molecular approach to chain entanglement in linear polymers
Authors: Tonelli A. E.
Published: April 2003

The phenomenon of chain entanglement in undiluted linear amorphous polymers is treated by calculating the probability of forming closed intramolecular loops. Adoption of the rotational isomeric state model of polymer chains permits an appropriate accounting of the detailed molecular structure to be made through the configurational characteristics of the polymer. The second (〈r〉0) and fourth (〈r〉0) moments of the vector rhk connecting groups h and k in the isolated polymer chain and averaged over all chain conformations are calculated and used to evaluate the probability Wx(0) that rhk is 0, or that an intramolecular loop of x = k − h bonds is formed. Several linear polymers with widely differing molecular structures are treated. An attempt is made to correlate the degree of chain entanglement they manifest in the bulk with their ability to fold back upon themselves to form closed intramolecular loops.
Crystallization kinetics of dilute polyethylene solutions
Authors: Devoy C. , Mandelkern L. , Bourland L.
Published: April 2003

The crystallization kinetics of a high molecular weight fraction of linear polyethylene was studied in dilute solutions of p‐xylene, n‐hexadecane, and decalin by dilatometric methods. For all solvents and temperatures, the experimental isotherms could be quantitatively described by the Avrami formulation for the complete transformation. This result is unique in the realm of polymer crystallization, since marked deviations from this theory are usually observed in more concentrated systems. The Avrami exponent is found to be n = 4 in all cases. The temperature coefficients of the rate constants are indicative of a nucleation controlled process. The data fit either a two‐dimensional or three‐dimensional nucleation mode, and a discrimination can not be made between these two cases. The interfacial free energies are found to be independent of the solvent medium. It is also shown that, irrespective of the type of nucleation control governing the kinetics, the same type governs the crystallite thickness of the lamella‐like crystals that are formed.
Mechanical properties of natural rubber vulcanizates in finite deformation
Authors: Obata Yutaka , Kawabata Sueo , Kawai Hiromichi
Published: April 2003

Mechanical properties of four kinds of natural rubber vulcanizates differing in vulcanization conditions, and consequently in degree of crosslinking (having values of the Mooney‐Rivlin constant C1 ranging from 0.68 to 1.98) were observed under orthogonal biaxial stretching in a range of strain invariants Ii from 3.4 to 9.0 (extension ratios λi from 0.7 to 3.0). The results obtained were analyzed by two methods. One method employed the Valanis‐Landel postulate that the strain‐energy function W(λ1, λ2, λ3) is a separable symmetric function of the principal extension ratios, i.e., W(λ1,λ2,λ3) = w(λ1) + w(λ2) + w(λ3); the other utilized the contour plots of ∂W(I1, I2)/∂I1 and ∂W(I1, I2)/∂I2 surface within the (I1, I2) domain. The postulate for W was examined in detail with good agreement with experimental results. The dependences of ∂W(I1, I2)/∂I1 and ∂W(I1, I2)/∂I2 surfaces on the degree of crosslinking and temperature were further investigated, with the following conclusions. The surfaces have fairly steep slopes for the region of relatively small deformation (i.e., I1 < 5) and become flat with increasing Ii for all the test specimens. The slope becomes less steep with decreasing degree of crosslinking. The values of ∂W/∂I1 increase linearly and the ∂W(I1,I2)/∂I2 surface becomes flat, both with increasing temperature: i.e., the temperature dependence of ∂W/∂I1 further depends on Ii. The ∂W(I1,I2)/∂I2 surface has a maximum near 40°C.
Topologically interpenetrating elastomeric networks
Authors: Klempner Daniel , Frisch H. L. , Frisch K. C.
Published: April 2003

Several partially interpenetrating polymeric networks (IPN) were made by combining chemically different linear elastomers. The polymer combinations were deposited as films from aqueous emulsions made by mixing the individual emulsions in equal proportions. The films were crosslinked to form two superimposed networks. In two cases, the networks were cleanly separated by hydrolysis of one of the component networks to demonstrate that there was no chemical interaction between the polymers. Measurement of crosslink density showed that, in most cases, partial interpenetration does occur as evidenced by an effective crosslink density of the IPN's greater than the arithmetic mean of the crosslink densities of the component networks. The swelling ratios, densities, and stress–strain properties were determined. For one of the network combinations, a poly(urethane–urea) and a poly(butadiene–acrylonitrile), a series of IPN's varying in polymer composition was made. The swelling ratios and densities are close to the arithmetic means; however, both the tensile strength and crosslink density exhibit a maximum at about 70% poly(butadiene‐acrylonitrile). The maximum tensile strength is actually significantly higher than that of either of the component polymers. The elongations all approach that of the poly(urethane–urea), the more extensible material, except for compositions approaching 100% poly(butadiene–acrylonitrile), which exhibit a very low extensibility.
Nucleation and growth of bubbles in elastomers
Authors: Stewart C. W.
Published: April 2003

The theory of homogeneous nucleation of bubbles is combined with an expression, for their rate of growth in elastomers to obtain approximate expressions for calculating the number of bubbles formed under a high degree of supersaturation. Experimental results are given for several elastomers with argon as the dissolved gas under a variety of foaming conditions. The theory adequately describes the manner in which the number of bubbles formed depends on the temperature, surface tension of the polymer, and permeability of the dissolved gas.
Fusion of homopolymers and ordered copolymers containing ethylene sebacate structural units
Authors: Theil M. H. , Mandelkern L.
Published: April 2003

The melting temperatures of homopolymers of poly(ethylene sebacate) possessing a most probable molecular weight distribution and ordered copolymers of ethylene sebacate/propylene adipate were studied by slow heating processes and by the analysis of the dependence of the melting temperature on the crystallization temperature utilizing rapid heating rates. For the ordered copolyesters, where the composition of the crystallizing co‐units ranged from 0.8 to 0.2 mole fraction the latter method gave results which were similar to those that have been obtained for the other polymer systems that have been studied. Extrapolated equilibrium melting temperatures could be obtained in a straightforward manner and were found to be independent of the copolymer composition in accord with theoretical expectations. On the other hand, a unique set of results were obtained for the homopolymers. A plot of the relationship between the melting temperature and the crystallization temperature for all the molecular weights studied gave a slope close to unity. This made it operationally impossible to extrapolate to the equilibrium melting temperature for this system.
Structure and properties of poly‐2,5‐distyrylpyrazine
Authors: Kanetsuna Hisaaki , Hasegawa Masaki , Mitsuhashi Shigenobu , Kurita Toshio , Sasaki Kanji , Maeda Katsuhiro , Obata Hiroko , Hatakeyama Tatsuko
Published: April 2003

Poly‐2,5‐distyrylpyrazine (poly‐DSP) was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and measurements of dynamic viscoelastic and electrical properties. From DTA and TGA studies it was confirmed that poly‐DSP melts at 321°C and depolymerizes rapidly to the monomer at temperatures between 335°C and 345°C in helium. The polymer is affected by oxygen above 200°C. The E′ value from dynamic viscoelasticity measurements on amorphous film is 2 × 1011 dyne/cm2 at room temperature. It decrease abruptly in the temperature range 140–150°C; but the net decrease of E′ within this temperature range is relatively small. The electrical properties of amorphous poly‐DSP are characterized by a small temperature dependence of the dielectric constant between room temperature and 100°C. The dielectric loss tangent was observed to be small, and the dc conductivity was extremely small. It is concluded that rotation of the phenyl branches in the polymer occurs above −30°C and the glass transition occurs at about 150°C. These properties are discussed in some detail in relation to the polymer structure.
Dielectric relaxation and molecular motion in poly(vinylidene fluoride)
Authors: Yano Shinichi
Published: April 2003

The dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 10 Hz to 100 kHz at temperatures between −196 and 150°C. Three dielectric relaxations were observed: the α relaxation occurred near 130°C, the β near 0°C, and the γ near −30°C at 100 kHz. In the α relaxation the magnitude of loss peak and the relaxation times increased not only with increasing lamellar thickness, but also with decrease of crystal defects in the crystalline regions. In the light of the above results, the α relaxation was attributed to the molecular motion in the crystalline regions which was related to the lamellar thickness and crystal defects in the crystalline phase. In the β relaxation, the magnitude of the loss peak increased with the amount of amorphous material. The relaxation times were independent of the crystal structure and the degree of crystallinity, but increased slightly with orientation of the molecular chains by drawing. The β relaxation was ascribed to the micro‐Brownian motions of main chains in the amorphous regions. The Arrhenius plots were of the so‐called WLF type, and the “freezing point” of the molecular motion was about −80°C. The Cole‐Cole distribution parameter of the relaxation time α increased almost linearly with decreasing temperature in the temperature range of the experiment. The γ relaxation was attributed to local molecular motions in the amorphous regions.
Structural studies of pressure‐crystallized polymers. I. Heat treatment of oriented polymers under high pressure
Authors: Hasegawa Ryozo , Tanabe Yasuhiro , Kobayashi Masamichi , Tadokoro Hiroyuki , Sawaoka Akira , Kawai Naoto
Published: April 2003

A convenient pressure apparatus was designed for crystallization of high polymers under hydrostatic pressure up to 5000 atm. Melt crystallization as well as heat treatment under various temperatures and pressures was carried out on several polymers, and the effects of pressure on the molecular and crystal structures of the samples are discussed. Heat treatment of syndiotactic polypropylene under high pressure yields a new crystal modification rather than the previously known helix and planar zigzag modifications. Of the three modifications of poly(vinylidene fluoride), modification III was found as a high‐pressure phase for specimens in the unoriented state, while modification I was obtained as the most stable one on heat treatment of oriented specimens under high pressure. Heat treatment under high pressure converts ordinary isotactic poly‐4‐methylpentene‐1 with a lower density than the noncrystalline value, to a new crystal modification with higher density. As is reasonable, the dense modification is stable in a high‐pressure range. For these three cases, the orientation of specimens was found to remain unchanged during the transitions, which must therefore occur in the solid state.
Study of reversible gelation of partially neutralized poly(methacrylic acid) by viscoelastic measurements
Authors: Silberberg A. , Mijnlieff P. F.
Published: April 2003

The gelation of poly(methacrylic acid) in water was studied as a function of degree of neutralization with NaOH. It was found that charging the molecular displaces the onset of gelation to higher concentrations but makes the transition occur over an even narrower concentration range. This extreme sensitivity of rheological properties to charge may play a role in biocolloidal systems. The phenomenon of reversible gelation is discussed in general and related to the properties of the particular system. The method of measurement, which involves the determination of the dynamic response in the 1 Hz region and the measurement of phase angle, is described in detail. A method of deriving the relaxation time spectrum from measurements of phase angle is given.
Scattering of light by films having nonrandom orientation fluctuations. II
Authors: Hashimoto T. , Stein R. S.
Published: April 2003

The theory for scattering of light from films in which the orientation correlation between two scattering elements depends upon the angle β between the optic axes and the vector connecting the two elements is extended. A delta‐function type dependence is assumed in which the correlation is strongest when β equals some preferred value β0. Calculated results of scattered intensities are shown to be similar to experimental observations.
Rheo‐optical studies of high polymers. XVIII. Significance of the vertical shift in the time‐temperature superposition of rheo‐optical and viscoelastic properties
Authors: Onogi S. , Sato T. , Asada T. , Fukui Y.
Published: April 2003

To determine the true reason for the increase in birefringence and the decrease in relaxation modulus for high‐density polyethylene with rising temperature, changes in crystalline structure as well as in thermal, viscoelastic, and rheo‐optical properties with temperature were measured, by several techniques, including DSC, DLI, infrared dichroism, x‐ray diffraction, and NMR. The values for degree of crystallinity obtained from the DSC fusion curve, density, and infrared absorbances coincide very well and show almost no divergence till about 80°C. The optical vertical shift factor pT can be related to the ratio of the orientation function for the crystal c axis at an arbitrary temperature to that at the references temperature, fε/fε0. The mechanical vertical shift factor bT, on the other hand, is associated with the temperature dependence of the mobile fraction, as determined by NMR measurements, but not with variations in degree of crystallinity.
Liquid–liquid phase separation in multicomponent polymer solutions. IX. Concentration‐dependent pair interaction parameter from critical miscibility data on the system polystyrene–cyclohexane
Authors: Koningsveld R. , Kleintjens L. A. , Shultz A. R.
Published: April 2003

Critical miscibility data obtained from measurements of phase‐volume ratios have been used to calculate the concentration dependence of the pair interaction parameter for the system polystyrene–cyclohexane. The measured temperature and concentration ranges are 11–30°C and 4–18% polymer by weight, respectively. With the Gibbs free energy of mixing expressed in polymer segment mole fractions, x*, the pair interaction parameter is g(x*, T) = 0.4961 + 71.92/T + 0.2312x* + 0.0750x*2. In a polymer volume fraction formulation the parameter is g(φ, T) = 0.4099 + 90.65/T + 0.2064 φ + 0.0518 φ2, which approximates to χ(φ, T) = 0.2035 + 90.65/T + 0.3092 φ + 0.1554 φ2. Comparison of the temperature and concentration dependence with that obtained by other authors shows very good agreement, even when extensive extrapolations in temperature and concentration are applied. The present function is believed to be the most accurate. Solutions of mixtures of two narrow‐distribution polystyrenes in cyclohexane show separation into three liquid phases under the exact conditions predicted by theoretical calculation with the present pair‐interaction function.
Spectroscopic study of the formation and structure of polyselenacyclobutane
Authors: Cozzens R. F. , Harvey A. B.
Published: April 2003

Selenacyclobutane (trimethylene selenide) readily undergoes photochemical reaction to give polymeric products. Also, the material polymerizes rapidly when the polycrystalline solid film liquifies on a salt substrate in vacuum. Upon polymerization of the sample, infrared and Raman spectra exhibit profound changes which definitely establish ring cleavage. The Raman spectra of the polymer reveal strong C–Se stretching peaks but little or no scattering in the region of Se–Se stretching, strongly suggesting that the polymerization process proceeds in a regular head‐to‐tail fashion. An EPR study of the monomer exposed to ultraviolet radiation at −180°C supports this fact, since the resulting spectrum is indicative of an intermediate radical species, (CH2CH2‐CH2Se)n., where n is sufficiently large that the terminal electrons do not interact. No triplet spectra were observed. Molecular oxygen apparently plays an important role in the polymerization kinetics, since it is found that degassed samples of the substance, in contrast to those which have not been degassed, polymerize rapidly even under room illumination. Freezing‐point depression measurements fix a lower limit to the average molecular weight of the polymer at 2700 (n = 23 monomer units).
General description of mechanical anisotropy of semicrystalline polymers in relation to orientation of structural units composed of crystalline and noncrystalline materials
Authors: Maeda Matsuo , Hibi Sadao , Itoh Fumihiro , Nomura Shunji , Kawaguchi Tatsuro , Kawai Hiromichi
Published: April 2003

A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single‐phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two‐phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements.
Equation of state and the thermodynamic properties of liquid polymers: Application of the Hirai‐Eyring model
Authors: Smith Richard P.
Published: April 2003

It is shown that the Hirai‐Eyring model for the liquid state is capable of accurately describing the p, V, T behavior of liquid polymers in the temperature range over which measurements are now made, and below. Once the parameter choices necessary to accomplish the fit are made for a particular polymer, the excess thermodynamic functions (differences in properties, liquid less solid) are determined by the same parameters. Above the glass transition temperature Tg the volume, excess enthalpy, and square of the excess entropy are predicted by the model to be essentially linear with temperature, in agreement with experiment. Below Tg, these functions do not remain linear (as is usually assumed in extrapolating the equilibrium behavior to low temperatures), but instead they rapidly approach zero in a continuous way as the temperature is lowered. These remarks apply to glass‐forming materials composed of small molecules, as well as to polymers. The “paradox” raised by Kauzmann is thus resolved, and the Gibbs‐DiMarzio second‐order transition appears to be unnecessary.
Determination of polymer branching with gel‐permeation chromatography. I. Theory
Authors: Drott E. E. , Mendelson R. A.
Published: April 2003

The effect of long‐and short‐chain branching in polymer molecules on gel‐permeation chromatographic (GPC) separation is discussed. The calculation of calibration curves for branched polymers is developed from the universal calibration technique based on the hydrodynamic volume concept and previously established relationships for the effect of branching on molecular dimensions. Typical calibration curves are shown for different branching models and degrees of branching. As branching increases, the curves are shown to converge. Methods of characterizing branching and molecular weight distributions of franctions and whole polymers from GPC and intrinsic viscosity data are presented.
Self‐seeded crystallization and its potential for molecular weight characterization. II. Experiments on narrow fractions
Authors: Keller A. , Sadler D. M.
Published: April 2003

The effect upon seeding behavior of adding well characterized fractions has been studied, so as to assess the technique as a measure of small amounts of high molecular weight. The material available to us restricted the study to fractions with comparatively low average molecular weights. Self‐seeding is shown to be an extremely sensitive measure of high molecular weight tails. Knowledge of the molecular weights concerned enabled estimates to be made of the weight of molecules involved in seeding. Instability of seeds has been observed, and is explained in terms of a particular amorphous crystalline “equilibrium” within the seeds.
Effect of optical rotation on low‐angle light‐scattering patterns
Authors: Picot C. , Stein R. S.
Published: April 2003

The effect of optical rotation of the environment is calculated for the Hv and Vv low‐angle light‐scattering patterns of two‐dimensional spherulites. As with the effect or birefringence, the change in the Hv pattern is greater than that of the Vv pattern. With increasing optical rotation, the patterns lose their characteristic shape and become more circular.
Dielectric absorption in polyoxymethylene obtained from tetraoxymethylene crystal by radiation induced polymerization
Authors: Tanaka Akira , Uemura Shinsaku , Ishida Yōichi
Published: April 2003

In order to study the dielectric behavior of polyoxymethylene prepared by radiation‐induced solid‐state polymerization, large crystals of tetraoxymethylene (2 cm in diameter) were prepared by Bridgman's method and polymerized by γ‐rays. The x‐ray diffraction pattern of the polymer did not reveal the existence of a so‐called amorphous region. In dielectric measurements, only one dielectric absorption was observed in the low‐temperature region, while in the high‐temperature region ε″ did not change up to about 120°C, where thermal decomposition started. When the specimen was stabilized by acetylating the endgroups in the solid state, ε″ did not change up to about 150°C. This dielectric absorption showed a significant anisotropy for the direction of an applied field. The dielectric absorption was much larger when the electric field was perpendicular to the fiber axis than when the field was parallel. The dielectric absorption was larger in a specimen which was estimated to be more imperfect according to DSC analysis. This leads to the conclusion that the dielectric absorption is attributable to defect regions. On the other hand, the dielectric absorption became larger with increasing numbers of terminal OH groups, and hence it is attributable to the response of the terminal OH groups. Moreover, the dielectric absorption was depressed by the acetylation of the OH groups in the solid state. It is, therefore, concluded that the dielectric absorption observed in polyoxymethylene prepared by solid‐state polymerization of tetraoxymethylene is due to the response of terminal OH groups localized in defect regions. Polyoxymethylene crystallized from the melt gives an asymmetric low‐temperature absorption. This asymmetry can be ascribed to the superposition of two relaxation processes. When its absorption curve is compared with that of the solid‐state polymerized polymer, the low‐temperature component can be assigned to crystal defects and the high temperature one to amorphous regions.
Swelling of thin films. I. Acrylamide–N‐isopropylacrylamide copolymers in water
Authors: Chiklis Charles K. , Grasshoff J. Michael
Published: April 2003

The swelling curves of 6μ films of low conversion homopolymers and copolymers of acrylamide (AM) and N‐isopropylacrylamide (NIPAM) were obtained in water by an optical microscope technique. Poly(AM) swelled appreciably faster than poly(NIPAM) but there was no apparent correlation between overall swelling rate and copolymer composition. A 57/43 (mole %) AM–NIPAM copolymer swelled fastest. Sequence distribution calculations indicated that its backbone structure tended toward comonomer alternation, which might reduce the extent of hydrogen bonding in the film. The amount of water sorbed during swelling, as approximated from increasing film thickness, was proportional to the square root of time and agreed well with previous work in the literature. Homopolymer films from runs of ca. 50% conversion consistently swelled slower than their low conversion counterparts, probably due to branching and increased entanglements. Heating also promoted slower film swelling due to a tightening of the film structure and/or a low degree of imidization. Monomer reactivity ratios and Alfrey‐Price Q and e values for NIPAM were calculated. Cloud points of 5% aqueous solutions of the copolymers were measured and found to decrease with increasing NIPAM content.
Dimensions of branched and linear polymer chains in solution: Modifications of flory's theory
Authors: Casassa Edward F.
Published: April 2003

It is pointed out that a theory proposed by Vrij for the expansion of a linear polymer chain in solution beyond its unperturbed size is also applicable formally to branched chains. The theory predicts the temperature at which the chain obeys random‐flight statistics to be lower for a branched chain than for a linear one (for a polymer–solvent system exhibiting the usual upper critical consolute point). Vrij's derivation follows a well‐known procedure of Flory, but refines it to take account of the variation of the time‐averaged segment density with distance from the center of mass of the chain. This modification in combination with a somewhat different derivation is shown to lead to a similar result. Yet another scheme for “correcting” Flory's theory is outlined. Some reasons are advanced for questioning the physical significance of these small modifications of Flory's theory, all of which depend on the retention of previously ignored terms in power series expansions.
Local deformation in stretched polybutene‐1 spherulites
Authors: Yee R. Y. , Stein R. S.
Published: April 2003

The orientation of crystals in spherulites of modifications I and II of polybutene‐1 was studied by micro‐x‐ray diffraction. Changes in such micro‐x‐ray diffraction patterns were measured in various regions of the spherulites as a function of strain and time. The relationship between micro‐x‐ray diffraction from parts of spherulites and macro‐x‐ray diffraction from entire spherulites is discussed. Changes are resolved into contributions arising from (1) deformation of spherulites with change in crystal orientation and (2) transformation of crystals from modification II to modification I.
Polymorphic forms of nylon 3
Authors: Masamoto Junzo , Sasaguri Kiichiro , Ohizumi Chihiro , Kobayashi Hidehiko
Published: April 2003

The crystal structure of nylon 3 was studied, and four crystalline modifications were observed. Modification I, as determined from the x‐ray diffraction pattern of drawn fibers, is similar to the α crystal structure of nylon 6. The unit cell is monoclinic; a = 9.33 Å, b = 4.78 Å, (fiber identity period), c = 8.73 Å, and β = 60°. The theoretical density for nylon 3 with four monomeric units in the unit cell is 1.39 g/cm3, and the observed density is 1.33 g/cm3. The space group is P21. The nylon 3 chains are in the extended planar zigzag conformation. Although other odd‐numbered nylon form triclinic or pseudohexagonal crystals when oriented, drawn nylon 3 crystals are monoclinic. In addition to modification I, modifications II, III, and IV were studied. Lattice spacings of modifications II and III are equal to those of modification I. However x‐ray diffraction intensities are different. Infrared spectra of those forms indicate an extended planar zigzag conformation of the chains. Modification IV is thought to correspond to the so‐called smectic hexagonal form. No γ crystals were found, and it appears that polyamide chains with short sequences of methylene groups cannot form crystals of this type.
Plastic deformation of polyethylene. I. Change of morphology during drawing of polyethylene of high density
Authors: Meinel G. , Morosoff N. , Peterlin A.
Published: April 2003

The transformation of microspherulitic quenched and annealed polyethylene film into highly oriented drawn material with the characteristic fiber structure was investigated by small‐angle and wide‐angle x‐ray measurements and by a study of the thermograms after the fuming nitric acid treatment. With the details of deformation depending slightly on the crystallinity, one observes generally a preferential tilt of the platelets against draw direction at draw ratios below 2. At least in annealed material, an increasing tilt of the molecule within the lamella is also observed, which leads at higher draw ratios to slipping of blocks in the crystallites. With further drawing a new fiber structure appears, which is practically independent of the thermal history of the original film. This fact is established by investigation of the crystal thickness by three different methods; investigations of small‐angle scattering, study of the width of the (002) reflection, and investigation of the debris after treatment with fuming nitric acid.
Quantitative analysis of gaseous diffusion in glassy polymers
Authors: Petropoulos J. H.
Published: April 2003

The current theoretical treatment of diffusion of gases in glassy polymers is based on the “dual sorption” model, but also includes certain other important assumptions, at least some of which cannot be fully justified a priori. They require experimental validation, which, however, is not possible by the procedures used or proposed so far. Methods suitable for this purpose are discussed here.
Thermal analysis of polysiloxanes. II. Thermal vacuum degradation of polysiloxanes with different substituents on silicon and in the main siloxane chain
Authors: Thomas T. Howard , Kendrick T. C.
Published: April 2003

Thermogravimetric (TG) investigations of various substituted polysiloxanes of the type \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm R}_1 {\rm R}_2 {\rm SiO\rlap{--} )}_n $\end{document} have been carried out in vacuo and the activation energies for the depolymerization processes calculated from the resulting thermograms. (R1 and R2 are methyl, ethyl, n‐propyl, trifluoropropyl, or phenyl.) It is postulated that the activation energy is mainly a function of the inductive effect of the substituent group and that electron‐withdrawing groups attached to silicon increase the activation energy, whereas electron‐donating groups decrease it. A linear relation is found between the Taft constant σ* for the substituent on silicon and the calculated activation energy for depolymerization. Product analysis results from isothermal degradations indicate that the degradation mechanism in a silmethylene siloxane polymer and a silethylene‐siloxane polymer
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is very similar to that in polydimethylsiloxanes (PDMS). For the \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm R}_1 {\rm R}_2 {\rm SiO\rlap{--} )}_n $\end{document} polymers, the amount of cyclotrisiloxane in the degradation products increases with the size of the substituent on silicon, and it is postulated that the rate of depolymerization is mainly influenced by short‐range steric interactions between the substituents on the silicon atoms of the siloxane chain.