bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology and physical properties of triblock copolymers with crystalline end blocks
Authors: Kuo C. , McIntyre D.
Published: April 2003

The morphology of crystalline end‐block copolymers of poly(thiacyclobutane‐b‐isoprene‐b‐thiacyclobutane) (TCB–I–TCB) was studied by optical microscopy, electron microscopy, and small‐angle x‐ray scattering (SAXS). A spherulitic texture was observed for both the TCB homopolymer and the TCB–I–TCB block copolymers. Well‐defined phases arranged in an ordered structure exist when the films are cast above the melting temperature of the crystalline end blocks. The dimensions and the arrangements of the domains have been derived from both SAXS and electron microscope measurements. The deformation mechanism of the 41% end‐block copolymer sample was also examined by a combination of SAXS and stress–strain studies. It was found that the interdomain spacing increased along the stretching direction as the extension ratio was increased. The morphology changes from hexagonally packed cylinders to rowtype cylinders upon the application of stress.
Nonlinear viscoelasticity of polystyrene solutions. I. Strain‐dependent relaxation modulus
Authors: Fukuda Mitsutoshi , Osaki Kunihiro , Kurata Michio
Published: April 2003

Strain‐dependent relaxation moduli G(t,s) were measured for polystyrene solutions in diethyl phthalate with a relaxometer of the cone‐and‐plate type. Ranges of molecular weight M and concentration c were from 1.23 × 106 to 7.62 × 106 and 0.112 to 0.329 g/cm3. Measurements were performed at various magnitudes of shear s ranging from 0.055 to 27.2. The relaxation modulus G(t,s) always decreased with increasing s and the relative amount of decrease (i.e.,–log[G(t,s)/G(t,0)]) increased as t increased. However, the detailed strain dependences of G(t,s) could be classified into two types according to the M and c of the solution. When cM < 106, the plot of log G(t,s) versus log t varied from a convex curve to an S‐shaped curve with increasing s. For solutions of cM > 106, the curves were still convex and S‐shaped at very small and large s, respectively, but in a certain range of s (approximately 3 < s < 7) log G(t,s) decreased rapidly at short times and then very slowly; a peculiar inflection and a plateau appeared on the plot of log G(t,s) versus log t. The strain‐dependent relaxation spectrum exhibited a trough at times corresponding to the plateau of log G(t,s). The longest relaxation time τ1(s) and the corresponding relaxation strength G1(s) were evaluated through the “Procedure X” of Tobolsky and Murakami. The relaxation time τ1(s) was independent of s for all the solutions studied while G1(s) decreased with s. The reduced relaxation strength G1(s)/G1(0) was a simple function of s (The plot of log G1(s)/G1(0) against log s was a convex curve) and was approximately independent of M and c in the range of cM <106. This behavior of G1(s)/G1(0) was in agreement with that observed for a polyisobutylene solution and seems to have wide applicability to many polymeric systems. On the other hand, log G1(s)/G1(0) as a function of log s decreased in two steps and decreased more rapidly when M or c was higher. It was suggested that in the range of cM < 106, a kind of geometrical factor might be responsible for a large part of the nonlinear behavior, while in the range of cM > 106, some “intrinsic” nonlinearity of the entanglement network system might be important.
Viscoelastic properties of heterogeneous network polymers from poly(D‐glutamic acid) and poly(oxyethylene glycol)
Authors: Mori Tetsuo , Tanaka Ryuichi , Tanaka Takehide
Published: April 2003

A series of five heterogeneous network polymers was prepared from poly(D‐glutamic acid) (PDG) and poly(oxyethylene glycol) (PEG), and their dynamic mechanical properties were studied. The content of PDG was fixed at 60% by weight, and the molecular weight of PEG was changed to obtain networks with various crosslink densities. An increase in the PEG molecular weight from 330 to 880 caused considerable broadening of tan δ and E″ curves, and peak temperatures for tan δ and E″ decreased slightly. Curves of tan δ and E″ for PDG–PEG 4000 (indicating a PEG component of molecular weight 4,000) were much broader and the existence of two peaks was recognized. These findings and x‐ray photographs suggest that PDG–PEG 330, 570, and 880 give films of fairly uniform phase, but that PDG–PEG 1830 and 4000 give films with two‐phase structure. The factors influencing the dynamic mechanical properties in decreasing order of effectiveness are found to be the proportions by weight of PDG and PEG, the compatibility of PDG with PEG, the crosslink density, and the concentration of free carboxyl groups. The infrared spectra of these polymers indicate that at least part of the PDG component retains the α‐helix conformation.
A comparison of two techniques for inducing fibrous crystallization from solution
Authors: McHugh A. J. , Forrest E. H.
Published: April 2003

Experimental results are presented and discussed comparing two techniques for inducing fibrous growth of polyethylene crystals from flowing solutions: a plunging cone device and a standard rotating cylinder (Couette) device. Comparison of crystal “overgrowth” diameter to spacing ratios for the several experiments with predictions based on an earlier postulated model lead to conclusions regarding the model inadequacy. A detailed comparison is made of the melting behavior of crystals produced by both flow fields and those results are discussed in light of a modified model for the growth process presented elsewhere. The conclusion is reached that differences in melting behavior may be attributed to differences in extension of the high molecular weight chains involved in the growth processes occurring in the two different flow fields.
High‐resolution preparative‐scale gel‐permeation chromatography
Authors: Kato Yoshio , Kametani Tomi , Furukawa Koichi , Hashimoto Tsutomu
Published: April 2003

Sharp polymer fractions have been obtained in preparative‐scale gel‐permeation chromatography by use of a column set packed with polystyrene gel particles of about 10 μ diameter. When 0.13 g of standard polystyrene NBS 706 was fractionated per injection, fractions with polydispersities of about 1.02–1.03 were obtained over the molecular weight range 104–106. Effects of a injection volume, solution concentration, and fraction volume on fractionation efficiency were also investigated. Polydispersities of fractions increased appreciably with increasing amounts of polymer injected.
Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. II. Free volume and configurational entropy theories
Authors: Naoki Motosuke , Nose Takuhei
Published: April 2003

The P–V–T relation and the heat capacity of a chlorinated polyethylene vulcanizate were measured. Several tests on the validity of thermodynamic treatments of the α relaxation process and the glass‐transition temperature were performed by using dielectric properties. From a study using excess variables, it was shown that the entropy theories represented by the equations of Goldstein and Adam–Gibbs' were slightly better than the free volume theory represented by Doolittle's equation. However the study provided no distinction between the two entropy theories. Some tests were also performed on the pressure dependence of the glass‐transition temperature, dTg/dP, and on H*V/H*V where H*V is the isochoric activation enthalpy and H*P is the isobaric activation enthalpy. Here, too, the entropy theories were better than the free volume theory. Goldstein's expression gave values of both dTg/dP and H*V/H*P closest to those from the dielectric experiments. The Adam–Gibbs' equation gave a temperature dependence for dTg/dP and H*V/H*P most similar to those from the experiments.
A rotational rheometer with a drag‐cup torque transducer
Authors: Berry Guy C. , Wong Chiu‐Ping
Published: April 2003

A rotational cone‐and‐plate rheometer incorporating a drag‐cup torque transducer and a frictionless, wire suspension has been designed and constructed. The instrument design provides for a controlled atmosphere for the sample, including anhydrous conditions necessary for studies on solutions of polymers in strong acids. The rheometer can be used to determine the shear deformation in response to an applied stress, including creep, recovery, and the shear stress in response to an applied steady shear. Both transient and steady‐state measurements are possible. Illustrative examples of the instrument performance are given.
Degrading mixtures of monodisperse poly‐α‐methylstyrenes: Rates and anomalous molecular weight distributions
Authors: Roestamsjah  , Wall L. A. , Florin R. E. , Aldridge Mary H. , Fetters L. J.
Published: April 2003

When a mixture of two monodisperse samples of poly‐α‐methylstyrene is thermally degraded, the components behave independently, as a first approximation, as shown by GPC and rate of volatilization data. The ratio Mw/Mn, before approaching the ultimate value of 2.0, first goes through a minimum at a much lower value.
ESR study of pressure dependence of free‐radical decay in irradiated polystyrene
Authors: Szocs F. , Plaček J.
Published: April 2003

Radicals giving the usual triplet ESR spectrum have been generated in polystyrene by γ‐irradiation at room temperature. The decay of the radicals has been investigated in the temperature interval between 90° and 200° and pressures ranging from 1 to 8000 atm. The effect of pressure on the mechanism of the free‐radical decay is discussed. There are two regions of free‐radical decay showing different activation volumes: VI = 11.5 cm3/mole and VII = 66 cm3/mole. The correlation between molecular motion in the α‐relaxation region and radical decay is pointed out.
Crystallization of isotactic polystyrene from dilute solutions
Authors: Lemstra P. J. , Challa G.
Published: April 2003

The overall rate of crystallization of isotactic polystyrene from dilute solutions, 1% by weight, in trans‐decalin and benzyl alcohol was studied as a function of temperature using dilatometry. These solvents were chosen because the dissolution temperatures of crystalline isotactic polystyrene are practically the same in both solvents. The overall rate of crystallization as a function of crystallization temperature showed a maximum in both solvents at about 50°C. At lower crystallization temperatures the rate of crystallization is much lower. The overall rate of crystallization of isotactic polystyrene in benzyl alcohol is far larger than in trans‐decalin at the same undercooling throughout the temperature range, which is in apparent contradiction to present crystallization theories. At very large undercooling (Tc lower than about 0°C) the solutions of isotactic polystyrene in both solvents quickly become “rigid” gels. Surface replicas of freeze‐etched gels indicate that a fringed micelle type of crystallization takes place at these low temperatures. The transition from folded chain crystallization to fringed micelle crystallization may be due to a stiffening of the polymer chain below about 50°C, with a reduced rotational mobility of the phenyl groups on the chain. If very dilute solutions, below 0.5% by weight, are crystallized at these low temperatures no gels were formed but fibrous crystals are produced which could be observed under the polarizing microscope.
High‐pressure phases in polymers. I. Spherulitic growth kinetics in cis‐polyisoprene
Authors: Phillips P. J. , Edwards B. C.
Published: April 2003

This is the first paper in a series dealing with the crystallization of high polymers at elevated pressures. Through an extension of the thin‐film technique using osmium tetroxide staining, the measurement of lamellar growth kinetics at high pressures as well as the observation of micromorphological changes has proved possible. Three different morphological species of cis‐polyisoprene have been detected in the pressure–temperature plane. A review is given of the conditions governing their formation and the growth kinetics of lamellar crystals are discussed in detail. Secondary nucleation theory is obeyed, the major effect of pressure being to alter the kinetics through the thermodynamic transitions. Variations in lamellar thickness with pressure may be explained simply in terms of the elevation by pressure of the equilibrium melting point.
Molecular orbital calculation of the electronic structure of poly(N‐vinylcarbazole)
Authors: Hattori Kazuo , Wada Yasaku
Published: April 2003

Energy levels and molecular orbital wave functions of π‐electrons in a carbazole ring are calculated by the ω‐method. The result agrees well with observed optical absorption spectra of carbazole and poly(N‐vinylcarbazole) (PVCA). Molecular orbital wave functions are obtained for a PVCA chain in a 3/1 helix. The overlap integral between adjacent carbazole rings is evaluated for each molecular orbital of the ring. The result affords evidence for hole conduction in PVCA and explains the photoconductivity spectrum under high de field.
Dielectric study of low‐temperature relaxations in poly(isobutyl methacrylate), poly(n‐butyl methacrylate), poly(isopropyl methacrylate), and poly(4‐methylpentene‐1)
Authors: Shimizu Kazuharu , Yano Okimichi , Wada Yasaku
Published: April 2003

Isochronal measurements of dielectric constant and loss are made for poly(isobutyl methacrylate) (PiBMA), poly(n‐butyl methacrylate) (PnBMA), poly(isopropyl methacrylate) (PiBMA), and poly(4‐methylpentene‐1) (P4MP1) at temperatures ranging from 4°K to 250°K. Loss peaks are found around 120°K (10–100 Hz) for PiBMA, PnBMA, and P4MP1. By comparing the activation energy with the calculated potential barrier for the internal rotation of alkyl group in the side chain, the motion responsible for the 120°K peak is concluded to be essentially the rotation of the isopropyl group as a whole for PiBMA and P4MP1 but, for PnBMA, the rotation of n‐propyl group accompanied by the rotation of the end ethyl group. Multiple paths of internal rotation are involved with the 120°K peaks of PiBMA and, in particular, PnBMA, which explain differences between PiBMA and PnBMA in the broadness and the temperature location of the 120°K peak. The 120°K peak is in general assigned to a side chain including a sequenceOCCC or CCCC. PiPMA without this sequence in the side chain does not show the 120°K peak, but it exhibits the 50°K peak (1 kHz) like poly(ethyl methacrylate). The 50°K peak is assigned to the rotation of ethyl or isopropyl group attached to COO group. Poly‐L‐valine in which the isopropyl group is directly attached to carbon does not have the 50°K peak. An additional loss peak at 20°K (1 kHz) for P4MP1 is also discussed on the basis of the calculated potential.
Dynamic mechanical properties of some novel ionene polymers
Authors: Tsutsui Tetsuo , Tanaka Ryuichi , Tanaka Takehide
Published: April 2003

Novel ionic polymers of the type
magnified image
x,y‐oxyethylene ionenes (x,y‐OEI), have been synthesized, for x and y varying from 2 to 5. The 2,2‐, 2,3‐, 2,4‐, and 3,3‐OEI are crystalline; the 3,4‐, 4,4‐, 4,5‐, and 5,5‐OEI are amorphous. The temperature dependence of the dynamic mechanical properties of these polymers, studied by torsional braid analysis over a temperature range from −170° to +150°C, shows two types of dispersion in each polymer. The dispersions lying between −6° and +90°C appear to be primary dispersions due to the amorphous phase. The dispersions between −110° and 0°C, on the other hand, are attributed to local modes. The temperature of the primary dispersion depends linearly on the charge density along the main chains of the polymer. However, the dependence of the local mode dispersion temperature on the charge density shows no regular pattern. Both dispersions are greatly influenced by the presence of absorbed water. Measurements of Tg at various water contents reveal the existence of abnormal plasticizing effects by water.
Mechanics of peeling of rubbery materials. I. Peel strength and energy dissipation
Authors: Igarashi Takashi
Published: April 2003

The peel strength found in the trousers‐type peeling process is treated for the case in which the adherends, assumed to be flexible but inextensible are bonded by rubbery viscoelastic adhesives.

Taking into consideration energy dissipation during deformation of the adhesive, Griffith's criterion is extended to the peeling of viscoelastic materials. For the peeling force per unit width f it is deduced that 2f = Γ + u′h, where T is twice the surface energy, u' is the energy dissipation per unit volume of adhesive, and h is the thickness of the adhesive layer. Values of u' obtained from peeling tests for various thicknesses are compared with those from the tensile tests and found to agree with the above relation. The deduction that the peel strength is independent of the thickness for adhesives with no energy dissipation is also verified experimentally.
Effect of molecular weight on the crystalline structure of polytetrafluoroethylene as‐polymerized
Authors: Suwa Takeshi , Seguchi Tadao , Takehisa Masaaki , Machi Sueo
Published: April 2003

Melting and crystallization behavior of polytetrafluoroethylene as polymerized in emulsion and suspension is shown to depend on molecular weight. DSC heating curves for virgin PTFE with low molecular weight below 3 × 105 have a single peak, whereas curves for higher molecular weight samples have double peaks. With increasing heating rate the areas of higher melting peaks become larger than the lower melting peaks. The morphology of polymer exhibiting double melting peaks is mainly folded ribbons or granular particles. The phenomenon of double melting is explained on the basis of two different crystalline states which correspond to the “fold regions” and the “linear segments” in a folded ribbon.

The melting temperature of virgin PTFE is almost constant at ca. 330°C for molecular weights below 1 × 106, and rises as the molecular weight increases above 1 × 106. The heat of melting of virgin PTFE is nearly independent of molecular weight.

On the basis of these results, we propose a model for melting and crystallization of low and high molecular weight PTFE and for the crystal structure.
A study of the fold surface structure of polyethylene single crystals by means of selective degradation with ozone
Authors: Patel G. N. , Keller A.
Published: April 2003

Previous studies on the fold surface of polyethylene single crystals by means of selective degradation with ozone, together with associated GPC analysis, have been taken further. This refined method led to improved accuracy and reproducibility which enabled new and more quantitative information to be obtained than was possible earlier, and this in turn has led to new conclusions as regards the nature of the fold surface. The postulated picture of the existence of a distribution of fold lengths has received further support together with much additional information about the nature of the distribution itself. Also, differences in this respect between different crystal types have become apparent. The salient feature of the newly mapped distribution is that the majority of the folds terminate within closely defined limits with one minority fraction protruding beyond this level while another is buried within the crystal interior. The protruding folds become progressively looser and can be visualized as collapsed chains on the top surface while the folds which are buried more deeply become gradually sharper when progressing towards the crystal interior. The data on which these conclusions are based can be expressed in quantitative terms by which it could be assessed that there are differences between crystals formed at 90°C and 70°C the latter having a larger proportion of loose folds along the top surface of the crystal. A reasonable agreement between results of GPC and low‐angle x‐ray analysis gives support to these conclusions.
An investigation on the chain‐folding structure of an ethylene–propylene copolymer by selective degradation
Authors: Patel G. N. , Keller A. , Martuscelli E.
Published: April 2003

A renewed explanatory study is reported on the fold structure and branch location in single crystals of an ethylene–propylene copolymer by means of the ozone degradation method. By analogy with concurrent studies on linear polyethylenes a distribution of fold lengths is inferred, this distribution being broader, more uniform, and spreading deeper into the crystal interior in the case of the copolymer than for the linear polyethylene. Perhaps the most salient points of the work is that in contrast to nitric acid the oxidation by ozone does not obscure then characteristic CH3 infrared absorption band enabling the branch content to be followed during degradation. The single exploratory experiment of the present work reveals that while there is a certain amount of preference for the branches to accumulate near the fold surface, a substantial portion of them can still be located in the crystal interior. The potential of the present method for a more systematic study is indicated.
Current reversal in the thermally stimulated current spectra of polyethylene
Authors: Hashimoto Toshimasa , Shiraki Masao , Sakai Tetsuya
Published: April 2003

Polyethylene thermoelectrets were prepared under static electric fields ranging from 70 to 750 kV/cm at various polarization temperatures. Thermally stimulated current (TSC) spectra were observed for those samples in the high‐temperature region above room temperature. The TSC spectra of polyethylene were complex and were composed of two current peaks, of opposite polarity and dependent on the applied voltage and temperature. This result suggests that there are two trapping mechanisms which result in different charge injection modes. In addition, TSC spectra were obtained on polyethylenes of various morphologies to examine the relationship between the mechanical relaxations and the trapping mechanisms.
The solid‐state thermal polymerization of bis(p‐toluene sulphonate) of 2,4‐hexadiyne‐1,6‐diol. III. An ESR study
Authors: Stevens G. C. , Bloor D.
Published: April 2003

Electron spin resonance (ESR) observations of the solid‐state thermal polymerization of bis(p‐toluene sulphonate) of 2,4‐hexadiyne‐1, 6‐diol at 60°C, 70°C, and 80°C are reported. The weak paramagnetism observed in polycrystalline samples is interpreted in terms of departures of the polymer chain from an equilibrium conformation. Decomposition occurs at 70°C and 80°C during the final phase of polymerization producing additional paramagnetic centers. Lineshape parameters measured during polymerization show changes which we attribute to changes in the delocalization and mobility of the paramagnetic center. We conclude that the nature of paramagnetism in crystalline conjugated diacetylene polymers is a chain defect property characteristic of interband electronic states close to the valence band.
Piezoelectric properties of oriented deoxyribonucleate films
Authors: Ando Yutaka , Fukada Eiichi
Published: April 2003

The piezoelectric effect due to shear in oriented films of DNA is strongly dependent on the relative humidity at which the films are equilibrated. Below about 60% relative humidity, the sign of the piezoelectric modulus is negative and its magnitude passes through a maximum with increasing temperature. This type of polarization appears to be due to the stress‐induced orientation of dipoles in sugar‐phosphate main chain. Above 75% relative humidity, water molecules are adsorbed by the bases and stabilize the ordered structure of double strand helices. In this crystalline state, the sign of the piezoelectric modulus is positive and its magnitude decreases markedly at about−75°C. This type of polarization appears to be due to the stress‐induced orientation of dipoles in bases attached to the main chain. From comparisons between piezoelectric, elastic, and dielectric measurements, it is concluded that the piezoelectric relaxation observed at−75°C and 75% relative humidity is mainly due to the dielectric relaxation of the bases in the double helix.
Low‐frequency dielectric behavior of hydrated poly(L‐proline)II
Authors: Guillet J. , Seytre G. , May J. F. , Chatain D. , Lacabanne C.
Published: April 2003

The dielectric behavior of poly(L‐proline) II has been studied by the dc transient method and a contactless pendulum technique. The comparison of measurements performed with and without contacting electrodes shows that the static and low‐frequency dielectric behavior are due to bulk phenomena. Both mechanisms are strongly dependent upon the water content of the sample. At low hydration, the static conduction may be attributed to an electronic process. The observed low‐frequency relaxation can be characterized by a relaxation time which increases with the water content. This behavior can be explained by an increase in stiffness of the poly(L‐proline) chain: two adjacent carbonyl groups of the chain may be hydrogen bonded by two water molecules.
Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. IV. Crystal orientation mechanism of nylon‐6 under uniaxial stretching
Authors: Matsuo Masaru , Hattori Hiroshi , Nomura Shunji , Kawai Hiromichi
Published: April 2003

A model relating crystal orientation to the deformation of nylon‐6 spherulites under uniaxial stretching is discussed in terms of the orientation distribution functions of reciprocal lattice vectors of crystal planes, such as the (002) and (200) planes. The distribution functions calculated from the model are compared with those obtained from x‐ray diffraction experiments. It is found that the crystalaaxis and, consequently, the direction of hydrogen bonds within the crystal (α modification) orient parallel to the lamellar axis in the undeformed state, and that the crystal orientation behavior of nylon‐6 is much different from that of low‐density polyethylene, being characterized by much smaller values of the reorientation parameters of crystallites within orienting lamellae.

Moreover, small‐angle light scattering forHvandVvpolarization is also calculated on the basis of the spherulite deformation model by taking the nylon‐6 crystal as having orthogonal–biaxial symmetry in optical anisotropy. It is concluded that theHvscattering can be realized in terms of the proposed model for spherulite deformation by taking into account a considerable contribution of hydrogen bonds to the molecular polarizability, so as to make the polarizability along the crystalaaxis larger than that along thebaxis. In other words, this conclusion suggests positively birefringent spherulites in the nylon‐6 samples studied.
Piezoelectric properties of oriented films of poly(γ‐methyl D‐glutamate)
Authors: Koga Kazunori , Kajiyama Tisato , Takayanagi Motowo
Published: April 2003

The dynamic piezoelectric stress constant e*25 of drawn films of poly(γ‐methyl D‐glutamate) (PMDG) cast from solutions in α‐helix‐promoting solvents 1,2‐dichloroethane (DCE) and chloroform and from the nonhelicogenic solvent dichloroacetic acid (DCA) was measured from −180°C to 200°C at 110 Hz. The drawn and annealed films cast from chloroform show a small peak for the real part of piezoelectric stress constant −e′25 in the temperature range of the mechanical α2‐crystalline relaxation, which is caused by the distortion motion of the backbone chain of the α‐helix. On the other hand, drawn films cast from DCE show the peak of the real part of the piezoelectric stress constant, whose magnitude decreases in the range of the mechanical α1‐crystalline relaxation or the β‐relaxation processes, which were previously ascribed, respectively, to mutual slipping of α‐helices and to the micro‐Brownian motion of disordered regions. Also, −e′25 becomes virtually zero near 180°C where the α2‐relaxation is located. These results suggest that the polarization change induced by applied strain is caused by distortion of the backbone chains in the α‐helix. Near 0°C, the temperature range of the side‐chain mechanical relaxation, −e′25 exhibits a marked peak both for films cast from chloroform and from DCE. The maximum value of −e′25 and the orientation function of the α‐helix axis are linearly related and extrapolation of −e′25,max to unit orientation function gives 1.3 × 104 cgs esu which corresponds to 2.4 Debye per residue. This value corresponds reasonably to the value of 3.71 Debye for the permanent dipole moment of NHCO bond if the correction for crystallinity is made. This result also indicates the piezoelectric properties of PMDG arise from distortion of the backbone chain of the α‐helix induced by applied strain.
Domain structure of nylon 6 fibers
Authors: Reimschuessel A. C. , Prevorsek D. C.
Published: April 2003

Stained and unstained sections of nylon 6 fibers are examined by means of transmission electron microscopy. Data are presented regarding dimensions and shape of macrofibrils, microfibrils, amorphous, and crystalline domains of the microfibril and the spacing between the microfibrils. The new results support the conclusions of a previous SAXS and diffusion study carried out with the same fibers.
Nonlinear relaxation of stress and birefringence in simple extension of 1,2‐polybutadiene
Authors: Noordermeer Jacobus W. M. , Ferry John D.
Published: April 2003

Relaxation of stress and birefringence in simple extension has been studied for two samples of 1,2‐polybutadiene with 95% and 88% vinyl content and weight‐average molecular weight 1.9 and 2.9 × 105, respectively. The extension ratio, λ, ranged from 1.14 to 2.08, temperatures from 0 to 15°C, and times, reduced to 0°C, up to 3 × 105 sec. The stress‐optical coefficient C was negative and positive, respectively, for the two samples, the difference being attributable to opposite signs and very different magnitudes of the contributions of the 1,2 and 1,4 moieties to the birefringence. For each polymer, C was independent of time but increased (algebraically) with temperature. For one polymer a very minor dependence of C on λ was observed. At any instant of time, the dependence of both stress and birefringence on λ could be described by equations of the Mooney–Rivlin form with coefficients C1,C2 and B1,B2, respectively. At short times the contributions of the C1 and C2 terms to the stress and of the B1 and B2 terms to the birefringence are roughly equal. With increasing time, C1 and B1 decrease gradually while C2 and B2 remain constant over several decades in time. Finally, C2 and B2 decrease rather rapidly. A tentative interpretation of these phenomena in terms of motions of entanglements is given.
Thermally stimulated and isothermal depolarization currents in low‐density polyethylene
Authors: Fischer P. , Röhl P.
Published: April 2003

Thermally stimulated and isothermal depolarization currents of three low‐density polyethylenes are investigated in the temperature range 80–320°K. The thermally stimulated current spectra can be analyzed in terms of a continuous relaxation time spectrum. This spectrum can be resolved into three Gaussian distributions of activation energies centered near 140°K (γ‐relaxation), 205°K, and 245°K (β‐relaxation) in agreement with electrical and mechanical loss factor measurements. The experimental observation are explained in terms of reorienting dipoles, coupling the molecular motion to the electrical field.
Relaxation time spectrum of dipolar reorientation in low‐density polyethylene
Authors: Fischer P. , Röhl P.
Published: April 2003

The Fröhlich model of discrete reorienting dipoles has been extended to include a continuous spectrum of relaxation times and applied to the measurement of thermally stimulated and isothermal depolarization currents of low‐density polyethylenes. The experiments can only be interpreted if the detailed history of polarization and depolarization prior to the actual current measurements are taken into consideration. With certain simplification the spectrum of activation energies can be directly derived from the complete thermally stimulated current profile.
Dynamic mechanical properties of poly‐α‐olefins containing ring structures in side chains
Authors: Seefried C. G. , Koleske J. V.
Published: April 2003

Dynamic loss modulus curves have been determined over a temperature range beginning at liquid nitrogen temperature for poly‐α‐olefin polymers containing various ring structures, i.e., phenyl, cyclohexyl, cyclopentyl, and naphthyl, in the side chain. Glass transition and appropriate secondary relaxation temperatures were observed for each polymer. Separation of each pendant ring structure from the main backbone chain by successive additions of methylene units results in lower glass‐transition temperatures. Comparison of polymers with similar side chains and different ring structures shows that the respective glass‐transition temperatures decrease in the order naphthyl > cyclohexyl > phenyl > cyclopentyl. Secondary relaxation peaks were obtained at about −150°C for polymers containing the cyclohexyl and cyclopentyl rings. A similar peak was observed for the polymer possessing a phenyl ring separated from the main chain backbone by two methylene units. The comparable polymer containing the naphthyl ring structure exhibited a broad secondary relaxation peak centered at −20°C. The polymers possessing cyclohexyl rings separated from the main chain backbone by one or two methylene units had an additional low temperature peak at −80°C. The molecular mechanism associated with this relaxation may be related to intramolecular transformations of the cyclohexyl ring between its “chair–chair” conformations.
Ultrathin sectioning of rubbery block copolymers: Thickness test and observations of separate microphase units
Authors: Odell J. A. , Dlugosz J. , Keller A.
Published: April 2003

A technique is described which enabled exceptionally thin sections of rubbery material to be cut for electron microscopy, and applied to samples of polystyrene‐polybutadiene‐polystyrene (SBS) copolymers which contain the segregated S phase in the form of cylinders arranged in a regular hexagonal macrolattice throughout the macroscopic specimen, with center to center distance of 300 Å. The technique consisted of sectioning the material hardened by a combination of osmic acid treatment and cooling with liquid air. By this method longitudinal sections containing single layer S rods could be obtained as verified by appropriate tilting tests. Such sections enabled the viewing of single cylinders without overlap which in turn enables the study of the structure of individual cylinders and the effect of various treatments on this structure. Examples quoted include the yielding or breaking of individual cylinders on longitudinal deformation of the macroscopic sample relating to our mechanical studies to be reported elsewhere. The technique also enabled sectioning in the swollen state of samples which are not sectionable other wise and this leads to the recognition of new structures and results in an overall improvement of image quality even when the thinness itself is not the prime requirement.
Quantitative information from x‐ray diffraction of nylon‐6 yarns. II. Physical aspects of some quantitative parameters
Authors: Huisman R. , Heuvel H. M.
Published: April 2003

A mathematical model developed in an earlier paper describes the experimental x‐ray profiles of equatorial nylon‐6 reflections in terms of Pearson VII functions. The present paper deals with the physical aspects and interpretations of the interrelations of the parameters obtained and the relation between these parameters and the results of other types of measurements. It was found that the growth of the crystallites perpendicular to the chain axis is not isotropic, the strongest growth being in the direction of the hydrogen bonds. Growth and perfection of the crystallites are found to be highly correlated. Large crystals are related to short distances between the planes containing the hydrogen bonds and so to densely packed, i.e., perfect unit cells. This correlation forms the basis for the observed similarity between our quantification technique and the method of the crystal perfection index introduced by Statton. Curve resolution, however, makes the method better applicable for poorly crystallized samples. Comparison of the results with those of small‐angle x‐ray scattering gave a high degree of consistency with respect to the determined crystal size. In the literature mention is made of a relation between the dimensions and the melting point of the crystals; this relation is confirmed by comparing the appropriate x‐ray parameters with DTA results of methoxymethylated nylon 6‐yarns.

Information about the γ‐phase can be obtained from equatorial and meridional reflections. The expected relationship between the relevant peak areas was established. This reported evidence shows the physical validity of the parameters obtained using the Pearson VII model for the analytical description of x‐ray reflections of nylon‐6 yarns.
The effect of casting solvent on the material properties of poly(γ‐methyl‐D‐glutamate)
Authors: Mohadger Youseph , Wilkes Garth L.
Published: April 2003

The effect of casting solvent on the material properties of poly(γ‐methyl‐D‐glutamate), PMDG, was investigated. The specific solvents used were chloroform, trifluoroacetic acid, dichloroacetic acid, methylene chloride, hexafluoroisopropanol, and tetrachloroethane. The different nature of these solvents controlled the degree of α, β, or random coil contents of the final film. The effect of the morphology on material properties induced by the respective solvents was investigated by dynamic mechanical measurements of the dry films, stress strain behavior of both wet and dry films as well as by wide‐angle x‐ray diffraction, small‐angle light scattering, and optical microscopy. Infrared spectroscopy was used to help determine α or β content. It was found that the casting solvent has considerable influence on material behavior and morphology. These differences are reflected in both the dynamical mechanical (small strain) and stress–strain (large strain) measurements as well as the x‐ray scattering and optical microscopy. It was noted by light scattering that all films gave rise to anisotropic rod scattering with the exception of the β film cast from trifluoroacetic acid. This latter film appeared to be optically isotropic.
Expansion coefficient of polyelectrolytes
Authors: Chien Homei W. , Isihara A.
Published: April 2003

The expansion coefficient of a flexible polyelectrolyte molecule is evaluated as a function of the concentration of simple salt added to the solution. It is shown that the coefficient has a term which is inversely proportional to the square root of the concentration of added salt.
Molecular transitions in an alternating copolymer of ethylene and chlorotrifluoroethylene
Authors: Sibilia John P. , Schaffhauser Robert J. , Roldan Luis G.
Published: April 2003

Three transitions have been found with peaks at 130°C (α), 88°C (β), and −65°C (γ), by mechanical relaxation techniques for a quick‐quenched sample of an alternating copolymer of ethylene and chlorotrifluoroethylene. The intensity of the α transition was found to increase with an increase in crystalline content. It was observed at 150°C by infrared and x‐ray diffraction techniques and by mechanical relaxation spectra on an annealed sample. X‐ray diffraction and dichroic infrared measurements were conducted on oriented specimens as a function of temperature. These data showed that the β transition was accompanied by a change in lateral bonding distances in the crystalline phase and a conformational change attributed to an “unkinking” of the molecular chain. The β transition was found to be related to the amorphous phase and the onset of the β peak corresponded to the transition at 35°C found by infrared techniques and previously by a torsional modulus method. It was tentatively assigned to the glass transition. A more definitive assignment of the β transition would depend on a detailed structural analysis of the γ transition. The γ peak was not studied in detail in the present work.
Vibrational analysis of polyethylene terephthalate and its deuterated derivatives
Authors: Boerio F. J. , Bahl S. K. , McGraw G. E.
Published: April 2003

The Vibrational analysis of polyethylene terephthalate, polyethylene‐d4 terephthalate, and polyethylene terephthalate‐d4 has been carried out using a valence force field calculated from the infrared and Raman spectra of a series of low molecular weight aromatic esters. The Raman spectra for polyethylene‐d4 terephthalate and polyethylene terephthalate‐d4 are presented and band assignments for these compounds and polyethylene terephthalate are discussed.
Methyl rotation in polydimethylsiloxane studied by neutron transmission
Authors: Amaral L. Q. , Vinhas L. A. , Herdade S. B.
Published: April 2003

Neutron transmission of polydimethylsiloxane has been measured as a function of neutron wavelength in the range 4–10 Å, at room temperature. Scattering cross sections per hydrogen atom have been obtained and the slope (12.2 ± 0.2) barns/Å has been derived. Comparison with calibration curves relating the slope to the barrier hindering internal rotation as well as comparison with calculated neutron cross sections using the Krieger–Nelkin formalism for different dynamical situations indicates practically free rotation of CH3 groups about their C3 symmetry axes.
Localized flow birefringence of polyethylene oxide solutions in a four roll mill
Authors: Crowley D. G. , Frank F. C. , Mackley M. R. , Stephenson R. G.
Published: April 2003

We report flow birefringence observations of polyethylene oxide solutions in a four roll mill where the flow field in the central region of the mill approximates well to that of pure shearing flow. When flow birefringence is observed it is seen to be highly localized within a region close to the “outgoing” asymptotic plane of flow. The phenomenon can be explained in terms of the flow birefringence corresponding to high extension of some polymer chains where the localization is caused by the chains requiring sufficient time in the flow field to become extended. This explanation has important consequences in all “persistently extensional flows” and can explain the origin of previously published results of localized flow birefringence observed for polyethylene solutions in axial compression and axial extensional flows.
Dynamic viscoelastic behavior of ABA block polymers and the nature of the domain boundary
Authors: Kraus Gerard , Rollmann K. W.
Published: April 2003

Dynamic viscoelastic properties of block copolymers of styrene with butadiene or isoprene are consistent with the growth of a diffuse interphase or interlayer as block lengths decrease. Under the conditions of the present study the interlayer does not lead to a secondary loss maximum between the two domain glass transitions. The pattern of shifts of the loss maxima characteristic of the domain Tg's suggests strongly that the interlayer composition profile must be asymmetric with an average volume composition rich in styrene. Typical block polymer viscoelastic behavior is observed even beyond the point at which the interlayer attains 100% of the polymer volume. Such block polymers no longer contain compositionally pure phases, but are visualized as retaining a residual domain structure in which composition fluctuates between ever narrowing limits as blocks become shorter, approaching homogeneity and the mechanical behavior of random copolymers.
Newtonian behavior of a styrene–butadiene–styrene block copolymer
Authors: Chung Chan I. , Gale John C.
Published: April 2003

The melt rheological behavior of an anionically polymerized styrene–butadiene–styrene (SBS) block copolymer sample (S: 7 × 103and B: 43 × 103) was studied using a Weissenberg rheogoniometer. Highly non‐Newtonian behavior, high viscosity and high elasticity, which are characteristics of ABA type block copolymers, were observed at 125°C, 140°C, and 150°C. The data at these temperatures superimposed well onto a master curve giving a constant flow activation energy. However, the data at 175°C indicated a marked change in the flow mechanism between 150°C and 175°C. At 175°C, the sample showed Newtonian behavior, negligible elasticity, and deviation from the master curve. These findings may be considered as an indication that the SBS block copolymer sample undergoes a structural change from a multiphase structure at low temperatures into a homogeneous structure at some temperature between 150°C and 175°C.
Influence of crystallization and annealing conditions on the morphology of bulk‐crystallized isotactic polystyrene
Authors: Overbergh N. , Berghmans H. , Reynaers H.
Published: April 2003

The influence of thermal history on the morphology of bulk‐crystallized isotactic polystyrene was investigated. Results from x‐ray diffraction (both wide‐ and small‐angle), DSC experiments, and electron microscope observations, were combined to define the influence of thermal history on the fold surface free energy σe. lamellar thickness, and crystallite perfection. The increase of the melting point with crystallization temperature is not only the consequence of an increase in lamellar thickness, but also of marked decrease of σe. Annealing above the crystallization temperature results in a fast reorganization to a more stable structure, as reflected in an increase in melting point. This reorganization, depending on the crystallization temperature, involves an increase in lamellar thickness, a decrease of σe, and eventually an increase in crystallite perfection.
Thermal expansion and compressibility in the chain direction of a polydiacetylene single crystal
Authors: Batchelder D. N.
Published: April 2003

An x‐ray back‐reflection rotating camera has been used to measure the lattice constant, thermal expansion, and compressibility in the polymer chain direction of a polydiacetylene, poly[bis(p‐toluene sulfonate) of 2,4‐hexadiyne 1,6‐diol]. The thermal expansion coefficient of the polymer chain is small and positive (0.9 ± 0.2 × 10−6 °K−) at 300°K, but negative below about 70°K. Application of 3.43 kbar hydrostatic pressure at 299°K changed the unit cell dimension in the polymer chain direction by less than 10 ppm.
Isothermal and nonisothermal dielectric relaxation studies on polycarbonate
Authors: Aoki Y. , Brittain J. O.
Published: April 2003

Dielectric relaxation measurements at very low frequency were carried out on polycarbonate. Two prominent peaks were resolved from the broad β‐relaxation peak with activation energies of 0.28 and 0.52 eV, respectively. Thermally stimulated discharge current was also studied and compared to the results obtained from the dielectric relaxation measurements.
Direct determination of interfacial energy between brittle and polymeric films
Authors: Chow T. S. , Liu C. A. , Penwell R. C.
Published: April 2003

Very few analyses exist for determining the adhesion f thin brittle films in the micron range on low modulus polymeric substrates. A theoretical model and experimental means are developed to determine the adhesion for this situation using the concept of fracture mechanics and Griffith's energy criterion. An expression for the adhesion is derived in terms of the external loading, material constants, and thicknesses of the films.

The model is compared with measurements of brittle films vacuum deposited onto polymeric substrates. Excellent agreement is obtained and interfacial energies are calculated. Since the moduli of thin films are very difficult to determine accurately, the effect of a variation in measurements of this material parameter on the adhesion is calculated. The effect of varying preparative conditions is also discussed.
Potentiometric titration of polyelectrolyte gels equilibrated with a solution of a strong polyelectrolyte: Influence of gel swelling
Authors: Merle Yves
Published: April 2003

A weak acid gel (carboxylmethyldextran) was titrated with sodium hydroxide while equilibrated with a solution sodium poly(vinyl sulfate), a salt of a strong acid polyelectrolyte.

It was found that the quantity

in which V/V0 is the volume of gel relative to its volume in acid form in pure water, is independent of the concentration Cp of the polyelectrolyte solution and of the relative volume of gel.

The relation

where α is the degree of ionization, pK′ is the apparent pK of the gel, γ is the activity coefficient of the counterion in the gel phase, and v is the number of ionizable groups, is found to be constant for all values of Cp and for 0.1 < α < 0.9. These results can be extended to highly crosslinked ionexchange resins.