bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermally induced phase separation of polystyrene‐poly(vinyl methyl ether) mixtures
Authors: Bank M. , Leffingwell J. , Thies C.
Published: April 2003

Past differential scanning calorimetry and dielectric relaxation measurements have established that polystyrene (PS)‐poly(vinyl methyl ether) (PVME) mixtures exhibit a degree of compatibility when cast from toluene, whereas they are incompatible when cast from chloroform or trichloroethylene. The present study reports that toluene‐cast mixtures can be phase‐separated by thermal treatment at temperatures exceeding 125°C. This is true for samples containing 20–80 wt‐% PS. The temperature of phase separation varies with heating rate; isothermal heating times needed to cause phase separation increase rapidly as the temperature approaches 125°C. Reversibility of the phase separation process depends upon such factors as cooling rate, annealing time, treatment temperature, and thermal history. By annealing and/or slow cooling, all thermally phase‐separated mixtures have been brought back to their original state of compatibility. That is, there is no evidence for true irreversiblity of phase separation in thermally treated samples. Quench‐cooled samples remain phase‐separated indefinitely at room temperature, but this is attributed to rapid cooling below the glass transition of the PS. Chloroform‐cast and trichloroethylene‐cast mixtures have not been brought to a compatible state by thermal treatment, even after lengthy annealing and slow cooling steps.
Far‐infrared spectra of piezoelectric polyvinylidene fluoride
Authors: Luongo J. P.
Published: April 2003

Poly(vinylidene fluoride) (PVF2) is currently used to form piezoelectric films. The PVF2 molecule can exist in more than one stable conformation and it has electrically polar groups making the polymer amenable to the electrification processes involved in the formation of the piezoelectric film. The two crystalline forms of PVF2 are distinguishable by far‐infrared spectroscopy. Polarized far‐infrared spectra (1000‐50 cm−1) of uniaxially oriented PVF2 show changes in the strong perpendicular dichroism in a number of absorptions before and after being made piezoelectric. The dichroism is attributed to a structural rearrangement from a staggered trans‐gauche‐trans‐gauché conformation to a planar zig zag conformation. In the latter conformation the permanent dipoles are oriented approximately at right angles to the surfaces of the film and result in an electrically polarized film.
Light scattering by anisotropic elliptical objects
Authors: Finkelstein R. S. , Sarko A.
Published: April 2003

The small‐angle light scattering in Hv and Vv modes is calculated for elliptical disks with the use of an elliptical coordinate system. The method is general for all degrees of ellipticity, from a circular disk to rodlike extensions, and permits the definition of any desired dipole orientations. The solution is obtained by computer‐assisted numeric integration. Two models are considered, an “elliptical” one an “affine deformation” one differing in the orientation of scattering dipoles. The calculated patterns show a significant dependence of the distribution of the scattered intensity on the size and the elliptical axial ratio in both models, permitting the determination of both the size and the degree of ellipticity of the disk from its patterns. In addition, the differences between the calculated results for the two models are sufficiently large to permit the selection of the experimentally appropriate model, at least within the range of moderate degree of ellipticity.
Crystallite size in drawn and then annealed polypropylene
Authors: Morosoff N. , Sakaoku K. , Peterlin A.
Published: April 2003

Crystallite sizes have been obtained from the breadth of equatorial x‐ray reflections from polypropylene samples subjected to a draw ratio of 6 at 21°C and then annealed at 155°C, 140°C, and 120°C, respectively. For all samples it was found that the ratio of the dimension of the crystallite perpendicular to the {110} planes to that perpendicular to the (040) plane is a constant. The ratio of the lateral crystallite size to the meridional long period was also found to be constant, independent of annealing temperature. In contrast, the thickness of the crystallites in the direction parallel to the draw direction, as calculated from the meridonal long period and density data, was not proportional to the lateral crystallite size.
Effect of heat treatment on the morphology and structure of crystals, powders, and fibers of polyacrylonitrile and saran
Authors: Boucher E. A. , Langdon D. J. , Manning R. J.
Published: April 2003

As part of a study of chemical and physical changes accompanying the formation of carbons by the pyrolysis of polymers, conventional electron microscopy, electron diffraction, and scanning electron microscopy techniques have been used to examine structural and morphological features of polyacrylonitrile (PAN) crystals, powder, and fibers, and of Saran and poly(vinylidene chloride) (PVDC) powder. Changes accompanying the heating of these polymers in air and in nitrogen have been investigated. PAN crystals grown from propylene carbonate were similar to those obtained by Klement and Geil. When heated in air at 220°C they retained their morphology, and electron diffraction gave the same reflections as PAN. On further heating to 400°C in nitrogen the morphology was retained, but the diffraction was lost. Crystals treated in nitrogen alone at 200°C showed morphology similar to that of the polymer. PAN powders and fibers retained discernable external features of their morphology on heating to 800°C. These results are discussed with reference to changes which take place when poly(vinylidene chloride) and Saran are heated in the range 150–180°C, which results in the loss of one hydrogen chloride per monomer unit, and are subsequently carbonized at 800°C. The development of pore structure and the adsorptive properties of Saran carbons are also discussed.
Glass transition temperature for epoxy‐diamine networks
Authors: Williams J. G. , Delatycki O.
Published: April 2003

The glass transition temperature of systems based on epoxy resin and a number of diamines has been determined by using a torsion pendulum. An equation relating composition and crosslink density with the glass transition temperature has been established which gives reasonable predictions of the glass transition temperatures for systems based on aliphatic or aromatic amines and methylated amines and for systems containing a monofunctional epoxy diluent. The equation may be used to predict Tg for systems with non‐stoichiometric quantities of curing agent and blends of amines. Deviation of the predicted and observed values for Tg is interpreted in terms of differences between definitions of Tg used by other workers and, also the occurrence of competing side reactions during polymerization which lead to additional crosslinks.
Studies of the morphology of emulsion‐grade polytetrafluoroethylene
Authors: Rahl Forrest J. , Evanco Michael A. , Fredericks Robert J. , Reimschuessel Annemarie C.
Published: April 2003

Two types of emulsion‐grade polytetrafluoroethylene particles have been studied. We refer to these as ribbons and rods. The ribbons consist of very thin ribbons or lamellae folded upon themselves a number of times. In typical emulsion‐grade material prepared at Allied Chemical, the unraveled ribbon measures about 3.25 μ in length, 0.25 μ in width, and 60Å in thickness. The folded ribbons, which form the particles, are about 0.5 μ long and 0.25 μ wide. Electron diffraction shows that the ribbons are single crystals with the chain axis parallel to the long axis of the ribbons thus forming extended chain crystals. This extended‐chain packing is consistent with the observed cleavage or fibrillation of the ribbons and with the molecular weight. The rods are formed in low–yield polymerizations. Electron diffraction also shows that the rods are single crystals with the chain axis parallel to the long axis of the rods. Striations parallel to the long axis are believed to result from stacking of parallel segments. Considerable bending of the long axis of rods is observed.
A simple representation of small‐angle light scattering from an anisotropic sphere
Authors: Holoubek J.
Published: April 2003

An explicit form of Mueller's phenomenological matrix has been derived which characterizes the small‐angle light scattering from an anisotropic sphere when the requirements of the Rayleigh‐Gans approximation are fulfilled.
Surface tension of polymer solutions. IV. Three‐component mixtures
Authors: Gaines George L.
Published: April 2003

The lattice‐theory equations for the surface tensions of polymer solutions based on the parallel‐layer model have been tested for three‐component systems. Surface tensions of solutions of some low molecular weight polyisobutylenes and polydimethylsiloxanes in n‐heptane–tetralin mixtures and solutions of mixtures of the polymers in these solvents were measured at room temperature. The results are in good agreement with the theoretical calculations.
Four‐center type photopolymerization in the crystalline state. V. X‐ray crystallographic study of the polymerization of 2,5‐distyrylpyrazine
Authors: Nakanishi Hachiro , Hasegawa Masaki , Sasada Yoshio
Published: April 2003

Changes in crystal structure during polymerization and oligomerization of 2,5‐distyrylpyrazine have been investigated by x‐ray crystallography. The polymer and the oligomer as obtained are three‐dimensionally oriented, and the directions of the three axes of the resultant crystals coincide with those of the original crystal. The space group of the products also agrees with that of the monomer. It is concluded that the polymer and the oligomer crystals approximately duplicate the molecular arrangement in the monomer crystal. The polymerization mechanism is discussed on the basis of the crystal structures.
Low‐angle x‐ray scattering from crazes and fracture surfaces in polystyrene
Authors: LeGrand D. G. , Kambour R. P. , Haaf W. R.
Published: April 2003

Both crazes and fracture surfaces in glassy polymers produce a low‐angle scattering of x‐rays. Scattering patterns are anisotropic and often show considerable streaking. In the one case (polystyrene) studied extensively so far, detalied analysis suggests that the craze is approximated as a collection of spheroidal or irregular‐shaped voids surrounded by material with anisotropic density distribution arising from its orientation in the stress direction. The void dimension is about 90–115 Å and the specific internal surface area about 170 m2/cm3 of craze. These results and those from electron microscopic studies are reasonably consistent.
High‐temperature annealing of drawn nylon 66 fibers
Authors: Statton W. O.
Published: April 2003

The structure and morphology of highly oriented fibers were modified by thermal treatments at varying tensions. The structural changes were characterized by wide‐ and small‐angle x‐ray diffraction, broadline nuclear magnetic resonance, and electron microscopy of surface replicas. Increasing temperatures caused increases in local ordering, number of regular chain folds, mobile fraction or amount of fluidlike mobility, and surface recrystallization in localized areas. Each of these changes was also a function of the amount of tension on the fiber during the annealing; each change was maximized when the fiber was free to shrink but minimized when the fiber was stretched.
Crystallinity in poly‐N‐methyllaurolactam and copolymers
Authors: Shalaby S. W. , Fredericks Robert J. , Pearce Eli M.
Published: April 2003

Fully methylated nylon 12 was prepared by the hydrolytic polymerization of N‐methyllaurolactam. The polymer, with about 20% crystallinity, has a crystal structure different from that of nylon 12. The X‐ray diffraction patterns of copolymers of N‐methyllaurolactam and laurolactam were shown to be composition‐dependent. Copolymers containing up to 15% laurolactam units exhibited a crystal structure essentially the same as poly‐N‐methyllaurolactam. Copolymers containing from 20 to 50% laurolactam are transition structures, whereas copolymers containing more than 50% laurolactam units exhibit a crystal structure characteristic of polylaurolactam. DSC data on the homopolymers and copolymers are also reported.
Transitions and relaxations in poly(1,4‐phenylene ether)
Authors: Wrasidlo Wolfgang
Published: April 2003

Transitions and relaxation phenomena in poly(1,4‐phenylene ether) were studied over temperature range from 100 to 800°K by applying a combination of calorimetric, dilatometric, dynamic mechanical, and dielectric techniques. Amorphous polymer, exhibiting no x‐ray crystallinity, is obtained only by quenching molten samples at extremely fast cooling rates (ca. 1000°C/sec) and by minimizing thermal gradients within specimens. A weakly active mechanical relaxation region with a loss maximum at 155°K of unknown origin was observed. The glass transition interval of completely amorphous polymer is characterized by a discontinuous jump in heat capacity of 2.76 cal/deg per chain segment occurring at 363°K (corrected for kinetic effects), and a fourfold increase in the coefficient of linear thermal expansion. Strongly active, dynamic mechanical relaxations occur in the Tg interval with a loss maximum at 371°K (f = 110 cps) and resulting in a drop in the dynamic storage modulus from 1011 to 109 dyne/cm2. Cold crystallization takes place just above Tg, to yield a polymer with an x‐ray crystallinity of 0.7 and a heat of crystallization of 270 cal/mole. The crystalline polymer shows a complex melt structure. Depending upon the thermal history, multiple endothermic peaks indicative of structural reorganizations occur just prior to fusion. Very high dielectric losses with a wide distribution of relaxation times were observed in the melt interval. The mechanical relaxation spectrum in this region is typical of viscous flow behavior.
Plastic deformation of polypropylene VII. Long period as function of temperature and rate of drawing
Authors: Baltà‐Calleja F. J. , Peterlin A. , Crist B.
Published: April 2003

Polypropylene fibers prepared by quenching in ice‐water were drawn at 25, 80, 120, and 140°C to a draw ratio between 6 and 8 at draw rates 0.05, 0.5, 5, and 50 cm/min. The long period increases almost linearly with the draw rate for drawing at 25°C and decreases for drawing at higher temperatures. The effect in the latter cases is an annealing effect. As a consequence of the shorter exposure of the drawn fibers to the high temperature at higher draw rate, the long‐period growth proceeds for a shorter time and hence results in a smaller increase of long period. At 25°C, however, the long‐period growth is negligible. The increase of long period with draw rate is the consequence of higher adiabatic heating as calculated from the energy input during the plastic deformation which transforms the spherulitic into the fibrous structure. One concludes that the long period established during this transformation depends on the maximum temperature reached in the micronecking zone and not on the macroscopically observed temperature of the sample in the neck.
High‐pressure phase of polytetrafluoroethylene
Authors: Flack H. D.
Published: April 2003

The effect of hydrostatic pressure on the crystal structure of PTFE has been studied up to pressures of ca. 25 kbar by x‐ray diffraction. The experimental method uses opposed diamond anvils of small surface area as transmitters of pressure with MoKα x‐radiation propagating through these anvils. A small specimen of oriented polymer is held in place with a molybdenum gasket. Pressures are measured by change in lattice spacing of sodium chloride included with some specimens. It is found that above 4.5 kbar the PTFE changes to a high‐pressure phase in which the molecules have transformed from their normal helical arrangement to that of a planar zigzag and that the planes of the molecules all lie parallel to one another. Further changes in the diffraction pattern on increase in pressure are attributed to slip and twinning in the high‐pressure phase rather than to another phase change.
Crystallization of polyethylene at high pressure: A kinetic view
Authors: Calvert P. D. , Uhlmann D. R.
Published: April 2003

A model for the crystallization kinetics of polymers is outlined and is used to interpret observations of the crystallization of polyethylene at high pressures. This model introduces a distinction between σe the lamellar surface energy which controls the lamellar thickness, and σe′, the surface nucleus surface energy which controls the growth rate. Differential scanning calorimetry and electron microscopy data for several polyethylenes crystallized at pressures of up to 8 kb are presented. From the dependence of lamellar thickness on the crystallization undercooling at 5 kb, it is found that σe increases markedly with pressure leading to the formation of very thick crystals at high pressures. The magnitude of the increase in σe is in agreement with σe values calculated from the dependence of melting temperatures on pressure. The nucleus surface energy σe′ is not expected to vary significantly with pressure, and estimates of growth rates of 5 kb which indicate that the growth rate does not vary significantly with pressure at constant under‐cooling confirm this. Fractionation effects and the differences in behavior between different polyethylenes are also discussed.
Polymer particle formation in suspension polymerization of vinyl chloride and vinyl acetate
Authors: Ueda Tsutomu , Takeuchi Katsuyuki , Kato Michiaki
Published: April 2003

Equipment has been designed and assembled in such a way that direct microscopic observation of polymer particle formation in suspension polymerization of vinyl chloride and vinyl acetate is possible. The apparent mode of transformation from monomer droplets into polymer particles has thus been studied under two sets of conditions: (1) with agitation and (2) without agitation. In both cases, as the initial vinyl acetate/vinyl chloride ratio was raised, the apparent change in the shape and transparency of particles occurring during the course of polymerization became less evident. In vinyl chloride homopolymerization and vinyl acetate–vinyl chloride copolymerization with relatively high vinyl chloride concentrations, the polymer particles burst during the course of polymerization. Some factors which affect the change in the size of particles are also discussed.
Long branching in poly(vinyl acetate) and poly(vinyl alcohol). IV. Polymerization of vinyl trimethylacetate in the presence of crosslinked poly(vinyl acetate)
Authors: Nozakura Shun‐Ichi , Morishima Yotaro , Murahashi Shunsuke
Published: April 2003

In order to clarify the grafting behavior of vinyl trimethylacetate (VTMAc) onto poly‐(vinyl acetate) (PVAc), the polymerization of a radioactive VTMAc in the presence of a crosslinked PVAc gel was studied in accordance with the experimental technique described in the previous papers. It was found that, at 60°C, the grafting onto the main chain of PVAc takes place about 2.8 times as readily as that onto the acetyl side group on PVAc.
Base cleavage of epichlorohydrin polymers
Authors: Vandenberg E. J.
Published: April 2003

Epichlorohydrin polymers cleave much more readily with organolithium compounds than do other poly(alkylene oxides). In dilute toluene solution (1–2%) at −78°C, the cleavage of polyepichlorohydrin occurs as rapidly as BuLi is added. The end‐groups formed are about equimolar amounts of hydroxyl and carbonyl with small amounts of acetylene ends. This same cleavage reaction but without acetylene ends can be obtained with NaOH or NaOCH3 in dimethyl sulfoxide at 65°C. The carbonyl groups can be reduced with LiAlH4 in tetrahydrofuran to give hydroxyl‐ended polymers. A mechanism is presented for this unusual cleavage reaction.
Complexation du chlorure de vinyle par le tetrahydrofuranne et le n‐butyraldéhyde: Étude par résonance magnétique nucléaire haute résolution
Authors: Tho Pham Quang , Taieb Maurice
Published: April 2003

Examination of the HR‐NMR spectra of vinyl chloride in the presence of tetrahydrofuran and n‐butyraldehyde suggests the formation of donor‐acceptor type complexes. The equilibrium quotients and NMR constants were estimated by using the Benesi‐Hildebrand method. The existence of these complexes would explain the anomalies observed: first, in the anionic polymerization of vinyl chloride initiated by tert‐butylmagnesium chloride is tetrahydrofuran. The initiation step seems to be governed by this complexation phenomenon; second, in the radical polymerization of the same monomer in n‐butylaldehyde the obtained poly(vinyl chloride) is more syndiotactic than the radical polymer prepared in bulk by the usual methods.
Kinetic study of amination of chloromethylated polystyrene with hydroxyalkylic tertiary amines
Authors: Drăgan Stela , Petrariu I. , Dima M.
Published: April 2003

The kinetics of the amination of chloromethylated polystyrene with two hydroxyalkylic tertiary amines (1‐dimethyl‐amino‐3‐propanol and 1‐dimethylamino‐2‐propanol) in dimethylacetamide and dioxane was studied. The amination of benzyl chloride with the two amines in dimethylacetamide was followed. It was found that the amination of chloromethylated polystyrene is a two‐step reaction taking place with different rates. The rate constants k1 and k2 were calculated for the two stages, and a self‐accelerating effect of the reaction was noticed. Also, the influence of the position of the hydroxyl group versus the tertiary nitrogen was investigated. The increase of the dielectric constant of the solvent favorably influences the reaction rate.
Copolyesters of glycols and bisphenols: A new preparative process
Authors: Hamb F. Lynn
Published: April 2003

A new process for the preparation of copolyesters of glycols and bisphenols is described. Employing a preformed polyester, an acid, and a bisphenol diacetate, the procedure is useful for a variety of copolyesters. It is illustrated with the preparation of copolyterephthalates of ethylene glycol and 4,4′‐isopropylidenediphenol. The reaction is proposed to proceed by an initial cleavage of the polyester, followed by polymerization of the acid‐ and acetate‐terminated products. Intermediate heterogeneous structures then equilibrate.
Production of organometallic polymers by the interfacial technique. XXVII. Reaction variables in the synthesis of poly[oxy(dicyclopentadienylzirconium)oxycarbonylferrocenylcarbonyl]
Authors: Carraher Charles E. , Reimer James T.
Published: April 2003

The synthesis of poly[oxy(dicyclopentadienylzirconium)oxycarbonylferrocenylcarbonyl] was studied as a function of several reaction variables. Yield varied greatly with pH, reaching a maximum around pH = 7.5; yield was greater for systems employing a saturated aqueous solution of the disodium 1,1′‐ferrocene dicarboxylate falling rapidly to a plateau; yield attained a maximum as the aqueous volume was varied but decreases throughout the range studied as the volume of CHCl3 increases; a plateau in yield was reached at around a stirring rate of 20,700 rpm. For more dilute solutions (6.7 × 10−3M) yield is dependent on the concentration of both reactants and seeks a maximum around a stirring time of 30 sec.
Polymerization of β‐carbomethoxypropionaldehyde
Authors: Sumitomo Hiroshi , Kobayashi Kazukiyo , Saji Toshihiro
Published: April 2003

High molecular weight crystalline poly(carbomethoxyethyl)oxymethylene was prepared from β‐carbomethoxypropionaldehyde with the use of organometallic compounds. The characterization, fractionation, x‐ray analysis, and viscosity measurement were carried out. Degradation by hydrochloric acid gave a highly crystalline but soluble polymer of a lower molecular weight. It was interesting to note the high solubility character of the polymer in organic solvents in contrast to the poor solubility of the isomeric poly(acetoxyethyl)oxymethylene. From the relationship among the intrinsic viscosity, Huggins' constant, and the solubility parameter of solvent, the solubility parameter of the polymer was determined to be 9.3 (cal/ml)1/2.
Dielectric relaxation of acrylonitrile–butadiene copolymers
Authors: Ikada Eiji , Watanabe Teizo
Published: April 2003

Dielectric constants and losses of four kinds of acrylonitrile–butadiene copolymers of different degrees of polymerization were measured in the glass–rubber transition region. Curves of the dielectric losses against frequency showed asymmetric loss curves as often seen in α‐relaxations of polar polymers. The loci of Cole‐Cole plots of the complex dielectric constants of these copolymers fitted well the loci of Havriliak‐Negami's equation,

The distribution parameters (1 − α) and β of the relaxation times were calculated. It is suggested that the mechanism of relaxation of the long chains is governed by a cooperative mechanism consisting of two concurrent motions: the first motion is the segmental relaxation of the polar chains, and the second is the induced motion of the neighboring segments successive to the first one.
Application of mass spectrometry to the study of fluoropolymers. II. The copolymer from trifluoronitrosomethane (CF3NO) and tetrafluoroethylene (C2F4)
Authors: Flowers W. T. , Haszeldine R. N. , Henderson E. , Lee A. K. , Sedgwick R. D.
Published: April 2003

The techniques of mass spectrometry have been applied to the copolymer from tri‐fluoronitrosomethane (CF3NO) and tetrafluoroethylene (C2F4). The copolymer yields spectra of a repetitive nature, typical of the repeating units in the polymer chain. Molecules with masses up to m/e 6400 can be distilled from the unfractionated polymer which is stable up to 220°C. Interpretation of the mass spectrum suggests a linear structure for the regular polymer.
Block copolymer formation from copolymers of phenylvinylene carbonate
Authors: Mulvaney J. E. , Sasaki Y.
Published: April 2003

Copolymers of phenylvinylene carbonate with styrene and p‐chlorostyrene are readily prepared with radical initiators. The carbonate portion of the copolymers has been hydrolyzed to a 1,2‐glycol which was then oxididatively cleaved with periodate–perman‐ganate to produce a polymer with carboxyl and keto endgroups. Block copolymers were then prepared by conversion of the carboxyl groups to an acid chloride, followed by coupling with diols or a diamine.
Preparation and polymerization of methylenecyclobutene and 1‐methyl‐3‐methylenecyclobutene
Authors: Wu Chester C. , Lenz Robert W.
Published: April 2003

Methylenecyclobutene (MCB) and 1‐methyl‐3‐methylenecyclobutene (MMCB) were synthesized, characterized, and polymerized by anionic and cationic initiators. Structural analyses of the polymers were carried out by infrared and NMR spectros‐copy. The cationic polymerization of MCB appeared to proceed entirely by a 1,5‐propagation mechanism to form low molecular weight polymers in low yields. Anionic polymerization of this monomer, on the other hand, proceeded primarily through a 1,2‐propagation path, again forming only low molecular weight polymeric products in low yield. In contrast to MCB, the methyl‐substituted monomer, MMCB, polymerized readily with cationic initiators to produce unusually high molecular weight polymers in high conversions. On the basis of both infrared and NMR spectroscopic analyses, it was concluded that the polymers also contained essentially only 1,5‐addition repeating units. Anionic initiators such as n‐BuLi were unable to induce polymerization of this monomer, but polymerization by Ziegler‐Natta catalysts proceeded readily to yield polymers virtually identical in structure and molecular weight to those obtained with cationic initiators.
Asymmetric interaction of optically active polymers with asymmetric small molecules. IV. Effect of hydrophobic groups on asymmetric interaction
Authors: Ihara Y. , Nakano H. , Koga J. , Kuroki N.
Published: April 2003

In order to investigate the mechanism of the asymmetric interaction between optically active polymers and small molecules, optically active copolymers of N‐acrylyl L‐amino acids(N‐acrylyl‐L‐phenylalanine, N‐acrylyl‐L‐tryptophan, and N‐acrylyl‐L‐leucine, respectively) and N,N′‐hexamethylene diacrylylamide were synthesized, and interaction of these polymers with the optical isomers of phenylalanine and tryptophan was investigated. In the interaction of these acidic polymers with amino acids performed at pH 5.0, significant difference in amount of adsorption between the D and L isomers of amino acids were observed, and the L form of amino acids was adsorbed preferentially. The interaction between optically active small molecules was also investigated: these results showed a similarity to the results for interaction between optically active polymers and amino acids. In some instances of asymmetric interaction the influence of hydrophobic interaction between a polymer and substrate was clearly perceived. The stereoselective effects on the asymmetric interaction are discussed.
Statistical nonstationarity of the composition of styrene with methyl methacrylate in the cooligomer
Authors: Tsuchida Eishun , Mishima Kunio , Kitamura Kiwamu , Shinohara Isao
Published: April 2003

It was found that the composition of cooligomer produced in the styrene(A)–methyl methacrylate(B)–CCl4(S) system deviates from the statistical steady‐state composition predicted from the Mayo‐Lewis equation on the low molecular weight side when the molar ratio of [A]/[B] is large. When the molar ratio of [A]/[B] is small, however, it is not obvious whether or not this phenomenon is observed, because the cooligomer of low molecular weight cannot be obtained easily since the chain transfer constant of the poly(methyl methacrylate) radical to CCl4 is very small in comparison, with that of the polystyryl radical. This behavior is shown to be attributable mainly to the preferential consumption of styrene monomer in the initiation step, based on the structure of the cooligomer, as inferred from the mechanism of the initiation, transfer, and termination, and the stochastic approach in which the cooligomerization process is regarded as a Markov process.
Polymerizations with homogeneous chromium catalysts
Authors: Zuech E. A
Published: April 2003

Homogeneous catalysts derived from chromium complexes and organo‐aluminum compounds have been discovered which effect the polymerization of ethylene and the oligomerization of simple olefins. The applicable chromium derivatives are halide complexes of the type CrX2L2, CrX2L2(NO)2, CrX3L3, and [CrX3L2]2, wherein the ligands L are pyridine, tri‐n‐butylphosphine, and the like. The nature of the systems with regard to polymerization or oligomerization has been demonstrated to be primarily a function of the organoaluminum halide cocatalyst and of the reaction conditions. In general, systems containing ethylaluminum dichloride cocatalyst afford simple oligomerization products at reaction temperatures above 50°C, while at lower temperatures those containing organoaluminums of the type R3Al2X3 or R2AlX effect the polymerization of ethylene as the principal reaction.
Phonon green's function for polymer chains. I. Treatment of conformational defects
Authors: Hölzl Klaus , Schmid Christhard
Published: April 2003

It is shown that the Green's function (GF) method of Lifshitz can be applied to conformational defects in polymers by taking correctly into account the actual geometrical configuration of the molecules. In contrast with methods currently in use in polymer dynamics, this method is not restricted to the calculation of the density of states, allows the treatment of infinitely long chains, and provides a direct assignment of typical frequencies to certain defect types. Furthermore, arbitrary frequency accuracy can be obtained with computer time drastically reduced from that required by other methods. A short review is given of the computation of experimental quantities which are related to phonons (in harmonic approximation, but in the presence of defects) and which can be obtained from the GF. Expressions are derived for the matrix elements of the harmonic GF of zigzag chains, valid for a general force field. The symmetry of the defects is taken advantages of by introducing symmetry coordinates.
Phonon green's function for polymer chains. II. a semianalytical method for the exact computation of the green's function for regular polymers
Authors: Schmid Christhard , Hölzl Klaus
Published: April 2003

An exact method is presented for calculating the density of states and any complex matrix element of the harmonic phonon Green's function of single polymer chains of infinite length. The method takes advantage of the one dimensionality of the Brillouin zone. In comparison to the standard root sampling method, the method presented here has all the advantages of a fully analytic procedure (in particular, smooth curves instead of histograms) and offers and enormous increase in accuracy while at the same time drastically decreasing the computer time. For illustrational purposes, the method is applied to the defect model of Opaskar and Krimm and to the diatomic linear chain. In addition to the reproduction of the results obtained by Opaskar and Krimm, explicit expressions for the resonance and localized modes are derived.
Crystallization during polymerization of poly‐p‐xylylene
Authors: Kubo Shigeo , Wunderlich Bernhard
Published: April 2003

Crystallization during polymerization of p‐xylylene from the gas phase has been studied between 200 and −196°C. From room temperature to −17°C the polymer crystal morphology changes in that the crystallinity decreases. In this range the process is thought to be of the successive polymerization and crystallization type. The morphology is in agreement with this mechanism, of the folded‐chain β‐polymorph type with proper epitactic orientation of the chains with respect to the support surface. At −78°C an intermediate, poorly crystallized polymer results. At 196°C the reaction is most likely of the simultaneous polymerization and crystallization type. The morphology is, in agreement with the changed mechanism, of a metastable, irregularly folded β‐polymorph type with no orientation of the chains relative to the support surface. No significant changes in molecular weight were observed in the polymers produced between 26 and −196°C.
Kinetics of strain‐induced crystallization of a trans‐polypentenamer
Authors: Kraus Gerard , Gruver J. T.
Published: April 2003

The kinetics of the strain‐induced crystallization of a crosslinked 89% trans‐polypentenamer was studied as a function of temperature and strain by using a combined birefringence—stress relaxation technique. The crystallization rate was found to be extremely sensitive to both variables and was, within experimental error, a function of the degree of undercooling alone, the increase in crystallization rate with strain being a direct consequence of the melting point elevation. From the isothermal, isometric crystallization rates, the development of crystallinity in constant‐rate‐of‐strain experiments was calculated and related to characteristics of the stress‐‐strain curve and of the temperature‐strain rate dependence of tensile strength. These calculations allow one to estimate under what conditions sufficient crystallinity may be expected for the attainment of high strength in absence of reinforcing fillers. Crystallinities measured in this work were of the order of 10% or less. A limited x‐ray diffraction study confirmed the low order of crystallinity indicated by the stress‐birefringence measurements. The relatively high precision of the latter makes this technique attractive for the estimation of small straininduced crystallinities in rubbers.
Determination of the coefficients of selective sorption in polymer solutions in multicomponent solvents from density increments
Authors: Kratochvíl Pavel , Pouchlý Julius , Sedláček Blahoslav
Published: April 2003

The density increment method has been used to measure the selective sorption coefficient of 2,2,3,3‐tetrafluoropropanol (TFP) onto poly(methyl methacrylate) from the solvent mixture benzene‐TFP (80:20 by volume). The results are in good agreement with the data obtained by the established refractive index increment method. The density increment method seems to be a promising tool for the characterization of polymer solutions in multicomponent solvents.
Conformations of branched poly(α‐amino acids) in solution and at the air—water interface
Authors: Williot J. P. , Ruysschaert J. M. , Jaffé J.
Published: April 2003

The validity of Silberberg's hypothesis concerning the conformation of branched polypeptides was tested by studies on solutions and on monolayers. The poly(α‐amino acids) investigated consisted of poly‐L‐lysine backbones with side chains of poly(gamma;‐benzyl L‐gutamate) and poly(β‐benzyl L‐aspartate). In solution, the conformation was studied in the mixed solvent chloroform–dichloroacetic acid. Optical rotatory dispersion measurements demonstrated the existence of a helix–coil transition which is a function of the length of the side chain. A significant “transition curve” appeared between 9 and 15 residues. From the results, it may be assumed that the poly‐L‐lysine backbone is extended in a coiled conformation and the side chains are coiled or helical, depending on the number of glutamate residues. At the air–water interface, a discontinuity in the surface‐pressure curve appears between 9 and 15 residues per side chain. The similarity with the results obtained in solution appears significant; however, this has to be confirmed with methods more specific for structural modifications.
Ionic contribution to the complex dielectric constant of a polymer under dc bias
Authors: Uemura Shinsaku
Published: April 2003

A diffusion equation for the distribution of ionic impurities in a polymer under a dc field has been solved analytically for the conditions that neither injection nor absorption of impurity ions takes place at either electrode and that the ions do not interact. By using the solution of the diffusion equation, an ionic contribution to the complex dielectric constant is calculated. The most important results are as follows. (1) At high temperatures and low frequencies, the dielectric loss factor of the polymer decreases exponentially with the time elapsed after the application of the dc bias. (2) The dielectric constant is not greatly affected by the bias. (3) The ionic contribution to the loss factor in the absence of the dc bias is represented as ϵi″ = 4πνDq2/ωkT, where ν is the density of mobile ions, D the diffusion coefficient, q the charge of an ion, ω the angular frequency, k the Boltzmann constant, and T the absolute temperature. (4) A method is presented for distinguishing between the apparent activation energy for diffusion and that for generation of mobile ions.
Kinetics of the 20°C phase transformation in polytetrafluoroethylene
Authors: Natarajan Raj T. , Davidson Theodore
Published: April 2003

The rate at which PTFE transforms from the triclinic to the hexagonal phase has been measured under isothermal conditions. Samples in a series of decreasing density and crystallinity show increased isothermal rates of transformation. Observed kinetic data are interpreted on the basis of a modified Avrami‐Johnson‐Mehl treatment. A model for the transformation in which planes of helix‐hand reversal propagate through the lattice is shown to fit the experimental results. The transformation rate is observed to be proportional to the total (001) surface area in the polytetrafluoroethylene specimens, suggesting that nucleation of the transformation takes place at grain boundaries.
Some morphological observations on polycaprolactam filament
Authors: Pasika W. M. , West A. C. , Thurston E. L.
Published: April 2003

Examination of longitudinal, cross, and skew sections of extruded polycaprolactam filaments with the polarizing light microscope reveal morphological features not previously described. In cross‐sectional view, three distinct layers enclose a “homogeneous” central matrix. The outermost layer is characterized by large, birefringent, truncated cones extending upward from the surface. Associated with the cones and an entity in its own right is what appears to be a second layer of ultrafibrils. Below the latter is a fine‐structured layer of submicroscopic spherulites. A combination of the above features forms the transcrystalline region of stressed melts. Row nucleation is evident on the surface of the filaments.
Structure of fibers drawn from polyethylene single crystals
Authors: Petermann J. , Gleiter H.
Published: April 2003

Transmission electron microscopy and electron diffraction were used to study the molecular structure of fibers drawn from polyethylene single crystals at 77, 293, and 383°K. The results suggest that the formation of the fibers occurs by a two‐step process. The first step is the breaking off of single blocks of folded chains from the single crystals so that a “string‐of‐pearls” structure is obtained. If the temperature is sufficiently high this process is followed by the thermally activated rearrangement of the molecules in the drawn fibers so that a “bamboo” structure results.
Light‐scattering method for investigation of the kinetics of crystallization of spherulites
Authors: Van Antwerpen F. , Van Krevelen D. W.
Published: April 2003

A description is given of an apparatus for the continuous recording during crystallization of the spherulite radius, in the range of one half micron to a few microns, by scanning the Hv scattering pattern. At the same time the apparatus measures the change in intensity of the transmitted depolarized light, which is a measure of the overall rate of crystallization. The theoretical aspects of this measuring procedure are briefly discussed on the basis of light scattering by perfect and imperfect spherulites.
Fractography of a phenol—formaldehyde polymer
Authors: Nelson B. E. , Turner D. T.
Published: April 2003

Samples of a phenol‐formaldehyde polymer with a deliberately introduced flaw were fractured in tension. The appearance of the fracture surface near the flaw suggested the disruption of particles pre‐existing in the polymer. At a greater distance from the flaw, a featureless surface was observed which was succeeded by one showing interference colors. At still greater distances, linear features were observed to be lying in the direction of crack propagation which, in most areas, were regular and evenly spaced. There were indications that these features were formed by the curling of a surface film. The above observations are interpreted as providing evidence that tensile fracture is accompanied by plastic defórmation at the fracture surface.
The thermal stabilization of poly(vinyl chloride) by allyl xanthate substitution
Authors: Nichols J. Dudley
Published: April 2003

The reaction of PVC with potassium allyl xanthate in DMF is discussed. Thermogravimetric analysis and differential scanning of calorimetry were used to evaluate the thermal stability. The allyl xanthate‐modified PVC (AX‐PVC) was shown to be significantly more thermally stable than the unmodified PVC homopolymer. The AX‐PVC is completely crosslinked at temperatures > 180°C. It was found that dibutyltin di‐2‐ethylhexanoate, a commercial PVC stabilizer, does not produce the same effect on the thermal stability of the AX‐PVC as it did on the unmodified PVC homopolymer.
Ring‐opening polymerizations of cyclic olefins
Authors: Hein Paul R.
Published: April 2003

A ziegler‐type catalyst system consisting of tungsten hexachloride and alkyl or aryl tin compounds was found to polymerize cyclopentene and other cyclic olefins through a ring‐opening mechanism. This catalyst system also polymerized α‐olefins such as ethylene and 1‐octene. An attempt was made to copolymerize cyclopentene and ethylene. Other catalyst systems were also employed for ring‐opening polymerizations with limited success.
Universal calibration in GPC: A new approach for the calculation of molecular weights
Authors: Ambler M. R.
Published: April 2003

A method has been developed for determining simultaneously the molecular weight of a broad‐distribution polymer and the Mark‐Houwink coefficients for that polymer type by using only GPC and intrinsic viscosity data. Standardized samples of poly(vinyl chloride), polystyrene, polybutadiene, and an experimental cycloolefin polymer were analyzed by this method. Shear‐corrected intrinsic viscosities were used in all cases because of the high molecular weights involved. Molecular weight data for all samples were found to be in good agreement with molecular weight data obtained by membrane osmometry and from other GPC techniques. The proposed technique provides a means for calculating the molecular weight of a single polymer sample through universal calibration of GPC without knowledge of the Mark‐Houwink coefficients for that polymer type.
Crosslinked polymers containing adamantane groups
Authors: Burreson B. J. , Levine H. H.
Published: April 2003

Diglycidyl ethers of 1,3‐bis‐(p‐hydroxyphenyl)adamantane (BHPA) and 3,3'‐bis‐(p‐hydroxyphenyl)‐1,1'‐biadamantane (BHPBA) were prepared and condensed with m‐phenylenediamine and methyl tetrahydrophthalic anhydride to give polymers with good high temperature mechanical properties and good oxidative stability. These bisphenols were also condensed with formaldehyde to give phenolic resins containing adamantane moieties.
Stereoregulation in the radical polymerization of vinyl esters
Authors: Nozakura Shun‐Ichi , Sumi Masao , Uoi Michitake , Okamoto Takehiko , Murahashi Shunsuke
Published: April 2003

To determine favorable conditions for preparation of syndiotactic polymers, various factors which influence the stereoregulation of vinyl esters were studied. In bulk polymerizations, vinyl esters having bulky substituents or polar substituents were found most suitable for the syndiotactic polymerization. Tri‐n‐butylborane and azobisisobutylonitrile showed some difference in stereoregulation, the magnitude of the difference being dependent on the type of vinyl ester used. Solvents were found to have a significant effect on stereoregulation. Some gave higher syndiotacticity than bulk and some gave lower syndiotacticity.
Preparation and properties of aromatic poly(amide–benzothiadiazine dioxides)
Authors: Imai Yoshio , Koga Hiroshi
Published: April 2003

New thermostable poly(amide–benzothiadiazine dioxides) of high molecular weights have been prepared by the two‐step cyclopolycondensation of diaminobenzenesulfonamides and aromatic bisacyl chlorides. In the first step, the low‐temperature solution polymerization technique afforded open‐chain polyamides (I) having high molecular weights. In the second step, the polymeric precursors (I) underwent chemical cyclodehydration in the presence of organic basic catalysts at 160°C to give poly(amide–benzothiadiazine dioxides) (II), whereas thermal cyclodehydration gave unsatisfactory results. Not only the open‐chain polymers (I) but also the cyclized polymers (II) were soluble in polar solvents, such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone; tough films were cast from these solutions. Thermogravimetric analyses indicated that the cyclized polymers (II) began to decompose at 450–470°C under nitrogen or in air. It is interesting to note that both polymers I and II exhibited self‐extinguishing properties against free flame. The cyclodehydration of model compounds was also investigated.
Maleimide polymers. I. A polymeric color reaction
Authors: Haas Howard C. , MacDonald Ruby L.
Published: April 2003

Certain copolymers of maleimide and N‐substituted maleimides yield brilliant colors when treated with sufficiently strong basic reagents under nonhydrolytic conditions. For color generation, the copolymer must be capable of HX elimination. The chromophores which account for color probably result from the ionization of acidic protons in structures involving one or more double bonds conjugated with imide carbonyl. The analogy to the color reactions of aconitylanil is pointed out. Spectra covering the range of 330–700 mμ are presented for a number of copolymer–amine color‐generating systems. The colors produced in base with radical‐initiated polymaleimide and imidazole‐initiated poly‐N‐alkylmaleimides as well as the absence of color with anionic polymaleimide and radical poly‐N‐alkylmaleimides are discussed in light of what is known about their polymerization kinetics and mechanisms. Corresponding maleic anhydride copolymer systems are mentioned.