bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR study of molecular motion in oriented long‐chain alkanes. III. Oriented n‐C32H66
Authors: Olf H. G. , Peterlin A.
Published: April 2003

The NMR second moment of a uniaxially oriented mat of single crystals of n‐C32H66 (in the orthorhombic form) was measured at temperatures from −170°C to 70°C and at various alignment angles γ between the orientation axis (preferential direction of the molecular chains) and the NMR magnetic field. Accurate expressions are given for the NMR second moment of an orthorhombic normal paraffin CnH2n+2 of arbitrary molecular chain length n for n ≥ 10, in the following states of molecular motion: no motion (a rigid lattice), rotation of CH3 groups, and rotation of the chains around their axes with superimposed rotation of CH3 groups. In addition to these well‐known motions, n‐C32H66 is found to exhibit an α process. The corresponding decrease of the NMR second moment shows the dependence on γ predicted for “flip‐flop” motion, i.e., rotational jumps of the chain molecules around their axes through 180° and a simultaneous translation along these axes by one CH2 group. The overall decrease in second moment occuring at the transition to the hexagonal rotator phase in n‐C32H66 can be quantitatively accounted for. The dependence of this decrease on the alignment angle γ, however, is in disagreement with calculations based on a simple rotation of the chains around their axes. Considerable torsion of the chains superimposed on the rotation would improve agreement between theory and experiment.
Viscoelastic behavior of polyvinylcyclohexane
Authors: Kelchner R. E. , Aklonis J. J.
Published: April 2003

The tensile stress relaxation master curve for polyvinylcyclohexane (completely hydrogenated polystyrene) has been measured. Direct relaxation experiments were carried out at several temperatures above the glass transition temperature over the rather long time range of four orders of magnitude. This long time span was realized by calculating the modulus during the period when a constant small strain rate was applied to the sample as well as during the usual constant strain interval. A computer solution to the Boltzmann superposition equation allowed data from these two regions to be joined into a smooth curve representing E(t), a parameter indicative of an instantaneous strain experiment. The measured Ti was found to be 143°C; Tg is expected to fall within several degrees of this temperature. This result is apparently at odds with a previously reported Tg value of 120°C. More importantly, the maximum value of the negative slope of the stress relaxation master curve of polyvinylcyclohexane in the primary transition region was only slightly different from that for polystyrene. This observation clearly indicates that the molecular factors which result in the highly coupled nature of the primary transition in polystyrene are not strongly dependent upon any side‐chain π–π interactions which might be present in polystyrene.
Determination of thermodynamic parameters of polymer–solvent systems from sedimentation–diffusion equilibrium in the ultracentrifuge
Authors: Scholte Th. G.
Published: April 2003

Sedimentation equilibrium in the ultracentrifuge means that there is such a distribution of molecular species throughout the cell, that the centrifugal forces are balanced by differences in the activities. This provides a method for determination of the activities and the chemical potentials in polymer solutions which, in principle, is very simple and reliable. A complication is caused by polydispersity of the dissolved polymer. If one assumes that the interaction parameter depends on concentration and temperature, but not on molecular weight, it is possible to determine the chemical potential of polymer and solvent from the ultracentrifugal data. Experiments have been carried out on the systems polystyrene–toluene and polystyrene–cyclohexane at different temperatures and in the concentration range 0–80 wt‐%. The results are expressed in the data for the chemical potential of the solvent, the number average chemical potential of the polymer and the interaction parameter χ.
Unperturbed dimensions of poly(2‐methyl‐6‐phenyl‐1,4‐phenylene oxide) and poly(2,6‐diphenyl‐1,4‐phenylene oxide) chains
Authors: Shultz A. R.
Published: April 2003

The unperturbed chain dimensions of unfractionated poly(2‐methyl‐6‐phenyl‐1,4‐phenylene oxide) and poly‐(2,6‐diphenyl‐1,4‐phenylene oxide) have been measured by combining molecular weight data from light scattering with intrinsic viscosity data in chloroform. The unperturbed chain dimensions of the former polymer were also measured directly by light scattering dissymmetry in a critical consolute solvent mixture (methyl cyclohexane: 1,4‐dioxane 50:50 by volume). The results of these measurements and of measurements reported by other investigators are satisfactorily explained by postulating no dimension‐expanding prejudice in azimuthal angle in chain conformers of the 2,6‐substituted‐1,4‐phenylene oxide polymers. This corresponds to equal population of the two chain rotation energy minima at azimuthal angles 90° and 270°. Accepting this postulate, one calculates from the observed chain dimensions that the COC bond angle is 118–120° in these aromatic polyethers in solution.
Yield condition and propagation of Lüders' lines in tension–torsion experiments on poly(vinyl chloride)
Authors: Bauwens J. C.
Published: April 2003

We have derived from the Eyring theory of non‐Newtonian flow a yield condition which is valid for an arbitrary state of stress. Experimental data obtained in simple axial compression tests show the influence of the hydrostatic stress on the yielding of poly(vinyl chloride). This fact confirms the proposed condition and disproves the von Mises criterion. Tension–torsion tests performed on thin tubes lead to results which fit our condition fairly well. The pattern of Lüders' lines appearing on the surface of thin tubes subjected to simple tension, simple shear, and tension–torsion are parallel to the direction where the value of the normal stress is equal to the hydrostatic stress.
Wide‐line proton magnetic resonance spectra of some celluloses
Authors: Pittman Robert A. , Tripp Verne W.
Published: April 2003

Characteristic wide‐line proton magnetic resonance absorption spectra of a number of representative cellulose preparations have been obtained in the dry state and after addition of about 7% water. Line widths, second moments, spin‐spin and spin‐lattice relaxation times have been determined. The second moment of the absorption curve of dry cellulose was found to correlate well with the crystalline fraction for most specimens. A technique is described for determining the number of water‐cellulose protons exchanging relative to the number of cellulose protons not exchanging. The reduction in absorption line width observed when water is added to cellulose is shown to be quantitatively consistent with such a proton exchange phenomenon.
Measurements of the relaxation spectra of unplasticized poly(vinyl chloride) melts
Authors: Horsma D. A.
Published: April 2003

We have measured the relaxation modulus in the temperature range 150–220°C of two samples of poly(vinyl chloride) resin with different molecular weights. The data were treated by the principle of reduced variables to yield composite curves. The shift factors (aT) when plotted against reciprocal temperature gave good straight lines from which apparent activation energies were obtained. An apparent activation energy of 50 kcal/mole was obtained for both samples. A relaxation spectrum for each resin was calculated from the relaxation modulus data. These spectra showed a marked molecular weight dependence. The spectra were in the range characteristic of the terminal zone of the entanglement plateau. Zero‐shear‐rate viscosities were obtained from the integration of relaxation modulus plots. From extrapolation of capillary viscosity data it is shown that the viscosity of the higher molecular weight resin used in this study does not approach its zero‐shear value until shear rates less than 10−3 sec−1 are reached. The effect of supermolecular flow units is briefly discussed.
Diffusion of radioactively tagged 1,1‐diphenylethane and n‐hexadecane through rubbery polymers: Dependence on temperature and dilution with solvent
Authors: Wong Chiu‐Ping , Schrag John L. , Ferry John D.
Published: April 2003

The diffusion of 1,1‐diphenylethane in trace amounts through eight rubbery polymers has been studied by radioactive tagging of this penetrant with 14C. For several polymers, the dependence on temperature and on dilution (swelling) by untagged diphenylethane was investigated. In the diluted systems, tagged n‐hexadecane was also used as a trace penetrant. The temperature and concentration dependences were interpreted rather successfully in terms of the free volume. In comparing different polymers, with a 4000‐fold range of diffusion coefficients, the translatory friction coefficient of 1,1‐diphenylethane was found to be proportional to that of n‐hexadecane to the power 1.06. This is interpreted qualitatively by the free volume concept to indicate a slightly less efficient mobility mechanism for the diphenylethane.
On the determination of molecular weight distributions from sedimentation–diffusion equilibrium data at a single rotor speed
Authors: Lee D. A.
Published: April 2003

The problem of inferring molecular weight distributions from concentration gradient data taken at sedimentation‐diffusion equilibrium for a single rotor speed is ill posed: significantly different distributions correspond to concentration gradients which differ so slightly that they cannot be distinguished by the experiment. It is this intrinsic property of the problem which accounts for the lack of success of the several schemes proposed for its solution. Integral equation theory is applied to show explicitly just what can be inferred with bounded error. Several methods for recovering this information are discussed and applied to example problems.
Comonomer and stereosequence distributions in high polymers
Authors: Pyun Chong Wha
Published: April 2003

Comonomer and stereosequence distributions in linear high polymers are considered from the point of view of the general theory of stationary random sequences. Although the discussion is centered about binary polymerizations which may be regarded as stationary Markov processes of low order, attention is paid to distinguish results valid for any stationary random process including stationary non‐Markov processes from those special to a particular Markov process. Alternative derivations of copolymer composition equations are given along with a corrected version of a previously suggested scheme of relating conditional probabilities of different orders. The nature and relative merits of the several measures proposed in the literature to characterize comonomer and stereosequence distributions are also discussed in some detail.
Dynamic mechanical relaxation effects in some poly(arylene sulfones)
Authors: Kurz James E. , Woodbrey James C. , Ohta Masao
Published: April 2003

Poly‐4,4′‐oxydiphenylenesulfonyl and poly‐4,4′‐methylenediphenylenesulfonyl were synthesized by an electrophilic substitution polymerization of the arylene monosulfonyl chloride monomers. The glass‐transition temperatures Tg of these polymers were determined by calorimetric and dynamic mechanical measurements, and the number‐average molecular weights were determined by vapor‐pressure osmometry. Both polymers were found to have the same Tg at equivalent molecular weight; the limiting value at high molecular weight is 238°C. Both polymers have two dynamic mechanical relaxation peaks at temperatures far below Tg. One is in the neighborhood of 0°C, and the other is at −110°C. Plausible origins for these relaxations, and the absence of any near 0°C in poly(4,4′‐isopropylidenediphenylene‐co‐4,4′‐sulfonyldiphenylene dioxide), are discussed.
Polymer characterization by coupling gel‐permeation chromatography and automatic viscometry
Authors: Goedhart D. , Opschoor A.
Published: April 2003

A method is proposed for use of the universal calibration curve, i.e., the product of molecular weight and intrinsic viscosity versus retention volume, in calculating the molecular weight distribution of a polymer from gel‐permeation chromatography (GPC) when the Mark‐Houwink relation of the polymer in the solvent used for the GPC is unknown. This is achieved by measuring the viscosity of each fraction with an automatic capillary tube viscometer. Application of this technique to poly(vinyl chloride) and poly(vinyl acetate) proved to be successful.
Viscoelastic behavior of an amorphous polymer under oscillations of large amplitude
Authors: Vinogradov G. V. , Yanovsky Yu. , Isayev A. I.
Published: April 2003

The influence of periodic shear deformation and steady flow on a typical amorphous polymer is discussed. Forced sinusoidal vibrations were applied and the complex viscosity was determined. The action of a vibration of finite amplitude is equivalent to steady flow with a definite finite shear rate. Both processes cause truncation of the long‐time part of the relaxation specturm. It may be accepted to a first approximation that the long‐time boundary of the remaining part of the relaxation spectrum conforms to the long‐time part of the initial spectrum, even if the plateau region of the spectrum is truncated. The concept of limiting truncation of the short‐time part of the spectrum is introduced, this corresponding to the minimum absolute value of the complex viscosity versus reduced frequency and the lowest values of the dynamic and apparent viscosities. With an approximate representation of the relaxation spectrum, calculations were made of the maximum values of the viscosity and the coefficient relating the first difference of normal stresses to the square of the shear rate, and also of the apparent viscosity and normal stresses as functions of the shear rate. The calculated values are compared with experimental measurements, and it is shown that the correlation of the apparent viscosity and the absolute value of the complex viscosity is distributed at high frequencies, being superseded by a correlation between the apparent and dynamic viscosities.
Determination of polymer branching with gel‐permeation chromatography. II. Experimental results for polyethylene
Authors: Drott E. E. , Mendelson R. A.
Published: April 2003

The recently developed methods of characterizing branching in polymers from gelpermeation chromatography and intrinsic viscosity data are verified experimentally. An iterative computer program was written to calculate the degree of branching in whole polymers. Long‐chain branching in several low‐density polyethylene samples was determined by both the fraction and whole polymer methods. The two methods gave consistent ranking of the branching in the samples although absolute branching indices differed. Effects of various experimental errors and the particular model used for branching were investigated. For polyethylene, the data show that the effect of branching on intrinsic viscosity is best described by the relation 〈g3〉W1/2 = [η]br/[η]1 where 〈g3〉w is the weight‐average ratio of mean‐square molecular radii of gyration of linear and trifunctionally branched polymers of the same weight‐average molecular weight.
Heats and entropies of fusion of linear aliphatic polyesters. I. Experimental determinations
Authors: Hobbs Stanley Y. , Billmeyer Fred W.
Published: April 2003

Poly(ethylene adipate), poly(ethylene suberate), and poly(ethylene sebacate) were synthesized by a modified ester interchange procedure. Polydispersity was reduced and low molecular weight material removed by fractional crystallization. Samples of 50–60% crystallinity were prepared by bulk crystallization and annealing. Melting points and amorphous densities were obtained by dilatometry. Melting points were 7–12°C higher than previously reported. Heats of fusion were measured by differential scanning calorimetry and extrapolated to 100% crystallinity by using measured amorphous densities and recently redetermined crystalline densities. Entropies of fusion were calculated and separated for the first time into volume expansion and conformational contributions.
Heats and entropies of fusion of linear aliphatic polyesters. II. Molecular origins
Authors: Hobbs Stanley Y. , Billmeyer Fred W.
Published: April 2003

The conformational contribution to the entropy of fusion was calculated for poly(ethylene adipate), poly(ethylene suberate), and poly(ethylene sebacate) from consideration of rotational potentials and steric interactions in model systems. An enumeration scheme similar to that applied to polyethylene was used. Comparison of the observed and calculated conformational entropies indicated the importance of a high‐energy chain twist in the crystalline polyesters in reducing their measured conformational entropies. The rigidity of the polyester chains in the melt is discussed in comparison to polyethylene. The contribution of the polar ester groups to the heats of fusion of the polyesters is evaluated semiempirically.
Thickness of the interphase layer determined from volume changes produced by mutual diffusion in binary microheterogeneous polymer mixtures
Authors: Letz Ján
Published: April 2003

The mutual diffusion of pairs of polymers has been studied at 160°C for two systems: isotactic polypropylene with polyethylene and poly(vinyl chloride) with polyethylene. From the assumption that Fick's law is valid and with a rhombohedral lattice model for the microheterogeneous system, it was possible to obtain from volume changes the thickness of the interphase layer after various diffusion times. It was found that the values so calculated differ considerably from the experimental values, the greatest deviations occuring after 20 min diffusion. From this it follows that non‐Fickian diffusion strongly influences the distribution of concentrations in the diffuse interface, and thus affects the calculated value of the interphase layer thickness. For both polymer pairs Fickian behavior was confirmed for up to about 10 min diffusion time, in good agreement with experimental data.
Size distribution analysis of polymer latex systems by use of extrema in the angular scattering intensity
Authors: Wallace Thomas P. , Kratohvil Josip P.
Published: April 2003

The angular position of the extrema of the vertically polarized scattering intensity has previously been utilized for a method of particle size analysis for systems of monodisperse, spherical, isotropic particles which conform to the Rayleigh‐Gans‐Debye theory. The consequences of a finite polydispersity, which is always present in real systems, was not assessed and the application of the method has resulted in erroneous characterization of some latex systems. This work is concerned with (1) reporting the effects of finite polydispersity on the method of analysis, (2) pointing out previous misuse of the method, and (3) introducing a method of analysis which is based on the position of the extrema but which also considers polydispersity and the exact Mie calculation. This method enables one to characterize a scattering system in terms of a modal diameter and a distribution‐width parameter by utilizing prepared diagrams for a particular relative refractive index.
Self‐seeded crystallization and its potential for molecular weight characterization. I. Experiments on broad distributions
Authors: Keller A. , Willmouth F. M.
Published: April 2003

The effect of varying molecular weight distribution on the self‐seeding phenomenon was investigated by using high molecular weight polyethylene fractions prepared by the stirring‐induced crystallization method of Pennings. The numbers of self‐seeding nuclei per gram were determined by measuring crystal dimensions, and were found to increase with increasing molecular weight of the polymer, in accord with previous findings. In another experiment, self‐seeded single crystals were grown from materials of various molecular weights, prepared by blending two samples of differing molecular weight in various proportions. The concentration of nuclei varies linearly with the weight fraction of high molecular weight polymer in the mixture. This result is shown to be consistent with the proposition that each nucleus contains on the average an identical number (most plausibly one) of molecules of very high molecular weight. The application of this finding to the determination of molecular weights is discussed, and it is shown that the technique provides a method of unprecedented sensitivity for the characterization of the very high end of the molecular weight spectrum. Some morphological results are also presented. In particular, direct observations of the nuclei were found to be consistent with the loosely connected multiple nucleus structure, which had been proposed previously to account for certain light‐scattering results.
Surface crystallization of polypropylene
Authors: Fitchmun D. R. , Newman S.
Published: April 2003

Crystallization of compression‐molded isotactic polypropylene and polyethylene is invariably spherulitic; generally, nucleation occurs randomly throughout the sample. In a special case where nucleation predominates at the surface, spherulitic growth centers become crowded and are forced to propagate unidirectionally into the bulk (transcrystallinity). Conditions for the formation of transcrystallinity have been investigated by optical and scanning electron microscopy. The occurrence of transcrystallinity is attributed to heterogeneous nucleation induced at the mold surface. To be effective, the mold surface must have a nucleating efficiency equal to or greater than that of adventitious nuclei present in the polymer. As the crystallization temperature approaches the melting point, the activity of mold surfaces is found to increase leading invariably to transcrystalline formation. The degree of activity of various mold surfaces correlates with the known activity of specific dispersed nucleating agents having similar chemical structures. Contrary to claims in the literature, the surface energy of the mold surface and temperature gradients across the melt surface do not play a primary role in transcrystalline formation of polypropylene.
Polymerization of monolayers. V. Tacticity of the insertion poly(methyl methacrylate)
Authors: Blumstein Alexandre , Malhotra Shadi. L. , Watterson Arthur C.
Published: April 2003

Insertion poly(methyl methacrylate) (PMMA) formed within a monolayer of monomer adsorbed on montmorillonite was studied by means of NMR spectroscopy and shown to be composed of short stereosequences with a predominant isotactic component. The stereospecificity of the insertion PMMA can be understood in terms of the organization of the monomer adsorbed on the surface of the mineral. The monolayer of monomer is assumed to be composed of monads and isotactic diads due to dipole‐ion interactions between the molecules of methyl methacrylate and exchangeable cations. Results of experiments relating factors such as temperature, density of ion population of the surface, and the nature of ions are discussed. It is shown that the populations of isotactic and syndiotactic triads Pi and Ps determined experimentally in the insertion PMMA are in a reasonable agreement with values calculated from the model. It is shown, furthermore, that Pi increases with increase in the density of the ion population, in agreement with the equations derived from the model.
Effect of pressure on dissociation of poly(methacrylic acid) in aqueous solution
Authors: Suzuki Keizo , Taniguchi Yoshihiro
Published: April 2003

The effect of pressure (up to 6300 atm) on the electrical conductivity of poly(methacrylic acid) (PMA) in aqueous solution was investigated in the concentration range 0.001M to 0.1M (in equivalents of carboxyl groups) at 30°C. The degree of ionization α calculated from the conductivity data increased linearly with pressure. From dilatometric measurements of volume changes when PMA was partially neutralized with NaOH, a conformational transition was confirmed to take place above α = 0.12, and the volume change accompanying the dissociation of the side chain groups (carboxyl groups) was found to be − 12.5 ml/H+. It may be inferred from the values of α at each polymer concentration and from the dilatometric data that there is no conformational transition from a compact structure to the coiled form below at least 6,000 atm in the absence of Na+ counterions.
Crystallization of isotactic polystyrene from solution
Authors: Keith H. D. , Vadimsky R. G. , Padden F. J.
Published: April 2003

Difficulties previously encountered in the growth of chain‐folded single crystals of isotactic polystyrene suitable for study by electron microscopy and electron diffraction have been overcome using very poor solvents (including atactic polystyrene of low molecular weight). The hexagonal lamellar crystals produced are relatively stable under electron bombardment and, as a consequence, dark‐field moiré patterns produced by double diffraction from overlapping layers are easy to study. These patterns show no evidence of differences in lattice spacing between fold and nonfold planes such as have been reported in single crystals of several other polymers. Such differences were attributed to congestion at fold surfaces and their absence in polystyrene, for which the surface energy of fold surfaces is small, supports this interpretation. A comparison of crystallization kinetics of polystyrene crystals grown from good and from poor solvents reveals differences in growth rates of three or more orders of magnitude at comparable supercoolings. This disparity cannot be accounted for by acceptable adjustments of thermodynamic parameters in current theories of crystallization with chain folding. The role of molecular conformation in solution appears to exert an unexpectedly large influence on crystallization rate.
The polymeric nature of selenium crystallization. I. Morphology and thermodynamic considerations
Authors: Crystal Richard G.
Published: April 2003

The morphology of selenium has been studied in light of present concepts of crystallinity in crystalline organic polymers. Spherulitic crystallization and resultant morphology were examined as a function of temperature by transmission and replication electron microscopy, electron diffraction, and optical microscopy. Evidence is given for polymer chain folding during crystallization of trigonal selenium. Theoretical thermodynamic calculations presented yield several thermodynamic values including an equilibrium melting point of 219.2°C, a fold surface energy of 337 ergs/cm2 and a lateral surface energy of 9.8 ergs/cm2.
Melting behavior of drawn films from polyethylene single‐crystal mats
Authors: Maeda Masahiko , Miyasaka Keizo , Ishikawa Kinzo
Published: April 2003

Drawing of mats of linear polyethylene single crystals prepared from dilute solution is possible at temperatures above about 90°C. The structure and properties of the drawn specimens are much different from those ordinary drawn bulk polymer. Drawn mats have been investigated by differential scanning calorimetry. The characteristic experimental results are: (a) a broad melting curve, (b) considerable superheating depending on the rate of heating, (c) constancy of the melting point and the heat of fusion with annealing, (d) deviation from the relation between the heat of fusion and the density obtained for the drawn bulk specimens, (e) appearance of two melting peaks in samples annealed at temperatures above about 130°C. These results imply that the structure of the drawn mat is characterized by a larger number of the tie chains connecting the neighboring crystals (the structure postulated in earlier papers) than is the case in ordinary drawn bulk polymer. It can be concluded that the transformation of a fringed micellar type of structure to the folded lamellar structure may be difficult during annealing unless crystals melt and then recrystallize during cooling.
Viscoelastic properties of blends of “entangled” polymers
Authors: Prest W. M.
Published: April 2003

The effect of molecular weight distribution on the viscoelastic properties of “entangled” polymers has been examined with blends of narrowly distributed polystyrene and broadly distributed polydimethylsiloxane. It is shown that blending laws established for nonentangled polymers do not apply to high molecular weight systems. The steady‐state shear compliance of a blend is examined as a function of its molecular weight and the molecular weight of its components, and an approximation is given for the longtime viscoelastic response of entangled blends.
Thermal history and melting behavior of poly(ethylene terephthalate)
Authors: Nealy D. L. , Davis T. G. , Kibler C. J.
Published: April 2003

Low molecular weight poly(ethylene terephthalate) samples were crystallized isothermally at 120–245°C from both the amorphous state and the melt. Isothermal annealing of these polymers at 215°C provided polymers which exhibited multiple melting peaks in thermal analysis, referred to as form I and form II, as assigned by Bell and Dumbleton. In these samples the peak temperature of the form II melting endotherm and the average crystallite size are dependent on the temperature of initial crystallization. This result requires a mechanism for retaining some structural feature during the conversion from morphological form I to form II. DSC thermograms obtained at varying heating rates on samples showing only form II endotherms support the assignment of superheating as the cause of the shift to higher peak temperatures with increasing heating rate.
Alternating copolymerization of carbonyl sulfide with aziridines
Authors: Yokota Hisao , Kondo Masatsune
Published: April 2003

The copolymerization of carbonyl sulfide with aziridines such as ethylenimine, propylenimine, and N‐ethylethylenimine was studied in various organic solvents. The copolymerizations occurred easily without the addition of any catalyst and gave white powdery crystalline copolymers. The copolymers produced were insoluble in many organic solvents, but soluble in p‐chlorophenol and dimethyl sulfoxide. The elementary analyses and the infrared spectra showed that alternating copolymers which have a thiourethane structure were produced. In the copolymerization of carbonyl sulfide with ethylenimine, both the polymer yield and the molecular weight of the resulting polymer increased with the use of a solvent having a higher dielectric constant, and also with an increase in the ratio of carbonyl sulfide to imine in the feed. The rate of copolymerization of carbonyl sulfide with aziridines was in the order of ethylenimine > propylenimine > and N‐ethylethylenimine. Irradiation of the copolymers improved their thermal properties and increased their melting point.
Polymers containing polyhedral borane rings I. Condensation polymers
Authors: Schaefgen J. R. , Miller H. C. , Sauer J. C. , Sharkey W. H.
Published: April 2003

The preparation and properties of a unique new class of polymers containing polyhedral borane cages as part of the backbone polymer chain are described. The synthesis of polyamides, polyesters, polyureas, and polyurethanes proceeds from suitably chosen B10 and B12 polyhedral borane dicarbonyls, diols, and diisocyanates by typical condensation polymer techniques. Each complementary monomer may be a borane compound, but more often higher molecular weight products are provided when one monomer is a conventional organic reagent such as an aromatic diisocyanate. The polyamides prepared from 1, 12‐B12H10(CO)2 and organic diamines were crystalline and soluble, but molecular weight were limited because the amidation reaction was reversible and/or the amide linkage could be split by nucleophilic attack by some solvents. The polyurethanes prepared from Na2B12H10(OH)2 and aromatic diisocyanates were high molecular weight and relatively more stable. Clear, colorless, tough films were prepared. These polymers were soluble in many polar solvents and exhibited typical polyelectrolyte behavior.
Influence of free and copolymerized triplet quenchers on the photolysis of poly(vinyl phenyl ketone) in solution
Authors: Lukáč Ivan , Hrdlovič Pavol , Maňásek Zdeněk , Belluš Daniel
Published: April 2003

The influence of free, diffusion‐control quenchers of triplets (naphthalene, biphenyl, 2,5‐dimethyl‐2,4‐hexadiene) on the photolysis of poly(vinyl phenyl ketone) in benzene solution has been investigated. The Stern‐Volmer plots for quenching of main‐chain scission were linear, and the quenching constants were independent of the macroviscosity of the solutions. Copolymers of vinyl phenyl ketone with 1‐vinylnaphthalene and 2‐vinylnaphthalene containing as much as 10% (by weight) vinylnaphthalene were prepared. The photolysis of the copolymers was compared with the photolysis of poly(vinyl phenyl ketone) in the presence of free naphthalene. It was found that the quenching efficiency of found naphthalene units was about 21 times higher. The possibility of migration of the absorbed energy along the polymer chain is discussed. The relation between average‐number molecular weight Mn and intrinsic viscosity [η] has been determined osmometrically. For unfractionated poly(vinyl phenyl ketone) in benzene at 30°C, the relation [η] = 2.82 × 10−5 Mn0.84 has been found.
Effects of pulses of current on the cationic electropolymerization of isobutylvinylether
Authors: Funt B. L. , Blain T. J.
Published: April 2003

The cationic electropolymerization of isobutyl vinyl ether was induced and controlled by sequences of pulses of current of various lengths and of similar or opposite polarity. A remarkable degree of control over the rate of the reaction was demonstrated for a system that is subject to “flash” polymerization by conventional chemical initiators. The mechanism is shown definitively not to correspond to the electric field effects proposed by Tanaka, Ise and Sakurada as applicable to all such electropolymerizations.
Cationic polymerization of 1‐ethoxy‐1,3‐butadiene
Authors: Fueno T. , Tsunetsugu T. , Arimoto K. , Furukawa J.
Published: April 2003

cis‐ and trans‐1‐Ethoxy‐1,3‐butadienes were polymerized by a variety of cationic agents in various solvents at −78°C. The trans ether, which is the more stable isomer, was found to have greater polymerizability than the cis ether. The trans monomer gave polymers predominantly of the trans‐1,4 type, whereas the cis monomer showed a tendency toward the formation of polymers having the microstructure of the 1,2 type. It was concluded that, in the cis ether, the carbon atom which is the most vulnerable to the attack of carbonium ions is the one at the 2‐position, whereas, in the case of the trans isomer, the terminal 4‐carbon is the most reactive center. The conclusion was confirmed from the results of acetal addition reaction catalyzed by boron trifluoride etherate. The marked contrast in the mode of reaction of the two isomeric ethers toward carbonium ions was interpreted in terms of the difference in the degree of bonding in the transition state.
Cationic copolymerization of tetrahydrofuran with epoxides. I. Polymerization mechanism in the presence of a glycol
Authors: Hammond J. M. , Hooper J. F. , Robertson W. G. P.
Published: April 2003

Polymerization of several epoxides and their copolymerization with tetrahydrofuran have been studied. The polymerizations were carried out by use of BF3·O(C2H5)2 as catalyst in the presence of 1,4‐butanediol. Variations of catalyst and 1,4‐butanediol ratio and concentration affect polymerization rate, molecular weight, and the formation of cyclic oligomers. The latter is also influenced by monomer fed ratio in the case of the copolymerizations. These effects are discussed, and some observations are made concerning the mechanism, particularly with respect to the role of the 1,4‐butanediol. Mayo‐Lewis monomer reactivity ratios were determined. The ratios found differed from previously published figures.
Syntheses and properties of photochromic polymers of the mercury thiocarbazonate series
Authors: Kamogawa Hiroyoshi
Published: April 2003

Photochromic vinyl polymers of the mercuric thiocarbazonate series were synthesized via the three sequences: (1) synthesis of p‐(meth)acrylamidophenyl mercuric acetate(II) by the reaction of (meth)acrylyl chloride with p‐aminophenyl mercuric acetate, followed by polymerization to afford corresponding polymers(III) and subsequent reaction with diphenyl‐ or di‐β‐naphthyl‐thiocarbazone, (2) alternative preparation of III by the reaction of (meth)acrylyl chloride polymers with p‐aminophenyl mercuric acetate, and (3) reaction of N‐hydroxymethyl (meth)acrylamide polymers with p‐amidophenyl mercuric thiocarbazonates. The photochromic behavior of these polymers was investigated to provide data which might indicate the effect of steric conditions on the isomerization of the photochromic components in polymers both under illumination and in dark recovery.
Reduction of composite NMR spectra by using an analog computer
Authors: Mochel V. D. , Claxton W. E.
Published: April 2003

An analog computer program has been devised to resolve complex composite curves such as might be encountered in various forms of spectroscopy or chromatography. Seven Gaussian or Lorentzian curves, or any combination of seven curves, can be used and displayed simultaneously to resolve the composite curves. Various degrees of skew and truncation, as well as slanted and curved baselines, can be introduced. The peak amplitude, width and position can be determined from potentiometer settings. The integrated relative area of each of the peaks is read out on a digital voltmeter with a reproducibility of about ±0.1%. The utility of the technique is demonstrated by resolving highly overlapped peaks in NMR spectra of butadiene–styrene copolymers. It is necessary to use as many as eight curves to resolve the styrene aromatic proton resonance. This analysis yields styrene‐centered distributions and styrene sequence distributions from the NMR spectra of butadiene–styrene copolymers. In addition, it is shown that a distinction can be made between short styrene sequences, which contain two and three styrene units, and long styrene sequences, which include all sequences longer than three units.
Sequence distribution of poly(ether)urethane elastomer
Authors: Suzuki Hajime
Published: April 2003

Poly(ether)urethane elastomers (PEUE) having different sequence distributions can be synthesized by the reaction of p‐phenylene diisocyanate, poly(oxytetramethylene glycol), and hydrazine by four different routes. The degree of the sequence distribution of PEUE was determined by high‐resolution NMR spectroscopy. The sequence distribution of PEUE synthesized by the prepolymer method in solvent (method 1) was found to coincide with the sequence distribution calculated from the reactivity ratio of two isocyanate groups in p‐phenylene diisocyanate. On the other hand, the sequence distribution of PEUE obtained by the prepolymer method without solvent (method 2) was found to deviate from that expected from the reactivity ratio. The degree of the distribution of monomers in PEUE having the same composition ratio corresponded to the infrared absorbance ratio at 1720 and 1700 cm−1.
Some studies on a polymer from urea
Authors: Bandyopadhyay Pranab C. , Das Asoke K.
Published: April 2003

A polymer having the structure of guanidinopolyhydroxynitrile has been produced by heating an equimolar mixture of urea and anhydrous ZnCl2 in nitrogen at 300°C and 27 atm. The structure has been established from elemental analysis, percentage of nitrogen as primary amine, and ultraviolet and infrared spectra of the polymer and its derivatives. A mechanism of the polymerization based on some experimental evidence has been suggested. Its physical properties have been attributed to its skeletal structure and ring closure by hydrogen bonding. Thermograms reveal that it is stable to 150°C, after which it decomposes slowly till a 75% weight residue is obtained at 575°C with a constant weight plateau extended to 680°C. In acid solvents, protonation occurs at the NH2 group or the azomethine nitrogen atoms, producing polycations. The polyelectrolytic character in acids has been confirmed by viscometric and osmotic studies and the molecules tend to be both coiled up and associated in solutions. [n] in anhydrous formic acid is 0.3636 dl/g. The molecular weights of the polymer and its various fractions range between 39,500 and 25,900. Dielectric constants, dielectric losses, and conductivities of the polymer have also been measured as functions of frequency and temperature and it has been proved that the dispersion is due to dipole polarization. The average energy of the dipole is 1.73 × 10−2 eV/°K, the intrinsic activation energy for conduction is 0.186 eV, the conductivities being of the order of 2 × 10−6 to 7 × 10−7 mho‐cm−1. The polymer is therefore a semiconductor. The number of charge carriers is 2.12 × 1016/cm2, which agrees reasonably well with the value, 6.66 × 1016, obtained from spin‐density calculations from ESR signals.
Chemorheological treatment of crosslinked EPT
Authors: Murakami Kenkichi , Tamura Saburo
Published: April 2003

Stress relaxation mechanisms were investigated on three types of (EPT) ethylene–propylene terpolymers in air at 109°C. These polymers differe only by the structure of the crosslinkage in which there is a carbon–carbon bond, a polysulfide linkage (S◯) or a monosulfide linkage (S). All the stress relaxation of peroxide‐cured EPT polymer was not due to the oxygen‐induced cleavage of the main chain but to a physical flow. In the case of sulfur‐cured EPT polymer, the relaxation curve is divided into three straight lines when the procedure X is used and log f(t)/f(0) is plotted linearly with time. It was concluded that this graph was in agreement with an interchange reaction of the polysulfide linkage by an oxidative cleavage of the monosulfide linkage. On the other hand, a TT‐cured EPT polymer gave a plot with a straight line. This stress relaxation could be explained by an oxidative cleavage of the monosulfide linkage.
Radiation‐induced polymerization of tetraoxane in the solid state
Authors: Nakase Yoshiaki , Yoshida Masaru , Ito Akihiko , Hayashi Koichiro
Published: April 2003

The radiation‐induced polymerization of tetraoxane in the solid state has been investigated in air and in vacuo. The polymerization rate was higher in air than in vacuo, whereas the molecular weight of the polymer obtained at high conversion in air was considerably lower than in vacuo. A large decrease in the molecular weight with increasing polymer yield observed in air may be explained mainly by degradation during polymerization.
Polymerization of propylene by the three‐component system comprising titanium(III) chloride, ethylaluminum sesquichloride, and sodium sulfate
Authors: Matsumura Kiichiro , Atarashi Yuji , Fukumoto Osamu
Published: April 2003

Sodium sulfate increases the polymerization activity of the titanium(III) chloride (AA)–ethylaluminum sesquichloride system for the polymerization of propylene. The reaction of ethylaluminum sesquichloride with sodium sulfate at mild conditions isolates diethylaluminum chloride, which is responsible for the polymerization activity. The reaction of these components at severe conditions forms an organometallic compound containing sulfate, (C2H5)4Al2SO4, and this compound is a powerful activator for titanium(III) chloride.
Polymerization of asymmetric polyfunctional monomers. III. Ionic polymerization of acrylic and methacrylic esters of 2‐allylphenol
Authors: Solomon O. F. , Corciovei M. , Gabe I. , Beral E.
Published: April 2003

The polymerization of acrylic and methacrylic esters of 2‐allyphenol with different anionic, cationic and coordination catalysts was studied. The polymerization occurs exclusively or predominantly through (meth)acrylic CC double bonds in all the studied cases. With anionic catalysts the allylic groups are not polymerizable and the polymers have linear structure. Polymerization with catalysts based on dialkylaluminum chloride (alone or associated with some metal salts) yields soluble or partially crosslinked polymers, depending on the reaction conditions. The crosslinking is due to the participation of allylic groups in the polymerization reactions. Copolymers of acrylic and methacrylic esters of 2‐allylphenol with styrene, acrylonitrile, methyl methacrylate, N‐vinylcarbazole and 1,3‐pentadiene were synthesized by copolymerization in the presence of anionic catalysts and of systems based on dialkylaluminum chloride.
Collision between polymeric radicals for termination rate constants
Authors: Ito Katsukiyo
Published: April 2003

The motion of each polymeric radical during a collision between the polymeric radicals with the same radius is treated as completely random motion. The result obtained is: kt = 0.250ks (where kt is the chain‐termination rate constant and ks is the reaction rate constant between radical chain ends). On taking the motion of the primary radical during a collision between a primary radical and a large polymeric radical to be completely random, the result obtained is: kti = 0.250ksi (where kti is the primary radical termination rate constant and ksi is the reaction rate constant between primary radical and radical chain end). On substituting ks for ksi in the second equation, the rate constant obtained becomes the chain termination rate constant between the very small polymeric radical and the very large polymeric radical, and identical to the former equation. This identity indicates that the effect of the difference of the size of the polymeric radicals on the collision process relating to the chain termination rate constant should not be large.
Solid‐state polymerization of acrylamide and some acrylates initiated by ultraviolet radiation
Authors: Baysal B. M. , Erten H. N. , Ramelow Ü. S.
Published: April 2003

The solid‐state polymerization of acrylamide, potassium acrylate, and calcium acrylate by ultraviolet radiation have been investigated. For these polycrystalline monomers both in‐source and post‐irradiation reactions were studied by using various sources of different intensities at constant temperatures. It is concluded that the polymerization reactions take place primarily on the surfaces of crystals. The high molecular weight material obtained at low conversions show a rapid decrease in intrinsic viscosities, probably due to degradation. Both the rate and degree of polymerization were decreased by the presence of oxygen. The various behaviors observed for these three monomers under ultraviolet radiation were regarded as another indication of the importance of crystal structures upon the solid‐state polymerization reactions.
Polymerization by oxidative coupling. II. Co‐redistribution of poly(2,6‐diphenyl‐1,4‐phenylene ether) with phenols
Authors: White Dwain M.
Published: April 2003

Poly(2,6‐diphenyl‐1,4‐phenylene ether) reacts with phenols in the presence of an initiator to form a mixture of low molecular weight hydroxyarylene ethers. Although the reaction is similar to the equilibration of poly(2,6‐dimethyl‐1,4‐phenylene ether) with phenols, higher reaction temperatures and larger initiator concentrations are required. Compounds as 3,3′,5,5′‐tetraphenyl‐4,4′‐diphenoquinone, tert‐butyl perbenzoate, and benzoyl peroxide are active initiators. The structure of the polymer affects the extent to which the polymer equilibrates.