bluuebunny/crossref_metadata_2025 huggingface dataset:
Lactone polymers. II. Hydrodynamic properties and unperturbed dimensions of poly‐ε‐caprolactone
Authors: Koleske J. V. , Lundberg R. D.
Published: April 2003

Poly‐ε‐caprolactone prepared by a dibutylzinc‐catalyzed bulk polymerization process was fractionated, and the solution properties of the fractions were studied in benzene and in dimethylformamide. In these solvents at 30°C the Mark‐Houwink relations were [η] = 9.94 × 10−5 M and [η] = 1.91 × 10−4 M, respectively. The value of KΘ was found to vary from 1.1 to 1.2 × 10−3 when determined by three known extrapolation techniques. Poly‐ε‐caprolactone chains appear to be quite flexible in solution, and the steric hindrance parameter σ had the low value of 1.37. Root‐mean‐square end‐to‐end dimensions were approximated from the experimental data and calculated from the Debye‐Bueche and the Kirkwood‐Riseman theories.
Rheological properties of ionic and nonionic polyacrylamide solutions
Authors: Bruce C. , Schwarz W. H.
Published: April 2003

Non‐Newtonian shear viscosities were measured over six decades of strain rate k for 13 solutions of both the ionic and nonionic forms of polyacrylamide. By using the Weissenberg rheogoniometer with both the cone‐and‐plate and the parallel‐plate attachments, the normal stress functions σ1 (k2) and σ2(k2) were obtained for four of the solutions. From the measurements of the shear viscosity and the normal stresses at low rates of strain, characteristic times τ and τN, respectively, were determined for each solution. The quantity τ was then used to nondimensionalize the strain rate τk, and when plotted versus the reduced shear viscosity, found successfully to correlate the experimental data for all the polyelectrolyte solutions over the entire range of τk and the data for the concentrated solutions of the nonionic polymer over a smaller range of τk. However, in order to correlate the normal stress data for the polyelectrolyte solutions, a second reduced strain rate (τNk) was used. Thus, two different times were required to correlate all the observed data. The shear viscosity data for the dilute solutions of the nonionic polymer were well represented by the two‐parameter, non‐Newtonian intrinsic viscosity function that has been computed by Fixman.
Rotating frame proton spin‐lattice relaxation measurements of poly(ethylene oxides)
Authors: Connor T. M. , Hartland A.
Published: April 2003

Measurements of T1ρ as a function of temperature have been made on three polyethylene oxides (PEO) with molecular weights of 550, 6000, and 2.8 × 106 in order to try to elucidate various problems arising in the interpretation of previous T1 measurements on PEO. In contrast to the T1 measurements, the T1ρ measurements show discontinuities at the melting or softening points of the respective polymers concerned, and also show nonexponential magnetization decay in the case of PEO 6000 and 2.8 × 106, which is presumbly due to the existence of “mobile” and “crystalline” regions, in qualitative agreement with NMR studies and x‐ray measurements. Motional correlation frequencies and activation energies have been derived where possible by using the BPP theory adapted to the rotating frame and also the strong collision Slichter‐Ailion theory. There is reasonable correlation with other data on motional frequencies where it is available, although the overall situation for the so‐called α transition in PEO 6000 and 2.8 × 106 is still not clear. It is suggested that spin‐diffusion is an important mechanism for all three polymers; for PEO 550 because it contains CH3 endgroups which act as sinks, and for the other two polymers where the mobile fraction performs the same function.
Relation between melting behavior and physical structure in polymers
Authors: Bell J. P. , Dumbleton J. H.
Published: April 2003

The phenomenon of double melting, as manifested by two characteristic endotherms in the melting region on a differential thermal analysis (DTA) scan, has been studied in nylon 66 and polystyrene as a function of sample treatment by annealing or drawing. A variety of techniques were used in these studies including DTA, x‐ray diffraction, electron microscopy, and mechanical testing. It is shown that the two endotherms are not caused by a bimodal crystal size distribution, by recrystallization, by orientation changes, or by phase changes. It is proposed that one endotherm is caused by the melting of foldedchain crystals, while the other is due to the melting of less perfect bundle crystals. This view is well supported by the results, especially by the DTA measurements made at different heating rates. Published data on the thermal behavior of annealed and drawn poly(ethylene terephthalate) and on polyethylene crystallized at various pressures may also be explained on this basis if it is allowed that in polyethylene the chains may be more extended.
Infrared studies of cryogenic transitions in poly(ethylene terephthalate)
Authors: Hannon M. J. , Koenig J. L.
Published: April 2003

Measurements of infrared absorbance as a function of temperature down to 77°K have been made on poly(ethylene terephthalate). Transitions observed by other techniques such as torsion pendulum measurements are reflected in the infrared measurements by an abrupt change in the slope of the absorbance versus temperature. The infrared measurements are made on bands of known structural origin so the structures contributing to each transition can be determined. The β transition is shown by infrared to be a composite of two peaks with the lower‐temperature portion arising from the amorphous regions and the higher‐temperature portion from the crystalline regions.
Swelling of crosslinked poly‐4‐vinylpyridine
Authors: D'Aprano Alessandro , Fuoss Raymond M.
Published: April 2003

Polyvinylpyridine of molecular weight 0.77 × 106 was crosslinked by 2.5, 5, and 10% BrCH2C6H4CO(CH2)8COC6H4CH2Br and by 10% ClCH2C6H4CH2Cl; quaternization of the gel was completed with n‐butyl bromide. Swelling ratios in aqueous solutions of lithium, sodium, and 4‐isopropyl‐N‐n‐butylpyridinium bromide and in methanolic lithium bromide were determined. Selectivity increased in the sequence Li+ <Na+ <PrN+−C5H5. The Flory parameter χ1, which measures interaction between solvent and polymer, decreased from 1.5 kT to nearly zero with increasing density of crosslinks in the aqueous solutions, and from 3 kT to 0.5 kT in the methanol solutions. The inverse proportionality of q2/3 (q = swelling ratio) to the crosslinking density was approximately verified for swelling of the resins in water, methanol, and dimethylformamide.
Stress‐optical coefficient of cis‐1,4‐polybutadiene and cis‐1,4‐polyisoprene networks. Measurements on cis‐1,4‐polybutadiene networks and theoretical interpretation
Authors: Ishikawa Toshihide , Nagai Kazuo
Published: April 2003

Stress, strain, and birefringence measurements have been carried out on swollen and unswollen networks of ′cis‐1,4‐polybutadiene polymers. Neither stress‐strain nor birefringence‐strain relations of unswollen specimens obey the Gaussian network theory, but both can be fitted by the Mooney‐Rivlin equation. On the contrary, data on specimens swollen in tetralin, decalin, benzene, and carbon tetrachloride strictly obey the Gaussian network theory. Existing methods for evaluating the temperature coefficient of the unperturbed dimensions, d In 〈r2〉/dT, from the stress‐temperature relation are applied to the present data and discussed in some detail. It is concluded that reliable values of d In 〈r2〉/dT are not obtainable from data on unswollen samples because of the pronounced non‐Gaussian effect. The value 7.5 Å3 for the optical anisotropy Å3 (an alternative to the stress‐optical coefficient) for unswollen specimens is markedly larger than values (5.8 Å3 on the average) for swollen specimens. This is interpreted as due to the shortrange orientational order among polymer segments. The quantities 〈r2〉, ΔΓ, and their temperature coefficients are calculated for both cis‐1,4‐polybutadiene and cis‐1,4‐polyisoprene chains, on the basis of the rotational isomeric state approximation for bond rotations. Values of ΔΓ for cis‐1,4‐polybutadiene calculated using Clément and Bothorel's set of anisotropic bond polarizabilities are in good agreement with observed values for swollen specimens. Those for cis‐1,4‐polyisoprene obtained using the same set of anisotropic bond polarizabilities are somewhat smaller than observed values for unswollen specimens. This departure is in the direction expected from the behavior of ΔΓ upon swelling (i.e., a decrease in ΔΓ upon swelling).
Thermodynamic interpretation of domain structure in solvent‐cast films of A–B type block copolymers of styrene and isoprene
Authors: Inoue Takashi , Soen Toshiichi , Hashimoto Takeji , Kawai Hiromichi
Published: April 2003

Electron microscopic textures of A–B type block copolymers of styrene and isoprene cast from several solvents were investigated by means of the osmium tetroxide fixation technique. The two‐phase structure, i.e., the semimicro heterogeneous structure due to the microphase separation of block segments, was observed to change systematically with the fraction of block segments and the kind of solvent. Three types of fundamental domain structure were found. With the assumption that domain structure originates from micellar structure at a critical concentration in relatively dilute solution during solvent casting, the formation of the three types of domain structure and the sizes of their elements were treated in terms of the equilibria governing the formation of micelles at the critical concentration. This analysis takes into account such thermodynamic and molecular parameters as the incompatibility between the A and B segments, the solvation of the segments, the casting temperature, the total chain length of the block copolymer, and the weight fraction composition of the block copolymer. It was concluded that the block segments are preferentially oriented along the direction perpendicular to the interface between the two phases. This particular orientation‐aggregation of the block segments must make the bulk properties of the block copolymer much different from those of merely mechanical mixtures of the corresponding homopolymers, even if the same semimicro heterogeneous structures are formed in the mechanical mixtures.
Origin of the γ relaxations in polyethylene and polytetrafluoroethylene
Authors: Gray R. W. , McCrum N. G.
Published: April 2003

Mechanical relaxation has been studied at 0.67 cps in linear polyethylene (LPE) and polytetrafluoroethylene (PTFE) between −190 and −20°C. Specimens were prepared by use of various thermal treatments to produce in LPE a range of crystalline fractions from 0.690 to 0.825 and in PTFE from 0.615 to 0.870. An empirical theory is proposed relating the modulus of the crystalline–amorphous composite solid to the moduli and the volume fractions of the two phases. The empirical theory is shown to be in accord with the bounds of Hill and of Hashin and Shtrikman. The theory is used to determine the magnitudes of the crystalline and amorphous components of the low temperature relaxations in LPE and PTFE from measurements of logarithmic decrement and shear modulus. In PTFE the γ relaxation occurs in the amorphous fraction alone. In LPE the γ relaxation is a composite one, formed from the superposition of a small crystal relaxation and a large amorphous relaxation. For the crystal relaxation in LPE the ratio of relaxed to unrelaxed modulus equals 0.78; for the amorphous relaxation, the ratio equals 0.23. In a specimen of LPE with crystal fraction 0.69 the crystal contribution to the relaxation is 25% of the total. The magnitude of the unrelaxed modulus of the crystal fraction of LPE (modulus of polycrystalline LPE at −190°C) is in reasonable agreement with theoretical calculations of Odajima and Maeda.
Fractionation of styrene–acrylonitrile copolymers
Authors: Lovrić Ljerka
Published: April 2003

Three types of commercial styrene–acrylonitrile copolymer were fractionated by coacervate extraction and by column‐elution techniques. Both methods were studied with two different solvent–nonsolvent pairs. Glass wool was used as the support material in the column. Fractionation by the coacervate extraction method was studied with benzene–triethylene glycol as a solvent–nonsolvent system at 60°C and with dichloromethane–triethylene glycol at 25°C. Column elution was carried out with acetone–methanol as the solvent–nonsolvent system at 30°C, and with dichloromethane–methanol at 20°C. Results of excellent reproducibility were obtained by these two methods. Characterization of fractions involved determination of both the molecular weight and chemical composition. It was established that the fractionation of the samples tested was dependent upon molecular weight only. The two methods described above are compared. Each gives an efficient procedure for fractionation of styrene–acrylonitrile copolymers.
Electron microscopy of crazes in glassy polymers: Use of reinforcing impregnants during microtomy
Authors: Kambour R. P. , Holik A. S.
Published: April 2003

Attempts to prepare undamaged microtomed sections of crazes without reinforcement have failed. Several methods of reinforcing crazes in glassy polymers with impregnants prior to microtomy have been tried. Generalized characteristics of successful impregnant systems are suggested on the basis of this experience. The most successful system has involved the infusion of liquid sulfur into crazes in poly(2,6‐dimethyl‐1,4‐phenylene oxide). After quenching, the solid sulfur reinforces the crazes successfully during microtomy but subsequently sublimes away under vacuum. The resultant, largely undamaged craze structure is seen by transmission electron microscopy to resemble an open‐cell foam, the holes and polymer elements of which uniformly average ∼200 Å in diameter. A moderate degree of orientation in the original tensile stress direction is observed. Implications drawn from craze structure for the existence of order in the glassy state are discussed.
Dielectric relaxations in poly(vinylidene fluoride)
Authors: Sasabe Hiroyuki , Saito Shogo , Asahina Mitsuo , Kakutani Haruko
Published: April 2003

Molecular motions in poly(vinylidene fluoride) were studied by the dielectric technique. Three distinct absorption peaks (αc, αa, and β) were observed in the frequency range from 0.1 cps to 300 kcps and in the temperature range from −66 to 100°C. The molecular mechanisms for these absorptions and their temperature dependence are discussed, and results are compared with x‐ray diffraction and the NMR measurements. It is concluded that the αc absorption located at 97°C (1 kcps) is related to molecular motion in the crystalline region. The αa absorption located at −27°C (1 kcps) can be interpreted as due to the micro‐Brownian motion of the amorphous main chains. The β absorption located at −47°C (1 kcps) is attributed to local oscillation of the frozen main chains.
Mechanical and dielectric absorption of poly(vinyl chloride) and some related polymers
Authors: Kakutani Haruko , Asahina Mitsuo
Published: April 2003

The mechanical and dielectric low temperature absorptions of poly(vinyl chloride) (PVC) and several modified PVC's have been studied over the temperature range from −60 to +60°C. with some tests extending to −150°C. and others to +170°C. The results indicate that the low‐temperature absorption near −50°C (β2 absorption) decreases in intensity with chlorination, while the absorption at a higher temperature near 0°C (β1 absorption) decreases in intensity with hydrogenation. The apparent activation energies of the β1 and β2 absorptions were calculated to be 16 kcal/mole and 10.7 kcal/mole, respectively. Besides, the β2 absorption markedly decreases in intensity with addition of plasticizer, while the intensity of β1 absorption is not much affected by increasing plasticizer content. From these results, the β1 and β2 processes are concluded to be the results of molecular motion in crystalline and amorphous region in PVC, respectively. For samples of reduced Cl content, another low‐temperature absorption was located near −120°C (γ absorption) and attributed to the presence of short sequences of ethylene units. It has also been observed that the temperature location of the high temperature absorption near 100°C (α absorption) shifts linearly to higher temperature with increasing chlorine content and to lower temperature with increasing hydrogen content.
Study of the side‐chain relaxation of methacrylate homopolymers and copolymers by the dielectric method
Authors: Kawamura Yasuaki , Nagai Satoshi , Hirose Juichi , Wada Yasaku
Published: April 2003

Dielectric constant and dielectric loss of copolymers of methyl methacrylate (MMA) with n‐butyl methacrylate (nBMA) and isobutyl methacrylate (iBMA) have been measured in the frequency range 30 cps to 1 Mcps at temperatures from 70°K to 370°K. Results lead, together with those of previously published investigations on copolymers of MMA, to the following conclusions. (1) The loss‐peak temperature attributed to side‐chain relaxation (β peak) of PMMA varies with the comonomer ratio when the comonomer does not have an α‐methyl group, but remains almost unchanged for comonomers having an α‐methyl group. (2) In both cases, the β peak height of PMMA decreases with increasing ratio of comonomer B and completely vanishes for poly‐B, and the loss peak temperature plotted against the fraction of B does not extrapolate to the β peak of poly‐B. It is suggested on the basis of the above facts that the moving unit in the side‐chain relaxation consists of a single side chain with a segment of the backbone chain and that the change in mobility of the side chain upon copolymerization results from the distortion of the helical structure of the backbone chain due to random distribution of α‐methyl groups. Dielectric studies of the low‐temperature side‐chain relaxation (β2 peak) in PnBMA, poly(n‐octyl methacrylate), and poly(n‐dodecyl methacrylate) (130°K at 1 kcps) have been made and an interpretation is offered for the molecular nature of this relaxation.
Elasticity and structure of chemically crosslinked polyurethanes
Authors: Blokland R. , Prins W.
Published: April 2003

A combination of electron‐microscopy, light‐scattering, and stress‐birefringence studies on chemically crosslinked polyurethanes point toward the existence of rodlike regions (“bundles”), approximately 3000–8000 Å in length and involving about 5% of the volume, in which molecular orientations are correlated. The elastic behavior of these networks—as indeed that of most rubberlike networks—deviates substantially from the Gaussian behavior. The empirical representation of the data in Mooney‐Rivlin plots yields C1 and C2 constants which depend on the type of imposed strain. It is thus impossible to identify C1 with the Gaussian behavior and C2 with the deviation there‐from. Instead, it is found that the elastic behavior can be adequately described if it is assumed that, as a result of the bundle structure, about 5% of the segments of each chain are not free to assume the normal random‐walk configurations. The determination of the number of chains in the network from the elastic behavior remains ambiguous, however, and the behavior upon swelling is not (yet) adequately reproduced by the theory. It is conceivable that in many cases deviations from Gaussian elasticity behavior may be caused by an intermolecular structuring effect, rather than by various minor deficiencies in the Gaussian model for the single chain statistics or by anisotropic excluded volume effects, as has been proposed in the past. In the present case, the amount of bundle structure, as well as the C2/C1 values, increase with the number of urethane couplings per chain, and this suggests that the interaction of the highly polar urethane couplings is responsible for the structuring. In other networks one often finds a dependence of C2/C1 on the previous history of the sample, which suggests that an accidentally trapped order may be responsible for the elastic behavior.
Influence of an interfacial free‐energy correction on the expansion of a polymer coil in a solvent
Authors: Vrij A.
Published: April 2003

A new type of long‐range interaction between chain segments and solvent molecules in a polymer molecule is introduced. It can be depicted as an “interfacial” free energy, due to the more or less diffuse interface between the interior of a polymer coil and the surrounding solvent. Flory's calculation of the coil expansion α is extended for this effect, by using theoretical approaches developed by van der Waals, Cahn and Hilliard, and Debye for inhomogeneous systems (interfaces). It is found that Flory's equation for α is replaced by:

where the last term is due to the “interfacial” free‐energy correction. The Debye molecular interaction length l is also found in theories on light scattering of binary mixtures near the critical solution temperature. An important result of this equation is that at T = θ, α is not equal to unity, as before, but somewhat larger, depending on the molar mass of the polymer and the solvent type. A calculation shows that the “interfacial” free energy correction may contribute substantially to the “solvent” effects on the expansion of a polymer molecule at the θ temperature, as has recently been reported in the literature.
Rates of crystallization of polyethylene fractions by calorimetry
Authors: Fatou J. M. G. , Barrales‐Rienda J. M.
Published: April 2003

Rates of crystallization of polyethylene fractions have been studied at high undercoolings by differential calorimetry to demonstrate the utility of this technique for fast crystallization analysis. It has been shown that there is continuity in the crystallization kinetics from low to high undercoolings. On the other hand, the influence of molecular weight on the crystallization rates, as the undercooling increases, is very moderate, as would be expected.
Fast gel‐permeation chromatography. I. A study of operational parameters
Authors: Little James N. , Waters James L. , Bombaugh Karl J. , Pauplis William J.
Published: April 2003

A systematic study of factors affecting the GPC separation showed that peak spreading with increasing flow rate was much less than predicted from the Van Deemter equation. Viscous fingering decreased and peak symmetry improved at increased flow rates. As a result, fast GPC analysis was shown to be readily attainable through optimization of operating parameters.
Calculation of molecular weight distributions for polymers undergoing random crosslinking and scission
Authors: Kells D. I. C. , Guillet J. E.
Published: April 2003

A simple, practical calculation procedure has been developed for predicting the changes in molecular weight distribution of a polymer undergoing random crosslinking and/or degradation. Simulations of the random crosslinking and degradation of narrow and broad Poisson‐type distributions have been made. The results agree with those calculated from Kimura's analytical solutions to Saito's general equations after a correction has been made for a mathematical error in Kimura's solution. This method can be applied to determining the probabilities of crosslinking and scission for any arbitrary molecular weight distribution expressed in tabular form. The importance of using narrow distribution samples to estimate crosslinking from changes in molecular weight distribution is graphically demonstrated.
Dynamic strain‐birefringence apparatus for polymer films
Authors: Hopkins Robert C.
Published: April 2003

A new apparatus for investigating dynamic strain birefringence in polymer films at frequencies up to 10 Hz and at various degrees of internal sample orientation is described. Samples are elongated at constant low rates while simultaneously being strained sinusoidally. Fast changes in sample retardance are recorded while slow changes are automatically compensated with a servo‐controlled Soleil‐Babinet compensator. The signal‐to‐noise ratio of the system is greatly enhanced by incorporating a highly monochromatic laser light source, a synchronous amplifier, and a light beam modulator based on a rotating polarizer. Data obtained from this apparatus can be used to elucidate polymer relaxation mechanisms at various frequencies over a wide range of static strains.
Molecular weight distribution in branched polymers
Authors: Saito O. , Nagasubramanian K. , Graessley W. W.
Published: April 2003

The distribution of molecular weights in realistic free‐radical polymerizations with branching was analyzed theoretically. Series solutions were obtained for the fraction of molecules with r repeating units and the number of branch points contained in molecules with r repeating units. Branching by transfer processes was found to increase the proportion of both high and low molecular weight components in the system. The apportioning of branch points among r‐mer molecules was shown to be somewhat narrower than a Poisson distribution. The major difference between the calculated distributions and previous model distributions for branched systems was the absence of discontinuities in the moments at all levels of branching.
Intrinsic viscosity in branched free‐radical polymers
Authors: Nagasubramanian K. , Saito O. , Graessley W. W.
Published: April 2003

The intrinsic viscosity ratio [η]B/[η]L was calculated as a function of average branching density for trifunctionally branched, free‐radical polymers. Calculations were made for the g1/2, g3/2, and h3 rules, using realistic distributions of molecular weights and branches. Experimental data on branched poly(vinyl acetate) lay between the curves obtained from the g1/2 and h3 relations.
Laser‐excited Raman scattering in polybutene‐1
Authors: Cornell S. W. , Koenig J. L.
Published: April 2003

Raman spectra are described for the three crystalline modifications of polybutene‐1. The Raman frequencies are compared with infrared results and give good agreement. A normal‐coordinate analysis for A‐mode vibrations is presented for five possible helical conformations. The behavior of several calculated helix‐sensitive bands is characterized. These results are applied to the experimental Raman frequencies and lead to the prediction of a 103 helix for the orthorhombic form III modification.
Extended‐chain crystals. I. General crystallization conditions and review of pressure crystallization of polyethylene
Authors: Wunderlich Bernhard , Davidson Theodore
Published: April 2003

This is the first paper of a series of reports concerning extended‐chain crystals of flexible, linear high polymers. The general conditions for crystal growth are discussed. Polymer crystallization is described as a two‐step process: nucleation of each crystallizing molecule to a folded‐chain conformation, followed by an increase in fold length in a solid‐state reorganization step. This reorganization step is enhanced in the case of polyethylene by crystallization at high temperature under elevated pressure. Mechanical deformation during crystallization is also able to produce extended‐chain crystals. The most promising method, however, is crystallization during polymerization. Previous work on crystallization of polyethylene under elevated pressure is critically reviewed.
Extended‐chain crystals. II. Crystallization of polyethylene under elevated pressure
Authors: Davidson Theodore , Wunderlich Bernhard
Published: April 2003

A report on crystallization of polyethylene at elevated pressures to an extended‐chain morphology is presented. The crystals have been characterized by electron microscopy and density determination. Pressure, supercooling (temperature), and crystallization time have been varied to find the best conditions for production of perfect crystals. At 10–30°C supercooling completely crystallized polyethylene was obtained between 4.5 and 7 kb crystallization pressure in 1–8 hr. Analysis of fracture surfaces of samples crystallized for different lengths of time shows an increase in size and number of crystal lamellae and an improvement of extended chain crystals in the early stages of crystallization. A further improvement of the less well crystallized material between the lamellae occurs after 15 min of crystallization time.
Extended‐chain crystals. III. Size distribution of polyethylene crystals grown under elevated pressure
Authors: Prime R. Bruce , Wunderlich Bernhard
Published: April 2003

Extended‐chain crystals of high molecular weight polymethylene, a polyethylene with a broad molecular weight distribution, and three fractions of polyethylene were grown from the melt under elevated pressure. Comparison of the crystal size distribution in the molecular chain direction (measured on fracture surfaces by electron microscopy) with the molecular weight distribution (measured by gel‐permeation chromatography) gave the following results. Up to molecular weight 10,000 all samples showed eutectic separation into fully extended chain crystals of narrow molecular weight distribution. Above molecular weight 10,000 mixed crystals were formed. Under the chosen crystallization conditions larger chain extension was achieved with higher molecular weights. However, an increase in molecular weight by a factor of 1000 led only to a tenfold increase in chain extension. These facts are discussed in the light of a proposed mechanism of crystal growth.
Extended‐chain crystals. VI. Annealing of polyethylene under elevated pressure
Authors: Gruner Charles L. , Wunderlich Bernhard , Bopp Richard C.
Published: April 2003

Polyethylene crystals of different degrees of perfection were annealed at 5.1 kb pressure for 20 hr at various temperatures and analyzed by electron microscopy, thermal analysis, and density determination. No annealing took place until the temperature was close to the melting point of the starting material. Up to 235°C increasing solidstate annealing was observed. Mixed crystals of up to 0.989 g/cm3 density and 1500 Å thickness in the chain direction could be produced. At slightly higher temperature recrystallization to extended‐chain crystals rather than annealing occurred. The annealing process at atmospheric pressure seems to be similar in nature, but takes much longer for comparable perfection. From a comparison of annealing and crystallization it is concluded that polymer crystallization goes through a stage of internally imperfect order during which most of the observed chain extension occurs. Estimates of this outer imperfect layer of a growing crystal place its depth at 30,000 Å.
Birefringence and dichroism of rubbery copolymers
Authors: Shindo Y. , Stein R. S.
Published: April 2003

The Kuhn‐Grün theory for the birefringence and dichroism of rubbery polymers is extended to the case of copolymers consisting of two or more statistical segments of differing lengths. It is shown that the previous equations are applicable provided that the anisotropy of polarizabilities and absorptions are replaced with suitable averages in which the segment anisotropies are weighted by the squares of their segment lengths. This indicates that the stress‐optical coefficient will not generally vary linearly with composition. The orientation measured from the dichroism of bands arising from different segments will be different.
Ketone‐zinc chloride combination as an initiator of polymerization
Authors: Dutt Prabir K. , Palit Santi R.
Published: April 2003

Dihydrocivetone, a macrocyclic ketone, has been found to be a weak initiator of vinyl polymerization. Anhydrous zinc chloride strongly promotes this to form a novel initiating system. Monomers tried successfully are methyl methacrylate, acrylonitrile and α‐methylstyrene. The characteristic feature of polymerization of α‐methylstyrene differs greatly from those of other monomers and those have been discussed and compared.
ESR studies of vinyl polymerization. II. Initial reactions of vinyl esters with redox systems in aqueous media
Authors: Takakura Koichi , Rånby Bengt
Published: April 2003

ESR measurements of transient radicals during redox polymerization of various vinyl esters in aqueous solutions have been made by using the rapid‐mixing flow method. The initiation was by means of hydroxyl and amino radicals from the systems titanous chloride‐hydrogen peroxide and titanous chloride‐hydroxylamine, respectively. The well resolved hyperfine structures obtained at monomer concentrations of about 0.05 mole/1. are unambiguously assigned to the monomer radicals formed by addition of initiator radicals to monomers. At higher monomer concentrations, additional weak signals attributed to the growing polymer radicals were observed. The effect of reaction conditions on the signal intensity has been studied in particular for vinyl acetate. The coupling constants of monomer radicals from various vinyl esters (acetate, propionate, butyrate, crotonate, and isopropenyl acetate) were obtained and the spin densities calculated. From the ESR spectra, the monomer radicals have a conformation with the substituent R (R = HO or NH2) of RCH2CH(OCOR′) locked in a position above or below the radical plane. This is tentatively interpreted as due to formation of intramolecular hydrogen bonds to ring structures or complexes with titanium ions. In addition, hydrogen abstraction reactions of some model compounds for poly(vinyl acetate) have been briefly studied in relation to chain transfer and grafting reactions.
Thermal stability of structurally related polymers containing carborane and phthalocyanine groups
Authors: Delman A. D. , Kelly J. J. , Simms B. B.
Published: April 2003

These studies were undertaken to determine the thermal behavior of structurally related polymers having a carborane nucleus in the recurring unit. Three of these products also contained phthalocyanine rings in their molecules. Results of thermal analysis studies show generally that the relative heat stability of the polymers conforms closely with indications given by similar investigations of structurally related intermediate and model compounds. A polymer with dimethylsiloxane units exhibited more resistance to thermal decomposition than similar products having urethane groups in their molecules. The urethane polymers derived from tolylene diisocyanate were found to be somewhat less heat‐stable than analogous materials synthesized from methylenebis‐(p‐phenyl isocyanate). The relative order of thermal resistance of these materials follows that of more conventional polyurethane elastomers.
Equilibrium concentration of trioxane in cationic polymerization
Authors: Miki T. , Higashimura T. , Okamura S.
Published: April 2003

In the cationic polymerization of trioxane and tetraoxane near room temperature, the equilibrium trioxane concentration is not negligible during polymerization. In this work, tetraoxane was polymerized with BF3 • O(C2H5)2 in various solvents and the equilibrium concentration of trioxane produced during the polymerization of tetraoxane and equilibrated with the growing polyoxymethylene chain was determined. The equilibrium trioxane concentrations were 0.05, 0.13, and 0.19 mole/l. in benzene, ethylene dichloride, and nitrobenzene at 30°C, respectively, and 0.20 mole/l. in thhylene dichloride at 50°C. The values in ethylene dichloride showed that the approximate values of ΔHp and ΔS were −4.2 kcal/mole and −9.7 cal/mole‐deg., respectively.
Benzimidazole polymers from aldehydes and tetraamines
Authors: Higgins Jerry , Marvel C. S.
Published: April 2003

A new method for the preparation of benzimidazole polymers is described. The solution polymerization of aromatic tetraamines with isophthalaldehyde bis bisulfite adduct in N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (MP), and dimethyl sulfoxide (DMSO) produced polybenzimidazoles with viscosities (ηinh) in the range of 0.3–0.5 measured in formic acid solution. Also a model compound study with benzaldehyde, benzaldehyde diethyl acetal, and benzaldehyde bisulfite adduct with o‐phenylenediamine was carried out. The results showed that the reaction of benzaldehyde bisulfite adduct with o‐phenylenediamine in DMAc as the solvent gave quantitative yields of 2‐phenylbenzimidazole. Excellent yields of 2‐phenylbenzthiazole, 2‐phenylbenzoxazole, and 2‐pyridylbenzimidazole were also obtained with the benzaldehyde bisulfite adduct and picoline‐2‐carboxaldehyde bisulfite adduct with o‐aminothiophenol, o‐aminophenol, and o‐phenylenediamine. The reaction conditions for the preparation of the polymers and the model compounds are very mild and the reaction times range from 15 min to 1 hr for the model compounds and 3–5 hr for the polymers. Longer reaction times did not increase the viscosities of the polymers to any extent.
Reactions of polyolefins with strong lewis acids
Authors: Carrick Wayne L.
Published: April 2003

Treatment of a cyclohexane solution of low density polyethylene and polystyrene with anhydrous aluminum chloride causes chemical reaction between the two polymers which results in the formation of a graft copolymer. The initial copolymer‐forming reaction is very rapid, and prolonged contact of the polymers with aluminum chloride causes subsequent degradation in molecular weight. Treatment of separate solutions of polyethylene, isotactic polypropylene, and ethylene–propylene copolymers with aluminum chloride was studied as a function of time. The intrinsic viscosities of the polymers dropped from initial values of 2.4–6.5 to 0.55–0.85 in 5 min, followed by a slower decline over the next 2 hr. In the case of polypropylene, the low molecular weight fragments largely retained the isotactic structure, which demonstrates that stereochemical isomerization is not a major reaction.
Uses of electron paramagnetic resonance in studying fracture
Authors: Devries K. L. , Roylance D. K. , Williams M. L.
Published: April 2003

The uses of electron paramagnetic resonance (EPR) in studying aspects of polymer fracture are discussed. The sensitivity of EPR is such that all phases of fracture are not amenable to investigation by these means. This paper attempts to define those areas where the authors' experience would indicate that success might or might not be expected. A discussion of the difference between the tensile fracture of drawn polymer fibers, in which strong signals are obtained, and cast and molded materials is given.
Stereoregular poly(methacrylic acids)
Authors: Aylward N. N.
Published: April 2003

A convenient method is described for the preparation of isotactic and syndiotactic poly(trimethylsilyl methacrylates) by using the monomer trimethyl silyl methacrylate and butyllithium initiation in toluene and tetrahydrofuran, respectively. The structure of these polymers enables complete hydrolysis to the corresponding poly(methacrylic acids), which were characterized with respect to tacticity and molecular weight. The asymmetric induction in toluene produced 89% isotactic polymer, while that in tetrahydrofuran gave polymer <90% syndiotactic and heterotactic in terms of triads. A method of fractionation of the polyelectrolytes by gel‐permeation chromatography on a preparative scale was shown to be applicable.
Synthesis and reactions of polyvinylcyclopropane
Authors: Overberger C. G. , Halek G. W.
Published: April 2003

Vinylcyclopropane was polymerized with a catalyst of diethylaluminum chloride and titanium trichloride and fractionated to yield isotactic, atactic, and stereoblock fractions, as shown by a combination of physical and chemical evidence. The atactic fraction contained a significant portion of product from 1,5‐polymerization as well as the usual 1,2‐polymerization, and this occurrence is explained by modifications in a mechanism for normal 1,2‐coordination polymerization such that abnormal alkylations occur during the propagation step in the coordination sphere of the catalyst surface. Addition of hydrogen bromide to the isotactic fraction yielded predominantly poly‐3‐bromo penten‐1 and in‐chain cyclohexane and vinylidene structures. A mechanism is proposed for these occurrences involving a hydride shift and various reactions of the initially generated carbonium ion with neighboring cyclopropyl rings. Addition of acetic acid yielded 25% addition and 25% cyclization and crosslinking. Hydrogen sulfide did not add to the cyclopropyl ring. Hydrogenation of the atactic fraction yielded poly‐3‐methylbutene‐1 quantitatively, demonstrating that the polymeric environment did not affect the direction of ring opening but that the state of crystallinity as compared to the isotactic polymer did affect the extent of reaction. In general, the cyclopropyl ring in a polymeric environment underwent its usual reactions but was subject to reactions with neighboring groups resulting from its fixation in a polymer chain.
Polymerization initiated by an electron donor–acceptor complex. Part IV. Kinetic study of polymerization of methyl methacrylate initiated by the charge‐transfer complex consisting of poly‐2‐vinylpyridine and liquid sulfur dioxide
Authors: Matsuda Minoru , Ishioroshi Yasuhiro
Published: April 2003

A kinetic study has been made of the polymerization of methyl methacrylate (MMA) initiated by a charge‐transfer complex of poly‐2‐vinylpyridine (electron donor) and liquid sulfur dioxide (acceptor) in the presence of carbon tetrachloride. It is concluded that the polymerization proceeds through free‐radical intermediates, as with the pyridine‐liquid sulfur dioxide complex system. The association constants K of acceptor and polymer electron donors which range widely in their molecular weight were determined spectrophotometrically, and it has been found that both K and overall rate of polymerization Rp of MMA decrease with increasing molecular weight of polymer donor; contrary to this, molecular weight of PMMA formed increases with increasing molecular weight of the polymer donor. Other kinetic behaviors was essentially the same as in the pyridine–liquid sulfur dioxide system, i.e., Rp is proportional to the square root of the concentration of the complex and to the 3/2‐order of the monomer concentration; Rp is clearly sensitive to the carbon tetrachloride concentration at low concentration of carbon tetrachloride, but for a higher concentration it is practically independent of the carbon tetrachloride concentration. It has been deduced from a kinetic mechanism for the initiation that a primary radical may be produced from the reduction of carbon tetrachloride by an associated complex consisting of liquid sulfur dioxide–polymer donor and the monomer.
Polymerization of vinyl acetate in aqueous media. Part III. Distribution of free monomer and its effect upon the particle size of poly(vinyl acetate) latices
Authors: Netschey A. , Alexander A. E.
Published: April 2003

The distribution of the monomer vinyl acetate between an aqueous phase and its polymer (the latter in the form of a latex) has been measured at 20 and 40°C. The diameter of particles in a fine poly(vinyl acetate) latex has been measured in the presence of various concentrations of monomer in the aqueous phase, by means of the analytical ultracentrifuge. Comparison of the diameters so measured with those calculated from the distribution data show quite reasonable agreement (<3.7%).
Polymerization of vinyl acetate in aqueous media. Part IV. Influence of preformed (“seed”) latex upon polymerization kinetics and particle size
Authors: Netschey A. , Alexander A. E.
Published: April 2003

The polymerization of aqueous solutions of vinyl acetate initiated by K2S2O8, has been studied in the presence of different concentrations of a fine “seed” latex, both in the absence and in the presence of a surfactant (sodium hexadecyl sulfate). Both kinetics and final latex size were measured, the latter showing whether fresh nucleation had occurred or not. The results suggest that surfactant adsorbed on the latex surface greatly influences the capture, by the latex surface, of oligomers formed in the aqueous phase and this, in turn, markedly affects both nucleation and kinetics. The number of free radicals per particle does not appear to be constant even with the finest particles used (ca. 50 mμ).
Effect of hydrogen on the γ‐radiation‐induced polymerization of ethylene
Authors: Mitsui Hiroshi , Hosoi Fumio , Kagiya Tsutomu
Published: April 2003

The effects of hydrogen on the γ‐radiation‐induced polymerization of ethylene were studied from the viewpoint of polymer structure and kineties. All experiments were carried out at 30°C. In the polymerization of ethylene containing 21.6% hydrogen, the solid polymer was obtained as a main product, while no liquid product was found. There was no difference in hydrogen contents before and after the irradiation; and acetylene, ethane, butane, and butene‐1 were found as gaseous products. The polymer yield increased almost proportionally with dose rate in the presence of 8.0% hydrogen; on the other hand the molecular weight was independent of dose rate. At hydrogen contents of 0–8%, the polymerization rate increased with reaction time and decreased with hydrogen content. The molecular weight also increased with the time, and the extent of the increment decreased with the time and hydrogen content. The number of moles of polymer chain increased proportionally with the reaction time and increased linearly with hydrgen concentration. These results were analyzed by using a graphical evaluation method for kinetics, and the effects of hydrogen on the each elementary step in the polymerization were discussed.
Polymerization of coordinated monomers. IV. Copolymerization of methyl methacrylate– and methacrylonitrile–Lewis acid complexes with styrene
Authors: Ikegami Tadashi , Hirai Hidefumi
Published: April 2003

Complexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl4, AlCl3, and BF3) were copolymerized with styrene at −75°C under irradiation with a high‐pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl4 complex system had a higher cosyndiotactieity, while those from the AlCl3 and the BF3 complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge‐transfer complex between the styrene and the methyl methacrylate coordinated to SnCl4. The concentration of the charge‐transfer complex was estimated to be about 30% of monomer pairs at −78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl3 complex–styrene system and a styrene radical for the SnCl4 complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high‐pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl4 complex a certain interaction of SnCl4 with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge‐transfer complex copolymerization scheme.