bluuebunny/crossref_metadata_2025 huggingface dataset:
Separated aluminum alkyl–titanium tetrachloride catalysts for isoprene polymerization
Authors: Saltman William M.
Published: April 2003

The liquid portions of triisobutyl–aluminum TiCl4 catalysts were partially or completely removed from catalysts formed at Al/Ti ratios of 0.5, 0.6, 1.0, 1.2, 2.0, 3.0, and higher. The partially separated catalysts (0.5–1.2 Al/Ti) are still highly active for the polymerization of isoprene to a high cis polymer. The completely separated solid is inactive, but regains polymerization activity if triisobutyl aluminum or diisobutyl‐aluminum chloride is added back. Polymer yield quickly reaches a maximum and then falls off sharply on addback of more trialkyl; the drop in yield is much slower on addback of excess dialkyl halide. The results indicate that trialkyl or dialkyl halide plus β‐TiCl3 make active catalyst systems for cis‐polyisoprene; the alkyl dihalide is not satisfactory. Excess trialkyl changes the solid surface or mechanism and results in lowered solid polymer yield and increased oily oligomer formation. Completely separated high ratio (2.0 and 3.0 Al/Ti) catalysts are more active than those only partially separated but still much less active than catalysts formed at lower ratios. Addbacks of either aluminum trialkyl or dialkyl halide depress the solid cis polymer yield. Without any separation no solid polymer at all forms. The results suggest that the catalyst at these high ratios is a solid complex of β‐TiCl3 with an organometallic. A simple coordination mechanism is sufficient to correlate all the experimental results.
Hydrogen bonding in amine–epoxide adducts
Authors: Harrod J. F.
Published: April 2003

The infrared spectra of several alcohols and aminoalcohols were measured in bulk and in dilute solution in the 2800–4000 cm.−1 region to determine the nature of hydrogen bonding in these compounds. An epoxy resin was cured with both an aliphatic monoamine and a diamine, and the OH‐stretching bands of the polymers were studied in the temperature range 30–200°C. It is concluded that the hydroxyl groups in the polymers are extensively involved in long‐range hydrogen bonding, particularly of the OHN type, at room temperature. The shift in the bonded OH band to lower frequency with increasing temperature is attributed to a shift from long range to short range bonds. Even at 200°C. there are relatively few free hydroxyl groups in these polymers.
The molecular weight distribution in polypropylene
Authors: Westerman Lowell
Published: April 2003

Light scattering, osmotic pressure, and dilute solution viscosity measurements were utilized to determine the weight‐average, number‐average, and viscosity‐average molecular weights of 10 unfractionated commercial and pilot unit polypropylene samples. Weight‐average molecular weights evaluated from angular scattering data by the method of Zimm were found to agree with those determined by means of the “dissymmetry” method when proper solution clarification procedures were employed. As would be predicted, the z‐average dimension, \documentclass{article}\pagestyle{empty}\begin{document}$\overline{{R_Z ^2 }}$\end{document}, for these polydisperse samples was found to be larger than those reported by Chiang for fractionated samples of comparable weight‐average molecular weight. A general trend toward increased breadth of molecular weight distribution with increasing average molecular weight was detected from the variation of M̄w/M̄n values with average molecular weight, and is supported by the [η]‐M̄w relationship found for these unfractionated samples as compared with the relationship established by Chiang for fractionated samples. The log‐normal distribution function of Wesslau was applied to data on M̄w, M̄n, and M̄v, demonstrating that commercial Ziegler‐type polypropylene displays this type of molecular weight distribution within the molecular weight range studied.
Kinetics of propylene polymerization catalyzed by α‐titanium trichloride–diethylaluminum chloride
Authors: Chien James C. W.
Published: April 2003

The kinetics of propylene polymerization catalyzed by α‐titanium trichloride–diethyl‐aluminum chloride in heptane diluent were studied. Initiation and transfer processes were followed by using C14‐labeled (C2H5)2AlCl. There was no important termination process in this system. The initial C14 activity found in the polymers gave the concentration of active ethyl groups on the surface, [C]. The propagation step was first order in [monomer] and [C], with an activation energy of 13.0 kcal. mole−1; kp at 50°C. was 0.426 ± 0.018 l. mole−1 sec.−1. There were two transfer processes: (1) Rtr1 = ktr1[C] − [(C2H5)2AlCl]1/2, with an activation energy of 18.6 kcal. mole−1, and a value of ktr1 at 50°C. of 6.54 × 10−5 mole−1/2 sec.−1; and (2) Rtr2 = ktr2 [C] [α‐TiCl3], with an activation energy of 7.6 kcal. mole−1, and a value of ktr2 at 50°C. of 9.45 × 10−4 l. mole−1 sec.−1. These kinetic data were used to calculate number‐average molecular weights M̄n, which agreed well with the ones obtained directly from the C14 specific activity in the polymer. Furthermore, fractionation of four polypropylene samples gave values of M̄n in agreement with those obtained above. At low temperatures, [C] is sensitive to the Al/Ti ratios. This dependence was interpreted as the result of an equilibrium between an active complex containing (C2H5)2AlCl and a much less active complex containing (C2H5)AlCl2. At higher temperatures, [C] is insensitive to the Al/Ti ratios, and polymerization to give amorphous polymers becomes important. Qualitative information was obtained about the processes which give amorphous polymers.
Behavior of polymer solutions in a velocity field with parallel gradient. I. Orientation of rigid ellipsoids in a dilute solution
Authors: Takserman‐Krozer Rachela , Ziabicki Andrzej
Published: April 2003

The spatial orientation of rigid ellipsoidal particles was analyzed as proceeding in a dilute solution flowing in a velocity field with parallel gradient, i.e., in a field characterized by the deformation rate tensor:

On the basis of general relations given by Jeffery, the hydrodynamic equations of motion of a single ellipsoid were obtained as Ψ = 0, φ = 0, θ = −¾qR sin 2θ, where q = ∂Vκ/∂κ is the parallel velocity gradient and R = (a2 − b2)/(a2 + b2) is the shape coefficient of ellipsoids. Considering the action of velocity field and that of Brownian motion (rotational diffusion), a distribution density function ρ(t, θ) was derived, which describes the spatial orientation of the axes of symmetry of the ellipsoids:

where

is the steady‐state distribution. In a similar way, the axial orientation factor f0 = 1 − 3/2 sin2θ was obtained:
Behavior of polymer solutions in a velocity field with parallel gradient. II. Viscosity of dilute solutions containing rigid ellipsoids
Authors: Takserman‐Krozer Rachela , Ziabicki Andrzej
Published: April 2003

On the basis of Jeffery's general relations, formulas for the rate of dissipation of energy due to the motion of a rigid rotational ellipsoid in a liquid, uniaxially drawn, were derived. By use of the previously found distribution function, intrinsic viscosity v, was calculated and effects of ellipsoid shape, velocity gradient, diffusion rate constant and time were discussed. The intrinsic viscosity monotonically increases with velocity gradient and with time t. This behavior is quite different from that observed in shear flow. It was stated that phenomena connected with a velocity field with parallel gradient (i.e., flow with uniaxial deformation):

such as liquid jets, fiber spinning etc., cannot be explained in terms of experiments or theories concerning the shear flow (velocity field with perpendicular gradient):

as obtained in viscosity measurements in common types of viscometers (capillary, rotational, falling body), or investigations of flow birefringence in coaxial apparatus.
Water sorption of titanium dioxide–poly(vinyl acetate–vinyl chloride) copolymer films
Authors: Kumins Charles A. , Roteman Jerome , Rolle Clifford J.
Published: April 2003

Crystalline solids, as exemplified by TiO2 incorporated within a film of a model polymer, poly(vinyl chloride–vinyl acetate) copolymer, have been shown to absorb relatively large amounts of water vapor on the surface. In some cases all of the crystal surface may participate in the sorption process, despite evidence that the polymer has been initially present on the surface of the former. This, coupled with anomalous density changes in the film, suggests the possibility of measuring crystal flocculation within the membranes as well as the displacement of adsorbed polymer segments by means of water vapor. The anomalous density determinations were correlated with water transport measurements, and an equation for calculation of the heat of wetting of a crystal with a solid polymer is presented.
Polymerization of acrylonitrile by electron transfer catalysts
Authors: Zilkha Albert , Avny Yair
Published: April 2003

The heterogeneous polymerization of acrylonitrile in tetrahydrofuran by chain transfer catalysts: monosodium anthracene, disodium anthracene, sodium naphthalene, monolithium anthracene, and lithium naphthalene was investigated. The free radical formed in the initiation was found to participate in the polymerization process only in the case of lithium naphthalene at low catalyst concentrations. Also, block copolymerization with styrene, which is more reactive in free radical polymerization than acrylonitrile and less in anionic, succeeded only with lithium naphthalene. The absence of dimerization of the free radicals is mainly due to their occlusion caused by the high rate of the anionic polymerization of acrylonitrile and the low polymerization temperature, and in the case of the anthracene catalysts also due to inhibition of the free radical dimerization by the liberated anthracene. The mechanism of the termination of the polymerization was found to depend on the catalyst concentration and the ratio [MI]/[C]. At high catalyst concentrations and relatively low [M]/[C] values, termination was by chain transfer to the monomer, as can be seen from the independence of the molecular weights on both monomer and catalyst concentrations. At low catalyst concentrations and relatively high [M]/[C] values, the molecular weights were found to increase with monomer concentration and decrease with catalyst concentration. This was found to be due to the anionic mechanism of the polymerization, and the results are similar to those obtained in a typical anionic polymerization of acrylonitrile with butyllithium.
Electron spin resonance study of radiation oxidation of polymers. IIIA. Results for polyethylene and some general remarks
Authors: Ohnishi Shun‐Ichi , Sugimoto Shun‐Ichi , Nitta Isamu
Published: April 2003

The effect of oxygen on ESR spectra of various kinds of irradiated polymers has been examined by using a saturation technique developed in the present investigation. The radiation oxidation of some polymers has been studied by means of ESR as well as infrared spectroscopy. Results for polyethylene (PE) are given in this paper, with some general remarks as introduction. In PE three kinds of radicals are produced on irradiation: CH2CHCH2 (FRVI), CHCHCH (FRVII), and CH(CHCH)nCH2(FRI). On introduction of air, FRVII gave the asymmetric singlet of the peroxide radical which showed anisotropy. Reversible oxygenation of FRVII took place even as low as −113°C. Radiation oxidation of PE proceeds mainly via FRVII, which produced eventually about 12 carbonyl groups and about 5 hydroxyl groups in the course of post‐oxidation, the trans‐vinylene group decreasing by an amount nearly equal to the amount of initial FRVII. FRVI played only a minor role in the oxidation. An oxidation mechanism involving chain reaction has been proposed. It suggests an intramolecular free‐back reaction of hydrogen to the peroxide radical of FRVII. FRI (polyenyl radicals of longer conjugations) is oxidized to form carbonyl and hydroxyl groups, although it does not give the spectrum of the peroxide radical. Polyenyl radicals of shorter conjugations reacted faster.
Electron spin resonance study of radiation oxidation of polymers. IIIB. Polypropylene and poly(vinyl chloride)
Authors: Ohnishi Shun‐Ichi , Sugimoto Shun‐Ichi , Nitta Isamu
Published: April 2003

Results of ESR and infrared studies of radiation oxidation of polypropylene (PP) and poly(vinyl chloride) (PVC) are reported. The effect of oxygen on the free radicals, FRVIII (CH2Ċ(CH3)CH2) and FRIX (CH2Ċ(CH3)2), FRI′ (polyenyl radicals with shorter conjugations), FRI (polyenyl radicals with longer conjugations) in PP and FRI′, FRI in PVC was studied. On introduction of air, FRVIII and FRIX in PP and FRI′ in PP and PVC showed the asymmetric singlet spectrum of the peroxide radical. Oxygenation of the radicals began at low temperatures: −135°C. for FRVIII and FRIX, −144°C. for FRp in PP, and −170°C. for FRI′ in PVC. By reevacuation, the oxygen molecule could be removed from the peroxide radical of FRI′ in PP and PVC, while deoxygenation was impossible from FRVIII and FRIX. Oxidation of the radicals in PP and PVC gave carbonyl and hydroxyl groups. The number of carbonyl groups produced per radical was estimated as 3.4 and 1.6 for FRI′ in PP and PVC, respectively.
Strain birefringence of sodium hyaluronate films
Authors: Dersarkissian Vahak M. , Bettelheim Frederick A.
Published: April 2003

Strain birefringence of swollen sodium hyaluronate films was measured. Typical Wiener curves were obtained in solvents with different refractive indices. The orientation birefringence of sodium hyaluronate was evaluated from the minima of the Wiener curves and was found to increase with increasing elongation. Up to 30% elongation, the swollen hyaluronate films show quasi‐rubberlike behavior. Above this elongation, the interchain hydrogen bonding further hinders the chain mobility and the orientation increases only slightly.
Effect of side‐chain structure on poly‐α‐olefin properties
Authors: Dunham K. R. , Vandenberghe J. , Faber J. W. H. , Contois L. E.
Published: April 2003

Series of α‐olefins were prepared and polymerized with Al(C2H5)3–VCl3 catalyst. Melting points, softening points, and degrees of crystallinity of the polymers were measured and the physical nature of the systems was discussed. Olefins studied were those having the general formula CH2CH(CH2)xR, where x = 0−3, and R is methyl, isopropyl, tert‐butyl, phenyl, or cyclohexyl.
Kinetic study of the crosslinking of gelatin by formaldehyde and glyoxal
Authors: Davis P. , Tabor B. E.
Published: April 2003

A study has been made of the effect of concentration of the crosslinking agent, gelatin concentration, and pH on the rate of increase of viscosity with time, for gelatin solutions containing either formaldehyde or glyoxal. The results are consistent with the kinetic relationship:

For formaldehyde, n is 2. For glyoxal, n is 1, as was expected for this bifunctional hardener. Initial formation of gelatin–methylol compounds is proposed in both cases. With formaldehyde, it is suggested that this leads to a methylene‐ether crosslink between a gelatin amino‐methylol compound and an unspecified gelatin–methylol compound, while in the case of glyoxal, there is evidence to suggest that the crosslinkage involves two side‐chain amino groups and results in a charged crosslink.
Polymer NMR spectroscopy. VII. The stereochemical configuration of polytrifluorochloroethylene
Authors: Tiers G. V. D. , Bovey F. A.
Published: April 2003

The NMR spectrum of polytrifluorochloroethylene in 3,3′‐bistrifluoromethylbiphenyl solution at 150°C. consists of two doublets having unequal components. Those at lower field correspond to CF2 chain units, while those at higher field correspond to CFCL units. In the CF2 doublet, the weaker component (at lower field) is found to have half the area of the stronger (at higher field), for polymers prepared over a 120°C. range of polymerization temperatures. By comparison to the spectra of the model compounds meso‐ and dl‐CF2ClCFClCF2CFClCF2Cl, the peaks of which closely coincide with those of the polymer when both are compared at 150°C., it is concluded that of the two CF2 peaks in the polymer spectrum, the weaker one represents CF2 groups which are between monomer units in isotactic dyads whereas the stronger one represents CF2 groups which are between monomer units in syndiotactic dyads. It follows that in trifluorochloroethylene propagation, syndiotactic dyad formation is twice as probable as isotactic dyad formation. This preference for syndiotactic placement corresponds to an activation entropy for isotactic propagation 1.38 e.u. more negative than that for syndiotactic propagation; there is no difference in the activation enthalpies. This behavior is in contrast to that previously found for methyl methacrylate propagation; here, preference for syndiotactic placement is entirely dictated by a greater activation enthalpy for isotactic placement.
Polyamides containing phosphorus. I. Preparation and properties
Authors: Pellon Joseph , Carpenter W. G.
Published: April 2003

This study has for the first time provided a series of high molecular weight polymers having trivalent phosphorus in the backbone structure (as phosphine‐containing polyamides) and has extended the series of phosphine oxide polyamides beyond the previously disclosed bis(carboxyphenyl)phosphine oxide types. It was found that bulk polymerization rather than solution or interfacial procedures was the preferred method of preparing these materials. The phosphorus polyamides generally were found to be amorphous, relatively low softening materials having an extended solubility range. Most polyamides containing trivalent phosphorus slowly degrade in formic acid solution. A comparison of the thermal stability, adhesive bond strengths, and mechanical behavior of typical polyamides containing phosphine or phosphine oxide groups in their backbone structure to those of analogous regular nylons disclosed no major differences.
Experimental data on dilute polymer solutions. I. Hydrodynamic properties and statistical coil dimensions of poly (n‐butyl methacrylate)
Authors: Van Leemput R. , Stein R.
Published: April 2003

Viscometric, light‐scattering, and osmotic pressure measurements were carried out on poly(n‐butyl methacrylate) fractions in methyl ethyl ketone and acetone. Relationships between the limiting viscosity number, the average molecular weight, and the mean dimensions were obtained. Heterogeneity corrections were applied to all relationships, assuming a Schulz‐type distribution. Values of Φ, calculated according to the Flory‐Fox equation, were found to be 2.3 × 1023 and 2.1 × 1023 in MEK and acetone, respectively. No significant trend with molecular weight was noticed in the range investigated, though the dependence of [η] on the mean radii of gyration is less than that predicted by the Flory theory.
Crosslinking of natural rubber by dicumyl peroxide in the presence of oxidation inhibitors
Authors: Scanlan J. , Thomas D. K.
Published: April 2003

A number of phenols, simple and N‐substituted aromatic amines, thioamides, and thioanilides which are known to inhibit free radical reactions have been introduced into dicumyl peroxide–natural rubber cures, and their influence upon the degree of crosslinking has been determined. A simple kinetic scheme allows a calculation of the relative reactivities of these additives and the values obtained are compared with those of other workers for the same additives but in different systems. It is concluded that the additives interfere with the crosslinking reaction by exchanging a hydrogen atom with the free radicals involved, and the sequence of reactivities is readily explained in terms of current theories for the effect of substituents upon the reactivity of organic compounds. Types of materials likely to be useful as antioxidants in dicumyl cures are discussed.
Radiation‐induced cationic polymerization of ethylene
Authors: Tabata Yoneho , Shibano Hiroshi , Sobue Hiroshi , Hara Kiyoshi
Published: April 2003

Radiation‐induced polymerization of liquid ethylene was investigated at −78°C. No induction period was observed. The rate of polymerization was proportional to the first power of the dose rate. Radical scavengers did not inhibit the polymerization. On the other hand, methylene chloride accelerated the polymerization appreciably. It was concluded that the polymerization of liquid ethylene at low temperature proceeds by a cationic mechanism.
Calculation of the displacement distance for a three‐choice cubic lattice chain
Authors: Tokita Noboru , Krigbaum W. R.
Published: April 2003

The matrix procedure of Hoeve for the chain displacement length calculation is applied to a three‐choice cubic lattice model. Although rotation about each link is correlated, the model is simple enough for the final result to be obtained as a closed algebraic expression. Certain special cases, resulting from particular assignments of the probability parameters, are examined.
Corresponding state relations for the viscosity of moderately concentrated polymer solutions
Authors: Utracki L. , Simha Robert
Published: April 2003

Corresponding state relationships are considered for good (toluene) and θ‐solvents. The polymers investigated are polystyrene, polymethyl methacrylate, and a copolymer of approximately 49 mole‐% of methyl methacrylate with styrene. The choice of the reduced variables ηsp(c[η]) and c/γ permits the construction of master curves, characteristic of a given polymer‐solvent system over a wide range of molecular weights. The concentration parameter γ varies with the degree of polymerization less rapidly than c0, the concentration for overlap of average coils, particularly in the good solvent. Here γ is independent of temperature. In cyclohexane, γ is proportional to the critical concentration for phase separation. The existence of such universal relations results in an explicit form for the coefficients of the power series expansions of the viscosity as a function of c. In particular the parameter k1 is predicted to be a slowly decreasing function of molecular weight in the good solvent, but to be almost independent in cyclohexane. This is in accordance with recent observations for polystyrene fractions below 50,000. However, the scatter in the experimental data does not permit a quantitative comparison. Moreover, the results must be sensitive to polydispersity and depend on higher moments of the distribution, as is indicated by the relation between γ and the critical concentration.
On the helical structure of polytetrafluoroethylene
Authors: Iwasaki Machio
Published: April 2003

The molecular parameters of polytetrafluoroethylene were determined from x‐ray diffraction data (Bunn and Howells) as CC = 1.54 A., CF = 1.36 A., ∠CCC = 114°36′, ∠FCF = 108°30′; each angle of internal rotation around each CC bond is 16°28′ from the trans position. Calculation of the angle of internal rotation for the most stable configuration of the polymer chain was carried out based on the steric and electrostatic interactions. The minimum position of the potential energy seems to be subject chiefly to the steric interaction. The effect of the electrostatic interaction on the minimum position was rather small as compared with the steric interaction. The calculated angle of internal rotation and the fiber period are, respectively, 19° and 16.78 A., which are in very good agreement with the experimental values 16°28′ and 16.8 A.
Copolymerization characteristics of methyl acrylate and methyl methacrylate. I. Study of copolymerization kinetics by a deuterium tracer method
Authors: Shima Mikiko , Kotera Akira
Published: April 2003

The kinetics of copolymerization for the methyl acrylate–methyl methacrylate system was studied by using monomers which contain deuterium as a tracer. The experiments were made on two series of copolymerizations: methyl acrylate–deuteromethyl methacrylate, (CH2C(CH3)COOCH2D), and deuteromethyl acrylate (CH2CHCOOCH2D)–methyl methacrylate copolymerization systems. Mass spectrometric analysis was employed for determining the composition of copolymers. The agreement of the experimental results of the two series was reasonable. The monomer reactivity ratios for the methyl acrylate (M1)–methyl methacrylate (M2) system were determined as r1 = 0.47 ± 0.09 and r2 = 2.3 ± 0.5 at 130°C. These values were compared with those calculated from the Price‐Alfrey Q‐e scheme.
Electron spin resonance of gamma‐irradiated cellulose
Authors: Florin Roland E. , Wall Leo A.
Published: April 2003

Irradiation of purified cellulose with cobalt‐60 gamma rays in vacuo produces moderate yields of radicals detectable by electron spin resonance. The ESR spectrum is asymmetric, with five partially resolved peaks occupying a total region of about 50 gauss wide and a spectroscopic splitting factor near g = 2. The peaks show differing saturation behavior with increasing microwave power. Differences of crystallinity have no obvious effect on the yield or nature of the radical ESR spectrum. The presence of about 8% water during irradiation decreases the yield greatly and modifies the hyperfine structure. For dry cellulose the initial G value for radicals is near 2.8 radicals per 100 e.v. absorbed, but the concentration levels off at doses a little over 6 × 1020 e.v./g. Despite the early falling‐off in yield, the radicals in stored irradiated specimens do not decay appreciably in several days. Even upon contact with air the decay is quite slow. Thermal decay is imperfectly second‐order, fairly rapid above 120°C., and indicates several radicals of differing lifetimes.
Molecular motion in polyethylene. III
Authors: McCall David W. , Anderson Ernest W.
Published: April 2003

Proton magnetic resonance studies of polyethylene have been extended. The relationship of the rigid fraction (NMR) to the crystalline fraction is discussed, and a case is presented for the relative importance of the rigid fraction (or its complement, the mobile fraction). When the polymer has been swollen by low molecular weight solvents, the NMR spectra yield rather direct evidence that the rigid, and presumably crystalline, regions are unaffected. The nature of the molecular motion is discussed in terms of a model, and it is shown that NMR data imply a rather general type motion.
The second newtonian viscosity number
Authors: Merrill E. W. , Mickley H. S. , Ram A. , Stockmayer W. H.
Published: April 2003

The second Newtonian viscosities η2 of solutions of polystyrene and polyisobutylene were determined in a coaxial cylinder viscometer at shear rates near 105 sec.−1. The second Newtonian viscosity numbers (η2 — ηs)/ηsc, where ηs is solvent viscosity and c is polymer concentration, were determined as a function of concentration. For polymer species of viscosity‐average molecular weight \documentclass{article}\pagestyle{empty}\begin{document}$\overline M _v {\rm less than }1 \times 10^6 , {\rm }\mathop {\lim }\limits_{c \to 0} (\eta _2 - \eta _ {\rm s} )/\eta _ {\rm s} c$\end{document} appears almost identical to intrinsic viscosity [η]. Above M̄v ⋍ 1 × 106, a plateau of constant (η2 — η2)/ηsc is found when this function is plotted against c. For good solvents the plateau value: {(η2 — ηs)/ηsc}p lies below [η], but in poor solvents (near the θ temperature) the opposite is true. Correlation of plateau values vs. M̄v can be achieved in the manner of the Mark‐Houwink equation: [η] = K′M̄va, by writing: {(η2 — ηs)/ηsc}p = K″M̄vb. The sum of a + b of any species in two given solvents is approximately unity. Though the data are inconclusive, it appears that even above M̄v ⋍ 1 × 106, the second Newtonian viscosity number tends to approach [η] as c approaches zero.
On the ultraviolet absorption spectrum of polyvinyl alcohol
Authors: Haas Howard C. , Husek Helen , Taylor Lloyd D.
Published: April 2003

A study of the ultraviolet absorption spectrum of polyvinyl alcohol (PVA) was made. Spectral examination of the solvolysis products of vinyl acetate and 1‐methoxyvinyl ester copolymers shows unequivocally that the absorption bands in PVA at 225, 280, and 330 mμ are related to carbonyl‐containing structures. The high intensities of these bands in the solvolyzed copolymers is additional evidence that the absorbing groups cannot be unconjugated carbonyl and are probably of the type \documentclass{article}\pagestyle{empty}\begin{document}$ - (\rm{C} \hbox{=\hskip-1.5pt=} \rm{C})_{n} \hbox{---} \mathop C\limits^{\mathop {||}\limits^O }\hbox{---}.$\end{document} Ultraviolet dichroism measurements tend to confirm this view. The ultraviolet absorbing bands in PVA arise predominantly from two sources: the presence of acetaldehyde, and dissolved air in the vinyl acetate monomer during polymerization. In the case of the latter, the formation of the vinyl acetate—oxygen copolymer and its subsequent decomposition to aldehydic‐type products introduce, into the polymer, chain structures similar to those introduced by acetaldehyde. By the careful exclusion of acetaldehyde and air during vinyl acetate polymerization and by a judicious choice of initiator, PVAs having minimal ultraviolet absorptions can be prepared. Treatment of PVA at room temperature with dilute aqueous alkali results in a marked diminution in the intensities of all three absorption bands. Hot dilute acid, while essentially removing the 330 mμ band, produces no consistent change in the relative intensities of the 225 and 280 mμ bands.
Reaction kinetics and tacticity of macromolecules. II. Acrylic acid copolymers
Authors: Smets G. , Van Humbeeck W.
Published: April 2003

The influence of steric effects and of the microtacticity of polymeric chains has been examined during the hydrolysis of acid–ester copolymers. Four different acrylic acid–ethyl ethacrylate copolymers have been prepared; their molar acid content was 50, 67, 77, and 85%. The rate of hydrolysis was examined at different degrees of neutralization in buffered aqueous solutions at 113°C. The rate was directly proportional to the content of (acid–ester–acid) triads and was highest where the degree of neutralization was equal to 0.5. The final degree of conversion is, however, limited on account of the existence of different stereochemical structures of these (acid–ester–acid) triads. Conventional and isotactic acrylic acid–methyl acrylate copolymers have also been prepared; their molar acid content was 64.5 and 80.5% for the conventional and 67 and 80% for the isotactic copolymers. From the rates of hydrolysis measured at 103°C. in buffered aqueous solutions, it becomes evident that the isotactic polymers hydrolyze 3 to 5 times more rapidly than the conventional polymers; moreover, the final degree of conversion is much higher. Finally conventional and isotactic acrylic acid–tert‐butyl acrylate copolymers have been examined; these copolymers hydrolyze only in the presence of mineral acid; any intramolecular functional interaction is absent in both cases. This stability has been explained on the basis of a different mechanism of hydrolysis of these tertiary butyl esters.
The effect of pressure on the crystallization of polyethylene from dilute solution
Authors: Wunderlich Bernhard
Published: April 2003

Linear polyethylene has been crystallized isothermally from 0.05% toluene solution at atmospheric pressure and up to 6000 atm. hydrostatic pressure. At atmospheric pressure a high temperature form of unknown structure was found crystallizing above 90°C. Single crystal lamellae crystallized between 75 and 90°C. Dendrites were formed below 75°C. The temperature dividing the dendritic growth from single crystalline growth increases with increasing pressure. The thickness of crystals grown at approximately constant supercooling, but at elevated temperature and pressure increased only slightly. A discussion in the light of present day theories is attempted.
Grafting vinyl polymers onto cellulose by high energy radiation. I. High energy radiation‐induced graft copolymerization of styrene onto cellulose
Authors: Huang R. Y.‐M. , Immergut B. , Immergut E. H. , Rapson W. H.
Published: April 2003

Styrene has been grafted onto cellulose in the form of cotton linters, cotton cloth, and rayon by ionizing radiation. Styrene was brought into intimate contact with cellulose by extension of the “inclusion” technique of Staudinger and Krässig, and graft copolymers were prepared by exposure to high energy electrons or to gamma‐rays from Co60. Substantial grafting was obtained by irradiation in air, nitrogen, or in vacuum. The products were purified by exhaustive extraction with benzene in a Soxhlet apparatus to remove the polystyrene homopolymer. The graft copolymers were characterized by removing the cellulose backbone by hydrolysis and determining the molecular weights of the residual polystyrene. Molecular weights of the grafted polystyrene were found to be considerably higher than those of the extracted homopolymer polystyrene or the polystyrene formed by irradiating styrene in bulk. Calculations based on the molecular weights of cellulose and polystyrene in the graft copolymer indicate that despite the substantial grafting, only one in 5,000–10,000 anhydroglucose units or one in 10–20 cellulose chains carried a grafted polystyrene chain.
NMR study of molecular chain structure of polyvinylidene fluoride
Authors: Wilson Chas. W.
Published: April 2003

Improved resolution of the 40 and 56.4 Mcycle F19 NMR room temperature spectra of solutions of polyvinylidene fluoride in dimethylacetamide has resulted in a clearer understanding of the polymer chain structure. The spectra indicate that the structure of polyvinylidene fluoride consists predominantly of head‐to‐tail sequences of CH2CF2 monomer links, with 5–6% of the monomer links added “backwards” to give occasional CF2CF2CH2CH2 configurations along the chain. Identifying the four principal chemically shifted lines in the NMR spectrum with four specific local chain structures, and applying simple probability theory to compare predicted and observed spectral intensities, it was possible to compute the probabilities of head‐to‐tail monomer addition (p), head‐to‐head addition (1‐p), tail‐to‐tail addition (q), and tail‐to‐head addition (1‐q). The values of both p and q varied somewhat from sample to sample, depending on the temperature and pressure of polymerization; however, both p and q were found to be in the general vicinity of 0.94. This is believed to be the first reported instance in which the relative probabilities of head‐to‐head, tail‐to‐tail, head‐to‐tail, and tail‐to‐head monomer addition in free‐radical polymerization have been determined.
The locus of adhesive failure
Authors: Huntsberger J. R.
Published: April 2003

The problem of the locus of adhesive failure is discussed. It is proposed that real systems will show departures from regularity and that the interaction between phases is frequently diminished by stearic effects leading to interfacial separation. This is counter to some recently proposed views. Estimates of the magnitude of these effects required to lead to interfacial separation are given in terms of failure criteria. Interferometry was used to provide experimental evidence that interfacial separation can occur between poly‐isobutylene and a crosslinked alkyd resin. The performance of this system was also shown to be in harmony with the proposed failure criteria.
Stability of helical conformations of simple linear polymers
Authors: De Santis P. , Giglio E. , Liquori A. M. , Ripamonti A.
Published: April 2003

The potential energy of polyethylene, polytetrafluoroethylene, polyoxymethylene, polyisobutylene, polyvinylidene chloride, and isotactic polypropylene with a helical conformation has been calculated as a function of the angles of rotation around the bonds of the backbone chain. The use of appropriate functions to describe the interaction between nonbonded atoms in the chains, has allowed prediction with surprising accuracy of the most stable conformation for the each polymer considered, in spite of the rather drastic assumptions involved in the calculations. The most prominent feature of the potential energy diagrams are discussed with reference to the possibility of predicting the allowed helical conformations for the isolated unperturbed polymer chains considered.
Some novel effects in solution polymerization
Authors: Anderson D. B. , Burnett G. M. , Gowan A. C.
Published: April 2003

The polymerization of methyl methacrylate initiated by 2,2′‐azoisobutyronitrile in the presence of halogenated benzenes and naphthalene has been investigated. In each case the order of reaction with respect to monomer is apparently of an order less than unity. Suggestions as to the possible participation of the solvent in the initiation process are discussed and shown to be in agreement with experimental measurements.
Electron spin resonance spectra of aged, γ‐irradiated polystyrenes
Authors: Florin R. E. , Wall L. A. , Brown D. W.
Published: April 2003

The electron spin resonance spectrum of polystyrene that has been γ‐irradiated at −196°C. changes gradually with time from a broad three‐peaked structure with outer derivative peaks at ±46 gauss to a much narrower structure with poorly separated outer derivative peaks at ±21–24 gauss. The deuterated polystyrenes behave likewise in general. The aged radicals of α,β,β‐trideuterostyrene and β,β‐dideuterostyrene exhibit only a single peak with derivative maxima at ±7 or 8 gauss from center. The aged spectra are all consistent with the hypothesis of major hyperfine interaction with β hydrogens. During the aging about 80% of the original radicals are lost, but the remainder are very long‐lived. Poorly evacuated samples or those with added benzene decay much more rapidly.
Nuclear radiation effects in polytetrafluoroethylene
Authors: Kline D. E. , Sauer J. A.
Published: April 2003

Dynamic mechanical studies of polytetrafluoroethylene, subjected to a total reactor radiation dose of about 108 rads, have shown that a decrease occurs in the height of the three damping peaks which are observed in unirradiated samples near 200, 300, and 400°K. Since the 200°K. and 400°K. peaks are associated with configurational changes in the amorphous regions of the material, the experimental observations are compatible with an increased degree of crystallinity. The effects observed in the dynamic modulus–temperature relation upon irradiation are consistent with those found in the internal friction spectrum. The changes that occur in degree of crystallinity upon irradiation have been studied by both infrared and density measurements, and an increase in crystallinity has been found. The changes in the dynamic mechanical properties in the vicinity of room temperature are not well understood, but possible reasons for the observed behavior are given.
Isomorphism in polycarbonates. Copolymers of hydroquinone and substituted hydroquinones
Authors: Rubin Isaac D.
Published: April 2003

Copolycarbonates were synthesized by phosgenating various proportions of chlorohydroquinone with hydroquinone, toluhydroquinone, and 4,4′‐dihydroxydiphenylmethane. It was found, by means of x‐ray diffraction diagrams and melting point–composition data, that the copolymers prepared from hydroquinone–chlorohydroquinone and toluhydroquinone–chlorohydroquinone mixtures were isomorphous over their entire composition range. The copolymerizations of 4,4′‐dihydroxydiphenyl with chlorohydroquinone resulted in products characterized by reduced crystallinity. The effect of the monomer structure on changes in the lattice constants of the crystalline copolymers was investigated briefly.
The molecular structure of polyethylene. XII. Intrinsic viscosities of polyethylene solutions
Authors: de la Cuesta M. O. , Billmeyer F. W.
Published: April 2003

While the intrinsic viscosity of polyethylene solutions is reported in the literature for at least 6 different solvents and 14 different temperatures in 23 combinations, few relations exist for converting from one set of conditions to another. Likewise, intrinsic viscosity–molecular weight relations are reported for several sets of conditions and polymer types, in some cases leading to inappropriate comparisons. The following relations are established between the intrinsic viscosities of branched polyethylene in different solvents:

where α denotes α‐chloronaphthalene at 125°C. d, decahydronaphthalene at 70°C.; t, tetrahydronaphthalene at 125°C.; and x, p‐xylene at 85°C. The relations for linear polyethylene are significantly different from those for branched polyethylene, but have not been established in detail. The literature is examined for the appropriateness and reliability of intrinsic viscosity–molecular weight relationships for polyethylene. Analysis of the experimental data leads to the following relations for linear polyethylene which are proposed as the most consistent, reliable, and appropriate currently obtainable (in‐trinsic viscosities are expressed in deciliters/gram for measurement conditions of decahydronaphthalene at 135°C., within experimental error of those specified in ASTM D 1601–58T). For the number‐average molecular weight of fractions of linear polyethylene, [η] = 2.3 × 10−4 Mn0.82; for the weight‐average molecular weight of whole polymer samples of linear polyethylene, [η] = 2.55 × 10−4 Mw0.74; for the weight‐average molecular weight of fractions of linear polyethylene, [η] = 3.9 × 10−4 Mw0.74
Homogeneous anionic polymerization. IV. Kinetics of butadiene and isoprene polymerization with butyllithium
Authors: Morton Maurice , Bostick E. E. , Livigni R. A. , Fetters L. J.
Published: April 2003

The kinetics of polymerization of butadiene and isoprene with butyllithium initiator have been studied both in n‐hexane and tetrahydrofuran solution. The overall polymerization rates were much faster in the THF solutions than in n‐hexane, and the latter also exhibited relatively slow initiation rates compared to propagation. By use of a preinitiation technique, where necessary, it was possible to study the propagation kinetics without any interference by initiation. The propagation reaction was found to be first‐order with respect to monomer in both solvents, but much faster in THF. Furthermore, it was first‐order with respect to growing chain concentration in the THF system, but only half‐order in the n‐hexane system. This was taken to indicate the existence, in n‐hexane solution, of an association equilibrium between active single chains and inactive chain pairs. The activation energy for propagation was found to be 6–7 kg. cal. in THF and about 22 kg. cal. in n‐hexane for both monomers, but the latter value obviously includes the heat of dissociation of the associated chain pairs. The Arrhenius expression for the propagation rate in THF contains a very low frequency factor (∼︁104) and leads to a propagation rate constant at least two orders of magnitude less than the corresponding value for free radical propagation.
Anisotropic properties of strained viscoelastic fluids. III. Birefringence of polystyrene solutions
Authors: Toggenburger Robert , Gill Stanley J.
Published: April 2003

Birefringence relaxation has been studied in concentrated polystyrene solutions. The birefringent state is induced by a sudden application of strains and the subsequent relaxation effect is observed by photoelectric monitoring. The effect of temperature concentration on the decay of induced birefringence follows the general patterns observed for stress relaxation. Samples of different molecular weights and different molecular weight distributions have been studied. A particularly simple empirical result was found to express the relaxation behavior of highly fractionated materials. In such instances the birefringence decays with exponential dependence upon the square root of time. The results for samples with broad distributions show curvature when plotted in a similar fashion. This simple relaxation behavior has a simple LaPlace transform, so that a comparison of the exact relaxation distribution function with approximate methods can be made. The general behavior of birefringence relaxation distribution functions is similar to that noted for stress relaxation functions. The method of reduced variables likewise is applicable to bring the birefringence relaxation results into correspondence at different temperatures.
Theoretical calculations of stress relaxation in concentrated solutions
Authors: Toggenburger R. , Beck K. , Gill S. J.
Published: April 2003

The Mooney theory for stress relaxation of polymer materials has been numerically evaluated in unmodified and modified forms. The modified expressions include such effects as molecular weight distributions and entanglement or polymer interaction distributions. The relaxation behavior was found to be highly dependent upon the number of interaction points per chain molecule particularly for small numbers. The distributions in molecular sizes and in the number of interaction points have a much smaller effect on the shapes of the relaxation curves. A comparison of the theoretical stress relaxation behavior is made with birefringence relaxation data. The region of correlation indicates a number of five interaction points per molecule of polystyrene at 10 wt. % in benzene.
Olefin polymerizations and polyolefin molecular weight distribution
Authors: Chien James C. W.
Published: April 2003

A method for rapid determination of the nonuniformity coefficient, Mw/Mn, of linear polyethylenes and crystalline polypropylenes is described. The number‐average molecular weight Mn was determined by counting the number of C14‐labeled alkyl groups introduced into the polymers during the initiation step. The weight‐average molecular weight Mw was calculated from viscometric data. The errors in these calculations were estimated. The values of Mw/Mn thus obtained for eleven samples of linear polyethylenes and three samples of crystalline polypropylenes are compared with the corresponding results obtained by polymer fractionations. The agreement was good for all the polyethylene and polypropylene samples studied except for three high viscosity polyethylene samples with high Mw values and low Mn values from fractionation data. The Mw/Mn values were determined for polymer samples taken during ethylene polymerizations initiated by the (C5H5)2TiCl2–(CH3)2AlCl system. This ratio at first decreased with the polymerization time, then reached a minimum as the concentration of growing chains reached a maximum. Comparison of polyethylene produced at various temperatures reveals that the width of polymer distribution decreases with rising polymerization temperatures. This decrease is attributed to the increase in the rates of initiation and termination and the higher activation energy for the termination processes. High catalyst concentrations yielded polyethylenes of broad distributions. At high catalyst concentrations, the concentrations of growing chains are also high. Consequently, more low molecular weight chains terminate early to give products with large Mw/Mn. On the other hand, increase of the Al/Ti ratio increases chain transfers giving polyethylenes having a low Mw/Mn. An additional effect of increasing the Al/Ti ratio is the decreased variation of Mw/Mn with t. The Mw/Mn values of crystalline polypropylene samples taken during polymerizations initiated by α‐TiCl3‐(C2H5)2AlCl are also presented. They were high at the beginning of the polymerizations and decreased gradually to a lower constant value. At higher temperatures, this variation was less pronounced; and the Mw/Mn values were lower than those for the polymers obtained at lower temperatures. The Mw/Mn values were insensitive to experimental variables such as the catalyst concentrations, the Al/Ti ratios, and the monomer pressures in agreement with the kinetic results. The Mw/Mn values of amorphous polypropylene samples taken during propylene polymerizations did not vary with t or with the other polymerization conditions. These results support the earlier kinetic interpretation that extensive chain transfers occur during the formation of amorphous polypropylenes.