bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusive and hydraulic permeabilities of water in water‐swollen polymer membranes
Authors: Yasuda H. , Lamaze C. E. , Peterlin A.
Published: April 2003

The diffusive permeability of water P, which relates to diffusive flux of water under a concentration gradient of water (measured by diffusion of tritiated water), and the hydraulic permeability of water K, which relates to the water flux under a hydraulic pressure gradient are defined. For the case of diffusive transport one has P = KRT/ν1, where ν1 is the molar volume of water. The relationship between P and K was investigated as a function of hydration H, i.e., the volume fraction of water in swollen polymer membranes. The following characteristic features of water permeability are revealed. (a) In the lowhydration region (H < 0.2), water permeates by diffusion even under an applied hydraulic pressure gradient and KRT/ν1 = P. (b) In the higher hydration region KRT/ν1 is greater than P, and the ratio ω = KRT/ν1P increases nearly exponentially with decrease of (1‐H)/H. Water in this region moves partly by bulk flow under an applied hydraulic pressure gradient but moves only by diffusion in the absence of a pressure gradient. (c) The dependence of log P on (1‐H)/H is nearly linear in regions of both high and low hydration but the slopes are different. The transition occurs in about the same H range where the discrepancy between P and KRT/ν1 becomes significant. Excellent agreement was found between the experimental data for P as a function of H and the theoretical prediction based on the free‐volume concept of diffusive transport in hydrated homogeneous membranes.
Glass transition temperatures of some linear polymers containing phenyl side groups
Authors: Pizzirani Giovanna , Magagnini Pierluigi , Giusti Paolo
Published: April 2003

The glass transition temperatures of a number of poly(vinyl phenyl ketones), poly‐(vinyl benzoates), and poly(phenyl acrylates) have been measured by a refractometric method. The effects exerted on Tg by the nature and position of the ring substituents and by the different groups binding the pendant phenyl rings to the polyvinyl chain are discussed. The importance of knowledge of the side‐group motions in the glassy state for the interpretation of glass temperature data is emphasized.
Viscoelastic properties of linear polymers in the high‐elastic state
Authors: Vinogradov G. V. , Dzyura E. A. , Malkin A. Ya. , Grechanovskiǐ V. A.
Published: April 2003

The relation between molecular weight, chain rigidity and the length of the high‐elasticity plateau is determined from frequency and temperature dependences of the storage modulus for polybutadienes and polystyrenes with Mw/Mn ⩽ 1.1. Use is made of the concept of equivalence of high‐elastic states characterized by equal lengths of high‐elastic plateaus for linear polymers. The high‐elastic states of the linear polymers studied are equivalent if the polymer chains have equal numbers of dynamic segments and if the reference temperature is T0 = 1.22Tg, where Tg is the glass transition temperature. The viscoelastic properties of the polymers in the high‐elastic state are determined unambiguously by Tg and the molecular weight of the dynamic segment. The quantitative relation between thermomechanical characteristics obtained by measuring deformation versus temperature under a constant time regime and dependence of storage modulus versus frequency under isothermal conditions is discussed.
Study of low‐frequency motions of extended chains in polyethylene by Neutron inelastic scattering
Authors: Berghmans H. , Safford G. J. , Leung P. S.
Published: April 2003

The low‐frequency skeletal and intermolecular modes (below 900 cm−1) have been studied for a sample of “as‐polymerized” Ziegler‐Natta polyethylene for which extended‐chain conformations have been proposed. These results have been compared with data from a sample of stirred‐solution‐crystallized polyethylene and with previous measurements for highly crystalline samples of folded‐chain polyethylene. Measurements were also made of the temperature dependence of these modes for the as‐polymerized material and of the polarization dependence of these modes for an oriented sample of solution‐stirred polyethylene. In the neutron spectra and the corresponding derived frequency distributions, the observed major “singular” frequencies for both the skeletal and intermolecular modes are in reasonable accord with those previously observed for folded‐chain samples of high crystallinity and in Raman measurements. In addition, these frequencies agree with those predicted by theory for the singular frequencies corresponding to the phase‐frequency relationships for the skeletal and intermolecular modes of an infinitely extended chain in a crystal. However, in the spectra of the extended‐chain materials, these singular frequencies, in general, appear sharpened and enhanced in intensity relative to those for previously reported results on folded‐chain polyethylenes; consequently, assignment of their characteristic frequencies is easier. In addition, evidence is presented to show that, for the extended‐chain materials, these frequencies broaden less rapidly with increasing temperature, and the corresponding average vibrational amplitudes are smaller than those observed for highly crystalline samples of folded‐chain material. It is suggested that in these materials the reduction of the number of chain folds and the increased intramolecular ordering give rise to increased thermal stability of the configurations with regard to segmental rotation and to decreased vibrational amplitudes relative to folded‐chain materials. When the aspolymerized materials is preheated above the normal melting point for polyethylene, the neutron spectra revert to those more characteristic of the folded‐chain materials, indicating that a relaxation of chain extensions has occurred. However, on the basis of these results, on quantitative estimates of the characteristic relaxation time can be presented. Additional frequencies, besides those predicted by theory for the skeletal and intermolecular modes and those associated with either multiphonon contributions or the presence of chain folds, are observed. The origin of these frequencies remains unclear but may warrant further theoretical consideration.
Crystal deformation during the growth of kink bands in oriented polyethylene
Authors: Robertson Richard E.
Published: April 2003

When oriented polyethylene is sheared at an angle to the orientation axis, kink bands often develop and grow, with a resulting change of the crystalline orientation. Beside the crystalline reorientation, the following changes within the kink bands have been observed with wide‐angle x‐rays: (a) partial transformation to a monoclinic from the normal orthorhombic unit cell; (b) partial alignment of the orthorhombic b axes; (c) rotation of the orthorhombic c axes of a fraction of the crystals around the kinks by an extra 40 to 60° beyond that of the fibrils; and (d) misalignment of the orthorhombic (hk0) planes by a few degrees. These results are suggested to arise, at least in part, from crystal flattening and from crystal twinning or pseudotwinning on planes intersecting the molecular axes.
Halogenation of polyethylene. I. Bromination of single crystals
Authors: Harrison Ian R. , Baer Eric
Published: April 2003

It has been demonstrated that the fold surfaces of polymers can be specific towards chemical attack, if the reaction is mild and nondestructive of the fold. Bromination of suspensions of single crystals of polyethylene in carbon tetrachloride has been shown to be such a system. This chemical modification of a fold surface is a powerful means of extending the applications of the physical methods available. Several methods were used, among them DTA, DSC, infrared spectroscopy and small‐angle x‐ray diffraction. Experimental results from these methods lead to the following conclusions. (a) Bromination takes place preferentially at the folds and is consistent with a regular adjacent reentry fold model. (b) Annealing of these brominated crystals demonstrates the major role played by the crystal surface in this process. (c) The preparation and properties of a novel copolymer system has been demonstrated. It is felt that this copolymer system may prove a useful addition to those systems presently available.
Transport properties of methylene chloride in drawn polyethylene as a function of the draw ratio
Authors: Williams J. L. , Peterlin A.
Published: April 2003

The sorption and diffusion constants of CH2Cl2 at room temperature in quenched polyethylene film drawn at 60°C to different draw ratios λ between 6 and 25 drop drastically between λ = 8 and λ = 9 and then remain nearly constant, dropping only slightly up to λ = 25. Also, the exponential dependence of diffusion constant on concentration of sorbent increases abruptly in the same draw interval and then remains constant at the higher draw ratios. The data may be explained well by a composite madel: a low‐permeability fiber structure embedded in a high‐permeability spherulitic matrix. As the draw ratio is increased, the initially spherulitic film is gradually transformed into the fiber structure with the transformation being completed between λ = 8 and λ = 9. During subsequent drawing to λ = 25 the mutual arrangement of microfibrils, the basic elements of the fiber structure, changes by longitudinal sliding. However, their transport properties remain nearly constant. The diffusion constant drops a little as a consequence of the increased fraction of tie molecules which reduces the number of unperturbed sorption sites.
Crystal structure of methyl acrylate
Authors: Brown Allan , Gillbro Tomas , Nilsson Bo
Published: April 2003

Methyl acrylate, CH2CHCOOCH3, has been crystallized, and x‐ray data have been collected at −120°C. The crystals are orthorhombic, space group Pnma, with four molecules in the unit cell. The structure has been determined by using symbolic addition procedures, and refined to a final residual R factor of 0.10. The molecule is planar, and the intramolecular bond distances and angles are in good agreement with values obtained for the liquid monomer by electron diffraction techniques. Considerations of crystal geometry indicate that the packing hardly permits dimerization or polymerization of the molecules in regions of crystal perfection.
Transitions and relaxations in aromatic polymers
Authors: Wrasidlo Wolfgang
Published: April 2003

Transition and relaxation phenomena in 26 structurally related polyquinoxalines and other aromatic polymers were studied over a temperature range from 70 to 770°K by means of calorimetric, dilatometric, dynamic mechanical, and dielectric techniques. Differential thermal analysis and x‐ray data showed these polymers to be essentially amorphous. The lack of crystallinity is attributed to geometric isomerism, resulting in conformational as well as configurational disorder. Calorimetric measurements gave discontinuities in heat capacities ranging from 12 to 54 cal/°C per mole of repeat‐unit structures and provided unambiguous assignments of glass transition temperatures of these polymers. Depending upon structure, Tg varied from 489 to 668°K. Thermal expansion curves of annealed bulk polymer samples between 70 and 770°K exhibited only one discontinuity over the entire temperature range, namely at Tg, thus indicating the absence of any motion leading to transitions in the solid state of these polymers. Viscoelastic properties were obtained by means of torsional braid analysis and a longitudinal vibrational apparatus. In a typical case, the dynamic mechanical relaxation spectrum contained three loss maxima. A peak of low amplitude occurring at 483°K was attributed to impurity effects, resulting from endgroups and species of low molecular weight. The second and only major relaxation process occurred at 579°K, in the glass transition interval. A third, weak loss peak of unknown origin was found in the liquid state at 683°K. On the other hand, the dielectric loss curves of various polymers exhibited only one broad and strong absorption maximum at temperatures 30 to 100°K higher (depending upon a particular polymer) than equivalent major mechanical loss peaks. These differences are interpreted from a mechanistic point of view. Major mechanical relaxations occurring in the glass transition interval of these polymers are proposed to result from translational motions.
Polymerization of monolayers. VI. Influence of the nature of the exchangeable ion on the tacticity of insertion poly(methyl methacrylate)
Authors: Blumstein Alexandre , Parikh Kirit K. , Malhotra Shadi L. , Blumstein Rita
Published: April 2003

The influence of the nature of exchangeable cations on the tacticity of poly(methyl methacrylate) (PMMA) prepared from montmorillonite–MMA adsorption complexes was investigated. The strength of ion‐dipole interactions was estimated either by the value of the electrostatic interaction potential or by the value of the carbonyl‐stretching frequency shift. It was shown that Pi, the percentage of isotactic triads in the polymer, increases with increasing strength of the ion‐dipole interactions, while the persistence ratio and the mean length of closed isotactic (or syndiotactic) sequences remain essentially unchanged regardless of the nature of the cation. It was shown that values of Pi may vary from 0.15 for weakly interacting ions to 0.5 for strongly interacting ones, reaching at the upper limit the value calculated from the model proposed in a previous paper, thus confirming its validity.
Experimental determination of the relationships among various measures of fluid elasticity
Authors: Stratton Robert A. , Butcher Allan F.
Published: April 2003

The viscoelastic properties of a 4% solution of monodisperse polystyrene (molecular weight 394,000) in Aroclor 1260 were determined by the following techniques: creep recovery, stress relaxation upon cessation of steady flow, dynamic measurements, and normal stress difference and shear stress measurements in steady flow. All measurements were carried out with cone and plate geometry in a Weissenberg rheogoniometer. The modification of this instrument to perform creep and creep recovery experiments by use of an air‐bearing suspension and an air‐turbine drive is described. A broad range of shear rates and frequencies encompassing both linear and nonlinear behavior was employed. The elastic behavior is described in terms of the recoverable shear strain s or the steady‐state compliance Je°. The first three techniques gave identical results for Je° in the range of linear viscoelasticity for which it is defined. The normal stress difference measurements confirmed Lodge's relation s = (P11 − P22)/2σ21. Reasons for previous experimental disagreement with this result are discussed.
Fold surface of polyethylene single crystals as assessed by selective degradation studies. III. Application of the improved techniques to single crystals
Authors: Keller A. , Martuscelli E. , Priest D. J. , Udagawa Y.
Published: April 2003

Previous studies on selective degradation of polyethylene single crystals with fuming nitric acid have been extended, both by using acid of lower concentration which gave better control over the degradation, and by resorting to ozone as an oxidizing agent which among others enabled the degradation temperature to be conveniently lowered. The molecular weight distribution was followed by gel‐permeation chromatography in the course of degradation. Complete consistency between these different methods has been established, modifying some of the previous conclusions reached by this method. The principal feature which emerges is that we have a distribution of fold lengths. The largest straight fold stems can stretch across nearly the entire layer defined by the low‐angle x‐ray period, while there is a continuous distribution of shorter folds terminating deeper down in the crystals. The limiting depth at which the number of terminating folds becomes negligible can be identified and quantitatively assessed. The method of analysis is described, and individual data are discussed in detail. This picture of a fold surface layer containing essentially adjacently reentrant folds of uneven length agrees with quite recent results on other related chain‐folded systems (annealed crystals, short chains, bulk structures) obtained in these laboratories and thus appears to be of general validity. The consequences of the model for our picture on polymer crystals in particular on the nature of the “amorphous” component, are discussed.
Time‐dependent heat capacity in the glass transition region
Authors: Wolpert Stephen M. , Weitz Alexander , Wunderlich Bernhard
Published: April 2003

Time‐dependent, apparent heat capacities of glucose, poly(vinyl chloride), polystyrene, selenium, poly(methyl methacrylate), and poly(2,6‐dimethyl‐1,4‐phenylene ether) in the glass transition region were determined by differential thermal analysis. The thermal history was set by linear cooling at rates between 0.007 and 160°C/min. Linear heating for analysis was carried out at rates between 0.3 and 600°C/min. Average activation energies of 52, 81, 90, 54, 77, and 108 kcal/mole, respectively, were evaluated by using the hole theory of glasses previously developed. Within experimental limitations all data could be described quantitatively by the theoretical expressions using only one parameter, the number of frozen‐in holes, to described the thermal history. Experimental and theoretical limitations are discussed.
Structural evaluation of branched polyethylene by combined use of GPC and gradient‐elution fractionation
Authors: Wild L. , Ranganath R. , Ryle T.
Published: April 2003

A method is described and a computer program outlined whereby gel‐permeation chromatographic analysis of fractions from gradient‐elution fractionation of branched polyethylenes provides a complete molecular weight evaluation of each fraction and the parent resin. The procedure involves the use of the universal calibration concept of Benoit et al. in a way that eliminates the ambiguities present in attempts to apply it directly to whole polymers. The resultant molecular weight data for fractions, when related to their solution viscosity and low‐shear melt viscosity and to their infrared analysis, provides a total structural evaluation of a branched polyethylene resin, including molecular weight molecular weight distribution and the distribution of both long‐and short‐chain branching. The potential of this method for providing a comprehensive structural evaluation of branched polyethylene is illustrated by examples of its application in the analysis of some commercial resins.
Copolymerization of tetrahydrofuran with propylene oxide. III. 1,2,3‐propanetriol as cocatalyst
Authors: Blanchard L. P. , Kondo S. , Moinard J. , Pierson J. F. , Tahiani F.
Published: April 2003

The cationic copolymerization of tetrahydrofuran with propylene oxide was investigated with the use of boron trifluoride etherate, 1,2,3‐propanetriol, and ethylene chloride as catalyst, cocatalyst, and solvent, respectively. The reactions were carried out in the liquid phase under a blanket of dry nitrogen at atmospheric pressure and in the temperature range from −10° to +20°C. Comonomer consumption was followed by vapor‐phase chromatography, while the products were analyzed by gel‐permeation chromatography, nuclear magnetic resonance, vapor‐pressure osmometry, and chemical endgroup analysis (phthalation). The investigation was directed towards the elucidation of the influence of the initial cocatalyst content, the initial mole fraction of the comonomer, and the temperature of reaction, on the kinetics of the reaction (rates of disappearance of comonomers, reactivity ratios, comonomer conversions and product yields) and on the characteristics of the products formed (composition, molecular weight, and primary and secondary hydroxyl content). An attempt is made to interpret the results reported in the paper.
Grafting of acrylic acid onto radiation‐peroxidized polypropylene film in the presence of ferrous ion
Authors: O'Neill Thomas
Published: April 2003

Acrylic acid has been grafted from aqueous solution onto 70 μ isotactic polypropylene‐film previously peroxidized by irradiating in air with both 400 keV electrons and γ‐radiation from a 60Co source. Ferrous ion has been used to induce the redox decomposition of the macromolecular peroxy species at temperatures between 0 and 40°C. It has been shown that the effect of low [Fe2+] is to increase grafting rates, but that at [Fe2+] > 8 × 10−4 molal the retarding effect of the reducing ion becomes increasingly important. At constant [Fe2+] a pronounced maximum in rate is observed at around 50 wt‐% of acrylic acid; this may be related to increased swelling of the polymer matrix at this point. The initial rate of grafting increases as the square root of the preirradiation dose and, in the preirradiation dose rate range, 1.6–8.0 Mrad/sec, is independent of the dose rate. The grafting rate during the later stages of the reaction, however, increases as the preirradiation dose rate decreases. In the temperature range 0–40°C, the overall activation energy is 19 kcal/mole; from this value, the activation energy of initiation has been estimated to be around 20 kcal/mole.
Preparation and polymerization of someN‐(dialkylaminoalkyl)acrylamides
Authors: Hoke Donald I. , Surbey Donald L. , Oviatt William R.
Published: April 2003

A series ofN‐(dialkylaminoalkyl)acrylamides was synthesized by reductive amination ofN‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide (diacetone acrylamide) and by the reaction of either an alkenylamine or an amino alcohol with acrylonitrile. These monomers homopolymerize and copolymerize readily to form high molecular weight products. The solubility of the monomers and their homopolymers in water ranges from soluble to insoluble at room temperature. The insoluble materials can be quaternized readily to produce water‐soluble products. The solubility of the homopolymers in water decreases with increasing temperature. Glass transition and decomposition temperatures of the homopolymers are reported.
Magnetic circular dichroism studies of polystyrene solutions
Authors: Kaye H. , Hwang J. S.
Published: April 2003

The magnetic circular dichroism (MCD) spectra of “atactic” and isotactic polystyrene solutions have been found to be sensitive to configurational and conformational differences. The ratio of B terms for “atactic” polystyrene (predominantly syndiotactic) to that of cumene was found to pass through a minimum as the coil expanded in various solvents. The ratio of dipole strengths D also passed through a minimum. For isotactic polystyrene and cumene the ratio of B terms increased with increasing coil size in the range of solvents utilized. The ratio of B terms of isotactic polystyrene over atactic polystyrene was found to go through a maximum as the coil expanded whereas the ratio of dipole strengths was found to continuously decrease. These results have been interpreted on the basis of the change in short range and long range orientation and interaction distances between chromophores during coil expansion. It is concluded that the microscopic conformation of isotactic and atactic polystyrene are very different in very good solvents. The B/D ratio for cumene was found generally to decrease with increasing solvent power.
Telechelic diene prepolymers. III. Polymerization temperature study of polybutadienes
Authors: Reed Samuel F.
Published: April 2003

A study of the effect of the polymerization temperature on the yield and properties of hydroxyl‐ and carboxyl‐terminated polybutadiene prepolymers has been made. Polymerization reactions were conducted in dioxane with 4,4′‐azobis(4‐cyano‐n‐pentanol) and 4,4′‐azobis(4‐cyanovaleric acid) as the free‐radical initiators. The most significant result obtained was the observation that the polymerization temperature exhibited a pronounced effect on the heterogeneity index of the prepolymers.
Alternating copolymer of butadiene and propylene. III
Authors: Furukawa Junji , Amano Hirotoshi , Hirai Ryuichi
Published: April 2003

Alternating copolymerizations of butadiene with propylene and other olefins were investigated by using VO(acac)2–Et3Al–Et2AlCl system as catalyst. Butadiene–propylene copolymer with high degree of alternation was prepared with a monomer feed ratio (propylene/butadiene) of 4. Alternating copolymers of butadiene and other terminal olefins such as butene‐1, pentene‐1, dodecene‐1, and octadiene‐1,7 were also obtained. However, the butadiene–butene‐2 copolymerization did not yield an alternating copolymer but a trans‐1,4‐polybutadiene.
High‐resolution NMR spectra of the polysulfones of six monolefins
Authors: Ivin K. J. , Navrátil M. , Walker N. A.
Published: April 2003

100‐MHz NMR spectra are reported for solutions of the 1:1 copolymers of sulfur dioxide with hex‐1‐ene, cis‐ and trans‐but‐2‐enes, cyclohexene, cyclopentene, and norbornene, including the deuterated polymers made from hex‐1‐ene‐2‐d1, cis‐ and trans‐but‐2‐ene‐2,3‐d2, and cyclohexene‐3,3,6,6‐d4. The resolution of the spectrum of poly‐(hex‐1‐ene sulfone) was very poor in CCl4 as solvent but good in polar solvents. The main‐chain CH2 protons are nonequivalent, and their chemical shifts show sensitivity to dyad structure; the α‐CH2 protons are also non‐equivalent. The spectra of most of the other polymers are discussed in terms of possible preferential modes of addition as well as tacticity effects.
Determination of molecular weight distribution for polypropylene by column fractionation and gel‐permeation chromatography
Authors: Ogawa Toshio , Suzuki Yoshitake , Inaba Tadami
Published: April 2003

Investigations on the molecular weight distribution of cyrstalline polypropylene were carried out by column fractionation and gel‐permeation chromatography for the purpose of comparing the determination methods. Average molecular weight, standard deviation, skewness, and kurtosis were calculated as statistical parameters from the distribution curve of each, and the number‐average and weight‐average molecular weights were determined by osmometry and light scattering. The molecular weight distribution curves obtained from column fractionation were found to be narrower than those from gel‐permeation chromatography, and it was confirmed that the molecular weight distribution curve obtained from GPC was more accurate and reliable than that from column fractionation by the fact that the average molecular weight from GPC agreed fairly well with that from the absolute methods. On the other hand, no clear difference between these determination methods was observed with respect to skewness and kurtosis of the data, while the standard deviation from GPC seemed to be greater than that from column fractionation.
Effect of amines on the ceric ion‐initiated polymerization of vinyl monomers. II. Polymerization of acrylonitrile by ceric ion in presence of various substituted amines
Authors: Saha Sisir K. , Chaudhuri Ajit K.
Published: April 2003

The effect of various substituted amines on the polymerization of acrylonitrile initiated by ceric ammonium sulfate has been studied in aqueous solution at 30°C. It was found that the secondary and tertiary amines considerably increased the rate of polymerization, whereas the primary amines seemed to have no effect at all. From the kinetic studies it was found that the overall polymerization rate Rp is independent of ceric ion concentration and can be expressed by the equation: Rp = k1 [amine] [monomer] + k2[monomer]2, where k1 and k2 are constants (involving different rate constants). The accelerating effect of the amines was attributed to a redox reaction between the ceric ion and the amine involving a single electron transfer, the relative activity of the different amines being thus dependent on the relative electron‐donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.
Observation of pentads in deuterated polyacrylonitrile by NMR spectroscopy
Authors: Matsuzaki Kei , Okada Muneshisa , Goto Kojitsu
Published: April 2003

The deuterium‐decoupled methine proton spectra of polyacrylonitrile‐β,β‐d2 were measured at 156°C in dimethylsulfoxide‐d6 solution. Splittings of triad peaks caused by pentad sequences were observed. The isotactic triad resonance was resolved into three peaks and the heterotactic resonance into two peaks, while the syndiotactic resonance was unresolved or resolved into three peaks. The splittings were assigned by comparing the probability of each pentad sequence with observed intensities. The pentad signal shifted to the higher magnetic field with increasing number of meso configurations as neighbors of the central triad. It was observed that the pentad of atactic polyacrylonitrile‐β,β‐d2 obeyed Bernoullian statistics but that of isotactic polymer obtained by γ‐ray irradiation of the canal complex seemingly obeyed first‐order Markov statistics.
Ability of poly(vinyl alcohol) fibers to initiate graft copolymerization
Authors: Ogiwara Yoshitaka , Igeta Kikuji , Kubota Hitoshi
Published: April 2003

It was noted in a graft copolymerization reaction involving a system of poly(vinyl alcohol) fibers (PVA fibers), methyl methacrylate, and water that fibers oxidized with hydrogen peroxide or sodium hypochlorite or ferric ion‐adsorbing fibers effectively initiate the reaction as in the case of cellulose fibers. The initiation reaction of the sample was markedly activated by the presence of a pretreatment with an oxidizing agent at a concentration on the order of 10−9 mole/l., but the oxidized samples were sharply deactivated by such means as reduction and oximation. Since model initiators for the present system, such as iron(III) acetylacetonate‐adsorbing PVA fibers or ferric ion‐adsorbing fibres, with the co‐existence of acetylacetone were observed to initiate graft copolymerization effectively, it is believed that carbonyl groups in modified PVA fibers could be a major factor for initiating copolymerization through interaction with metallic ions.
Study of (π‐C5H5)2Ti(C2H5)Cl and its higher homologs in soluble Ziegler catalysts
Authors: Waters J. A. , Mortimer George A.
Published: April 2003

Soluble ethylene polymerization catalysts derived from (π‐C5H5)2Ti(R)Cl and R′AlCl2 where R is ethyl or higher alkyl and R′ may be methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. An early acceleration in rate occurred at this temperature in toluene solvent which was due to a solvent dependent increase in catalyst activity, not to a gradual formation of catalyst. No such solvent effect was found in nonaromatic solvents. The subsequent decay in rate, at least at low temperatures, did not depend upon valence reduction. The effect of Al/Ti ratio was studied, and certain discrepancies in the literature were shown to be due to the method of making kinetic measurements. Oxygen, which has previously been reported to affect the polymerization rate with these catalysts, was also found to eliminate the acceleration period in toluene when present in the amount of 1% of the catalyst. These catalysts gave polymers at low temperature for which the active site had long life and which did not undergo chain transfer. Therefore, they approximate many of the characteristics of living polymers.
Polymerization of vinyl chloride and copolymerization with propylene by a ternary catalyst system
Authors: Akimoto Akira , Yoshida Toshirō
Published: April 2003

Polymerization of vinyl chloride by the ternary catalyst system of VOCl3–AIRnCl3–n complexing agent was investigated. It was suggested that the formation of a polar complex (or charge‐transfer complex) between AlRnCl3–n and the complexing agent participated in the polymerization of vinyl chloride. In the copolymerization of vinyl chloride with propylene with the present catalyst system, it was more difficult to incorporate the propylene unit in the copolymer than with a typical radical catalyst.
Carbon‐13 NMR of polybutadiene
Authors: Mochel V. D.
Published: April 2003

By using the carbon‐13 NMR technique, it is shown that there are no cis‐1,4–trans‐1,4 linkages in a n‐BuLi‐catalyzed polybutadiene. The polymer consists of “blocks” of cis‐1,4 units and trans‐1,4 units separated by isolated vinyl units. Preliminary evidence suggests this might also be true for other types of 1,3‐diene polymerization. Some of the implications of this finding on the mechanism of polymerization are discussed. Tacticity triad distributions are readily determined in polybutadienes with high 1,2 addition contents.
Radiation‐induced grafting of styrene vapor to polyethylene
Authors: Kamel Ihab , Machi Sueo , Silverman Joseph
Published: April 2003

The radiation‐induced grafting of styrene vapor to low‐density polyethylene film of 0.063 mm thickness was studied at 23°C at a dose rate of 1.98 × 104 rad/hr. The concentration C of monomer in the film was measured as a function of pre‐irradiation exposure time to monomer vapor. The concentration‐dependent diffusion coefficient of styrene in polyethylene was calculated to be 4.9 × 10−9 exp {2.0C/C0} cm2/sec, where C0 is the saturation concentration of styrene in the film, and a linear boundary diffusion coefficient for styrene vapor into polyethylene film was found to be 2.0 × 10−7 cm/sec. The rate of grafting was determined as a function of the concentration of styrene absorbed in the film. The maximum graft yield was obtained with an initial styrene concentration in the film of 4 wt‐%. Under conditions of low initial monomer concentration, the grafting rate increases with irradiation time. The results are compared with previously published data on grafting of polyethylene from methanol–styrene solutions. They are explained in terms of the viscosity of the amorphous region as a function of styrene content and the resistance to the diffusion of monomer at the film–vapor interface.
Vinyl polymerization by metal complexes. III. Vinyl polymerization initiated by oligoamide and cupric ion system
Authors: Takemoto K. , Takata T. , Inaki Y.
Published: April 2003

Polymerization of methyl methacrylate and other vinyl monomers was studied in the presence of oligoamide (ϵ‐aminocaproic acid, its dimer, trimer, tetramer, and pentamer) and cupric ion in aqueous media. The polymerization was found to be of free‐radical character and selective for the type of vinyl monomer. Carbon tetrachloride can accelerate the polymerization. The initiation mechanism of the polymerization is discussed. Spectroscopic measurements were indicative of formation of 1:1 complex between oligoamides and cupric ion in aqueous NaClO4 solution. Some chemical and physical properties of the resulting polymers were measured.
Mechanism of thermal degradation of poly(vinyl chloride)
Authors: Bataille P. , Van B. T.
Published: April 2003

The mechanism of thermal degradation of poly(vinyl chloride) has been studied by pyrolysis up to 400°C in a thermobalance under four kinds of dynamic atmospheres: helium, oxygen, air, and hydrogen chloride. The gaseous product from the thermobalance was analyzed for hydrogen chloride by the argentometric determination of chloride ions by using Mohr's method. An attempt was made to analyze for other gases in the product stream by chromatography with the use of a glass column, but failed due to the accumulation irreversibly of hydrogen chloride on the column. The molecular weights of the samples were determined by measurements of viscosities at 25°C in cyclohexanone; their molecular weight distributions were studied by fractionation and gelpermeation chromatography (GPC). From the thermograms, the mechanism of degradation in different heating atmospheres, the rate, the heat effect, the energy of activation, and the order of decomposition were deduced.
Polymerization by amine–metalloid fluoride salts. I. Polymerization of ethyl vinyl ether by anilinium hexafluoroantimonate
Authors: Harris James J. , Temin Samuel C.
Published: April 2003

Anilinium hexafluoroantimonate is shown to be a very efficient cationic initiator for the polymerization of ethyl vinyl ether from −78°C to 25°C. The polymer molecular weight varied with temperature and solvent and ranged from very low to near 200,000. After a threshold concentration of catalyst had been obtained, yields were semiquantitative. The catalyst requirement was quite low, near quantitative yields being obtained at concentrations as low as 10−3 mole‐%. Polymer obtained in heptane had a small degree of isotacticity.
Solid‐state photopolymerization of α,α′‐bis(4‐acetoxy‐3‐methoxybenzylidene)‐p‐benzenediacetonitrile
Authors: Holm Myron J. , Zienty Ferdinand B.
Published: April 2003

One crystalline form of α,α′‐bis(4‐acetoxy‐3‐methoxybenzylidene)‐p‐benzenediacetonitrile is photopolymerized by a four‐center reaction to give a polymer containing alternating benzene and cyclobutane rings. The polymer is highly crystalline and insoluble in most solvents. Location of groups around the cyclobutane ring is deduced from the products obtained on thermal decomposition. Chain contained benzene rings are located in positions 1 and 3; aromatic groups alternate sides of the cyclobutane ring. Special characterization and quantum yield of the polymerization are reported, as well as polymer solution viscosity and alkaline depolymerization of the polymer.
Anionic polymerization of 1,2‐butylene oxide
Authors: Blanchard L. P. , Dinh K. T. , Moinard J. , Tahiani F.
Published: April 2003

Anionic polymerizations of 1,2‐butylene oxide were carried out in vacuum‐sealed dilatometers in the range of 30–60°C. Potassium terbutoxide and dimsyl sodium were used as initiators; dimethyl sulfoxide (DMSO) and mixtures of DMSO with tetrahydrofuran were solvents. The polymer products were analyzed by gel permeation chromatography and infrared spectroscopy. The object of the investigation was to obtain information on the mechanism of the reaction and to elucidate some of its kinetic aspects. It has been shown that the polymerizations occur by two different processes, depending on the choice of experimental conditions. One of the processes involves free ions and ion‐pairs, the other, ion‐pairs alone. In the first case, where dimethyl sulfoxide is used as solvent, the order of the reaction with respect to the initiator concentration far exceeds unity (∼1.8), while in the second case, involving mixed solvents, the order of the reaction, for all practical purposes, is one.
Peculiarities of redox polymerization of methacrolein in aqueous media
Authors: Andreeva I. V. , Madorskaya L. Ya. , Sidorovich A. V. , Koton M. M.
Published: April 2003

The effect of the amount of metabisulfite and of the change (spontaneous or deliberate) in the pH of the medium on the viscosity and structure of the polymers is shown. These data as well as evidence on the structure of the polymers formed in the presence of “foreign” aldehydes suggest that in addition to the polymerization proceeding by the radical mechanism, heterolytic processes occur at the carbonyl group. As a result, structures of the semiacetal ester type are formed in the polymer chains of methacrolein.
Catalytic action of metallic salts in autoxidation and polymerization. VIII. Polymerization of methyl methacrylate by various metal acetylacetonate–cyclic ether hydroperoxides
Authors: Osawa Zenjiro , Kawamata Toshio , Naya Motoji , Ogiwara Yoshitaka
Published: April 2003

Polymerization of methyl methacrylate by cyclic ether hydroperoxide–metal acetylacetonate systems for a number of different metals was carried out to compare with the tert‐butyl hydroperoxide–metal acetylacetonate initiating systems. The rate of polymerization of methyl methacrylate with cyclic ether hydroperoxides as initiating systems was much higher than that with tert‐butyl hydroperoxide. In cyclic ether hydroperoxide initiating systems, V(III), Co(II,III), Fe(III), Cu(II), and Mn(II) promoted the polymerization rate markedly, and Zn(II), Ni(II), Al(III), and Mg(II) had little or no effect; in the tert‐butyl hydroperoxide initiating system only V(III), Co(II), and Mn(II) enhanced polymerization rate, and most of other metals showed little or no effect. Furthermore, noticeable differences in color of solution and appearance during polymerization, and in relation between conversion and the degree of polymerization were observed. The effect of metal acetylacetonates on hydroperoxide initiators in polymerization of methyl methacrylate was also compared with that on the decomposition of hydroperoxides.
Sulfur compounds as synergistic antioxidants
Authors: Chien J. C. W. , Boss C. R.
Published: April 2003

The decomposition of tert‐butyl, cumyl, and polypropylene hydroperoxides catalyzed by SO2, H2SO4, dilauryl thiodipropionate, metal dithiolenes, and metal dithiocarbamates were studied. The principal reaction pathways leading to different products, which depend on the nature of the hydroperoxide and the sulfur compounds, were discussed. Even though metal dithiolenes are remarkable hydroperoxide decomposers, they are prooxidants for polymers under accelerated aging conditions. This is attributed to the instability of the peroxy radical‐metal dithiolene complex intermediates. Expressions for optimum composition for each component of a synergistic antioxidant system have been derived.
Generalized ring‐opening mechanism in cycloolefin polymerizations
Authors: Dall'Asta Gino , Motroni Giuseppe , Motta Luigi
Published: April 2003

Ring‐opening polymerizations of cycloolefins under low strain induced by tungsten based Ziegler‐Natta catalysts were previously shown to proceed via metathesis. Now, these investigations have been extended to highly strained four‐membered rings and to molybdenum‐, titanium‐, and ruthenium‐based ring‐opening catalysts. Ozonolysis of 1[14C] cyclobutene‐3‐methylcyclobutene copolymers confirmed the general validity of the metathesis mechanism.
Asymmetric interaction of optically active polymers with asymmetric small molecules. III. The effect of pH on asymmetric interaction of optically active acidic polymer with tryptophan
Authors: Ihara Y. , Koga J. , Kuroki N.
Published: April 2003

The interaction of optically active polymer prepared from L‐lysine and adipyl chloride by interfacial polycondensation with D‐ and L‐tryptophan was studied. It was found that selective interaction occurred, and the amount of L‐isomer bound to the polymer was greater than that of D‐isomer in the range from pH 3.0 to 7.5 at 25°C. At near pH 5.0, the maximum asymmetrical ratio was obtained. The optical rotatory dispersion and viscosity of the polymer were measured. The relationship between conformational differences of the polymer and asymmetric interaction is discussed.
Influence of γ‐irradiation on the transition temperatures of crystalline polytetrafluorethylene
Authors: Kusy R. P. , Turner D. T.
Published: April 2003

The influence of γ‐irradiation on the melting and two solid‐solid transitions, occurring near 19° and 30°C, of polytetrafluorethylene was studied by differential scanning calorimetry. A continuous depression of all three transition temperatures, with increasing dose was observed in a first scan of highly crystalline samples at a heating rate of 20°C/min. Additional information was obtained about the accompanying heats of transition. Values for the number of CF2 units excluded from the crystal lattice per 100 eV energy deposition were calculated by using an equation for the depression of the melting point by chemical impurities. The value obtained of G(–units) = 3.3 ± 0.3 is in agreement with a value of G(chemically damaged units) = 3.0 ± 0.1 previously reported on the basis of scavenging techniques. It is concluded that chemical radiation‐induced damage in this polymer may be estimated by reference to changes in the melting temperature. A value of G(–units) = 1.6 ± 0.2 was obtained by reference to the 19°C transition.
Cationic copolymerization of tetrahydrofuran with propylene oxide. IV. Use of antimony pentachloride as catalyst
Authors: Alvarez E. J. , Hornof V. , Blanchard L. P.
Published: April 2003

Propylene oxide and tetrahydrofuran were polymerized cationically by an in situ catalytic system composed of antimony pentachloride and 1,2‐propanediol. The rates of polymerization were measured by vapor‐phase chromatography in the temperature range from −20°C to +20°C. The Arrhenius parameters pertaining to the reaction of each of the comonomers were evaluated and compared with data published earlier for other catalytic systems. The present catalyst system was incapable of initiating a homo‐polymerization of tetrahydrofuran in the absence of propylene oxide, while the latter was readily homopolymerized. In a copolymerization system, the rates of consumption of both monomers were first‐order in respect to the catalyst, but the reaction ceased when all of the propylene oxide had been consumed. The relative reactivity of the two monomers as characterized by the copolymerization parameters r1 (PO) = 1.15 and r2 (THF) = 0.70 suggests that in the copolymerization system, tetrahydrofuran is capable of a reaction with its own active center. This is discussed in terms of a possible mechanism involving the effects of penultimate units and extensive chain transfer. The latter is well evident from the molecular weights of resulting copolyethers, which do not exceed one thousand.
Synthesis and properties of stereoregular 2,3,4‐tri‐o‐acetyl‐[1 → 6]‐α‐D‐gluco‐, ‐manno‐, and ‐galactopyranans
Authors: Lin John Wei‐Ping , Schuerch Conrad
Published: April 2003

Polymerization 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐mannopyranose at −60°C with phosphorus pentafluoride (0.9 mole‐%) gives stereoregular 2,3,4‐tri‐O‐benzyl‐[1 → 6]‐α‐D‐mannopyranan with substantially higher viscosity ([η] = 2.8 dl/g) than the corresponding gluco‐ and glactopyranan derivatives prepared similarly. Debenzylation with sodium in liquid ammonia produces stereoregular [1 → 6]‐α‐D‐mannopyranan of viscosity up to [η] = 0.54 dl/g. Stereoregular 2,3,4‐tri‐O‐acetyl‐[1 → 6]‐α‐D‐glycopyranans are most simply prepared by acetylation of the corresponding crude [1 → 6]‐α‐D‐glycopyranans obtained directly from the debenzylation reaction. The galactan is extremely difficult to acetylate by conventional methods if isolated in a pure form. Physical and spectral properties of these highly stereoregular synthetic 2,3,4‐tri‐O‐acetyl‐[1 → 6]‐α‐D‐glycopyranans are presented. Optical rotary dispersion curves of 2,3,4, tri‐O‐acetyl‐[1 → 6]‐α‐D‐glycopyranans show small Cotton effects in the 200–230 nm region, superimposed on strong background rotation. Circular dichroism spectra show a single n →* acetate absorption band for each polymer. The sign of the band appears to be determined largely by the C‐2 configuration. Stereoregular 2,3,4‐tri‐O‐acetyl‐[1 → 6]‐α‐D‐glycopyranans in 2,2,2‐trifluoroethanol solution are likely to possess a random rather than helical conformation.
Synthesis of soluble, branched polyphenyls
Authors: Bracke W.
Published: April 2003

The cotrimerization of phenylacetylene and diethynylbenzene yields high molecular weight highly branched polyphenyls. The polymers obtained have the usual thermal stability. They are soluble in common chlorinated solvents.
Polymerization of 4‐vinylpyridine with acylating agents
Authors: Moore J. A. , Goldstein J. A.
Published: April 2003

The reaction of 4‐vinylpyridine (4‐VP) with acylating agents in diethyl ether was investigated. Acetyl chloride (AcCl) and trifluoroacetic anhydride [(TFAc)2O] yield colored oligomers with 4‐VP, denoted P‐4VP—AcCl (III) and P‐4VP—(TFAc)2O (IV). Nuclear magnetic resonance spectrometry was used to analyze these products. A structure (XII), representing a random copolymer resulting from 1,2‐polyaddition and 1,6‐polyaddition to 4‐VP, is proposed for III and IV. Alternative mechanisms which explain these observations are discussed. Acetic anhydride (Ac2O) does not acylate 4‐VP. It is proposed that this result is caused by the inability of Ac2O to quaternize 4‐VP as an initial step leading to polymerization.