bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation of polycarbonates. IV. Effect of molecular weight on flexural properties
Authors: Golden J. H. , Hammant B. L. , Hazell E. A.
Published: April 2003

The effect of radiation dose and molecular weight on the tensile and flexural properties of polycarbonate, poly‐[2,2‐propane bis(4‐phenyl carbonate)], have been examined in detail. Tensile strength, flexural strength, and flexural modulus can be expressed as linear functions of radiation dose and are almost completely independent of molecular weight when the material is ductile. The strength of the brittle material (molecular weights less than 13,000) is however shown to be a linear function of reciprocal molecular weight. The effect of molecular weight on flexural modulus is also discussed. The presence of the equilibrium water content in the plastic has been shown to cause a fourfold increase in the rate of chain scission and an explanation of this effect is advanced.
Cyclopolymerization. V. Copolymerization of acrylic and methacrylic anhydrides with vinyl monomers
Authors: Smets G. , Deval N. , Hous P.
Published: April 2003

The copolymerizations of acrylic (AA) and methacrylic (MAA) anhydrides (M1) with styrene (St) and methacrylonitrile (MAN) have been examined; similarly that of acrylic anhydride with allyl chloride. In these systems the reactivity ratio of an open unit radical (r1) is equal to that of a cyclized radical (r3), and the usual Alfrey‐Price equation is valid. By using a graphical method the ratios of the cross propagation rate constant to the cyclization rate constant (k12/kc) have been also evaluated. The following values for r1, r2, and k12/kc respectively have been found, M1 being the anhydride: for the system AA (M1)–St, 0.1, 0.17, and 4; for the system AA–MAN, 0.9, 0.04, and 0.14; for the system AA–allyl chloride, 11.5, 0.01, and 0. For the same systems with MAA, the values of r1, r2, and k12/kc were 0.26, 0.12, and 0.2 with St, and 1.6, 0.27, and about zero with MAN. These data indicate also that the cyclization reaction is always more pronounced for methacrylic anhydride than for the acrylic anhydride.
Some elastic moduli of bisphenol A polycarbonate
Authors: Robertson Richard E. , Buenker Robert J.
Published: April 2003

The Young's modulus of oriented bisphenol A polycarbonate films were measured along, 45° to, and normal to the direction of orientation by the vibrating reed technique. The change in modulus with the degree of orientation was fitted to a theoretical curve, using an IBM 704 electronic computer. The basis for fitting the data to the theoretical curve was the assumption that the process of orienting the polymer molecules could be described by an affine transformation. The elastic moduli calculated are as follows: The Young's modulus for stretching the chain is 5.4 × 1011 dyne/cm.2; the Young's modulus for separating a bundle of parallel chains laterally is 1.76 × 1010 dyne/cm.2; and the shear modulus for the relative displacement of a bundle of parallel chains along their length is 2.00 × 1010 dyne/cm.2.
Apparent transfer constants of mercaptans in emulsion polymerization. II. Effect of reactions other than polymer chain transfer
Authors: Meehan E. J. , Kolthoff I. M. , Sinha P. R.
Published: April 2003

When all the modifier is dissolved in the polymer particles the chain transfer constant, d log (RSH)/d log (M) of n‐octyl mercaptan at 90% conversion in the emulsion polymerization of butadiene (50°C) is 19, the same value as in bulk and in emulsion at 0% conversion. The relative rate of consumption of mercaptan and monomer is unaffected by variation of persulfate and presence of a diluent such as benzene. While mercaptan is consumed by addition to the polymer double bonds (nonmodifying reaction) in monomer‐free polybutadiene latex containing persulfate, this addition reaction is virtually suppressed completely in the presence of butadiene monomer. On the basis of the accuracy of the determinations of mercaptan and monomer a slight activation of polymer molecules at high conversion with subsequent cross linking cannot be excluded.
1,5‐hexadiene polymers. II. Copolymers of ethylene and 1,5‐hexadiene
Authors: Makowski Henry S. , Shim Benjamin K. C. , Wilchinsky Zigmond W.
Published: April 2003

A series of crystalline ethylene‐1,5‐hexadiene copolymers containing 15–93 mole‐% ethylene were prepared with an AIR3/TiCl3–AlCl3 catalyst system. X‐ray diffraction analyses showed two distinct crystalline phases in the copolymers; one phase had the polyethylene structure whereas the other had the poly‐1,5‐hexadiene structure. However, the unit cell sizes of these two phases were significantly different from those of the respective homopolymers, indicating that both types of monomeric units are present in each of the copolymer phases. Physical property measurements on the copolymers support these conclusions.
2,7‐disubstituted 1,3,6,8‐tetraazopyrene and related polymers
Authors: Dawans F. , Reichel B. , Marvel C. S.
Published: April 2003

2,7‐Disubstituted derivatives of 1,3,6,8‐tetraazopyrene were synthesized as model compounds for some polymers of similar structure. Conjugated and high molecular weight polymers were obtained by polycondensation of 1,4,5,8‐tetraaminophthalene with various diphenyl esters of bifunctional aromatic acids. The inherent viscosities of a number of polymers ranged from approximately 0.15 to 0.70. Most of the polymers are infusible and some of them are insoluble in the usual organic solvents. The thermal stability properties of the polymers were very good.
Dynamic mechanical behavior of some high polymers at temperatures from 6°K.: Polyethylene, nylon 66, polypropylene, poly(vinyl chloride), poly‐(d,l‐propylene oxide), polybutene‐1, poly(4‐methyl‐pentene‐1), poly(methyl methacrylate), poly(ethyl methacrylate), poly‐4‐methylpentene‐1 and poly(isobutyl methacrylate)
Authors: Crissman J. M. , Sauer J. A. , Woodward A. E.
Published: April 2003

Measurements of the dynamic mechanical properties of various polymers have been made in the 6–300°K. temperature range at resonant frequencies of about 104 cycles/sec. by using a longitudinal vibration apparatus. The polymers studied include polyethylene, nylon 66, three poly(methacrylate esters), and five poly‐α‐olefins and related polymers. Results for poly(methyl methacrylate) and poly(ethyl methacrylate) indicate the occurrence of low temperature relaxation processes (6°K. and 52°K., respectively) involving configurational rearrangements in the hydrocarbon portion of the ester side groups. The data provide no evidence for mechanical loss processes associated with hindered rotation of the main‐chain methyl groups in the poly(methacrylate esters) or polypropylene. Very weak relaxation processes or loss plateaus are observed in the 20°K. region for polypropylene, poly(vinyl chloride), poly(d,l‐propylene oxide), poly(isobutyl methacrylate) and possibly nylon 66, while for poly‐4‐methylpentene‐1 a sizeable loss peak is observed at 25°K. The mechanisms responsible for these loss peaks are not yet understood. No relaxation phenomenon is observed below 77°K. for either polyethylene or polybutene‐1. For poly(d,l‐propylene oxide) a loss maximum or shoulder appears at 70–120°K. which is possibly associated with chain motions accompanying the methyl reorientation process.
Cationic isomerization polymerization of β‐methylstyrene and allylbenzene
Authors: Kennedy J. P.
Published: April 2003

The structure of cationically obtained poly‐β‐methylstyrene and polyallylbenzene has been investigated by high resolution infrared spectroscopy. These studies indicate that under cationic conditions β‐methylstyrene polymerizes by a conventional 1,2 mechanism, whereas allylbenzene partly isomerizes to β‐methylstyrene prior to propagation and probably gives a “copolymer” of rearranged and unrearranged units.
Kishi lag times for O2 adsorption onto irradiated poly(bisphenol‐A carbonate) and poly(methyl methacrylate)
Authors: Barker R. E.
Published: April 2003

Re‐examination of some data which were originally taken to determine diffusion coefficients and their variation with applied stress in electron irradiated poly(bisphenol‐A carbonate) and poly(methyl methacrylate) has verified the existence of Kishi induction periods ti for the initial stages of O2 sorption by these polymers. The data conform to the relation \documentclass{article}\pagestyle{empty}\begin{document}$ t_i = t_{i^0 } e^{{E \mathord{\left/ {\vphantom {E {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} e^{{{ - p} \mathord{\left/ {\vphantom {{ - p} {p1}}} \right. \kern-\nulldelimiterspace} {p1}}} $\end{document}. Some new gas sorption data for poly(bisphenol‐A carbonate) by Norton are utilized in conjunction with data and equations from our previous paper to estimate initial concentrations of the free radicals associated with the visually sharp diffusion boundary which was the major topic of our previous paper. The value G[oxygen‐bleached color‐centers/h.e.v.] obtained for these radicals is compared with recent viscometric determinations by Golden and Hazell.
Conformation of styrene–maleic acid copolymer in aqueous HCl solutions
Authors: Kuppers James R.
Published: April 2003

The properties of dilute aqueous solutions of styrene–maleic acid copolymer at low degrees of ionization are not compatible with a random coil model. Based upon a study of hydrodynamic and other solution properties of the copolymer, a model is proposed which considers intermolecular and intramolecular interactions of phenyl groups as well as forces of electrostatic repulsion of ionized carboxyl groups. Values of [η]/[η]θ less than unity are better explained by intermolecular aggregation than by a hypercoiled conformation of individual chains. Difficulties previously encountered in copolymer fractionation were resolved.
Interaction parameters and heats of dilution for ethylene–propylene rubber in various solvents
Authors: Holly Earl D.
Published: April 2003

Crosslinked ethylene–propylene rubber gels were swollen in five solvents at 25–100°C. The solvent–polymer interaction parameter μ for each system was determined as a function of temperature and polymer concentration. A thermodynamic criterion of the sign of the heat of dilution, ΔH̄1, was pointed out. For three of the systems ΔH̄1 was negative. The entropy contribution to the interaction parameter was found to be smaller than usual for systems having a temperature‐dependent heat of dilution. The heats of dilution and the entropy terms may be consistently interpreted in terms of Prigogine's theory of solutions.
Polyelectrolytes in salt solutions
Authors: Leyte J. C.
Published: April 2003

It is shown that the exceptionally low expansion values expected by Kimball, Cutler, and Samuelson's theory result from their interpretation of the Gaussian distribution function for polymer chain segments rather than a statistical mechanical additivity problem.
Post‐modification of conjugated triene polymers via the Diels‐Alder reaction
Authors: Bell Vernon L.
Published: April 2003

Polymers from 1,3,5‐hexatriene, 1,3,5‐heptatriene, and 2,4,6‐octatriene were modified by means of the Diels‐Alder reaction. Several dienophilic agents were reacted with the polytrienes containing conjugated diene groups to yield cyclic structures incorporated into, and appended to, the polymer backbone. The mild conditions of the post‐reactions proved to be convenient for the conversion of highly unsaturated polyhydrocarbons into unique polymers bearing functional substituents. It was proposed that the incomplete reaction of tetracyanoethylene with the 1,3‐dienyl groups of the polymer substrates was a result of steric hindrance of the ring structures of the polymer adducts.
Kinetics of sorption of water vapor by hydrophilic polymers. Potassium and lithium forms of poly(vinyl methyl ether–maleic acid)
Authors: Spencer H. G. , Hunt O. L.
Published: April 2003

The rates of desorption of water vapor from the lithium and potassium forms of poly(vinyl methyl ether–maleic acid) were measured at several initial concentrations and temperatures. A few absorption experiments were performed, and the resulting curves were anomalous. The sorption rates were slower for the lithium form than for the potassium form and the rates for both forms were dependent upon the penetrant concentration. Sorption coefficients, defined by analogy with diffusion coefficients, were determined from the initial rates of desorption and were used to characterize the desorption rates. Limiting‐sorption coefficients were determined and found to be much smaller than the diffusion coefficients for water vapor in polymers which are more hydrophobic.
Polymerization of higher aldehydes. VII. Tacticity of elastomeric polyacetaldehyde,
Authors: Brame E. G. , Sudol R. S. , Vogl O.
Published: April 2003

High resolution NMR spectroscopy was used to determine the tacticity of elastomeric polyacetaldehyde. Spectra obtained at elevated temperatures and in solutions of carbon tetrachloride and tetrachloroethylene showed a weak line on the high field side of a strong line in both the methyl group and the CH group regions. Comparison of these results with those obtained on related model compounds indicated that the weak lines can be attributed to the isotactic structure and that the strong lines can be assigned to the heterotactic structure. After the lines were narrowed by spin‐decoupling procedures, the area measurement results suggested that polyacetaldehyde is a highly random polymer.
Poly‐1,3,4‐oxadiazoles. I. Polyphenylene‐1,3,4‐oxadiazoles
Authors: Iwakura Yoshio , Uno Keikichi , Hara Shigeyoshi
Published: April 2003

Polyphenylene‐1,3,4‐oxadiazoles have been prepared from benzenedicarboxylic acids or their derivatives and hydrazine by solution polycondensation in fuming sulfuric acid or polyphosphoric acid. These polymers were characterized by good thermal stability, and the molecular weights attained were high enough for the products to exhibit fiber‐or‐film‐forming properties. Concentrated sulfuric acid and polyphosphoric acid were the only solvents for these polymers.
Study of phenolic resins by PMR spectroscopy with arsenic trichloride as a solvent
Authors: Szymanski Herman A. , Bluemle Albert
Published: April 2003

The PMR spectra of several phenolic resins and model compounds related to these resins are reported. Arsenic trichloride as a PMR solvent for the resins is suggested. The PMR spectra of a resin which is linked in the ortho position only is compared to that of a resin where both ortho and para linkages occur. It is shown that the completely ortho‐linked resin gives a phenolic OH signal which does not shift when HCl gas is added, while it does shift if the resin has both ortho and para linkages. This observation is explained by assigning a strong intramolecular hydrogen bond to the ortho‐linked resin. The behavior of the phenolic OH signal when HCl is added can therefore be used to distinguish between ortho and ortho,para‐linked resins. A semiquantitative approach to obtaining average molecular weights is also presented. By integrating the PMR signals of various structural units of the resin it is possible to estimate the relative number and therefore the total number of units of this type in a molecule. The total number is a measure of the molecular weight. Spectral assignments are given for the various types of structural units present in the resins.
Radical displacement in allyl ester polymerization. I. Allyl acetate; evidence from gas‐phase kinetics
Authors: James D. G. L. , Troughton G. E.
Published: April 2003

Photolysis of diethyl ketone in the presence of allyl acetate in the range 35–175°C. leads to the addition and dismutation reactions:

The proposed reaction scheme is supported by the values: R(CO2)/[R(C5H10) + R(C4H8)] = 1.02 ± 0.03, and R(C5H10)/[R(CH4) + R(C3H8)] = 1.01 ± 0.03, and allows the evaluation of k7 and k8:

where k2 refers to: 2CH3CH·2 → C4H10 and k7a to: CH3CH·2 + ·C5H10OCOCH3 → C7H15OCOCH3. These results are discussed in relation to the radical displacement mechanism of effective chain transfer in the polymerization of allylic monomers.
Rheological properties of multichain polybutadienes
Authors: Kraus Gerard , Gruver J. T.
Published: April 2003

The introduction of one or two long chain branches into a polybutadiene molecule to form trichain or tetrachain molecules, respectively, leads to profound changes in rheological behavior. At low molecular weights the Newtonian (zero shear) viscosity is decreased relative to a linear polymer of the same molecular weight. At molecular weights exceeding 60,000 (trichain) or 100,000 (tetrachain), the Newtonian viscosity rises rapidly above the corresponding value for a linear polybutadiene. However, non‐Newtonian behavior of the branched polymers becomes more pronounced the higher the molecular weight, so that at moderate to high shear rates the viscosity of the branched polymers is uniformly lower than that of linear polymers of identical molecular weight.
Phase equilibria of polymer–solvent systems at high pressures near their critical loci. II. Polyethylene–ethylene
Authors: Ehrlich Paul
Published: April 2003

The system polyethylene–ethylene exhibits the same type of phase behavior as that described earlier for polyethylene‐n‐alkane systems well above the boiling points, or above the critical points of the solvents. In this case, the solvent is always above its critical temperature in the region investigated, and one has here another case of infinite polymer‐gas miscibility. The critical locus was determined, from its intersection with the crystallization surface at about 115 to 200°C., and the three‐dimensional phase model in (P, T, composition) space is visualized.
Experiments with a synthetic polyampholyte
Authors: Allison J. P. , Marvel C. S.
Published: April 2003

The synthesis of the polyampholyte of regular structure first devised by Marvel and DeTommaso has been improved. Viscometric studies have given some evidence of contractile properties. Low molecular weight of the polyampholyte has prevented the formation of strong fibers.
Polymerization of N‐methyl‐β‐propiolactam with ionic catalysts
Authors: Kagiya Tsutomu , Kishimoto Hiroshi , Narisawa Shizuo , Fukui Kenichi
Published: April 2003

The polymerization of N‐methyl‐β‐propiolactam with various ionic catalysts in bulk was carried out at 140–190°C. Organic compounds containing a carboxyl group have a high catalytic activity for the polymerization and gave crystalline polymer melting at 180–225°C. No polymer of N‐methyl‐β‐propiolactam was formed at 140°C., but the polymerization of N‐methylacrylamide took place. The polymer of N‐methylacrylamide was amorphous and its infrared spectrum was quite different from that of poly‐N‐methyl‐β‐propiolactam. The infrared spectrum of poly‐N‐methyl‐β‐propiolactam showed a major absorption peak characteristic of a polyamide structure. On the basis of the infrared spectrum of an equimolar mixture of monomer and catalyst heated at 130°C., a mechanism was proposed.
Kinetics of polymerization of butadiene, isoprene, and styrene with alkyllithiums. Part I. Rate of polymerization
Authors: Hsieh Henry L.
Published: April 2003

The kinetics were determined for the polymerization of butadiene, isoprene, and styrene with n‐, sec‐, and tert‐BuLi in hydrocarbon solvents. Polymerization has the mechanism of a homogeneous, “intermittent” stepwise addition reaction with no true termination reaction. In cyclohexane, n‐hexane or toluene at 5–50°C. there is no chain transfer. When n‐BuLi was used, the rate of polymerization was a combined rate of initiation and propagation. It was proportional to [M]2 and dependent on [n‐BuLi] at low initiator concentration and almost independent at high concentration. The limits are established and discussed. The rate constants calculated for the monomers were in the order styrene > isoprene ≫ butadiene. For the solvents the order was toluene ≫ cyclohexane > n‐hexane.
Kinetics of polymerization of butadiene, isoprene, and styrene with alkyllithiums. Part II. Rate of initiation
Authors: Hsieh Henry L.
Published: April 2003

By gas chromatographic analysis of the hydrolyzed polymerization solutions, the per cent of BuLi unreacted was measured at various conversions. The effects of BuLi concentration, the structure of the butyl group, and the solvent type were studied. The rates of initiation (Ri) for butadiene, isoprene, and styrene were determined. For dienes, the order was sec‐BuLI > i‐PrLi > tert‐BuLi > i‐BuLi > n‐BuLi. For styrene, it was sec‐BuLi > i‐PrLi > i‐BuLi > n‐BuLI > tert‐BuLi. With n‐BuLi, the order was styrene > butadiene > isoprene. For any particular monomer–initiator combination, the order was toluene ≫ n‐hexane > cyclohexane. The results obtained here proved that Ri = ki [RLi] [M] for all three monomers.
Molecular weight and molecular weight distribution of polymers prepared from butyllithiums
Authors: Hsieh Henry L.
Published: April 2003

The calculated kinetic molecular weight Mk was compared with experimentally determined viscosity molecular weight Mv of polybutadiene, polyisoprene, and polystyrene initiated with n‐BuLi, sec‐BuLi, and tert‐BuLi. The discrepancy between Mk and Mv depends on the ratio of rates of initiation Ri and propagation Rp, which in turn depends on initiator structure and monomer. In the alkyllithium‐initiated polymerization system, Mk based on the [RLi] consumed rather than charged, is almost equal to the actual molecular weight. The ratio of Ri and Rp also affects the molecular weight distribution. The order of monodispersity for polydienes is sec‐BuLi ≅ tert‐BuLi > n‐BuLi. For styrene, it is sec‐BuLi ≫ n‐BuLi ≫ tert‐BuLi. The fractionation data are in perfect agreement with the predictions of the kinetic data. The ideal conditions for the preparation of monodispersed polymer by means of anionic polymerization are also discussed.
Reactions of titanium tetrachloride (tetraiodide, dichlorodiiodide) with alkylaluminum compounds
Authors: Moyer Patricia H.
Published: April 2003

Titanium tetraiodide and titanium dichlorodiiodide are reduced by triisobutylaluminum or diisobutylaluminum iodide to form products analogous to those obtained with titanium tetrachloride. In the reaction products, the preferred site for iodide ligands is titanium, that for chloride ligands, aluminum.
Studies of the polymerization of butadiene by titanium(IV) compounds with alkylaluminums
Authors: Moyer Patricia H. , Lehr Marvin H.
Published: April 2003

Catalysts for the polymerization of butadiene consisting of an alkylaluminum compound with a titanium(IV) compound show variations in reactivity with Al/Ti ratio. The ratio at which maximum reactivity is obtained increases as the electronegativity of the ligands bound to titanium decreases. This is observed on replacement of the chloride ligands of titanium tetrachloride by either iodide or isopropoxy ligands. Catalysts prepared from titanium dichlorodiiodide or titanium chlorotriiodide behave like those from titanium tetraiodide, as would be expected from the previous observation that titanium is the preferred site of attachment for iodide in the reduction products of mixed salts. The cis content of the polymers obtained with the iodide‐containing salts can be 90% or more, but decreases with increasing titanium concentration, whereas the structure of polymers obtained with titanium tetrachloride is independent of catalyst concentration. Polymerization is not induced by either the soluble alkylaluminum compounds or the insoluble reduced titanium iodides which are produced by the reaction of triisobutylaluminum with titanium tetraiodide. The insoluble material can be activated by triisobutylaluminum or, less readily, by diisobutylaluminum iodide.
Viscosities of concentrated polymer solutions
Authors: Nishimura Norio
Published: April 2003

A general relationship between the viscosity and the concentration of polymer solutions has been derived for relatively low concentration regions by means of the method which was proposed by Brinkman. The relationship was extended so as to be applicable for extremely concentrated solutions by allowing for the volume shrinkage of polymers. With increasing concentration, the apparent volume which a polymer in solution occupies above some critical volume fraction ϕc, is assumed to be given by Ω = sv0ϕ−β, where s is the swelling factor at ϕ = 1 and β is a constant which measures a reluctance against the intermolecular permeation; v0 and ϕ are the net volume of the polymer molecule and the volume fraction of the polymer, respectively. The dependence of η on ϕ is given by the equation d log η/dϕ = C/ϕγ (1 − ϕ), where C and γ are constants to be determined empirically. In order to test the validity of the equation, our experimental and some other available data were used. Although neither temperature nor molecular weight factor is involved in this equation, it accounts well for the dependence of the viscosity on the concentration of polymers over a wide range of concentration, and fairly satisfactory agreement was found between theory and experiment.
Copolymerization of styrene and p‐divinylbenzene. Initial rates and gel points
Authors: Storey Bayard T.
Published: April 2003

Initial rates of polymerization were measured at 70.0 and 89.7°C. for styrene, p‐divinylbenzene, and mixtures of the two monomers initiated with 1% benzoyl peroxide. The rates relative to styrene increased linearly with mole fraction of p‐divinylbenzene: the latter monomer polymerized faster than styrene by a factor of 2.50 at 70.0°C. and 3.54 at 89.7°C. Times to gelation were also measured for those samples containing p‐divinylbenzene, and from these times the corresponding fractional conversion at the gel point was calculated. The conversion at the gel point passed through a minimum with increasing content of p‐divinylbenzene. The gelation behavior is explained by concurrent interchain crosslinking to give a network and intrachain crosslinking to give microgels which accumulate to give macrogel, the latter process being dominant at all but low concentrations of p‐divinylbenzene. The higher the content of crosslinker, the less swollen the microgels, and the greater the conversion required to give gelation by this process. The linear increase in rate with increasing p‐divinylbenzene content was also explained by intrachain crosslinking: growing polymer radicals which undergo this process have a reduced rate of termination. The factor by which the termination rate constant is reduced with increasing divinylbenzene content is the same factor as that by which the conversion required to give gelation by accumulation of microgels is increased.
Kinetics of polymerization of styrene initiated by substituted peroxides. II. Decomposition rate constants and efficiencies
Authors: O'Driscoll K. F. , White P. J.
Published: April 2003

The following bis‐substituted benzoyl peroxides were used as initiators for the polymerization of bulk styrene monomer at 90°C.: p‐methoxy‐, p‐methyl‐, p‐chloro‐, m‐bromo‐, 3,4‐dichloro‐, p‐cyano‐, and p‐nitro‐; in addition, unsubstituted benzoyl peroxide was also studied. From the observed rates of polymerization the rate constants for the unimolecular decomposition and for the radical‐induced decomposition of the peroxides were obtained, as well as the efficiency of initiation of polymerization. It was observed that substituents more electron‐withdrawing than p‐chloro did not change the unimolecular rate constant. Conversely, substituents less electron‐releasing than p‐chloro had little effect on the efficiency of initiation. The induced decomposition rate constant gave a simple linear Hammett plot with positive slope.
Studies of structure formation in poly(vinyl alcohol) solutions
Authors: Zubov P. I. , Osipov E. A.
Published: April 2003

Acetalation of PVA in aqueous solution with succinaldehyde yields a gel or globular structures with strong chemical intermolecular or intramolecular bonds, depending on the solution concentration. Similar structures formed by localized physical bonds may be obtained by cooling the PVA solutions in DMF–water mixtures of certain compositions or in anhydrous DMF. Comparison of the viscosity data for the solutions with turbidity of these systems and electron microscopy leads to the conclusion that globular particles obtained by cooling the PVA solutions in anhydrous DMF are super molecular structures of colloidal size. The diameter of these particles depends not only on the solution concentration but also on the temperature to which the PVA solutions are cooled. The dimensions of the particles decrease with the temperature at which the cooled solution is kept. The globular structures are stable in anhydrous DMF and are destroyed only at 120°C. In the presence of water a redistribution of intramolecular and intermolecular bonds proceeds at room temperature and results in the formation of a thixotropic structure. The structure formation influences considerably the mechanical and adhesion properties of PVA films prepared on solid surfaces.
Turbidimetric titration method for determining solubility distributions of polymers
Authors: Beattie W. H.
Published: April 2003

A turbidimetric titration method for determining solubility distributions (which are closely related to molecular weight distributions) has been developed. In this method, polymer is precipitated from its solution by addition of a nonsolvent of the same refractive index as that of the solvent. The precipitating particles of swollen polymer are allowed to agglomerate until the turbidity reaches a maximum. It is shown by the use of light‐scattering theory that under these conditions the concentration of polymer which is precipitated can be calculated from the maximum turbidity on an absolute basis. The effects of particle size and particle size distribution are discussed. The method was tested by using polystyrene, and is shown to be accurate. In principle the method is applicable to most kinds of polymers.
Determination of the molecular weight distribution of polyisoprenes from the sol dependence on crosslinking
Authors: Calderon Nissim , Scott Kenneth W.
Published: April 2003

A polyisoprene with a narrow molecular weight distribution was prepared with a polyisoprenyl lithium catalyst by the “seeding” technique. Dicumyl peroxide was shown to be a quantitative crosslinking agent for this polyisoprene. The dependence of the sol fraction on the amount of crosslinking introduced by dicumyl peroxide vulcanization was determined and found to give excellent agreement with gel network formation theory. Two procedures for estimating the breadth of the molecular weight distribution from the sol dependence on crosslinking yield the value of 1.05 ± 0.05 for the ratio of the weight‐average to number‐average molecular weight for this polyisoprene. These results demonstrate that it is possible to determine the molecular weight and molecular weight distribution of polyisoprenes, containing cis‐1,4, trans‐1,4, or moderate amounts of 3,4 addition structures, from the sol dependence on the amount of dicumyl peroxide used in crosslinking. Temporary or permanent molecular chain scission that might accompany the crosslinking by dicumyl peroxide was negligible, as there was no evidence of broadening of the molecular weight distribution due to scission. For the most likely set of recombination reactions that might occur it is estimated that less than 0.3% of the dicumyl peroxide is used in reactions leading to temporary molecular chain scission.
Surface energetics, adhesion, and adhesive joints. III. Surface tension of molten polyethylene
Authors: Schonhorn Harold , Sharpe Louis H.
Published: April 2003

The surface tension of polyethylene has been measured by the ring method over the temperature range 125–193°C. Because of problems with the viscousness of the liquid polyethylene, it was found convenient to use an Instron testing apparatus instead of the usual du Nouy torsion balance. The surface tension of the polyethylene decreased from a value of 28.5 dynes/cm. at 125°C. to 23.3 dynes/cm. at 193°C. with an average temperature coefficient of −0.076 dynes/cm./°C.
Copolymerization of secondary fumarates with styrene
Authors: Burgh L. F. Vander , Brockway C. E.
Published: April 2003

Reactivity ratios for the copolymerization of styrene (M1) with some secondary butyl fumarates (M2) indicate that the r1 values are more dependent on the inductive effect of the alkyl groups than on the steric effect and that the r2 values approach zero. Copolymerization rates of the secondary dialkyl fumarates with 65 mole‐% styrene were found to be consistent with the r1 values and the rate of styrene homopolymerization. However, mono(1‐methylpropyl) fumarate copolymerized with styrene at a rate more than twice that of styrene homopolymerization; this agrees very well with the modified copolymer equation which is obtained when the terms of the general copolymerization equation which contain r2 are set equal to zero.
Modification of polymers via the Wittig reaction
Authors: Mallavarapu L. X. , Ravve A.
Published: April 2003

Representative macromolecules containing either aldehyde or ketone groups were subjected to the Wittig reaction. As expected, the carbonyl content of the reaction products was drastically decreased, with concomitant increase in unsaturation. This is shown by spectral and chemical evidence. However, the molecular weights of the polymers before and after reaction showed significant differences; some degree of crosslinking was also noted.
Vinyl polymerization. XCII. Polymerization of propenyl chloride isomers
Authors: Otsu Takayuki , Shimizu Akihiko , Imoto Minoru
Published: April 2003

The effect of the substituent on polymerization of isopropenyl chloride (IPC), cis‐propenyl chloride (CPC), and trans‐propenyl chloride (TPC) has been investigated. These monomers homopolymerized only very slightly in the presence of radical or ionic catalyst, and only a low molecular weight polymer of IPC was isolated. However, these monomers copolymerized with radical initiator with vinyl acetate, vinyl chloride, and acrylonitrile, and their reactivities towards the poly(vinyl acetate) radical decreased in order of IPC ≫ TPC ≥ CPC. The Q, e values for the monomers were estimated as follows: for IPC, Q = 0.06, e = −0.85; for CPC, Q = 0.005, e = −1.66; for TPC. Q = 0.009, e = −1.33. Further results on copolymerization with maleic anhydride indicated that the steric effect of the substituent for these monomers increased in order IPC ≪ TPC ≤ CPC. On radical polymerization of IPC, its degradative chain transfer reactivity was suggested to be also significant.
Rubber elasticity of preswollen polymer networks: Highly crosslinked vinyl–divinyl systems
Authors: Shen M. C. , Tobolsky A. V.
Published: April 2003

The rubber elasticity of highly crosslinked, preswollen network polymers is studied. Copolymers of tetraethylene glycol dimethacrylate with ethyl acrylate, n‐butyl acrylate, methyl methacrylate, and styrene covering the whole range of composition are investigated. Dioctyl phthalate is used to preswell the polymers up to 50% by volume. Both shear moduli and front factors are found to increase with increasing crosslink concentration but to decrease with increasing diluent content. Crosslinking efficiencies are determined by a modified Loshaek‐Fox method. They are relatively invariant with the degree of preswelling. Factors contributing toward these observations are discussed.
Effect of constraints on the equilibrium swelling of rubber vulcanizates
Authors: Southern E. , Thomas A. G.
Published: April 2003

The swelling of natural rubber vulcanizates under equal two‐dimensional compression has been investigated. The degree of crosslinking of the vulcanizate and the nature of the swelling liquid have both been varied. The reduction in equilibrium swelling produced by the stresses is found to agree well with theoretical predictions, except for high degrees of swelling. This divergence from theory has been explained on the basis of surface instability, which takes the form of wrinkles of the rubber surface.
Application of transmission electron microscopy to polymer thin sections. I. Observations on nylon 66, bulk and filament forms
Authors: Rusnock John A. , Hansen David
Published: April 2003

A study was made on the internal morphology of molding pellets and filaments of nylon 66 by using transmission electron microscopy on ultrathin sections and polarized light microscopy. Nylon specimens embedded in an epoxy–phenolic resin alloy were sectioned to below 500 A. in thickness on an ultramicrotome with a 48° diamond knife. This resin combined good sectioning properties with strong adhesion to the nylon due to the interaction between the phenolic and the nylon. It was established that success in sectioning depended on embedding in a medium with proper wetting characteristics (to permit floating sections away from the knife edge) and obtaining a strong adhesive bond between specimen and embedding material. Contrast in the electron micrographs was enhanced by staining the nylon sections with phosphotungstic acid. Observations on nylon 66 molding pellets resolved the fibrillar structure of spherulites at the 100 A. level. Observations on undrawn monofilaments indicated a cylindrical rather than spherical symmetry of spherulitic crystallization. When the filaments were cold‐drawn, these spherulites retained their radial symmetry but were reduced in diameter.
Comparison of some mechanical and flow properties of linear and tetrachain branched “monodisperse” polystyrenes
Authors: Wyman D. P. , Elyash L. J. , Frazer W. J.
Published: April 2003

The strength and flow properties of narrow distribution polystyrenes have been studied as functions of molecular weight and branching (tetrachain star‐type molecules). Most of the mechanical properties of linear and branched narrow distribution polystyrenes were essentially the same as those for a broad distribution general‐purpose polystyrene. For the narrow distribution linear polymers the value of a given property increased rapidly with molecular weight until ca. M = 1.6 × 105. Thereafter the magnitude of the property increased only slightly for rather large increases in M and asymptotically approached a maximum. The same was true of the branched polymers except that certain properties, e.g., tensile strength, were found to level off in value at higher molecular weights than for the corresponding linear polymers. Studies of apparent melt viscosity, η, made with a capillary rheometer showed that at low shear rates (\documentclass{article}\pagestyle{empty}\begin{document}$ (\dot \gamma < 10) $\end{document} sec.−1), the branched polymers exhibited much lower apparent values of η than linear polymers of the same total molecular weight. At high shear rates (\documentclass{article}\pagestyle{empty}\begin{document}$ (\dot \gamma \sim 2000) $\end{document} sec.−1), this difference essentially disappeared and η approached a constant value independent of \documentclass{article}\pagestyle{empty}\begin{document}$ \dot M(1.5 \times 10^5 - 4.5 \times 10^5) $\end{document} and branching. Melt viscosity data for both the linear and branched narrow distribution polymers when plotted in the form of reduced viscosities versus a function of \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} (as suggested by Bueche) fell upon one master curve.
Kinetics of alternating copolymerization
Authors: Baldwin M. G.
Published: April 2003

The rates of copolymerization of three monomer pairs which form only alternating copolymers have been studied. The monomer pairs were vinyl isobutyl ether–diethyl fumarate, vinyl isobutyl ether–maleic anhydride, and 1‐octene–maleic anhydride. It was shown that the maximum copolymerization rate occurs at [M1]/[M2] ratios which differ significantly from unity, for a fixed total monomer concentration ([M1] + [M2]). An equation for the rate of copolymerization for alternating systems is given and the results are discussed in terms of the equation.
Stereospecific polymerization of 1,3‐butadiene. I. New catalysts based on TiCl4, AlI3, and some aluminum hydride derivatives
Authors: Marconi W. , Mazzei A. , Araldi M. , De Maldé M.
Published: April 2003

Some ternary catalytic systems used in the polymerization of butadiene to a prevailingly 1,4‐cis product are described. They make use of some aluminum hydride derivatives, aluminum iodide, and titanium tetrachloride. For each catalytic system we have adopted conditions to obtain the maximum yield of polymer and the highest content of 1,4‐cis units. Such optimum conditions are achieved at certain molar ratios of aluminum hydrides/TiCl4 and AlI3/TiCl4. In particular, for a constant amount of AlI3 and TiCl4, the choice of the optimum ratio of hydride/TiCl4 depends on the quantity of active hydrogens present in the aluminum compounds while it does not depend on the type substituents, e.g., chloro, amino groups, etc. The presence of Lewis bases, which tend to stabilize some aluminum hydrides and make them soluble in the reaction medium, does not influence the course of polymerization provided such bases are present in stoichiometric amount with respect to the aluminum. If, however, these complexing agents are in excess, a decrease of the catalytic activity and 1,4‐cis content is noticed. This is more so, the stronger the basicity of the complexing Lewis base added. The results obtained in the polymerization of butadiene by means of numerous laboratory runs were confirmed by pilot‐plant runs.
Preparation and characterization of some cellulose graft copolymers. Part III. The role of concurrent degradation during radiation grafting
Authors: Wellons J. D. , Stannett V.
Published: April 2003

The radiation degradation of cellulose acetate has been studied both in the dry state and in solution. The rate of degradation was greater in the solid state and was unaffected by oxygen. Conjugated solvents such as pyridine, toluene, and α‐methylstyrene were shown to exert considerable protection against the radiation degradation of cellulose acetate when in solution or as swollen films. α‐Methylstyrene has been used as a model for styrene to study the amount of degradation accompanying the grafting process. Matching experiments have been carried out by using both the mutual and the preirradiation methods of grafting. Considerably greater chain cleavage was found to accompany the grafting in the preirradiation case. With both methods the number of chain cleavages has been measured when α‐methylstyrene was present in the “grafting” solution and the number of grafted side chains when styrene was used. It was shown that at least twice as many grafted chains as cleavages occur with the mutual technique, but in the case of preirradiation the number of cleavages is comparable to the number of grafted chains. The G (grafted chain) value for cellulose acetate with styrene was determined and was about 1.1 in all cases. The G (chain cleavage) values varied, however, from 0.2 to 1.3, approximately. The proportion of grafted chains attached to the ester groups was determined by extraction with benzene after cold alkaline hydrolysis. About half of the grafts were found to be attached in each case, including the preirradiation product. In general, it can be said that in every case at least 50% of the graft copolymers are side‐chain grafts; this figure is probably considerably higher in the case of the mutual radiation preparations.
Distribution of short‐chain branching in low‐density polyethylene
Authors: Shirayama Kenzo , Okada Takayuki , Kita Shin‐Ichiro
Published: April 2003

The distributions of short‐chain branching in some commercial low‐density polyethylenes have been investigated by measuring the degree of short‐chain branching of their fractionated samples. The results obtained on the fractions which were fractionated with respect to molecular weight showed that some polyethylenes have broad distributions and others have narrow distributions, and these results have been considered to depend mainly on the polymerization conditions. These fractions of which the molecular weight is considered to be approximately uniform were further refractionated with respect to degree of short‐chain branching, and thus cross‐fractionations were accomplished. The distributions of short‐chain branching in those parent fractions were also examined, and it was found out that the parent fractions have fairly broad distributions, and the distribution is broader when the molecular weight is lower, but the difference of distribution is not so great in the different samples. The distributions in those parent fractions showed close agreement with the theoretical distributions which were calculated on the basis of statistical branch formation.
Chain stiffness in polyisocyanates
Authors: Schneider N. S. , Furusaki S. , Lenz R. W.
Published: April 2003

Light‐scattering measurements of the molecular conformation of n‐hexyl polyisocyanate (PIC) in tetrahydrofuran (THF) show that the ratio of the root‐mean‐square end‐to‐end distance to the maximum extension exceeds 25% even at a molecular weight of 3 × 105 and that the effective bond length in the equivalent freely linked chain is 23 A., corresponding to about 17 links per statistical segment. These results are at least twice as high as the values of cellulose trinitrate in acetone at a comparable degree of polymerization. Although a significant variation in intrinsic viscosity occurs in different solvents, the recently reported viscosity‐ and sedimentation coefficient–molecular weight exponents of 1.18 and 0.16 for n‐butyl PIC in THF indicate that the polymer behavior lies outside the Gaussian region and must result from the short range structure rather than from strong interactions with the solvent. In fact, by using a form of the Kirkwood‐Riseman theory, modified to take account of the expansion factor, a viscosity–molecular weight exponent of 0.9 is calculated for theta conditions. It is proposed that the chain is stiffened by restrictions to rotation imposed by resonance effects in the peptide bonds that make up the polymer backbone.
Homopolymerization of hydronopyl vinyl ether and 2‐hydronopoxyethyl vinyl ether
Authors: Marvel C. S. , Malzahn R. A. , Comp J. L.
Published: April 2003

The effectiveness of several free radical, cationic, and coordination initiators for the polymerization of hydronopyl vinyl ether and 2‐hydronopoxyethyl vinyl ether has been examined. The most effective initiator found for polymerization of hydronopyl vinyl ether is a coordination catalyst prepared from triisobutylaluminum and titanium tetrachloride. Generally, cationic initiators are less effective and free radical initiators much less effective with this monomer. Of the initiators investigated for polymerization of 2‐hydronopoxyethyl vinyl ether, only one, boron fluoride etherate, proved to be effective. This initiator yielded a rubbery polymer of high molecular weight.
Cyclic distribution in dimethylsiloxanes
Authors: Carmichael Jack B. , Winger Robert
Published: April 2003

Gas–liquid chromatography was used to determine the amounts of cyclic molecules present in an equilibrium polymerization mixture of high polymer and cyclic dimethylsiloxane molecules. The study was carried out as a function of polymerization temperature. For [(CH3)2SiO]4–10 the equilibrium concentration is shown to be independent of temperature. The change in cyclic concentration as a function of n for [(CH3)2SiO]4–10 does not follow the theoretical Stockmayer‐Jacobson distribution. The concentrations of [(CH3)2SiO]3,4 are qualitatively predictable by the Stockmayer‐Jacobson theory and by the model proposed by Carmichael and Kinsinger. For [(CH3)2SiO]4, Kexp = 0.74 mole SiO/l. The model calculations yield 0.12 (Stockmayer‐Jacobson) and 0.36 Carmichael‐Kinsinger. For [(CH3)2SiO]3, Kexp = 0.024 mole SiO/l. Model calculations yield 0.017–0.16 (Stockmayer‐Jacobson) and 0.056–0.52 (Carmichael‐Kinsinger). The range of values rises because of uncertainty in the cyclic strain energy.