bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal degradation of nylon 66
Authors: Peebles L. H. , Huffman M. W.
Published: April 2003

The rate of gel formation and color formation in poly(hexamethylene adipamide), nylon 66, is found to be dependent upon the rate of removal of the volatile products of degradation. If a sample of nylon is heated above its melting point in a sealed tube, the material will remain soluble for extended periods of time as the intrinsic viscosity first passes through a maximum, then a minimum, followed by the abrupt formation of insoluble material. The color remains reasonably white. On the other hand, if the volatile material is permitted to escape, rapid gelation and color formation will occur, even in the complete absence of oxygen. Intermediate rates of gelation and color formation can be obtained by control of the rate of volatile material distillation. The decrease in molecular weight evidenced in the sealed tubes is probably due to hydrolysis and ammonolysis of the amide groups which occur simultaneously with the formation of multifunctional crosslinking agents. The volatile material contains an intense absorption in the 290 mμ region. Analysis of the volatile material shows that it contains inter alia, water, carbon dioxide, ammonia, cyclic monomer, hexylamine, hexamethyl‐eneimine, hexamethylenediamine, cyclopentanone, 2‐cyclopentylcyclopentanone, 2‐cyclopentylidinecyclopentanone, and 1,2,3,5,6,7‐hexahydrodicyclopenta[b,e]pyridine, which has an intense absorption at 287 mμ, ε = 8.87 × 104l./mole‐cm, (methanol).
Organometallic polymers I. Solution polymerization of α‐ferrocenylmethylcarbonium fluoborate
Authors: Gal Alon , Cais Michael , Kohn David H.
Published: April 2003

The self‐condensation of α‐ferrocenylmethylcarbonium ion in nitroethane yielded polymers of Mn up to 20,000. The change of [η] and Mn with the reaction time indicated that the process consisted of a rapid primary growth stage, an induction period, a second growth stage, and a crosslinking stage. The [η]–Mn correlation for a series of polymeric fractions in the Mn = 0.1–7.2 × 104 range points to a highly branched structure.
Thermal stability of hydrogen networks by chemical stress relaxation
Authors: Shaw Montgomery T. , Tobolsky Arthur V.
Published: April 2003

The thermal stability of hydrocarbon networks by chemical stress relaxation was investigated in vacuo and in the temperature range 300–350°C. The polymers studied were low‐density polyethylene, high‐density polyethylene, and ethylene–propylene terpolymer. Carbon‐carbon crosslinked networks were produced either by dicumyl peroxide or by radiation. The results show that the overall thermal stability is in the order: peroxide‐cured EPT > peroxide‐cured LDPE > radiation‐cured HDPE. The results are in apparent contradiction to the belief that linear structures are more stable than branched structures. We believed that this can be explained in terms of weak linkages introduced during curing.
Equilibrium anionic polymerization of α‐methylstyrene in p‐dioxane
Authors: Léonard J. , Malhotra S. L.
Published: April 2003

The equilibrium anionic polymerization of α‐methylstyrene in p‐dioxane, with potassium as initiator, has been investigated at 5, 15, 25, and 40°C by using high‐vacuum techniques. The comparison of these results with those obtained previously for the equilibrium polymerization of α‐methylstyrene in tetrahydrofuran revealed that, although the values of ΔG1c, the free‐energy change upon the polymerization of 1 mole of liquid monomer to 1 bases‐mole of liquid amorphous polymer of infinite chain length, are the same for both systems, there is a distinct effect of the solvent. This effect is reflected in the value of monomer equilibrium concentration and its variation with polymer concentration and is explained in terms of a solvent–monomer and solvent–polymer interaction parameter.
Telechelic diene prepolymers. I. Hydroxyl‐terminated polydienes
Authors: Reed Samuel F.
Published: April 2003

Telechelic prepolymers of butadiene, isoprene, and chloroprene with hydroxyl end‐ groups have been prepared by the solution polymerization of the dienes under free‐radical initiation. 4,4′‐Azobis(4‐cyano‐n‐pentanol) was employed as the initiator. Liquid prepolymers were obtained with molecular weights of 2000 to 20,000 and with functionalities usually greater than 2. The preparative procedure and prepolymer characterization are described.
Oxidative crosslinking in poly(ethylene terephthalate) at elevated temperatures
Authors: Nealy D. L. , Jane Adams L.
Published: April 2003

Poly(ethylene terephthalate) oxidizes on being heated in air at elevated temperatures to form a crosslinked structure. The crosslinking occurs through a reaction which causes arylation of terephthalate rings to form a biphenyltricarboxylic acid derivative. This reaction is interpreted as a free‐radical cleavage generating a substituted phenyl radical which selectively attaches to a terephthalate residue via substitution.
Synthesis and properties of new polyamide‐imides
Authors: Alvino W. M. , Frost L. W.
Published: April 2003

Several new amide—imide polymers of good thermal stability have been synthesized by the reaction in solution of diacid chlorides with diamines containing cyclic imide linkages. Since these polymers incorporate preformed imide groups, they are not subject to some of the problems encountered in the preparation of polyimides by cyclizing polyamic acids. Their solutions in polar solvents such as dimethylacetamide are stable and will tolerate considerable proportions of hydrocarbon thinners without precipitation. Thick films can be cast from the solutions without degradation. A high‐temperature cure is not needed to produce tough, flexible films. The powdered polymers can be molded readily.
Influence of temperature on microstructure of anionic‐initiated polybutadiene
Authors: Uraneck C. A.
Published: April 2003

Application of the Arrhenius relationship for temperature and ratio of isomeric units in polybutadiene made in the presence of butyllithium initiator is consistent with the existence of three simultaneous competing reactions. Evidence in the literature is cited to support the possibility that the growing chain end exists in a composite equilibrium producing localized structures which on reacting with monomer result in fixed isomeric units. The compliance of the data with the thermodynamic relationship permits the extrapolation of a narrow set of data to a broad temperature range.
Structure of crystalline polymers with unbranched long side chains
Authors: Platé N. A. , Shibaev V. P. , Petrukhin B. S. , Zubov Yu. A. , Kargin V. A.
Published: April 2003

The structure and thermodynamic properties of atactic and isotactic acrylic and methacrylic polymers containing 16–18 carbon atoms in the n‐aliphatic side chains, and of copolymers of hexadecyl acrylate with isopropyl acrylate were studied by means of x‐ray and differential thermal analysis. The crystallization of branched acrylic and methacrylic polymers and of acrylic copolymers proceeds in the form of a hexagonal crystal, regardless of the configuration of the backbone chain. Methods of ordering branched macromolecules are proposed, and the melting points, heats and entropies of fusion determined. The role of flexibility of the backbone chains in ordering and the crystallization processes was determined. In the case of poly(n‐alkyl acrylates) the backbone chain is involved in the crystalline lattice; this is not the case in methacrylates and copolymers of hexadecyl acrylate with isopropyl acrylate. Some similarity was assumed between the structure of biopolymers and synthetic branched polymers.
Homogeneous polymerization of norbornene catalyzed by ruthenium complex–tertiary phosphine system
Authors: Hiraki Katsuma , Kuroiwa Akihiko , Hirai Hidefumi
Published: April 2003

Norbornene is polymerized by ruthenium complex–tertiary phosphine catalysts to polymers consisting of trans‐and cis‐olefinic groups and 1,3‐cyclopentylene group. The system derived from dichloro(dodeca‐2,6,10‐triene‐1, 12‐diyl)ruthenium‐(IV) (1) and triphenylphosphine has a fairly high activity for the polymerization, while I itself has only a very low activity. The system derived from dichlorodi‐μ‐chlorobis‐(2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl)diruthenium(IV) (II) and more moles of triphenyl‐phosphine than four shows almost the same activity as the I‐triphenylphosphine system does. However, II and dichloro(2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl)‐(triphenylphosphine)ruthenium(IV) each polymerizes norbornene in a very high yield, in contrast with I. In addition, both dichlorotris(triphenylphosphine)ruthenium(II) and dichlorotetrakis(triphenylphosphine)ruthenium(II) have been found to display a considerably high activity for polymerization of norbornene. On the basis of these facts and the NMR data of the I– and II–triphenylphosphine systems, the mechanism for the polymerization of norbornene has been discussed.
Sodium salts of sulfonated poly(phenylene ethers) as polysoaps
Authors: Cooper James E.
Published: April 2003

Polysoaps are of interest because, unlike most polyelectrolytes, their aqueous solutions become more viscous and often form gels upon the addition of salt. A new kind of polysoap was made by sulfonating phenylene oxide polymers that have a pendant alkyl group containing at least 14 carbon atoms on every phenylene unit. Copolymers made from a mixture of 2,6‐dimethylphenol and 2‐methyl‐6‐tetradecylphenol have the same composition as the monomer mixture. Tetradecyl substituents in the copolymer act as internal plasticizing agents and, by varying the number of substituents, a gradation in physical properties of the unsulfonated copolymer from rigid solid to heavy oil is possible.
60Co‐initiated polymerization of styrene, vinyl acetate, and their mixtures in the presence of a radical initiator
Authors: Niezette Joseph , Desreux Victor
Published: April 2003

Styrene and vinyl acetate have been polymerized by γ‐radiation in the presence of α,α′‐azobisisobutyronitrile or benzoyl peroxide. Benzoyl peroxide does not affect the vinyl acetate polymerization, but the rate of polymerization is greatly increased by the action of the initiator in the case of the following systems: styrene–α,α′‐azobisisobutyronitrile, styrene–benzoyl peroxide, and vinyl acetate–α,α′‐azobisisobutyronitrile. For these three systems, the experimental results are in good agreement with a kinetic scheme obtained by assuming an energy transfer process from monomer excited molecules to the initiator; this process does not occur in the first system, and the initiation rate is determined only by the vinyl acetate concentration. In the case of the polymerization of mixtures of the two monomers, the action of α,α′‐azobisisobutyronitrile and that of benzoyl peroxide are practically the same; that is, the shape of the polymerization curve may be understood on the basis of an energy transfer from styrene excited molecules to the initiator.
Effect of alkoxides on chain termination and chain transfer of sodium‐catalyzed polybutadiene
Authors: Cheng Tai Chun , Halasa A. F. , Tate D. P.
Published: April 2003

The reaction of butadiene with n‐butylsodium or metal alkoxide‐modified n‐butylsodium was studied. A loss of “live ends” was observed when the polymerization of butadiene‐1,3 with n‐butylsodium was conducted in hexane solvent. This occurs, presumably, by elimination of NaH or Na metal in the allylic system. Similar results were obtained when the polymerization was carried out in the presence of sodium‐tert‐butoxide‐modified n‐butylsodium. However, the modification of n‐butylsodium by lithium or potassium tert‐butoxide in the butadiene‐1,3 polymerization showed no loss of live ends for a period of two weeks. The results and an explanation are discussed.
Chemical thermodynamics of polymerization of formaldehyde in an aqueous environment
Authors: Bryant W. M. D. , Thompson John B.
Published: April 2003

A self‐consistent set of chemical thermodynamic values for the polymerization of formaldehyde in the gas phase and in aqueous solution is obtained with the aid of recent experimental thermochemical results and the use of selected methods of calculation of data not otherwise available. Enthalpies, entropies, and Gibbs free energies of formation are derived for the various intermediates and products, including the first six hydroxyl‐terminated oligomers. Simple equations for the logarithm of the equilibrium constant as a function of temperature are presented for a number of polymerization reactions, permitting comparison with experimental results. Reasonable agreement is obtained in almost all cases, even though ideal solutions are assumed.
Mechanism of initiation of methyl methacrylate with lithium tert‐alkoxides
Authors: Trekoval J.
Published: April 2003

An investigation of the solution polymerization of methyl, butyl, isobutyl, sec‐butyl, and tert‐butyl methacrylates and the polymerization of methyl and butyl methacrylates in the presence of methyl, butyl, and tert‐butyl isobutyrate and methyl pivalate showed that the complex order of the initiation reaction with respect to the monomer (about 2) has its cause in the ability of the ester group in the monomer and of methyl or butyl isobutyrate to activate lithium tert‐alkoxide. Owing to conjugation, the ester group in the monomer is less active than the ester group in isobutyrate. Steric hindrances of the formation of a complex between lithium tert‐alkoxide and ester were also investigated, because this complex is intermediate product necessary for the formation of an activated lithium tert‐alkoxide, capable of initiating the polymerization of alkyl methacrylates of the type CH2(CH3)COOCH2R.
Copolymers of vinyl chloride and vinylidene chloride with some acid chlorides
Authors: Janovič Z. , Marvel C. S. , Diamond M. J. , Kertesz D. J. , Fuller G.
Published: April 2003

Vinyl chloride and vinylidene chloride were copolymerized with 10‐acryloxydecanoyl chloride and 12‐acryloxystearoyl chloride by use of free‐radical initiator in solution to obtain copolymers with active chlorine groups. Alternative routes for making such copolymers which consisted of making the corresponding acrylic acid or acrylyl chloride copolymers, followed by reaction with hydroxy acid and finally conversion to the acid chloride by treatment with thionyl chloride, were investigated. The monomer reactivity ratios for the radical copolymerization of vinyl chloride (VCI) and vinylidene chloride (VCl2) with acrylic acid (AA) and acrylyl chloride (ACI) were determined: VCI–AA, r1 = 0.025, r2 = 6.40; VCl–ACl, r1 = 0.017, r2 = 2.65; VCl2–AA, r1 = 0.46, r2 = 1.26; VCl–ACl, r1 = 0.50, r2 = 1.12.
Vinyl polymerization. Part 268. Polymerization of acrylonitrile initiated by the system of tetramethyl tetrazene and bromoacetic acid
Authors: Sugiyama Kazuo , Nakaya Tadao , Imoto Minoru
Published: April 2003

The polymerization of acrylonitrile (AN) initiated by the system of tetramethyl tetrazene (TMT) and bromoacetic acid (BA) in dimethylformamide (DMF) was studied. The TMT–BA system could initiate the polymerization of AN more easily than TMT alone. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization Rp was expressed by the equation: Rp = [TMT]0.62‐[BA]0.5[AN]1.5. The overall activation energy for the polymerization was estimated as 9.4 kcal/mole. In the absence of monomer, the reaction of TMT with BA in DMF was also studied kinetically by measuring the evolution of nitrogen gas. The reaction was first‐order in TMT and first‐order in BA; the rate data at 49°C were k2 = 9.1 × 10−2l./mole‐sec., ΔH‡ = 17.0 kcal/mole, and ΔS‡ = − 6.6 eu. In addition, the treatment of TMT with BA in benzene led to the formation of tetramethylhydrazine radical cation, which was identified by its ESR spectrum. On the other hand, the relatively strong interaction between TMT and DMF was observed by absorption spectrophotometry.
Emulsion polymerization. VII. Effects of instantaneous chain termination during the interval of particle nucleation
Authors: Gardon J. L.
Published: April 2003

In the Smith‐Ewart treatment of particle nucleation all particles were assumed to grow as if they contained exactly one radical. Modification of particle growth rate by chain termination in growing particles and reinitiation of nongrowing particles by radicals entering them was neglected in this interval although such effects were taken into account after the particle number became constant. The present theory eliminates this inconsistency for the case where chain termination is instantaneous. This refinement does not change previous predictions for the final number of particles, the steady state rate or the particle radius. Unlike the old theory, the present theory predicts continuous decay of the average number of radicals per particle from the initial value of unity to the steady‐state value of one half. It also provides new theoretical predictions for the shape of the conversion‐time curve at the initial stages of the reaction. Experimental data are reviewed in the context of the theory. Experimental particle sizes, steady‐state conversion rates, and conversions at completion of particle nucleation were often in good quantitative agreement with the theoretical predictions. The predicted maximum in the conversion rate at the time when particle nucleation became completed was observed in a few instances. The theoretically predicted initial shape of the conversion‐time curve may not be always observable due to experimental difficulties mainly associated with induction effects.
Synthesis and characterization of poly‐β‐hydroxybutyrate. I. Synthesis of crystalline DL‐poly‐β‐hydroxybutyrate from DL‐β‐butyrolactone
Authors: Agostini D. E. , Lando J. B. , Shelton J. Reid
Published: April 2003

The polymerization of β‐butyrolactone was investigated as a possible monomer for a proposed synthesis of the naturally occurring polyester, D‐poly‐β‐hydroxybutyrate (D‐PHB). The racemic DL‐monomer was used in this initial study to determine the best conditions and catalyst system for use in a subsequent study of the polymerization of optically active β‐butyrolactone. In so doing it was found that certain organometallic catalysts (Et2Zn and Et3Al) plus a cocatalyst of water produced highly crystalline samples of polyester from the racemic monomer. This paper describes the synthesis and characterization of the racemic polymer obtained using these catalyst systems, and compares the results obtained with certain other catalysts that were also investigated for this purpose. Examination of the DL‐PHB by infrared, NMR, x‐ray, and electron microscopy shows that it is possible to synthesize a crystalline racemic polymer that is virtually identical (excepting optical activity) to the naturally occurring polymer, D‐PHB.
Radiation‐induced reaction of ethylene–cyclohexane–carbon tetrachloride system
Authors: Yamabe Masamori , Shimizu Harumichi
Published: April 2003

The γ‐ray‐induced reaction of ethylene with carbon tetrachloride in cyclohexane was carried under a pressure of 30 kg/cm2 and at a temperature of 20°C. The liquid and the solid products were obtained. Their structures were discussed on the basis of infrared absorption spectra and differential thermal analysis curves. The liquid product is considered to be ethylene–carbon tetrachloride telomer. The solid product consists of three components, differing slightly in molecular structure and molecular weight. To clarify the reaction process, some runs with the ethylene–cyclohexane–(ethylene–carbon tetrachloride telomer) system were also carried out. In this system, only solid product was obtained. Thus, it is concluded that the reaction proceeds stepwise, the first step being the telomerization reaction and the second the graft polymerization of ethylene onto the telomer produced in the first step.
Initiation of polymerization of alkyl 2‐cyanoacrylates in aqueous solutions of glycine and its derivatives
Authors: Kulkarni R. K. , Bartak D. E. , Leonard F.
Published: April 2003

The polymerization of methyl 2‐cyanoacrylate and heptyl 2‐cyanoacrylate was carried out with the use of aqueous solutions of 14C‐tagged glycine, methyl glycine, and acetyl glycine as initiators. When glycine and methyl glycine were used, radioactive polymers were formed. When acetyl glycine was used, the polymer formed was not radioactive. The data seem to indicate that free NH2 groups appear to be necessary for the incorporation of the glycine initiator in the polymer. A possible mechanism for the polymerization is presented.
Organometallic polymers. XIV. Copolymerization of vinylcyclopentadienyl manganese tricarbonyl and vinylferrocene withN‐vinyl‐2‐pyrrolidone
Authors: Pittman Charles U. , Grube Paul L.
Published: April 2003

N‐Vinyl‐2‐pyrrolidone(I) has been copolymerized with vinylferrocene(II) and vinylcyclopentadienyl manganese tricarbonyl(III) in degassed benzene solutions with the use of azobisisobutyronitrile (AIBN) as the initiator. The polymerizations proceed smoothly, and the relative reactivity ratios were determined asr1= 0.66,r2= 0.40 (for copolymerization of I with II, M1defined as II) andr1= 0.14 andr2= 0.09 (for copolymerization of I with III, M1defined as III). These copolymers were soluble in benzene, THF, chloroform, CCl4, and DMF. Molecular weights were determined by viscosity and gel‐permeation chromatography studies (universal calibration technique.) The copolymers exhibited values of M̄nbetween 5 × 103and 10 × 103and M̄wbetween 7 × 103and 17 × 103with M̄w/M̄n< 2. Upon heating to 260°C under N2, copolymers of III underwent gas evolution and weight loss. The weight loss was enhanced at 300°C, and the polymers became in creasingly insoluble. Copolymers of vinylferrocene were oxidized to polyferricinium salts upon treatment with dichlorodicyanoquinone (DDQ) oro‐chloranil (o‐CA) in benzene. Each unit of quinone incorporated into the polysalts had been reduced to its radical anion. The ratio of ferrocene to ferricinium units in the polysalts was determined. The polysalts did not melt at 360°C and were readily soluble only in DMF.
Organometallic polymers. XV. Synthesis and characterization of some ferrocene‐containing oxysilane polymers from bis(dimethylamino)silanes
Authors: Pittman Charles U. , Patterson William J. , McManus Samuel P.
Published: April 2003

Three bis(dimethylamino)silane monomers have been polymerized with 1,1'‐bis‐(hydroxymethyl)ferrocene to give ferrocene‐containing polyoxysilanes I and II. They were bis(dimethylamino)dimethylsilane (III), bis(dimethylamino)diphenylsilane (IV), and 1,4‐bis(N,N‐dimethylaminodimethylsilyl)benzene (V). Mixing of the diol and III or IV at O°C followed by heating resulted in polymerization to higher molecular weights than when the monomers were initially mixed at higher temperatures. At higher temperatures the formation of monomeric cyclic products seriously competed with polymerization, and the five atom bridged derivative, 3‐sila‐2,4‐dioxa‐3,3diphenyl[5]ferrocenophane (VI) was isolated in good yield. The use of silane V, where cyclization is not expected to compete, led to higher polymer yields and molecular weights. The polymers were low melting and I (R = C6H5) could be cast into films and weak fibers were drawn from its melt. The polymers were sensitive to hydrolytic decomposition; those containing Si‐CH3 linkages were completely hydrolyzed in refluxing THF‐H2O (10:1) in 1 hr. The polymers were characterized by viscosity studies, gel‐permeation chromatography, and infrared and NMR spectroscopy.
Transparent ultraviolet‐barrier coatings
Authors: Cohen S. M. , Young R. H. , Markhart A. H.
Published: April 2003

A number of phenyl polyesters have been synthesized to furnish molecules whose backbones rearrange under ultraviolet irradiation to ano‐hydroxybenzophenone structure. This photochemical Fries rearrangement produces ultraviolet opacity in the irradiated film while maintaining visual transparency. Thin coatings of these polyesters completely protect substrates ordinarily sensitive to ultraviolet light. Spectroscopic analysis of various rearranged films and coatings clearly shows that theo‐hydroxybenzophenone polymer formed is concentrated at the irradiated surface of the original polyester coating as a “skin”. Such a skin, formedin situduring the irradiation, functions to protect both the original polyester coating as well as the coated substrate from degradation by ultraviolet irradiation. Furthermore, a significant “healing” mechanism appears inherent in these coatings, for as the exposed skin ultimately degrades under extended ultraviolet irradiation, more of the underlying polyester layer apparently rearranges to compensate for the loss. Thus the clear coating functions both as a protective skin and a rearrangeable reservoir. Modified structures of the polyesters have been prepared which possess, in addition to their protective film properties, a useful solubility spectrum and a good solution shelf life.
Side‐chain crystallinity. II. Heats of fusion and melting transitions on selected copolymers incorporating n‐octadecyl acrylate or vinyl stearate
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Speca Anthony , Wrigley A. N.
Published: April 2003

The heats of fusion and the melting transitions of the crystallinity present in the side chains were determined for selected copolymers incorporating n‐octadecyl acrylate or vinyl stearate. A major purpose of this investigation was to ascertain the effect of interrupting the long ordered 18‐carbon side chains by randomly interspersed amorphous side chains of various lengths. For this purpose the lower acrylate homologs (C1 through C8 and including oleyl, C8) were copolymerized over the composition range with n‐octadecyl acrylate. It was found that simple dilution of the crystalline component (from comonomer b) by the amorphous component (from comonomer a) governed the decline in the heats of fusion and the fraction of crystallinity present. High crystallization rates were encountered because equilibrium crystallinity was nearly achieved for most of the copolymers. Melting point depression was less than theory in copolymers having short amorphous comonomer side chain lengths, but approached the theoretical depression as these side chains became very long. Thus the outer methylene sequences (the crystalline sequences) of the fatty co‐units could bridge the smaller amorphous a units, giving rise to larger crystal sizes than theory specified. Main‐chain stiffness, when present in the melt, had a small effect on the distribution of crystallite sizes but exhibited a much larger influence in preventing the attainment of equilibrium crystallinity, especially at high amorphous comonomer compositions. However, crystallinity was still high compared with that of copolymers described in the literature crystallizing through their main‐chain units. When long blocks of crystalline segments were present (as in compositionally heterogeneous vinyl stearate copolymers), melting point depression was small and followed the theoretical probability sequence function.
Temperature effects in γ‐initiated polymerization of styrene. II
Authors: Sood S. P. , Hodgins J. W.
Published: April 2003

Experimental data are presented for the γ‐initiated polymerization of commercial styrene at a series of temperatures above ambient. Examination of the early stages of polymerization (up to 10% conversion) has led to the following conclusions. For this system, there exists a critical temperature (109°C) above which the rate of polymerization is independent of dose rate, over a wide range of γ‐intensities. This dose rate independence is ascribed to a “limiting rate of initiation,” characteristic of the intensity range. A consequence of this is that at a given temperature above the critical temperature the degree of polymerization is also dose rate‐independent. The above phenomena can be expected in any vinyl monomer where the monomer is fairly active and produces relatively stable radicals. Experimental procedure is described, and kinetic analysis presented to substantiate the conclusions.
Effect of the polymeric ligand on electron‐transfer reactions: Iron(II) reduction of cis‐chloropoly‐4‐vinylpyridinebis(ethylenediamine)‐cobalt(III) complexes
Authors: Kurimura Yoshimi , Yamada Kazuo , Kaneko Masao , Tsuchida Eishun
Published: April 2003

Water‐soluble Co(III)–PVP complexes (where PVP = poly‐4‐vinylpyridine) were prepared, and the specific rates and activation parameters for the iron(II) reductions of cis‐Co(en)2XCl2+ (where X = PVP or pyridine and en = ethylenediamine) were determined in dilute sulfuric acid solutions. Under the conditions [H2SO4] = 0.50M, Σ[SO42−] = 1.25 M at 25°C, the second‐order rate constants and activation entropies, respectively, for the cis‐Co(en)2−XCl2+ are (4.10 ± 0.05) × 10−3l./mole‐sec and −14 ± 0.6 eu for × = pyridine, (2.1 ± 0.1) × 10−3l./mole‐sec and −6.0 ± 1 eu for × = PVP (Pn = 19), and (2.42 ± 0.08) × 10−3 l./mole‐sec and −2.5 ± 0.8 eu for × = PVP (Pn = 98), where Pn is the degree of polymerization of the PVP. The main feature of the polymer effect in the electron‐transfer reactions of the PVP complexes in which uncoordinated pyridine rings are present may be attributed to greater activation entropy. Such a greater entropy for the PVP complex may be partly ascribed to the intricate structure of the PVP ligand in the solution.
Optical rotatory properties of synthetic polymers. II. Optical rotatory dispersion of poly(propylene sulfide)
Authors: Tsunetsugu Toshiyuki , Furukawa Junji , Fueno Takayuki
Published: April 2003

Optically active propylene sulfide was polymerized in the presence of potassium hydroxide as catalyst to give optically active poly(propylene sulfide). Rotatory dispersion curves of the polymer thus obtained were measured in benzene and chloroform media. In both cases, the curves were anomalous in shape with the same sign, having troughs at 290 and 275 mμ, respectively. (–)‐1,2‐Diethylthiopropane was prepared as an optically active model compound of poly(propylene sulfide) in optical rotatory properties. It was found that the model compound also shows anomalous rotatory dispersion both in benzene and chloroform with the same sign. Thus it may be concluded that the anomalous dispersion of poly(propylene sulfide) must be attributed to an additional Cotton effect caused by the absorption of sulfide bonds, which are generally admitted to have absorptions at 200 and 230 mμ (shoulder).
Radiation chemistry of aqueous poly(ethylene oxide) solutions. II. Highly purified samples
Authors: Ward J. A.
Published: April 2003

The radiation chemistry of highly purified, rigorously degassed aqueous solutions of poly(ethylene oxide) is markedly different from solutions not so treated. Gelation doses are lower in the purified samples by almost two orders of magnitude. Degradation is unimportant in dilute solutions. The very broad molecular weight distribution as well as the very high molecular weight of these polymers makes the interpretation of the results difficult. Neither gel dose measurements nor solubility measurements give valid crosslinking yields. The crosslinking yield is highly concentration‐dependent.
Simulation of degradation processes. II. Testing some relations for random crosslinking without cyclization
Authors: Maláč J.
Published: April 2003

By use of a Monte Carlo method the course of crosslinking without cyclization was simulated. For the simulated case the following was determined: number‐average molecular weight and degree of polymerization of the system; weight‐average molecular weight and degree of polymerization of the system; number of molecules of a given degree of polymerization; quantity of gel; number‐average degree of polymerization of sol and branching. The values obtained by simulation were compared with some equations published to date. It was shown that the dependence of weight‐average polymerization degree and, consequently, of the weight‐average molecular weight on time and the dependence of the number of molecules of a given polymerization degree on time is probably more complicated than hitherto supposed.
Characterization of diene polymers. I. Infrared and NMR studies: Nonadditive behavior of characteristic infrared bands
Authors: Tanaka Yasuyuki , Takeuchi Yasumasa , Kobayashi Masamichi , Tadokoro Hiroyuki
Published: April 2003

Extinction coefficients of the characteristic infrared bands due to isomeric structural units were measured for polybutadiene and polyisoprene in CS2 or CCl4 solutions and were compared with the isomer composition determined by NMR. The NMR signal assignments were made on the basis of the spectra of deutero derivatives of the polymers. In the case of polyisoprene, linear relations were obtained between the extinction coefficients and the isomer contents determined by NMR for the absorption bands at 1385 cm−1 (characteristic of trans‐1,4 units), 1376 cm−1 (cis‐1,4 units), and 889 cm−1 (3,4 units). However, for the absorption bands at 840 cm−1 (characteristic of cis‐1,4 and trans‐1,4 units), isomerized polyisoprenes did not give such a linear relationship. In polybutadiene, the extinction coefficient for the atactic 1,2 units was found to be lower than that of the syndiotactic 1,2 unit. These experimental facts lead to the conclusion that additivity of the extinction coefficients does not always hold for diene polymers. The deviation from the linear relation may be associated with regular sequences of one isomeric conformation in the chain.
Planar organosilicon polymers
Authors: Linsky John P. , Paul Thomas R. , Kenney Malcolm E.
Published: April 2003

Work on two sheet organosilicon polymers, one derived from the mineral chrysotile and the other from the mineral apophyllite, is described. This work provides direct evidence that both these polymers are composed of sheets. In addition, it shows that in the chrysotile‐derived polymer the sheets curl into scrolls, and that in the apophyllite‐derived polymer the sheets are essentially flat.
Equilibrium melting points of the low‐melting and high‐melting crystalline forms of trans‐1, 4‐polyisoprene
Authors: Lovering Edward G. , Wooden David C.
Published: April 2003

Equilibrium melting points in trans‐1,4‐polyisoprene were calculated from plots of crystallization temperature versus the experimentally measured melting points. The melting points were found to be 78 ± 1.7°C for the low‐melting crystalline form and 87 ± 1.3°C for the high‐melting form. Within the experimental error, melting points were independent of molecular weight above a number‐average weight of 33,000.
Axial dispersion of solute zones in gel permeation chromatography
Authors: Halvorson Herbert R. , Ackers Gary K.
Published: April 2003

The two essential aspects of axial dispersion in gel permeation chromatography have been studied: (1) the relationship of axial dispersion to the continuity equations of chromatographic transport, and (2) the relationship to molecular size and the system parameters of an individual column. Theoretical analyses are presented for both of these problems and are applied to an experimental study of axial dispersion by both zonal (small‐zone) and frontal (large‐zone) experiments with a series of macromolecular species having discrete, precisely known molecular weights. Theoretically predicted non‐Gaussian elution profiles were observed for the small‐zone experiments, and axial dispersion coefficients for each molecular species were determined as a function of flow rate. Resulting values were found to be in good agreement with the theoretical equation relating axial dispersion to molecular size, flow rate, and two “calibration constants” of the column. These results provide a rational basis for axial dispersion effects in terms of the fundamental processes and system parameters of gel columns. Extension of the analysis to multicomponent systems is discussed.
Adhesion of viscoelastic materials to rigid substrates. II. Tensile strength of adhesive joints
Authors: Gent A. N.
Published: April 2003

Measurements have been made of the tensile force required to pull a disk of a model viscoelastic adhesive away from an inert rigid substrate. Over a wide range of temperature and rate of deformation of the adhesive the results were found to yield a single master relation in terms of deformation rate by means of the Williams, Landel and Ferry rate—temperature equivalence for viscous materials. Thus, the strength of adhesion is due mainly to dynamic effects in the adhesive of a viscous nature, in a similar way to the cohesive strength of viscoelastic materials. This similarity is attributed to a common failure mechanism: initial failure at a highly stressed point, followed by spreading of the failure zone under local stresses which are governed by the dynamic response of a compliant material. An increase in the strength of adhesion is observed with decreasing thickness of the adhesive layer. This is also explained by the proposed failure mechanism if failure starts at a critical amount of local deformation energy, a form of Griffith's fracture criterion.
Adsorption of polydimethylsiloxanes from solution on glass
Authors: Ashmead B. V. , Owen M. J.
Published: April 2003

The adsorption of polydimethylsiloxane polymers from solution on glass has been studied. The amount of polymer adsorbed depends markedly on the solvent because of specific solvent—surface interactions. The presence of silanol groups in the polymer, particularly as endgroups, markedly increases the amount of polymer adsorbed. Large differences are shown between the adsorption of the commercially available, and fully trimethylsilylated polydimethylsiloxanes of narrow molecular weight distribut on. Possible adsorption mechanisms are discussed.
Normal stress and shear stress in a viscoelastic liquid under steady shear flow: Effect of molecular weight heterogeneity
Authors: Endo Hiroshi , Fujimoto Teruo , Nagasawa Mitsuru
Published: April 2003

Under steady shear flow, the normal stress and the shear stress in both dilute and concentrated solutions of monodisperse poly‐α‐methylstyrenes and their blends were measured. It was confirmed that the molecular theories of Rouse and Zimm extended to concentrated solutions can explain the relation between the zero‐shear normal stress coefficient and the zero‐shear steady‐flow viscosity for both monodisperse and polydisperse systems. Shear‐rate dependence of steady‐flow viscosity can be understood fairly well by the molecular entanglement concept proposed by Graessley so long as the polymer is monodisperse or the amount of the higher molecular weight component is high. However, zero‐shear viscosity of blended systems cannot be explained quantitatively by the theory of Graessley. The shear‐rate dependence of steady‐state compliance of blended systems was also observed, and it can well be explained by the theory of Tanaka, Yamamoto, and Takano which interpreted the shear rate‐dependent steady‐state compliance in terms of the relaxation time spectrum and its variation with shear rate.
Dispersion and polar contributions to surface tension of poly(methylene oxide) and Na‐treated polytetrafluoroethylene
Authors: Kaelble D. H. , Cirlin E. H.
Published: April 2003

Average values for dispersion γsd and polar γsd contributions of the solid surface tension γs γsd + γsp for poly(methylene oxide) (PMO) and Na‐treated polytetrafluoroethylene (PTFE) are determined by a new computational analysis of wettability data. PMO displays γsd equals; 21.8 ± 0.9 and γsp = 11.5 ± 1.5 dyn/cm while Na‐treated PTFE displays γsd = 36.1 ± 3.0 and γsp = 14.5 ± 2.9 dyne/cm. These surfaces present the highest fractional surface polarity ps = γsp/γs = 0.29‐0.35 yet encountered for organic polymers or oriented monolayers. These unusual surface tension properties are correlated with surface chemistry and adhesion phenomena.
Graphical representation of the state of orientation of polymer systems
Authors: Nomura Shunji , Nakamura Nobiru , Kawai Hiromichi
Published: April 2003

The orientation distribution function for noncrystalline structural units in polymer systems cannot be determined completely from any experimental source; only the second and/or fourth moments of the distribution function, i.e., the second and/or fourth orders of the generalized orientation factors Flmj, can be evaluated. It is there‐fore necessary to estimate the distribution function from F2mj and F4mj. In this paper, a graphical representation of the state of orientation is first discussed in terms of plots of F40j against F20j for several types of distribution functions for uniaxial orientation. These are three types of extreme concentration of the distribution at particular polar angles θ0 given by θ0 = 0, 0<θ0<π/2, and θ0 = π/2; five types of rather realistic distributions having single maxima at θj = 0, θ0, π/2 and double maxima at θj = 0, π/2, and a single minimum at θj = θ0; and four types of more realistic distributions including Kratky's floating rod model in an affine matrix. Second, estimation of the distribution function for uniaxial orientation from F40j and F20j is discussed quantitatively in terms of the mean‐square error by three approximation methods: (a) expansion of the distribution function in finite series of spherical harmonics through the fourth order, (b) approximation of the distribution function as a composite of two components, random orientation and a particular orientation distribution given by Na (cos2θj)a, Na being a constant, and (c) approximation of the distribution function by Na (cos2θj)a alone. It is concluded that when the orientation distribution is sharp, estimation by the second method of approximation gives a smaller error than the first.
Adhesion of viscoelastic materials to rigid substrates. III. Energy criterion for failure
Authors: Gent A. N. , Kinloch A. J.
Published: April 2003

Measurements are described of the strength of a model adhesive joint subjected to (1) tensile rupture, with the interface containing a small unbonded region of varying size, and (2) pure shear deformation, in the form of a partly unbonded sheet. These, and previous measurements of resistance to peeling separation, are all shown to be consistent with an energy criterion for adhesive failure. The characteristic failure energy per unit area of interface has been determined for the model adhesive material as a function of the effective rate of detachment, over a wide range covering almost the entire spectrum of viscoelastic response. The values obtained are found to increase from levels only slightly higher than thermodynamic considerations would predict, i.e., 102−103ergs/cm2, at low rates of crack propagation, up to a value of about 106ergs/cm2at high rates when the material responds in a glasslike manner. These results suggest that the failure energy has two components: the (reversible) work of adsorption and the (irreversible) work of deformation of the adhesive in effecting separation.
Laser‐Raman spectra of vinyl chloride‐vinylidene chloride copolymers
Authors: Meeks M. , Koenig J. L.
Published: April 2003

Several copolymers as well as homopolymers of vinylidene chloride and vinyl chloride have been examined by Raman spectroscopy. Probabilities of concentrations of monomer sequences have been calculated from known reactivity ratios. Surface scattering intensities at some frequencies were found to be linearly proportional to specific microstructure concentrations. Normalization of scattering intensities was accomplished using the intensity of the CH2 asymmetric stretching mode at 2926 cm‐1, which is common to all samples examined. Good correlation was found for the concentrations of comonomer sequences {B}, {BB}, {BBB}, {AA} and {AAAA} in which A denotes vinylidene chloride and B vinyl chloride.
Determination of the pressure coefficient and pressure effects in capillary flow
Authors: Penwell Richard C. , Porter Roger S. , Middleman Stanley
Published: April 2003

General expressions for determining the pressure coefficient and axial distribution of the viscosity and pressure in capillary flow are derived for Newtonian and shear‐thinning fluids. The pressure‐dependent viscosity model is obtained from the WLF equation as derived from Doolittle's free volume theory. The model has also been derived from Eyring's hole theory for viscosity. Poiseuille's equation is modified to correct for the pressure effect on viscosity. A Newtonian, low‐molecular‐weight polystyrene and a shear‐thinning, high‐molecular‐weight polystyrene were tested in an Instron capillary rheometer. The axial velocity distribution was found to be negligibly affected by pressure whereas the viscosity was shown to increase markedly with a decrease in volume. The resulting pressure effects on the viscosity of both samples were analyzed by using the derived expressions.
Electronic states at defects in infinite polyenes
Authors: Begg A. H. , Pugh D.
Published: April 2003

The electronic states localized at defects in a polyene chain with alternating bond lengths have been investigated in the Hückel approximation by direct computation on large rings. The defects considered include substitutional impurities and bond distortions. None of the cases treated seem likely to be thermally activated donor or acceptor centers, but several examples of deep or shallow traps for electrons in the conduction band are found.
Nuclear magnetic resonance study of rubber–carbon black interactions
Authors: Kaufman Stanley , Slichter W. P. , Davis D. D.
Published: April 2003

The mobilities of polymer chain segments in mixtures of rubber and carbon black were investigated by nuclear magnetic resonance. Spin–spin relaxation time (T2) measurements on cis‐polybutadiene and ethylene–propylene–diene rubber (EPDM) bound rubbers detected at least two relaxing regions: an immobile region and a relatively free region. The molecular motions in the relatively free region are still constrained compared to those of the pure gum.
Mechanical relaxations in polyamides
Authors: Prevorsek D. C. , Butler R. H. , Reimschuessel H. K.
Published: April 2003

Dynamic mechanical measurements were carried out as a function of temperature (−100 to + 180°C) and frequency (3.5 to 110 cps) for a series of aliphatic terpolyamides, nylon 6 and nylon 12. Effect of crosslinking with toluene diisocyanate, of absorbed water, and of frequency are used to estimate the statistical segment length associated with the α′ relaxation. The effects of variations in the aliphatic chain length in the repeating unit on the temperature of the α′ relaxation are examined by means of copolymer rules with a view to explaining the reported insensitivity of the glass transition temperature of these polymers to changes in (CH2)/(amide) group ratio. From the estimated length of the segmental motion associated with the α′ relaxation it is inferred that in a series of polyamides of the type nylon X or nylon X,Y (where X or Y = 3, 4, 5, 6, etc.) there should be a relatively small change in the temperature of the α′ transition for those polyamides having X or Y less than about 45. Experiments which are intended to establish the position of the crystalline α–γ transition are discussed.
Contact angle of polyethylene on copper and its effect on adhesion
Authors: Sykes J. M. , Hoar T. P.
Published: April 2003

To determine whether the large differences in adhesion for polyethylene coatings applied to different types of copper surface could be attributed to changes in work of adhesion or wettability, the variations of contact angle with time has been measured for molten polyethylene droplets on these surfaces. It is concluded from these measurements that the low peel strengths obtained on certain substrates cannot be accounted for by a low work of adhesion of poor wetting of the surface.