bluuebunny/crossref_metadata_2025 huggingface dataset:
Salt effect on polymer solutions
Authors: Saito Shuji
Published: April 2003

The salt effect was investigated by measurements of viscosity, cloud point, and solubility of aqueous solutions of poly(vinyl alcohol—acetate) copolymers, as these copolymers in water are sensitive in various ways to addition of various electrolytes. The major role in the salt effect is played by the anions, and water‐structure breaking anions produce salting‐in of the copolymers. Tetraalkylammonium halides (bromides and iodides) cause salting‐in of the copolymers more effectively with increase of size of the hydrophobic cations. The Setschenow equation does not hold for the polymers except for very dilute polymer concentration. In salts of monoalkyl‐substituted anions (RCOONa and RSO4Na) and cations (RNH3Cl and Br), so long as the alkyl chain is short, the salt effect is also dominated by the anions. With increase of the alkyl chain length, sodium salts of the monoalkyl‐substituted anions exert a stronger salting‐in effect upon the polymers than chlorides of similar long‐chain cations. The significance of the counteranions is suggested for the interaction of nonionic polymers and the long‐chain cations. The action of the salts on the copolymers is discussed in terms of medium effects (change of the water structure) and of the binding effect of the single ions to the polymers.
Polyindoloquinoxalines
Authors: Schopov I. , Popov N.
Published: April 2003

Two polymers, containing 6H‐indolo [2,3‐b] quinoxaline as a repeating unit, have been prepared by polycyclization of 5,5′‐biisatyl with 3,3′‐diaminobenzidine, and of 5,5′‐diisatyl ether with 3,3′,3,4′‐tetraaminodiphenyl ether in polyphosphoric acid. Their structure was established by comparing the infrared and electronic spectra of the newly obtained polymers with the corresponding spectra of four model compounds synthesized for the purpose. The electronic spectra showed conjugation along the chain of both the polymer with ether bonds and the one with single bonds between the rings. The two polymers gave an electronic paramagnetic resonance signal. The polyindoloquinoxalines showed good thermal stability in air and in nitrogen, the better stability being manifested by the polymer with single bonds between the rings.
Anionic graft polymerization of ethylene oxide on starch. I
Authors: Tahan Menashe , Zilkha Albert
Published: April 2003

Graft polymers of polyethylene oxide on various starches were obtained by anionic graft polymerization of ethylene oxide on the starch alkoxide derivatives. The polyalkoxides were prepared by reaction of potassium naphthalene with starch in DMSO solution. It was found that increase of monomer or alkoxide concentration led to transformation of the grafts from solids to syrups. Rice starch, having a more complex structure than soluble starch or wheat starch, led to graft polymers having higher melting ranges than the others. The graft polymers were very soluble in water or methanol.
Anionic graft polymerization of ethylene oxide on starch. II. Structure of the graft polymers
Authors: Tahan Menashe , Zilkha Albert
Published: April 2003

Starch–poly(ethylene oxide) graft polymers were prepared in DMSO at various monomer and starch alkoxide concentrations. Complimentary and varied information on the structure of the graft polymers was obtained from NMR and periodic acid oxidation of the polymers. From the NMR spectra of the graft polymers in pyridine containing a trace of HCl, which causes shifting of the resonance of the internal CH2O protons from the terminal CH2OH protons, the polyethylene oxide content, the DPn of the grafted side chains, and the efficiency of the alkoxides were calculated. With increase of the alkoxide concentration there was a small decrease in DPn, and in the efficiency of the alkoxides in initiating graft polymerization. With increase of monomer concentration, there was only a small increase in DPn but a large increase in the efficiency, indicating the existence of transfer reactions between the growing anions and the free hydroxyl groups on the starch. The results of he periodic acid oxidation showed that with increase of alkoxide concentration there was no significant change in the per cent oxidation of the graft polymers, but with increase of monomer, there was an increase in the participation of the secondary hydroxyl groups in initiation. This supports the NMR evidence for the existence of transfer reactions leading to DPn values much lower than those calculated from [monomer]/[catalyst] ratios.
Production of radicals in polyoxymethylene by ultraviolet photolysis: An EPR study
Authors: Hughes O. R. , Coard L. C.
Published: April 2003

Polyoxymethylene (POM) was photolyzed at 2537 and at 3130 Å at −196°C. The EPR spectra of the radical intermediates were recorded. Photolysis in vacuo produces a small number of radicals, apparently due to the presence of traces of chromophores. Photolysis in oxygen, however, is a type of photo‐oxidation. The radicals HCO, , CH3·, and HOO· were detected and identified as intermediate products of photolysis. Hydrogen atoms and hydroxyl radicals were too reactive (i.e., mobile) at −196°C to be observed. Alkoxy and alkyl radicals and the POM peroxy radical
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were probably formed as well but could not be characterized with certainty.
Syntheses and reactions of functional polymers. XLVI. Preparation and reactions of N‐benzyloxyisomaleimide–styrene copolymer
Authors: Akiyama Masayasu , Yanagisawa Yasuhiro , Okawara Makoto
Published: April 2003

Polymerization of N‐benzyloxymaleimide(I) was attempted to obtain a polymer with the N‐hydroxysuccinimide unit in the chain. In the light of infrared and NMR data the compound reported by Ames as N‐benzyloxymaleimide is N‐benzyloxyisomaleimide (III). Homopolymerization of III did not give polymer. Copolymerization of III with styrene was carried out in dioxane at 70°C. A strong alternation tendency like that of maleimides was observed. Monomer reactivity ratios and Q‐e values were determined. Copolymer having the isoimide structure showed infrared absorptions at 1815 and 1675 cm−1 in the carbonyl region. The copolymer was isomerized to N‐benzyloxymaleimide type copolymer and debenzylated to N‐hydroxymaleimide type copolymer. An insoluble copolymer was prepared by using divinylbenzene as a crosslinking agent and was converted to N‐acetoxymaleimide type copolymer, which was used as an insoluble acetylating agent.
Sulfur modification of polyethylene surfaces. I. Insertion of sulfur into polyethylene surfaces
Authors: Olsen Douglas A. , Osteraas A. Jean
Published: April 2003

Atomic sulfur generated respectively by the pyrolysis of carbonyl sulfide and by the photolysis of carbonyl sulfide, carbon disulfide, and sulfur vapors has been shown to modify irreversibly the surface of polyethylene as shown by wettability measurements. The nature of the modification is not completely apparent from this portion of the study, however, insertion of the atomic sulfur into a carbon—hydrogen bond to form a surface thiol group appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions, as determined by wettability measurements.
Stereoblock polymerization of methyl methacrylate with VOCl3Al(C2H5)3 catalyst system
Authors: Dixit S. S. , Deshpande A. B. , Anand L. C. , Kapur S. L.
Published: April 2003

Kinetics of the polymerization of methyl methacrylate with the VOCl3AlEt3 catalyst system at 40°C in n‐hexane have been studied. A linear dependence of rate of polymerization on the monomer and catalyst concentrations as well as an overall activation energy of 5.87 kcal/mole were found. Characterization of the structure of the polymer by NMR spectra revealed the presence of stereoblock units. The mechanism of polymerization is discussed in relation to the kinetic data obtained.
Determination of penetrant solubility from transient permeation measurements
Authors: Paul D. R.
Published: April 2003

The permeability coefficient for the transport of a gas, vapor, or liquid through a polymer film is the product of the penetrant solubility and a diffusion coefficient. A transient permeation experiment known as the time‐lag technique can be used to separate this product, provided the diffusion coefficient is independent of penetrant concentration. In this well‐known experiment the polymer is initially free of penetrant. A new transient permeation experiment where the polymer is initially saturated with penetrant is suggested here. A general mathematical proof is given to show that by using the results form these two transient experiments which have different initial conditions one can determine the penetrant solubility no matter how the diffusion coefficient depends on penetrant concentration. Also one can determine two different concentration averaged diffusion coefficients from the results.
Application of preparative gel‐permeation chromatography to studies of low molecular weight carboxy‐polybutadienes
Authors: Law Ronald D.
Published: April 2003

Low molecular weight carboxy‐polybutadiene liquid polymers are used as the binderfuel fraction in solid composite propellants. Analytical GPC determinations of low molecular weight materials (100 through 500 molecular weight range) were previously found to correlate significantly with final propellant properties. These low molecular weight materials are being characterized, and studies of their role in determining propellant physical properties are being conducted. Sufficient quantities of material in the 100–500 molecular weight range have been isolated by using preparative scale GPC to establish the chemical nature of these materials. Infrared and chemical analysis of fractions collected by using preparative GPC also has permitted the construction of functional group distribution profiles. In addition, narrow fractions isolated over the molecular weight range of the whole polymer were analyzed for average molecular weight by vapor pressure osmometry and have been used as calibration standards for analytical GPC.
Formation of free radicals during machining and fracture of polymers
Authors: Backman D. K. , Devries K. L.
Published: April 2003

Electron paramagnetic resonance measurements of the number of free radicals formed during cutting and grinding of polymers are described. It was found in the semicrystalline polymers studied that below the glassy transition temperature that the number of free radicals formed is about 2 × 1013/cm2 of surface formed. It is proposed that this number results from the crack progressing selectively through the glassy regions about more ordered regions in the polymers.
Polymers from 12 α‐hydroxymethylabiet‐7,8‐enoic acid and vinyl 12 α‐hydroxymethylabiet‐7,8‐enoate
Authors: Saga Motoo , Marvel C. S.
Published: April 2003

12 α‐Hydroxymethylabiet‐7,8‐enoic acid has been homopolymerized by melt condensation, and a partially crystalline polyester has been obtained. Vinyl 12 α‐hydroxymethylabiet‐7,8‐enoate has been prepared from 12 α‐hydroxymethylabiet‐7,8‐enoic acid by vinyl interchange with vinyl acetate and has been homopolymerized, copolymerized with vinyl chloride, vinyl acetate, butadiene, and acrylonitrile, and terpolymerized with styrene and acrylonitrile. Polymers thus obtained have been characterized.
Low‐temperature polymerization of lactams by using as catalyst the salt derived from NaAlEt4 and monomer and with several compounds as initiator
Authors: Konomi T. , Tani H.
Published: April 2003

Low‐temperature polymerization of α‐pyrrolidone, α‐piperidone, and ϵ‐caprolactam was examined by using the salts derived from NaAlEt4 and monomer, sodium lactamates, or the salt derived from AlEt3 and monomer as catalyst and with N‐acetyl lactams, ethyl acetate, or lactones as initiator. Sodium lactamate catalyst gave unsatisfactory results in the cases of ethyl acetate or lactones initiators, and gave the following order for the relative efficiency of initiators: N‐acetyl lactam > ϵ‐caprolactone ≥ ethyl acetate > β‐propiolactone. The polymerization results obtained by the salt from NaAlEt4 catalyst–ethyl acetate initiator system were nearly the same as those with N‐acetyl lactam. The increases in the degree of polymerization and in the yield of polymer were observed in case of the salt from NaAlEt4 catalyst‐lactone initiator system, particularly in the cases of α‐piperidone and ϵ‐caprolactam. Also an incorporation of initiator into polymer chain was observed.
Methyl methacrylate polymerization initiated by triethylborane–peroxide mixtures
Authors: Contreras J. , Grotewold J. , Lissi E. A. , Rozas R.
Published: April 2003

The polymerization of methyl methacrylate initiated by triethylborane or triethylborane–peroxide mixtures was studied. The rate of initiation by a mixture of triethylborane and tert‐butyl peroxide was found to be first‐order in peroxide. The order in triethylborane changes from one at low triethylborane/peroxide to nearly zero at high triethylborane/peroxide. The possibility of a mechanism involving a fast reaction followed by a slow reaction that would initiate the polymerization is discussed.
Cationic polymerization behavior of hydroxystyrenes
Authors: Kato Masao
Published: April 2003

Solution polymerizations of o‐, m‐ and p‐hydroxystyrene with boron trifluoride etherate were investigated. The results of infrared and ultraviolet spectroscopic investigations of the polymers thus obtained indicate that p‐hydroxystyrene polymer consisted mainly of the structure formed through the normal vinyl polymerization mechanism, whereas o‐ and m‐hydroxystyrene polymers contained considerable portions of the structures due to the reaction of the vinyl group with the phenol nucleus. The rate of polymerization and the intrinsic viscosity of the polymer decreased in the order p‐hydroxystyrene ≫ o‐hydroxystyrene > m‐hydroxystyrene. It was of interest that on the cationic polymerization only p‐hydroxystyrene gave polymer of high molecular weight. Plausible polymerization mechanisms were considered. Solid‐state polymerization of p‐hydroxystyrene at solid carbon dioxide temperature with the use of boron trifluoride etherate was also investigated. Appreciable polymerization occurred only at fairly high catalyst concentrations.
A novel method of metal ion removal and recovery from water by complex formation with polyelectrolytes
Authors: Jellinek H. H. G. , Luh Ming Dean
Published: April 2003

A novel method of metal removal and recovery and recovery is described. This method may be useful in connection with various types of water pollution. It is based on the fact that metal ions form water‐soluble complexes with water‐soluble polyelectrolytes, such as polyacids. These complexes can be precipitated with polybases and the metal can be recovered by treating the precipitate with mineral acid. The remaining polymer complex can be used again for further precipitation. Experiments with Cu2+ and Co2+ ions are given in some detail; general observations concerning other cases are included.
Investigations on aromatic polyesters with polynaphthalene systems in the main chain. I. Low‐temperature solution polycondensation
Authors: Jedlińaski Zbigniew , Sek Danuta
Published: April 2003

A series of aromatic polyesters has been prepared by low‐temperature solution polycondensation of derivatives of dihydroxydinaphthyl or dihydroxydinaphthylmethane with terephthaloyl chloride. The chemical, physical, and thermal properties of some polyesters have been investigated. Some of the polyesters obtained have high melting temperatures (340–420°C) and very good thermal resistance. In spite of their high melting temperatures some polymers give solutions in organic solvents which make it possible to produce films and coatings with good dielectric and mechanical properties and with a relatively high thermal resistance.
Chain transfer constants for vinyl monomers polymerized in methyl oleate and methyl stearate
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Wrigley A. N.
Published: April 2003

Chain transfer constants were obtained for styrene, methyl methacrylate, methyl acrylate and vinyl acetate, polymerized in methyl oleate and methyl stearate at 60°C. Transfer constants increased in the order: methyl methacrylate < styrene < methyl acrylate ≪ vinyl acetate in both solvents. Average values of the transfer parameters were: for methyl oleate, Qtr = 2.04 × 10−4, etr = 1.08; for methyl stearate, Qtr = 0.373 × 10−4, etr = 1.01. Indication that polar species predominate in the transition state is supported by the observed order of reactivity. The usual rate dependence appeared to be followed by all of the monomers except vinyl acetate, which was retarded, severely in methyl oleate. Transfer in methyl oleate was about 5.8 times greater than that found in methyl stearate for these four monomers. The internal allylic double bond of methyl oleate had about the same reactivity in transfer as had the terminal unsaturation in N‐allylstearamide at 90°C. Rough estimates were obtained of the monomer transfer constants for the long side‐chain homologs of these four monomers from the respective monomer transfer constants and the experimental transfer constants, corrected for transfer to the labile groups of the solvent. It was concluded that the rate of polymerization would determine in large measure the degree of polymerization for the reactive 18‐carbon homologs but that the molecular weight of poly(vinyl stearate) and (oleate) will be regulated primarily by transfer to monomer.
Reaction mechanism of the alternating copolymerization of aziridines with cyclic imides
Authors: Kagiya Tsutomu , Adachi Teruho , Fukui Kenichi
Published: April 2003

The copolymerizations of N‐substituted aziridines and cyclic imide were studied. N‐Ethylsuccinimide copolymerized with ethylenimine, but N‐ethylethylenimine did not copolymerize with succinimide and N‐ethylsuccinimide without catalyst. The effect of additives on the copolymerization of ethylenimine with succinimide and that of N‐ethylethylenimine with succinimide and N‐ethylsuccinimide was also examined. The rate of copolymerization of ethylenimine with succinimide was accelerated by the addition of N‐acetylethylenimine or water. The copolymerization of N‐ethylethylenimine with succinimide was initiated only by water, but N‐ethylethylenimine did not copolymerize with N‐ethylsuccinimide in the presence of water. Gas evolved on heating the copolymer of ethylenimine and succinimide was analyzed and confirmed to be ammonia. On the basis of these results the reaction mechanisms of the copolymerization of ethylenimine with succinimide or N‐ethylsuccinimide and of N‐ethylethylenimine with succinimide initiated by water are discussed.
Structural study of alternating copolymerization of aziridines with cyclic imide
Authors: Kagiya Tsutomu , Izu Masatsugu , Adachi Teruho , Fukui Kenichi
Published: April 2003

The structures of copolymers of aziridines with cyclic imides were determined by means of infrared spectrometry, paper electrophoresis of the hydrolyzate, and NMR spectrometry. The structure of the repeating unit in the copolymer of ethylenimine with succinimide was \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} ({\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CONH}\rlap{--} ) $\end{document}. The endgroups of the copolymer were N‐acylethylenimine ring, N‐substituted succinimide ring, and primary amide group. The copolymer of ethylenimine with N‐ethylsuccinimide had the repeating unit of \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups of N‐acylethylenimine and N‐substituted succinimide ring. N‐Ethylethylenimine did not copolymerize with succinimide, but in the presence of water, the reaction occurred to give an amorphous polymer. This copolymer had the repeating unit \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups were N‐substituted succinimide ring and amine group but not N‐acylethylenimine ring. On the basis of this structural information, the initiation reaction was discussed.
Ferrocene‐terephthalaldehyde copolymerizations and analogous polyferrocenylene crosslinking processes
Authors: Bilow N. , Rosenberg H.
Published: April 2003

Ferrocene has been copolymerized with terephthalaldehyde and 1,1′‐ferrocenedicarboxaldehyde to produce thermosetting polymers suitable for the fabrication of reinforced structural composites. Both the terephthalaldehyde and 1,1′‐ferrocenedicarboxaldehyde were also found to be useful curing agents for polyferrocenylenes formed by other methods. Glass‐reinforced laminates have been fabricated from both types of copolymers and from both types of cured polyferrocenylenes. Laminate flexural strengths have been in the range of 35 000 psi.
The polymerization of pyromellitic dianhydride with diphenylmethane diisocyanate
Authors: Meyers R. A.
Published: April 2003

A novel polyimide forming reaction is reported. Pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt‐fusion conditions to give polydiphenylmethanepyromellitimide (II) and carbon dioxide. Polymer II was characterized by inherent viscosity, infrared spectrum, and thermogravimetric analysis. An intermediate Polymer I was isolated which appeared to contain seven‐membered rings in the backbone. It is postulated that these rings eliminate carbon dioxide to form polyimide II.
γ‐ray‐induced copolymerization of carbon monoxide with cyclic hydrocarbons
Authors: Kagiya Tsutomu , Kondo Masatsune , Fukui Kenichi , Yokota Hisao
Published: April 2003

The γ‐ray‐induced copolymerization of carbon monoxide with saturated or unsaturated cyclic hydrocarbons, such as cyclohexane, cyclohexene, 4‐vinyl‐1‐cyclohexene, and cyclopentadiene was studied at 30°C. Resinous or powdery polymers were obtained in the copolymerization. The results of elementary analysis, infrared spectra, and NMR spectra showed that copolymers containing ketone and ring structures were produced. The copolymers were confirmed to be partially crystalline by the x‐ray diffraction diagram. Further, the influence of the addition of ethylenimine on the copolymerization of carbon monoxide with cyclohexane or cyclohexene was examined. A powdery polymer formed in the copolymerization was concluded to be a terpolymer of carbon monoxide with cyclic hydrocarbon and ethylenimine. On the basis of the experimental results, a mechanism of the copolymerization is proposed.
Thermal polymerization of levoglucosan
Authors: Houminer Yoram , Patai Saul
Published: April 2003

The uncatalyzed polymerization of neat levoglucosan (1,6‐anhydro‐β‐D‐glucopyranose) was studied at 190–210°C under argon, and the course of the reaction was followed by analyzing samples at various reaction times; the residual levoglucosan was determined by GLC, and the optical rotation of the mixture was also measured. The plots of percentage reaction versus time were sigmoid, indicating the occurrence of an autocatalytic reaction. A. kinetic equation of the form, dA/dt = k2[A1]2 + k1[At] ([A0] − [At]), where [A0] and [At] denote the concentrations of levoglucosan at zero time and time t, was found to fit the results. A reaction scheme is proposed, consisting of a slower dimerization (k2) followed by a faster reaction between levoglucosan and the dimers and other oligomers formed (k1). This scheme results from the mechanistic assumption that axial hydroxyl groups in the unchanged levoglucosan are less reactive than equatorial hydroxyl groups present only in the oligomers, while the highest reactivity is ascribed to the primary hydroxyl at C6, again only present in the oligomers. The relation between the mechanisms of the reactions occurring and the structure of the product are discussed.
Polythiazolines
Authors: Iwakura Yoshio , Kurita Keisuke , Hayano Fusakazu
Published: April 2003

Polythioureas having pendant hydroxyl groups were prepared by the polyaddition reaction of bisaminoalcohols and diisothiocyanates. The polythioureas had inherent viscosities in the range of 0.22–1.08 dl/g and gave transparent films by solution casting. These polythioureas were converted to polythiazolines by treatment with poly(phosphoric acid) or to poly(thiazoline–oxazolines) by treatment with a mixture of poly(phosphoric acid) and a polar solvent.
Radiation‐induced polymerization of styrene in the presence ofn‐dibutyl disulfide
Authors: Miller L. A. , Stannett V.
Published: April 2003

The γ‐radiation‐induced polymerization of pure styrene and styrene‐n‐dibutyl disulfide mixtures has been studied at a number of temperatures and dose rates. Up to 0.04 Mrad/hr the rates were proportional to the square root of the dose rate. By measuring the rates at a number of disulfide concentrations and at three different dose rates, the relative rates of radical formation were determined by kinetic analysis. Considerable energy transfer from the styrene to the disulfide was found. The relative contributions of energy transfer and radical formation were separated by using the kinetic scheme of Nikitina and Bagdasaryan. Values of 8.5 and 3.1 were found for the relative rates of radical production and energy transfer, respectively. This leads to aG(radical) value of 3.1 forn‐dibutyl disulfide. With azobisisobutyronitrile as the initiator, the chain transfer constant to the disulfide was determined at 55°C. Finally, the sulfur content of a number of the polymers were determined, an average of two sulfur atoms per polymer chain was found. In general, the rate of polymerization was found to increase in the presence of dibutyl disulfide.
Acid‐catalyzed polycondensation of bisdiazoalkanes
Authors: Koninck L. De , Smets G.
Published: April 2003

Dimerization reactions of diphenyldiazomethane have been applied to the polycondensation of six bisdiazobenzyl arylenes, namely 1,4‐ and 1,3‐bis(α‐diazobenzyl)‐benzenes C6H5CN2(C6H4)CN2C6H5; 1,4‐ and 1,3‐bis(α‐diazo‐p‐methoxybenzyl)‐benzenes, p,p′‐MeOC6H4CN2(C6H4)CN2C6H4OMe; 4,4′‐bis(α‐diazobenzyl)‐diphenylmethane, C6H5CN2(C6H4CH2C6H4)CN2C6H5; and 4,4′‐bis(α‐diazobenyl)‐diphenyl ether, C6H5CN2(C6H4OC6H4)CN2C6H5. Depending on the nature of the catalysts, polyene‐arylenes (C(Ar)C(Ar)C6H4)n, and polyazine‐arylenes, (C(Ar)NNC(Ar)C6H4)n, can be obtained selectively by acid‐catalyzed decomposition of these bisdiazoalkanes at room temperature. With perchloric acid and with arylsulfonic acids in strong polar media, polyene‐arylenes are formed. On the other hand, boron trifluoride and arylsulfonic acids in solvents of low dielectric constant afford polyazine‐arylenes. Less selective is the thermal decomposition at 75°C in toluene solution; it gives a polymer containing about 90% azine and 10% olefinic groups. All these polymers are soluble in common solvents. Their molecular weight vary from 3 200 to 5 000, i.e., X̄n from 12 to 20. The polyene‐arylenes are very stable and decompose only around 500°C; the polyazine‐arylenes are less stable and decompose around 370°C by losing nitrogen.
Determination of degree of crystallinity of drawn polymers by means of density measurements
Authors: Fischer E. W. , Goddar H. , Schmidt G. F.
Published: April 2003

The well known procedure of determining the degree of crystallinity by means of measuring the density presupposes the knowledge of both the densities ρc and ρa of the crystalline and of the noncrystalline regions. By combination of small‐angle and wide‐angle x‐ray scattering and of density measurements it can be shown that this method is not justified in the case of drawn polyethylene if the values of ρc and ρa known from isotropic material are used. Both ρc and ρa depend considerably on annealing and drawing conditions. In addition the effective density ρc* of the more densely packed phase in a two‐phase structure is much lower than the value ρc calculated from the positions of the x‐ray reflections due to a large number of lattice defects. This conclusion is based on the results of three independent sets of experiments: determination of the mean‐square fluctuation of density 〈η2〉 by means of x‐ray small‐angle scattering; x‐ray wide‐angle measurements of the positions of the crystal reflections and of the halo arising from the noncrystalline regions; and comparison of densities and long periods of samples treated at various annealing temperatures.
Determination of branching distribution by concurrent GPC and sedimentation velocity experiments
Authors: Tung L. H.
Published: April 2003

A method of determining the distribution of branching in polydisperse polymer samples is proposed. This method uses data from concurrent gel permeation chromatography and sedimentation‐velocity experiments. Tedious fractionation, which must precede other methods of determining long‐chain branching, is eliminated. An example of use of the method on the data of a sample of styrene–divinylbenzene copolymer is given.
Effect of annealing conditions on the structure of drawn nylon 66 yarns
Authors: Buchanan D. R. , Dumbleton J. H.
Published: April 2003

Differences in structural parameters, shrinkage, and retractive forces have been compared for nylon 66 tire yarns annealed at several temperatures in silicone oil and in air. It is found that significantly different structural changes occur for oil‐annealing and air‐annealing. Retractive forces measured in hot oil are characterized by a high initial force, followed by a rapid decay and a second, more gradual, increase which is also followed by a decay at sufficiently high temperatures. In heated air, the first, short‐term, retractive force is absent. It is postulated that these differences are due to the different rates of heat transfer at gas–solid and at liquid–solid interfaces, and that rapid heat transfer (as in the case of oil‐annealing) promotes two mechanisms of molecular change which are characterized by different degrees of structural parameter change, and by different amounts of shrinkage.
Formation of spherulities in polyamides. IV. Even–odd polyamides and poly(ω‐aminocarboxylic acids)
Authors: Magill J. H.
Published: April 2003

Isothermal and nonisothermal spherulitic crystallization in even–odd and poly(ω‐aminocarboxylic acids) has been studied for a range of fusion conditions and solidification temperatures. The variety of spherulites so formed are classified mainly by optical microscopy. It is found that polyamides with similar types of repeat units generally exhibit similar morphological features under corresponding crystallization conditions. The basic patterns are illustrated in the text. Changes in spherulitic birefringence with temperature are also discussed. In some cases, at temperatures not far below the polymer melting point, platelet‐like crystalline aggregates are formed in thin film preparations. These platelets exhibit properties characteristic of single crystals.
Resolution of GPC columns
Authors: Smith W. V. , Feldman G. A.
Published: April 2003

A resolution index for gel‐permeation chromatograph (GPC) columns is defined by the relation log (RI) = αW, where RI is the resolution index, α is the slope of the calibration curve of logarithm of molecular weight against peak position for narrow polymer fractions, and W is the width of the GPC curves for narrow fractions. This resolution index is calculated approximately for several GPC columns individually and in series combinations by using data obtained on narrow fractions of polystyrene. The index increases with number of columns and with flow rate over a limited range of flow rate, does not vary much with solvent, and does not correlate well with plate count obtained with low molecular weight molecules. It is believed that the resolution index provides an improved indication of the performance of GPC columns.
Rheo‐optical studies of high polymers. XIV. Study of the deformation mechanism in polymer blends of polypropylene with ethylene–propylene rubber
Authors: Onogi Shigeharu , Asada Tadahiro , Tanaka Akira
Published: April 2003

To clarify the deformation mechanism in polyblends of polypropylene with ethylene–propylene rubber having different compositions, simultaneous measurements of the infrared dichroism with stress and strain under a constant rate of strain of 1.64%/min have been carried out. The orientation function of the crystallographic c axis of polypropylene in the blends has been obtained as a function of strain ranging from 0 to 20% and of polypropylene content ranging from 0.3 to 1.0. These results have been compared with the temperature dependences of the dynamic Young's modulus and of the loss modulus, as well as of stress–strain curves for the same blends. The modulus data analyzed by Kerner's equation reveal the occurrence of phase inversion at polypropylene contents higher than about 0.5, and this is supported by the infrared dichroism data. The strong effect of quenching on crystalline structure and mechanical properties of pure polypropylene has also been elucidated.
Crystallite orientation in stretched polychloroprene networks. II
Authors: Krigbaum W. R. , Dawkins J. V. , Via G. H.
Published: April 2003

The orientation of crystallites grown isothermally in several drawn trans‐polychloroprene networks is studied as a function of crystallization temperature tx, degree of crystallinity ω, and elongation ratio α. The orientation distribution is particularly simple for this polymer since the crystallographic c axis (chain axis) orients preferentially along the stretching direction, while a and b are randomly arranged about c. Hence the parameter cos2 χc adequately characterizes the distribution, where χc is the angle between the c axis and the fiber axis, and the average is taken over all crystallites. A treatment due to Krigbaum and Roe is utilized to obtain values of v (the number of statistical segments comprising the crystallization nucleus of critical size) through comparison of the average orientation of crystallites and amorphous statistical segments. The behavior observed falls into two categories. First, if the initial amorphous network is well oriented, 〈cos2 χc〉 is independent of crystallinity during both crystallization and melting, and v varies with tz (or the degree of supercooling) as predicted by nucleation theory. If different networks are to have the same crystallite orientation distribution, they must not only be crystallized at the same supercooling, but must also have the same distribution of amorphous segment orientations. Both the relative elongation and the network crosslink density affect the latter distribution. Next, we consider the second category. If the initial amorphous orientation is poor, 〈cos2 χc〉 decreases linearly during crystallization and increases along approximately the same path during melting. Further, 〈cos2 χc〉 for a given tz yields v values which are too large. These two behaviors can be explained if, in the former case, nucleation involves the best oriented statistical segments of all network chains, while in the latter there is a selection according to the chain displacement vector orientation. Thus, if the amorphous orientation is poor, both the orientation and thermodynamic stability of the crystallites decreases with further crystallization. If this decreased stability is reflected in shorter fold lengths, the reversible variation of long period spacing with temperature reported earlier for an oriented polychloroprene network can also be explained as a preferential melting process.
Gel‐permeation chromatography of polydimethylsiloxanes
Authors: Kendrick T. C.
Published: April 2003

The molecular weight distributions of three polydimethylsiloxanes (PDMS) have been determined by gel‐permeation chromatography (GPC), by gas–liquid chromatography (GLC), and by precipitation fractionation. The GPC data are greatly improved by correction for band spreading. For a high molecular weight polymer the corrected distribution agrees closely with the theoretical molecular weight distribution calculated from polymerization kinetics.
Mechanical relaxation in polypropylene as a function of polymorphism and degree of lamella orientation
Authors: Crissman J. M.
Published: April 2003

Mechanical relaxation data as a function of temperature (ca. 1 Hz) have been obtained for several samples of isotactic polypropylene crystallized from the melt, which exhibit both α and β forms as well as varying degrees of lamella orientation. The samples ranged in morphology from an unoriented sample showing only the α form to one highly oriented having approximately 90 per cent the β form. Results for the logarithmic decrement Δ and loss modulus G″ are that the low temperature (ca. −75°C) and glass temperature (ca. 0°C) relaxations show little or no sensitivity to orientation in the α form, but that the intensity of the two processes is different in the α form than in the β form for samples of nearly equal overall per cent crystallinity. In both Δ and G″, the low‐temperature peak decreased and the glass temperature peak increased in intensity as the fraction of β form crystallinity present increased. Data for the high‐temperature relaxation (ca. 80°C) indicate a dependence upon orientation and/or crystal form in addition to a dependence upon per cent crystallinity.
Polymerization of cyclic imino ethers. VI. X‐ray study of some polyaziridines
Authors: Litt Morton , Rahl Forrest , Roldan Luis G.
Published: April 2003

Polymers of poly(N‐acyl and N‐aroyl aziridines) were studied by x‐ray diffraction. All the crystalline polymers studied have a triclinic unit cell with two monomer units per unit cell. The a and c (fiber direction) parameters (4.9 and 6.5 A, respectively) are essentially the same for all the cells. The b parameter for the N‐acyl polymers, however, increases steadily by a factor of 2 A per methylene group added to the lateral chains. The densities calculated for the unit cells are in agreement with the experimental values obtained. The most probable structure is one in which the molecules assume a planar configuration with the main chain not fully extended. The lateral groups are tilted from the c axis by an angle of 54° in a parallel configuration and alternate on each side of the main chain. This permits these lateral groups to assume packing similar to that of polyethylene. A brief description of the techniques used in this interpretation is included.
Steric exclusion and lateral diffusion in gel‐permeation chromatography
Authors: Yau Wallace W.
Published: April 2003

The peak separation in gel‐permeation chromatography (GPC) is attributed to the contributions of the steric exclusion and the lateral diffusion processes. The advantage of using the distribution coefficient KGPC of the solute molecule in interpreting the GPC separation mechanism is assessed. The physical significance of KGPC and its relation to measurable GPC parameters are examined in detail. A simple mixing experiment for determining the exclusion effect is described. The results of this experiment, as well as those of the flow rate study, show that the exclusion effect plays the primary role in GPC peak separation. For a column packed with Bio‐Rad porous glass of 200 Å designation, the diffusion effect does not contribute significantly to peak separation. However, for the case of a Waters Associates column packed with polystyrene gel of 104 Å designation, both the exclusion and the diffusion effects are shown to be important. A diffusion theory which includes the concept of a restricted diffusion coefficient is proposed to interpret the diffusion effect observed in the polystyrene gel column. The results of the theoretical calculation are found to agree with the observed flow rate dependence of the calibration curve.
Structure of poly(N‐butyl isocyanate)
Authors: Shmueli U. , Traub W. , Rosenheck K.
Published: April 2003

An x‐ray study of poly(N‐butyl isocyanate) (PBIC) was undertaken with the aim of providing the structural information required for the calculation of its ultraviolet absorption spectrum. Well defined diffraction patterns are obtained from powder samples and oriented films of the polymer cast from cyclohexane solution. All the reflections can be satisfactorily indexed in terms of a pseudo‐hexagonal unit cell with a = 13.3 Å and c = 15.4 Å. This indexing and the intensity distribution lead to the conclusion that PBIC has a helical structure with a translation of 1.94 Å and a rotation of 135° per monomeric unit (i.e., the c axis corresponds to 8 units in 3 helical turns). In the absence of single‐crystal data on closely similar model compounds, a range of possible bond lengths and angles was assumed. The atomic coordinates of the chromophoric group of PBIC were then computed using the restrictions imposed by the helical parameters. From an investigation of all the assumed range of bond lengths and angles, a few closely similar structures having no unacceptably short van der Waals contacts were found. A comparison of calculated and measured densities indicates that there are two molecules per unit cell. Construction of space‐filling models of PBIC supports this conclusion.
Light scattering and intrinsic viscosity investigation of polymethyl‐3, 3, 3‐trifluoropropylsiloxamer
Authors: Buch Robert R. , Klimisch Helen M. , Johannson O. K.
Published: April 2003

Solution parameters for the polymer poly‐γ‐trifluoro‐propylmethylsiloxamer has been determined in cyclohexyl acetate, methyl hexanoate, and ethyl acetate. Interpretation of data follows the theory of Fox and Flory. In contrast to poly‐dimethylsiloxane, an increased steric hindrance to rotation about the siloxane bond occurs as evidenced by the characteristic ratio of root‐mean‐square end to end dimensions, (r02/r0f2)1/2, found to be 1.90 and 1.96 at 25.0 and 72.8°C, respectively. This increase is considered to be primarily due to nearest‐neighbor interaction of the polar substituent on the silicon atom. The relation, [η]θ ∝ M1/2, was observed to hold for this polymer system. The hydrodynamic model appropriate for the polymer is a random coil considerably more permeable to solvent flow than is generally reported for linear polymers. The universal parameter ϕ was determined to be 1.5 × 1021. The effect of temperature on polymer configuration is indicated to be negligible.
Mechanism for twisting in polyethylene spherulites
Authors: Burns Joanne R.
Published: April 2003

A model is proposed to account for the regular twisting of radial ribbons in certain polymer spherulites. The model assumes that the ribbons have crystallographically regular fold surfaces and that growth of the ribbons is nucleation‐controlled. The model leads directly to a possible mechanism of spherulitic growth in some polymers.
Temperature dependence of secondary crystallization in linear polyethylene
Authors: Schultz J. M. , Scott R. D.
Published: April 2003

A specimen of linear polyethylene was subjected to isothermal secondary crystallization at a series of temperatures below the primary isothermal crystallization temperature, the melting and primary crystallization stages being held constant throughout the investigation. Dilatometric measurements exhibit an S–character at low values of undercooling Tp − Ts, where Tp and Ts are, respectively, the primary and secondary crystallization temperatures; at larger undercoolings, however, an initial very rapid crystallization is followed by a very slow stage. When corrected for thermal contraction of the polymer, the net degree of secondary transformation is seen to peak at a temperature in the range 109–113°C. The S‐character of the isotherms and the peaked temperature variation of degree of transformation lead to the conclusion that a large portion of the secondary crystallization consists of the nucleation and growth of the new crystallites. Johnson‐Mehl‐Avrami analysis leads to a model of heterogeneous nucleation within the remaining amorphous zones, followed by one‐dimensional, diffusion‐controlled growth.
Chain folding in oriented poly(ethylene terephthalate)
Authors: Dumbleton J. H.
Published: April 2003

Drawn poly(ethylene terephthalate), PET, yarns have been heated for 1 min in silicone oil. The resulting samples were studied by x‐ray diffraction and mechanical properties were measured. The results suggest that drawn PET consists of highly extended molecules essentially parallel to one another, with few folds present. On heating, chain folding occurs. This model is very similar to that proposed by Dismore and Statton for drawn nylon 66 yarns.
Viscoelastic properties of epoxy‐diamine networks
Authors: Delatycki O. , Shaw J. C. , Williams J. G.
Published: April 2003

Eight epoxy–diamine networks have been formed, diamines with 2 to 12 methylene groups being used as curing agents. Dynamic mechanical tests revealed four transition regions in the dynamic loss modulus/temperature relationship. Two possible explanations for the relaxation of the glycidyl portion of the structure are proposed. One of the relaxations could be due to the breakdown of hydrogen bonds through the hydroxyl and ether groups. The second could be ascribed to the relaxation of the unbonded glycidyl groups or a second relaxation of the glycidyl groups after the breakdown of the hydrogen bonds.
Measurement of hydrogen isotope transport in poly(vinyl fluoride) films by the permeation‐rate method
Authors: Ziegel K. D. , Frensdorft H. K. , Blair D. E.
Published: April 2003

A novel gas‐flow method of measuring the diffusion, solubility, and permeability of gases and vapors in polymer films is described. The specific advantages of this system over the time‐lag technique are discussed. Transport data, including activation energies and enthalpies of solutions, for hydrogen and deuterium in poly(vinyl fluoride) are presented, and the effects of the glass transition and of orientation on the observed transport rates are discussed.
Conformational energy contribution to the heat of solution in polymer–solvent systems. Part I. Theory
Authors: Bianchi Umberto , Cuniberti Carla , Pedemonte Enrico , Rossi Corrado
Published: April 2003

The conformational energy contribution (ΔUconf) to the heat of solution in polymer‐solvent systems is presented and discussed in connection with chain conformational properties. In particular, ΔUconf has been discussed in terms of various possible mechanisms of coil deformation.
Conformational energy contribution to the heat of solution in polymer–solvent systems. Part II. Experimental results
Authors: Bianchi Umberto , Cuniberti Carla , Pedemonte Enrico , Rossi Corrado
Published: April 2003

Heats of solution (ΔHexp) in solvents of increasing thermodynamic power have been measured for four polymers: polystyrene (PS), poly(vinyl acetate) (PVAc), polyisobutylene (PIB) and polydimethylsiloxane (PDMS). After subtraction from ΔHexp of an interaction term (calculated by the Hildebrand treatment based on solubility parameters) and the excess volume term, the quantity remaining is interpreted as the conformational energy contribution (ΔUconf) to the heat of solution. ΔUconf appears to correlate well with some basic conformational properties of the chain, such as the sign of the temperature coefficient of unperturbed dimensions derived from solution properties, and shows a monotonic behavior with α, the expansion coefficient of the polymer coil in the final solution. Numerical values of ΔUconf, at least for those cases in which polymer solubility parameters are known with some certainty, are much larger than those evaluated from rubber elasticity experiments (through the experimentally accessible value of the energy component of the force of retraction im simple elongation).
Diffusion in glassy polymers. I
Authors: Kwei T. K. , Zupko H. M.
Published: April 2003

Synopsis

The diffusion of six solvents in three crosslinked, glassy epoxy polymers is studied. Case II swelling and Fickian sorption are observed as two simple limiting cases. The mechanism of diffusion changes from one limit to another as the nature of the solvent or the crosslink density of the polymer is altered. With mixed solvents, properly chosen, a superposition of Fickian diffusion and case II swelling is observed.