bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermally degrading polyethylene studied by means of factor‐jump thermogravimetry
Authors: Dickens Brian
Published: April 2003

Degradation of polyethylene in both linear (NBS 1475) and branched (NBS 1476) form has been studied in the range 410–475°C using factor‐jump thermogravimetry. In vacuum, the rate of weight loss was erratic because of bubbling in the sample. The apparent overall activation energy was determined to be 65.4 ± 0.5 kcal/mol (273 ± 2 kJ/mol). There was no distinguishable difference between linear and branched samples. In slowly flowing N2 at 8 mmHg (1 mmHg = 133 Pa), the overall activation energy was determined to be 64.8 ± 0.3 kcal/mol (271 ± 1 kJ/mol) for linear PE and 64.4 ± 0.2 kcal/mol (269 ± 1 kJ/mol) for a sample of PE with one percent branches. In N2 at 800 mmHg, the values were 62.6 ± 0.5 kcal/mol for linear PE and 61.2 ± 0.6 kcal/mol for the branched sample, the rate of weight loss being smooth in both cases. Changing the linear flow velocities over the range 1–4 mm/sec at 800 mmHg did not affect the results. From the insertion of typical values in the equation relating the overall activation energy for weight loss from linear polyethylene to the activation energies of the component steps, a degradation mechanism involving scission β to allyl groups, with rapid hydrogen abstraction, slower subsequent β scission, and bimolecular termination, is indicated. The activation energy of β scission for secondary alkyl radicals is estimated to be 33 kcal/mol. The reason for the lower activation energies in N2 is related to the effects of preformed molecules. The average molecular weights of the volatiles in vacuum and for 8 and 800 mmHg N2 have been shown to be in the ratios 1 to 1/4 to 1/10, respectively, at these imposed rates of weight loss. The activation energies to use for the initial stage of degradation are 70.6 kcal/mol (295 kJ/mol) in vacuum and 67.8 kcal/mol (284 kJ/mol) at atmospheric pressure.
Direct synthesis of a polyamide by an enol phosphite and imidazole
Authors: Yamaguchi Kazuo , Rokicki Gabriel , Kawanobe Wataru , Nakahama Seiichi , Yamazaki Noboru
Published: April 2003

Direct polycondensation of various dicarboxylic acids and diamines was effected under mild conditions by using an enol phosphite, diethyl 1‐methyl‐3‐oxo‐1‐butenyl phosphite (I), in the presence of imidazole. To check the activity of the enol phosphite and various organic bases in an amidation reaction, the model reaction of acetic acid and aniline was carried out, and the yield of acetanilide was estimated by means of gas chromatography. Among organic bases, imidazole was the best in terms of yield of acetanilide. Polycondensation performed by varying solvents, temperature, and amount of imidazole resulted in high yields of polyamides with inherent viscosities of 0.1‐0.25.
Preparation of ion exchange resins from carbonaceous adsorbents
Authors: Ford Warren T. , Beasley Glenn H. , Chong Berni P. , Neely James W.
Published: April 2003

Carbonaceous adsorbents are obtained by thermolysis of sulfonated macroreticular polystyrene ion exchange resins at 300‐500°C. The hard, spherical, carbonaceous particles react exothermally with elemental chlorine to form products containing up to 38% Cl. The chlorinated particles react readily with polyamines to form anion exchange resins with capacities of up to 2.2 meq/g dry resin. Less than 60% of the nitrogen atoms in the particles are utilized as ion exchange sites. The carbonaceous particles can also be chloromethylated with chloromethyl methyl ether or chlorinated with sulfuryl chloride and then aminated with polyamines to form anion exchange resins, sulfonated with sulfuric acid or chlorosulfonic acid to form strongly acidic cation exchange resins, or chlorosulfonated and then aminated with polyamines to form anion exchange resins. Model structures of the thermolyzed resins containing polycyclic aromatic hydrocarbon fragments are proposed to explain their chemical reactivities.
Kinetics of epoxide resins formation from epichlorohydrin and bisphenol‐A
Authors: Enikolopyan N. S. , Markevitch M. A. , Sakhonenko L. S. , Rogovina S. Z. , Oshmyan V. G.
Published: April 2003

The kinetics of formation of epoxide resins based on epichlorohydrin and bisphenol‐A via synthesis with one‐ or two‐step addition of alkali are considered. The kinetics of the reaction were studied by taking into account the consumption of the alkali added and the change of molecular mass and epoxide value of epoxide oligomers. The results obtained are satisfactorily explained within the framework of a model containing the following postulates: all the alkali is bound as phenolate ions; all phenolic groups are of equal reactivity; the reactivity of epichlorohydrin is higher than that of glycidyl ethers; the stage of dehydrochlorination of chlorohydrin ethers in the synthesis with one‐step addition of alkali is rapid and does not limit the process; the first stage of the two‐step synthesis is the formation of chlorohydrin ethers and the second stage their consumption. The factors leading to differences between the experimentally obtained parameters of the resulting epoxide resins (molecular weight, epoxide value) and their calculated values are discussed. The synthesis of epoxide resins with two‐step alkali addition is shown to possess certain advantages over the one‐step process.
Diffusion‐controlled vinyl polymerization. I. The gel effect
Authors: Soh S. K. , Sundberg D. C.
Published: April 2003

It is well known that the reaction rate and molecular weight of vinyl polymers can change markedly during the course of polymerization and that these changes are due to the influence of diffusion on the termination reaction. The chain length dependence of the termination rate constant has been considered in this work and has resulted in a general method of treating the polymerization kinetics and molecular weight distribution. This method is independent of the form of the chain length dependency and is capable of dealing with both disproportionation and recombination modes of termination. A specific model for the termination rate constant with chain length dependence is proposed and is based on free volume theory and entanglement coupling. Master curves for the characteristics of the reaction rate and molecular weight distribution are presented with the application of this model.
Spontaneous copolymerization of 4‐methylene‐1,3‐dioxolanes with maleic anhydride
Authors: Fukuda Hiroyuki , Hirota Masahiro , Nakashima Yoshihiro
Published: April 2003

The copolymerization of methylenedioxolanes, such as 4‐methylene‐1,3‐dioxolane (I) and 2,2‐dimethyl‐4‐methylene‐1,3‐dioxolane (II), with maleic anhydride (Manh) gives rise spontaneously to the alternating copolymers by the participation of charge‐transfer (CT) complexes. The formation of CT complexes I‐Manh and II‐Manh was ascertained by UV and NMR spectroscopies. The equilibrium constants (K) could not be determined but were assumed to be small (K ≪ 1). For comparison with these systems an investigation of I‐dimethyl maleate (DMM) and II‐DMM systems was carried out to estimate K values 0.115 and 0.157 L/mol, respectively. To clarify the copolymerization mechanism I‐Manh‐acryronitrile was terpolymerized. Consequently it was concluded that the spontaneous copolymerization of I‐Manh and II‐Manh systems is effected by the CT complex monomer mechanism.
Synthesis of azido‐polymers of butadiene
Authors: Lillya C. Peter , Juang Rong‐Hwei , Chien James C. W. , Miller R. S.
Published: April 2003

Iodine azide adds to cyclohexene in acetonitrile or 4:1 methylene chloride/acetonitrile to give trans‐1‐azido‐2‐iodocyclohexane. In methylene chloride this reaction gives a mixture of the cis‐and trans‐iodoazides owing to competing radical addition. Iodine azide adds to 1‐hexene in acetonitrile by an ionic mechanism to give a 3:1 mixture of the 2‐azido‐1‐azido‐ and 1‐azido‐2‐iodohexanes. Dehydroiodination of the model iodoazides proceeds smoothly with potassium t‐butoxide in diethyl ether or THF in the presence of 5 mol % 18‐crown‐6 at room temperature, giving in the previous example a mixture of 2‐azido‐ and trans‐1‐azidohexenes. Polybutadiene, carboxyterminated poly(acrylonitrile‐co‐butadiene), and hydroxy‐terminated polybutadiene gave iodoazide derivatives with up to 96% of the theoretical maximum nitrogen content and strong azide IR absorption. High azidoiodination gave polymer with N3/I ratios slightly higher than unity while low percent azidoiodination led to polymer with N3/I ratios of as low as 2:3. All of the nitrogen introduced was in the form of azide function. Dehydroiodination gave polymers with vinyl azide functionality and caused loss of some of the azide groups. All the azidoiodinated polymers decomposed between 120 and 160°C. The dehydroiodinated materials were less stable, decomposing between 100 and 150°C. The temperature of initial decomposition decreased as azide content increased. Polymers with >55–60% of the theoretical maximum azide content were shock sensitive.
Copolymerization of isobutene and α‐methylstyrene as a function of reaction conditions
Authors: Wondraczek Reinhard H. , Müller Winfried , Schütz Heidrun , Heublein Günther
Published: April 2003

The influence of reaction conditions (solvent, Lewis acid, temperature) on the cationic copolymerization of isobutene and α‐methylstyrene was investigated. The crude product consists of low molecular nonprecipitable oligomers, polyisobutene, and poly(isobutene‐co‐α‐methylstyrene). The amount of poly(α‐methylstyrene) formed under the reaction conditions used was negligible. The degree of charge separation in the propagating cationic intermediate determines the selectivity of the reaction; that is, incorporation of monomer units into the polymer, ratio of different product fractions, and microstructure. Molecular weight distribution, copolymerization parameters, and sequence‐length distribution functions were determined. The softening range of the copolymers depended on their isobutene content but appeared to be constant up to 15% isobutene in copolymers. The degradation temperature of the copolymers was between 340 and 390°C.
Piezoelectric polymer films. I. Synthesis and properties
Authors: Liepins R. , Timmons M. L. , Morosoff N. , Surles J.
Published: April 2003

The synthesis of a new class of piezoelectrically active materials comprised of various co‐ and ter‐polymers of tributyltin methacrylate (TBTM) and trimethyltin methacrylate (TMTM) are described. In this article films of the various polymer compositions were evaluated for tin content, glass transition temperature (Tg), and crystallinity or “ordering” of the amorphous phase. A brief theory of piezoelectricity in polymers will be given in Part II with a description of sample preparation, poling techniques, and the measurement system, as well as piezoelectric evaluation results.
Investigations of stabilizing additives. I. A model system for studying radical scavenging activity in solution
Authors: Dunn T. S. , Williams E. E. , Williams J. L.
Published: April 2003

In the current study an electron spin resonance model system was developed to compare the thermal stability and radical scavenging activity of stabilizers in solution. High‐resolution spectra and the influence of molecular structure on radical stability provided a basis for the interpretation of spin concentration data in the model system. A correlation was established between the radical scavenging activity measured in the model system and actual behavior in irradiated polypropylene formulations measured by radiation‐induced degradation of mechanical properties.
Studies on stable free radicals. XIX. Copolymerization of N‐oxyl biradical with α‐chloro‐p‐xylylene
Authors: Fujita Takashi , Yoshioka Takao
Published: April 2003

Copolymerization of N‐oxyl biradical with α‐chloro‐p‐xylylene was carried out by varying the feed ratio of α,α′‐dichloro‐p‐xylene which was the precursor of α‐chloro‐p‐xylylene. The structures of the obtained copolymers were determined spectroscopically. The results that the N‐oxyl attacked the carbon‐bearing chlorine atom of α‐chloro‐p‐xylylene suggest a nucleophilic reactivity of N‐oxyl radical. The copolymerization process was also discussed.
Mass spectral characterization of polymers. Primary thermal fragmentation processes in polyureas
Authors: Caruso S. , Foti S. , Maravigna P. , Montaudo G.
Published: April 2003

The primary fragmentation processes in the thermal decomposition of polymers were studied in detail on a series of structurally related polyureas by direct pyrolysis with a mass spectrometer. Our results indicate that polyureas I–III undergo a quantitative depolycondensation process analogous to that observed for N‐monosubstituted polyurethanes. The thermal decomposition of polyureas IV–VI proceeds by intramolecular hydrogen transfer processes that occur at higher temperatures with respect to depolycondensation. Polycarboxypiperazine VI is decomposed by a single‐stage decomposition mechanism that leads to fragments with amino end groups and carbon oxide.
Effects of triphenylsulfonium hexafluorophosphate in the radiation‐induced cationic polymerization of styrene
Authors: Mah Soukil , Yamamoto Yukio , Hayashi Koichiro
Published: April 2003

Radiation‐induced cationic polymerization of styrene was studied in methylene chloride in the presence of triphenylsulfonium hexafluorophosphate. Acceleration in polymerization and an increase in molecular weight at a low temperature (−78°C) were observed in the presence of triphenylsulfonium salt. A study of pulse radiolysis revealed that both effects are due mainly to PF−6, which forms ion pairs with the cationic species involved in the polymerization.
Plasma polymerization. VII. An esca investigation of the RF plasma polymerization of perfluorobenzene and perfluorobenzene/hydrogen mixtures
Authors: Clark D. T. , Abrahman M. Z.
Published: April 2003

The composition and gross structural features of plasma polymers formed in the glow regions of an inductively coupled RF plasma with perfluorobenzene and perfluorobenzene/hydrogen mixtures were investigated by ESCA as a function of the operating parameters. The carbon‐to‐fluorine stoichiometries of the perfluorobenzene polymers are similar and close to those of the starting material but not of the polymers derived from perfluorobenzene/hydrogen mixtures. The rate of film deposition is dependent on the W/FM parameter. Angular and photon energy‐dependent studies confirm the vertical homogeneity of the plasma polymer films investigated.
Calculation of Alfrey–Price Q–e Values from 13C‐NMR Data
Authors: Borchardt John K. , Dalrymple E. Dwyann
Published: April 2003

A multiple‐correlation analysis program was used to generate equations relating the Alfrey–Price Q and e values of vinyl monomers to the 13C‐NMR absorption frequencies of the α‐ and β‐carbon atoms of the monomers. Separate equations for the calculation of Q and e values of styrenes, chlorinated olefins, acrylates, methacrylates, vinyl ethers, and esters, nitrogen containing monomers, allyl compounds, and miscellaneous olefins were developed. The correlation coefficients of most of these equations were greater than 0.99 and permit accurate calculation of the Q and e values. The Q and e values so calculated may then be used to obtain estimates of the reactivity ratios in copolymerizations prior to actually performing the experiments. Attempts to develop a single Q value equation and a single e value equation for 63 vinyl monomers of the above classes resulted in relations having correlation coefficients of 0.63 and 0.81, respectively, too low to permit sufficiently accurate calculation of the Q and e values.
An ESCA study of the surface ozonation of polystyrene film
Authors: Peeling James , Jazzar Mohammad S. , Clark David T.
Published: April 2003

Polystyrene film was treated with 0.27 mol % ozone in oxygen at room temperature. Changes in the surface were monitored by ESCA. Reaction occurred uniformly in at least the outermost 60 Å of the film. Reaction was rapid, giving a surface composition that corresponded to C1.8O after about 8 h, with no apparent yellowing or embrittlement of the polymer. Ether, ketone, and carboxyl groups were formed at uniform, but not equal, rates in the outer 60 Å of the polymer. With short reaction times the less highly oxidized groups were the main oxidation product, but after about 4 h the highly oxidized groups predominated. The aromatic rings underwent reaction as indicated by the rapid disappearance of the C1s shake‐up satellites on ozonation.
Alternating copolymerization of N‐benzylidine aniline (NBA) with α‐haloacrylic acids (XAA). IV. Synthesis, characterization, and kinetics
Authors: Balakrishnan Thayikkannu , Periyasamy Mookkan
Published: April 2003

This article describes a new, spontaneous, 1:1 alternating copolymerization between a Schiff base, N‐benzylidine aniline (NBA), and α‐haloacrylic acids (XAA) such as α‐chloroacrylic acid (ClAA) and α‐bromoacrylic acid (BrAA). The structure of the copolymers was identified by nuclear magnetic resonance (NMR) and infrared (IR) spectra. By using the isolation method we determined the order of each monomer. On the basis of kinetic studies, a mechanism that involves initiation, propagation, and termination by zwitterion is proposed. The effects of copolymerization under various conditions were studied and the intrinsic viscosity and number‐average molecular weight were measured. The overall energy of activation, ERp, for the copolymerization was determined and thermal degradation studies were made.
Complex formation of amphiphilic polymers with azo dyes and their photoviscosity behavior
Authors: Negishi Naoki , Ishihara Kazuhiko , Shinohara Isao
Published: April 2003

The hydrophobic interaction of amphiphilic copolymers, which contain 2‐hydroxyethyl methacrylate(HEMA) and 1vinyl‐2‐pyrrolidone (VPy), with Methyl Orange (MO) was compared with that of HEMA‐acrylamide (AAm) copolymers to deduce the correlation between their complexation ability in a photochromic azo dye and the photoviscosity effect in aqueous copolymer/dye complex solution. On the basis of the dialysis data and fluorometric analysis it appeared that the complexation dependence on HEMA content in the copolymers was due to the hydrophobic interaction between the polymer and the dye. For a comparable HEMA content AAm copolymers bound less MO than VPy copolymers. It was confiied by photoviscosity measurements that the conformation of the complex composed of photochromic azo dye and HEMA copolymer changed reversibly in response to the photo‐ and thermal isomerization of the dye. In HEMA‐AAm copolymer systems the photoviscosity effect was small compared with that of HEMA‐VPy copolymer systems. From these results it was concluded that the complexation ability of polymers due to the hydrophobic interaction was an important factor in producing a large photoinduced conformational change in water.
Phthalocyanine polymers. III. Poly(nickel phthalocyanine)benzimidazole as a novel high‐temperature‐resistant polymer
Authors: Achar B. N. , Fohlen G. M. , Parker J. A.
Published: April 2003

A new type of poly(nickel phthalocyanine)benzimidazole was prepared by the condensation reaction between nickel (11) 4,4′,4″,4″′‐phthalocyanine tetracarboxylic acid dihydrate and 3, 3′‐diaminobenzidine. The reaction was investigated by both the melt and solution condensation methods. This polymer showed good thermal and thermo‐oxidative stability. Also noteworthy is its high thermal stability with a char yield of 88% at 800°C in nitrogen. No catastrophic decomposition was observed up to 1100°C. A qualitative study of decomposition in both air and nitrogen is presented. Elemental analyses agreed well with the proposed structure. Infrared (IR) and thermogravimetric analysis (TGA) studies were performed to characterize this polymer, and isothermal gravimetric analysis was done to determine its long‐term thermal stability. The apparent activation energies for the thermal degradation in air and nitrogen are given.
Vinyl polymerization. 410. Polymerizations of vinyl monomers initiated by poly(styrene‐co‐sodium acrylate) or poly(methyl methacrylate‐co‐sodium methacrylate). A verification of the concept of hard and soft hydrophobic areas and monomers
Authors: Ouchi Tatsuro , Inaba Masaya , Tadano Kohei , Imoto Minoru
Published: April 2003

It was found that the copolymers of sodium acrylate (AA‐Na) with styrene (St) and of sodium methacrylate (MAA‐Na) with methyl methacrylate (MMA) could polymerize vinyl monomers in an aqueous phase without the usual initiator. Interestingly, there was a definite composition of the copolymer for the polymerization of a given monomer; for example, when poly(St‐co‐AA‐Na) was used, St, MMA, vinyl acetate, ethyl acrylate, methyl acrylate, and acrylonitrile were polymerized by the copolymer having mole ratios of AA‐Na:St of 0.61:0.29, 0.47:0.53, 0.38:0.62, 0.30:0.70, 0.24:0.76, and 1.00:0, respectively. The copolymers of various compositions can form hydrophobic areas (HAs) in the water phase. As has been repeatedly reported, the polymerization proceeds in the HAs, and the following new hypothesis was recently proposed that the hard (the less hydrophilic) HA prefers to incorporate the hard monomer and the soft (the less hydrophobic or the more hydrophilic) HA prefers to incorporate the soft monomer. The results mentioned above support this hypothesis.
The base‐catalyzed transformation of polyacrylonitrile
Authors: Endrey A. L.
Published: April 2003

In an effort to produce high‐molecular‐weight, linear ladder polymer by linking the nitrile groups within the molecule of polyacrylonitrile, polyacrylonitrile homopolymers were heat treated in N,N‐dimethylformamide and N,N‐dimethylacetamide solutions, in the presence of tertiary alkylamine catalysts. The products were soluble in formic acid, had relatively low molecular weight, and could be cast into brittle films. The infrared spectra indicated that the polymerization of the nitrile groups is initiated by a self‐initiation mechanism based on the active methine groups in polyacrylonitrile, as proposed by Grassie and Hay, and that the reaction is complicated by molecular weight degradation via reverse Michael addition, as proposed by Hamada and Takahashi. The inherent viscosities of the products increase with increasing catalyst concentration, and further increases can be achieved by the addition of anionic chain coinitiators of phenolic nature. Density measurements indicated that the ladder structures undergo rearrangement into a more stereoregular form after formation, and that some aromatization occurs when the reaction is carried out in the presence of air.
Evolution of HCN during high‐temperature thermal degradation of polyurethanes
Authors: Jellinek H. H. G. , Dunkle S. R.
Published: April 2003

The thermal degradation of an aliphatic, aromatic, and secondary polyurethane has been studied over a range of temperatures from 500 to 1000°C with respect to the kinetics and mechanism of HCN evolution. This evolution shows a rapid linear increase of evolved HCN with time, passing into a plateau when the polymer has been consumed. In high temperature ranges, thermal decomposition of the evolved HCN also takes place, and in some temperature regions the degradation is diffusion controlled. Overall, the process is governed by a depolycondensation reaction which is the slowest step in a sequence of reactions. The reaction sequence is kinetically evaluated and the respective rate constants, diffusion constants, and energies of activation are presented. The reaction mechanism accounts well for the experimental results in spite of some simplifications which had necessarily to be applied.
Head‐to‐head vinyl polymers. VII. Hydrolysis of head‐to‐head poly(methyl acrylate)
Authors: Quach Loc , Otsu Takayuki
Published: April 2003

Head‐to‐head (H–H) and head‐to‐tail (H–T) poly(methyl acrylate)s (PMAs) were hydrolyzed in a mixture of acetone and water (4:1 by volume) at 30°C by using various alkali hydroxides as catalysts. For comparison, the H–T copolymer with 26% H–H units, dimethyl succinate (DMS), dimethyl glutarate (DMG), and dimethyl adipate (DMA) as model compounds were also hydrolyzed. It was found that the hydrolyses of all PMAs proceeded autocatalytically; i.e., the rates increased as a function of the reaction time. Both the initial rate constant k0 and the autoaccelerating effect observed markedly depended on the structures of polymer chains and they decreased with increasing of the H–H sequences. The molecular weights of either H—H or H—T PMA did not show remarkable changes in either k0 value or accelerating effect. The k0 values were almost independent of the kinds of bases and were calculated to be 0.06 and 0.18 L mol−1 min−1 for H–H and H–T PMA, respectively. On the other hand, the autoaccelerating effect decreased in the order NaOH ⋍ KOH > LiOH > CsOH for H–H PMA and NaOH > LiOH > KOH > CsOH for H–T polymer. When the ratio of acetone to water increased, the k0 value was found to decrease, whereas the accelerating effect increased. The results obtained are described and discussed.
Stereocontrol in the cationic polymerization of N‐vinylcarbazole
Authors: Terrell David R. , Evers Fritjof
Published: April 2003

The dependence of the steric microstructure of cationically polymerized poly(N‐vinylcarbazole) (PVK) upon catalyst, polymerization temperature, and polymerization solvent has been investigated. The effect of polymerization temperature variation was found to be small, whereas the choice of catalyst and polymerization solvent was found to have a strong influence upon the PVK steric microstructure. A correlation was found between the syndiotacticities Xs and the π* solvent polarities of the polymerization solvents for a given catalyst. A decrease in Xs with increasing π* solvent polarity was observed using BF3OEt2 and AlEt2Cl catalysts and has been interpreted in terms of propagation via contact ion‐pair ring structures reversibly formed between the active end group and a preceding repeating unit. The increase in Xs with increasing π* solvent polarity observed with several of the catalysts investigated has been interpreted in terms of chain ion pairs whose separation increases with increasing π* solvent polarity. The influence of the various Lewis acid catalysts upon the steric microstructures of cationically polymerized PVK allowed the following order of nucleophilicity to be established:
Reaction rate of crosslinkings by using metallated polymer. I. Grafting and intramolecular crosslinkings at the first stage
Authors: Ishizu Koji , Ino Kazuhide , Koshiro Yoshitaka , Fukutomi Takashi , Kakurai Toshio
Published: April 2003

Lithium‐metallated styrene–p‐benzylstyrene copolymer was reacted with chlorine‐terminated polystyrene as a crosslinker polymer in tetrahydrofuran (THF) at 25°C. The rate constant was estimated from the changes in the concentration of metallated polymer by using photometrical measurements. The various reaction conditions were chosen and it became clear that the rate constants of grafting (k1) and intramolecular crosslinkings (k2intra) were gotten separately at the first stage. As a result, k2intra showed larger values than k1 and decreased with increasing degree of polymerization of crosslinker polymers.
Metal‐acetylacetonate chelate crosslinked gels
Authors: Yeh Horng Chin , Eichinger B. E. , Andersen N. H.
Published: April 2003

Polymers containing pendant acetylacetonate (acac) groups suitable for crosslinking through metal complex formation are described. Diene‐based copolymers, polystyrene, and polydimethylsiloxane, each containing a measurable number of acac groups distributed along the chains, were synthesized. The polymers were studied both for the amount of acac ligand and for their crosslinking reactions with selected transition metals by ultraviolet (UV) second‐derivative spectroscopy. The UV analyses of the polymer systems were compared with their monomer analogs, and the results confirm that the crosslinking chelation reactions of polymer compounds are similar to those of model compounds. Homogeneous chelate crosslinking conditions were developed by using transition‐metal salts such as Cu(laurate)2, Fe(laurate)3, and Cr(laurate)3 in solvents such as chloroform and benzene. Polymeric ligands containing 1–5% acac in solution at various concentrations were reacted to form both inter‐ and intramolecular crosslinkages. The kinetic stability of the chelate crosslinks has been studied by a unique ligand exchange–gel solubility relationship.
Polymerization of phenylacetylene by WCl6·Ph4Sn: Synthesis of high polymer achieved by selection of solvents
Authors: Masuda Toshio , Takahashi Toru , Yamamoto Kaoru , Higashimura Toshinobu
Published: April 2003

Phenylacetylene was polymerized by WCl6·Ph4Sn (1:1) in 1,4‐dioxane to provide in high yield a polymer whose molecular weight reached 1 × 105. The polymerization also proceeded in other oxygen‐containing solvents (ethers, esters, and ketones) but the polymer molecular weights were lower than 1 × 104. Certain hydrocarbon solvents such as cyclohexene, tetralin, and indan also afforded high‐molecular‐weight polyphenylacetylene [Mn = (5–8) × 104], as compared with those (Mn ≤ 1.5 × 104) obtained in conventional aromatic hydrocarbons like benzene. A high polymer (Mn = 1.6 × 105) was also formed from β‐naphthylacetylene in 1,4‐dioxane. It was inferred that the active hydrogens of these solvents prevent the formed polymer from being decomposed by a radical mechanism and/or modify the nature of active species.
Thermal and pyrolysis studies of copolyesters
Authors: Vijayakumar C. T. , Ponnusamy E. , Balakrishnan T. , Kothandaraman H.
Published: April 2003

Random copolyesters of dimethyl terephthalate (DMT), ethylene glycol (EG), and butane‐1,4‐diol (BD) and the homopolyesters poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) have been subjected to degradation and pyrolysis studies. Differential thermal analysis (DTA) showed that the decomposition temperature is dependent on the percentage of EG and BD present in the copolyesters. Thermal volatilization analysis (TVA) also showed that the decomposition temperature is dependent on the percentage of EG and BD present in the copolyesters. The trend for the decomposition temperatures obtained from TVA studies for these copolyesters is similar to such other thermal properties as melting temperature Tm, ΔHf, ΔHc, etc. The subambient thermal volatilization analysis (SATVA) curves obtained for these polymers are also presented. The SATVA curve is the fingerprint of the total volatile products formed during the degradation in high vacuum. The isothermal pyrolysis of these materials was carried out in high vacuum at 450°C. The products formed were separated in a gas chromatograph and were subsequently identified in a mass spectrometer. The major pyrolysis products from PBT were butadiene and tetrahydrofuran, whereas those from PET were ethylene and acetaldehyde. The ratio of acetaldehyde to ethylene increases with the EG content in the copolyester, suggesting a different decomposition mechanism compared to the decomposition mechanism of PBT and PET.
Phthalocyanine polymers. V. Novel type of thermally stable polyimides derived from metal phthalocyanine tetraamines and pyromellitic dianhydride
Authors: Achar B. N. , Fohlen G. M. , Parker J. A.
Published: April 2003

New poly(metal phthalocyanine) pyromellitimides of copper, cobalt, nickel, and zinc were synthesized and elemental, IR, TGA, and inherent viscosity measurement studies were done to characterize these polymers. They showed exceptional thermal and thermo‐oxidative stability with char yields at 800°C ranging from 75 to 87% in a nitrogen atmosphere. The ratio of the polymer decomposition temperatures in air and nitrogen (PDT) (air)/PDT (N2) varied from 0.91 to 0.97, which indicated that the onset of degradation of these polymers is greatly affected by the presence of an oxidizing atmosphere. Isothermal studies were done to evaluate the long‐term thermal stability of these polymers.
New acetylene‐terminated quinoxaline oligomers
Authors: Ishizu Koji , Prabhu Usha Devi G. , Draney Dan , Lee Byung H. , Marvel C. S.
Published: April 2003

A series of acetylene‐terminated quinoxaline oligomers was synthesized for testing as possible adhesives for airplane manufacturing.
Free‐radical synthesis of poly(urethane‐g‐N‐vinyl pyrrolidone)
Authors: Egboh H. S. , George M. H. , Barrie J. A. , Walsh D. J.
Published: April 2003

Relatively high‐molecular‐weight segmented polyurethanes based on methylene bis(4‐phenyl‐iso‐cyanate), poly(propylene glycol), butane‐1,4 diol, and cis‐2‐butene‐1,4 diol have been synthesized and characterized. These unsaturated polyurethanes were successfully grafted using N‐vinyl pyrrolidone as monomer and 2,2′‐azobisisobutyronitrile as free‐radical initiator. However, grafting experiments involving benzoyl peroxide as initiator were unsuccessful. The graft copolymers were isolated from the ungrafted polyurethane and poly(N‐vinyl pyrrolidone) by selective solvent extraction. Elemental microanalysis, IR, NMR, thermogravimetric analysis, and equilibrium water sorption measurements were used to characterize the graft copolymers.
The synthesis and thermal curing parameters of a novel quinoxaline monomer with terminal ethynyl thermoset and phenylethynyl intramolecular cycloaddition postcure capability
Authors: Hedberg Frederick L. , Lindley Patricia M. , Lee Charles Y‐C. , Goldfarb Ivan J.
Published: April 2003

The Synthesis of 3,3′‐bis(4‐[3‐ethynylphenoxy]phenyl)‐7,7′‐bis(phenylethynyl)‐2,2′‐diphenyl‐6,6′‐biquinoxaline (I) was accomplished by the reaction of 2,2′‐bis(phenylethynyl)‐5,5′‐diaminobenzidine (II) and 4‐(3‐ethynylphenoxy)benzil. Thermal analysis of I indicated a softening temperature of 107°C, followed by an exotherm above 150°C that corresponded to a independent crosslinking reaction of the terminal acetylene groups and an intramolecular cycloaddition (IMC) reaction of the 2,2′‐bis(phenylethynyl)biphenyl moieties. In the synthetic work substantial improvements were made in the synthesis of II. The sample of I was cured at 200°C and the maximum partially cured transition temperature attained was 280°C. A sample of 3,3′‐bis(4,[3‐ethynylphenoxy]phenyl)‐2,2′‐diphenyl‐6,6′‐biquinoxaline (IV) was similarly tested as a model without IMC capability and its corresponding value was 250°C. The difference between these two values is discussed briefly.
Preparation and properties of polybenzimidazoles containing cardo groups
Authors: Srinivasan P. R. , Mahadevan V. , Srinivasan M.
Published: April 2003

Several polybenzimidazoles containing cardo groups were prepared: A cardodicarboxylic acid, 9,9‐bis(4‐carboxyphenyl)fluorene, and two cardotetramines, 9,9‐bis(3,4‐diaminophenyl)fluorene and 9,9‐bis(3,4‐diaminophenyl)10‐anthrone. The cardodicarboxylic acid was condensed with aromatic tetramines and the cardotetramines were condensed with aromatic dicarboxylic acids. Prior to polymer synthesis two model compounds, 9,9‐bis[4,(2‐benzimidazolyl)phenyl]fluorene and 2,2′‐diphenyl‐5,5′‐(9,9‐fluorenediyl)‐bibenzimidazole were prepared and characterized by spectral methods. The polymers were obtained in 60–70% yield and showed reduced viscosity in the range of 0.7–1.1 dL/g. They were soluble in dimethyl formamide (DMF) and chlorinated solvents like tetrachlorethane. The thermal stabilities of these cardopolymers were superior to noncardopoly‐benzimidazoles.
Substituent effect on the hydrolysis of side groups in poly(phenyl methacrylates)
Authors: Bortnowska‐Bareła B. , Połowiński S.
Published: April 2003

The kinetics of the basic hydrolysis of several poly(phenyl methacrylates) with different substituents in the aromatic ring were investigated. Using Keller's equations to describe the effect of neighboring groups on the kinetics of side‐group reactions in polymers, we computed the corresponding rate constants which correlated well with Hammett's substituent constants.
Synthesis of polyamide‐quinazolinediones from 2,2′‐disubstituted bis(1,3,4‐oxadiazolin‐5‐ones) and aromatic bis‐o‐amino esters
Authors: Chau Nguyen , Saegusa Yasuo , Iwakura Yoshio
Published: April 2003

A novel class of polyamide‐quinazolinediones was synthesized by the polymerization of 2,2′‐disubstituted bis(1,3,4‐oxadiazolin‐5‐ones) with aromatic bis‐o‐amino esters in m‐cresol. The polymerization probably proceeded in the formation of ring‐opening adducts, which in turn were cyclized by the elimination of alcohol to give polyamide–quinazolinediones. These polymers, which were soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, N‐methyl‐2‐pyrrolidone, and dimethyl sulfoxide, had, with one exception, reduced viscosities in the range of 0.12–0.32 dL/g. Thermogravimetric analyses indicated that they began to decompose at 310–360°C in air.
Some chemical and analytical aspects of polysaccharide modifications. II. A high‐yielding, specific method for the chemical derivatization of galactose‐containing polysaccharides: Oxidation with galactose oxidase followed by reductive amination
Authors: Yalpani Manssur , Hall Laurance D.
Published: April 2003

A versatile and high‐yielding method was developed for specifically modifying galactose‐containing polysaccharides, exemplified here by two representative galactomannans, guar gum1and locust bean gum5. Oxidation of the primary alcohol functions of1and5with galactose oxidase produced the corresponding aldehyde derivatives2and6which were subsequently derivatized in several ways. Reductive amination with sodium cyanoborohydride of2and6proceeded smoothly (60–90% yields) and led to stable amine derivatives (4,7–11), which included hydroxyalkylamine‐ (8), glycine‐ (9), and BSA‐ (11) derivatives. The cationic primary amine derivative12was similarly reductively alkylated with lactose to yield a product13with extended carbohydrate side chains. Oxidation of2produced the anionic carboxy derivative14, whereas reduction of2and6with sodium borodeuteride yielded the deuterium labeled neutral species15and16. The undegraded gums and some of their derivatives were studied by high resolution13C‐NMR (100.6 MHz) at 30°C, and the proposed chemical shift assignments were in good qualitative agreement with those of earlier studies. ESR spectroscopy was used to follow the chemical reactions and to derive information about the galactose distribution of1and5. Mean nearest neighbor distances (r̄) between nitroxides attached to1and5were 1.36 nm (±5%) for4and 1.75 nm (±5%) for7. Theser̄values agree favorably with the structural models recently proposed elsewhere, excluding earlier suggestions of homogeneous galactose distributions or regularly alternating blocks of branched and unbranched mannose units. The solution properties, such as viscosity and salt‐ and organic solvent‐compatibility, of some of the guar derivatives appear to be unique and interesting. An alternative oxidation procedure of the galactose residues of1and5with sodium periodate has been evaluated.
Cyclocopolymerization of diallyl ether with sulfur dioxide in acetone
Authors: Fujimori Kiyoshisa
Published: April 2003

The radical polymerization of diallyl ether (DAE) with sulfur dioxide produced soluble copolymers whose composition was between 1:1 and 2:1 in SO2. The overall rate was maximum at a 2:1 feed composition in SO2. A cyclocopolymerization scheme, which was based on cross propagations and the intramolecular cyclization of DAE radical, was applied. The energy of activation was larger for the uncyclized DAE radical in undergoing the cross propagation with SO2 than in undergoing the intramolecular cyclization with the pendent allylic group by 40 kJ/mol. Formation of rings made of DAE and SO2 and 3,4‐disubstituted‐tetrahydrofuran rings by the cyclized DAE units on the main chain was proposed on the basis of the 1H‐NMR spectra.
The formation of “inverted” core‐shell latexes
Authors: Lee D. I. , Ishikawa T.
Published: April 2003

It has been found that when hydrophobic monomers are polymerized in the presence of highly hydrophilic polymer seed particles, the second‐stage hydrophobic polymers form cores surrounded by the first‐stage hydrophilic polymers, resulting in “inverted” core‐shell latexes. The formation of core‐shell morphology by this inversion process has been found to be dependent on the hydrophilicity and molecular weight of the first‐stage hydrophilic polymers and the extent of phase separation between the two polymers involved. Particle morphology has been examined by electron microscopy, surface acid titration, alkali swelling of particles, and surface reactivity.
Reduction of aldehydes and ketones by sodium dithionite using viologens as electron transfer catalyst
Authors: Ageishi Kentaro , Endo Takeshi , Okawara Makoto
Published: April 2003

It was found that aromatic aldehydes and ketones could be reduced smoothly at room temperature by sodium dithionite using viologen derivatives as an electron transfer catalyst to obtain the corresponding alcohols in good yields. Viologens (methyl viologen and polymer) acted catalytically and active species in the reduction were quinoid forms which were obtained by two‐electron reduction of viologens.
Conformational and neighboring effects in graft polymerization of acrolein on 4(5)‐vinylimidazole‐acrylamide copolymer
Authors: Yamashita Natsuki , Morita Satoshi , Kanzaki Kazunari , Maeshima Toshihisa
Published: April 2003

The graft polymerization of acrolein (AL) on poly‐4(5)‐vinylimidazole or the copolymers of 4(5)‐vinylimidazole(VIm) and acrylamide of varying composition were carried out kinetically in an ethanol–water mixture at 0°C. The graft polymerization rate Rp increased with an increasing concentration of water in the solvent. On the other hand, the Rp of the copolymer which incorporated 50 mol % VIm showed the highest value. These results were discussed by assuming interaction between amide and imidazole groups in copolymer.
Additive effect of polyacrylamide on the anionic polymerization of acrolein
Authors: Yamashita Natsuki , Morita Satoshi , Nishino Masayuki, , Maeshima Toshihisa
Published: April 2003

The anionic polymerizations of acrolein (AL) in the presence of polyacrylamide (poly‐AAm) induced by imidazole (Im), pyridine (Py)–water, and sodium hydorxide as the anionic initiator were carried out kinetically in an ethanol‐water mixture at 0°C. The rate of polymerization Rp in the presence of poly‐AAm increased markedly in the Im and Py‐water systems, whereas the polymerizability of AL is little changed in the potassium persulfate and silver nitrate (redox systems). These results suggest and the interaction between the amide groups in poly‐AAm, the initiator, and the AL monomer is intramolecular. It also indicates the presence of interaction between the carbonyl group of the amide compound and the group of Im. On the other hand, the chemical shifts of the proton of Im in the presence of several amide compounds such as acetamide, propionamide, and N,N‐dimethylacetamide were observed in CDCl3 by nuclear magnetic resonance (NMR) spectroscopy. These results were discussed by assuming a conformational change in poly‐AAm in the ethanol–water mixture.
Polyimides containing oxyethylene units
Authors: Feld William A. , Ramalingam B. , Harris Frank W.
Published: April 2003

Four aromatic dinitro compounds containing oxyethylene units 1,2‐bis(4‐nitrophenoxy)ethane, bis(2)‐(4‐nitrophenoxy)ethyl ether, 1,2‐bis(2)‐(4‐nitrophenoxy)ethoxy)ethane, and bis(2‐(2‐(4‐nitrophenoxy)ethoxy)ethyl) ether were prepared by an aromatic nucleophilic substitution reaction that involved 1‐fluoro‐4‐nitrobenzene and the appropriate oxyethylene glycol. Each of the dinitro compounds could be reduced chemically or catalytically to produce the diamines 1,2‐bis(4‐aminophenoxy)ethane, bis(2‐(4‐amino‐phenoxy)ethyl ether, 1,2‐bis(2‐(4‐aminophenoxy)ethoxy)ethane, and bis(2‐(2‐(4‐aminophenoxy)ethoxy)ethyl) ether. Polymerization of the diamines was carried out in m‐cresol with toluene as an azeotroping agent. Polymides derived from 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuradione exhibited good solubility in chlorinated solvents, glass transition temperatures as low as 140°C, as evidenced by viscous flow, and good thermal stability; a 5% weight loss generally occured at greater than 450°C. Isothermal aging studies conducted at 600°F(315°C) for 200 h indicated that weight loss is directly related to oxyalkylene chain length–10% for the shortest and 50% for the longest chain.
Characterization of phenol‐terminated polystyrenes by means of 13C‐NMR spectroscopy
Authors: Hunter Brian K. , Redler Elaine , Russell Kenneth E. , Schnarr Wayne G. , Thompson Susan L.
Published: April 2003

In the presence of many alkylphenols, cationic polymerization of styrene by aluminium chloride leads to low‐molecular‐weight polystyrenes that contain end groups derived from the phenols. The fraction of phenolic end groups in the polymer is estimated by ultraviolet (UV) measurements to be 40–70% dependent on phenol and the reaction conditions. Phenol is incorporated into the polymer over the whole range of molecular weights (up to 7000). At high phenol concentrations, a significant proportion of the product consists of 1:1 and 1:2 phenol‐styrene adducts. The position of attack of the growing carbenium ion on the phenol can be determined by 13C‐NMR spectroscopy. With 2,6‐dialkylphenols, such as 2,6‐di‐tert‐butylphenol, the high field aromatic resonance near 119.7 ppm is shifted downfield by about 16 ppm when the phenol is incorporated into the polystyrene as an end group. This is interpreted as an exclusive attack of the growing carbenium ion on the 4‐position of the phenol. With 2,4‐dialkylphenols, such as 2‐tert‐butyl‐4‐methylphenol, a corresponding downfield shift shows that reaction occurs only at the 6‐position. The preferred site of attack for phenols such as 2‐alkylphenols which lack both ortho‐ and parasubstituents, is the 4‐position. With such phenols attack at the 6‐position is not excluded. Low‐molecular‐weight adducts contain 1‐methylbenzyl end groups and 13C‐spectra are consistent with their presence in the higher‐molecular‐weight polystyrenes.
The synthesis and characterization of nadimidized aromatic bisaspartimides and their polymerization to high‐temperature‐resistant laminating resins
Authors: Kumar Devendra , Fohlen George M. , Parker J. A.
Published: April 2003

4,4′‐Bis(N2)‐{4‐[4‐(2,3‐bicyclo‐[2.2.1]hept‐5‐ene‐dicarboximido)phenoxy]‐phenyl(‐aspartimido)‐di‐phenyl ether (2NAD/1020) and various similar polymer percursors were synthesized from bismaleimides by the Michael addition of two moles of aromatic diamine followed by end capping of the resultant amino‐terminated bisaspartimide groups with nadic anhydride. These precursors were characterized by using Fourier‐transform infrared (FT‐IR), proton, and carbon‐13 nuclear magnetic resonance spectroscopies (1H‐ and 13C‐NMR). Thermal polymerization of 2NAD/1020 by heating it above its melting point gave a reddish brown thermoset polymer. The curing behavior and thermal stability of these nadimides were evaluated by differential scanning calorimetry and thermogravimetric analysis studies. Graphite fiber laminates were prepared from these polymer precursors and their mechanical properties evaluated. Gas Chromatography/Mass Spectra of the precursors and thermosets have given an understanding of their decomposition behavior. The structures of the thermosets were examined by FT‐IR spectroscopy.