bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous oxidative degradation in irradiated polymers
Authors: Clough R. L. , Gillen K. T. , Quintana C. A. 
Published: April 2003

AbstractIn the presence of oxygen, polymeric materials may undergo diffusion‐limited heterogeneous degradation with significant oxidation occurring only near the surfaces. It is important in studying polymer degradation (and in designing accelerated aging experiments) to be able to determine under what conditions heterogeneous degradation occurs, and to estimate the extent of significant oxidative penetration under those conditions. We describe here the use of several techniques for identification of oxidative degradation gradients. A rapid determination of oxidation depth is accomplished by optical examination of metallographically polished cross‐sectioned samples; oxidized and nonoxidized regions are distinguished by differences in surface reflectivity. A more detailed determination of the shapes of degradation gradients is accomplished by performing a series of sensitive determinations of relative hardness changes across the surface of cross‐sectioned, polished samples. Typical oxidation depths for the commercial polymers examined are on the order of fractions of millimeters over a dose‐rate range of 104–106 rad/h. Significant variations among different materials are found, as would be expected given differences in oxygen consumption and permeation rates. A detailed example is given of the tensile property behavior of a Viton material over a range of dose rates where the degradation is seen to change from strongly heterogeneous at high dose rates to homogeneous as the dose rate is lowered. Degradation differences in this material are very pronounced: at high dose rates the polymer undergoes primarily crosslinking to give a hard brittle material, whereas under lower dose rates, where oxygen permeation is complete, the polymer undergoes predominantly scission to yield a soft, easily stretchable material.
Synthesis and characterization of styrene/isoprene/ethylene oxide block copolymers
Authors: Benson R. S. , Wu Q. , Ray A. R. , Lyman D. J. 
Published: April 2003

AbstractPoly(ethylene oxide/isoprene/styrene/isoprene/ethylene oxide) block copolymers were synthesized using potassium–napthalene catalyst in tetrahydrofuran. The dynamic and thermal properties and water absorption of these tri‐block copolymers were determined and related to their bulk morphology.
Nature and ESR anisotropy of trapped radicals in UV‐irradiated isotactic polypropylene at 4.2 K and 77 K
Authors: Faucitano A. , Buttafava A. , Martinotti F. , Gratani F. , Bortolus P. 
Published: April 2003

AbstractA comparative ESR study of low‐temperature photolysis at 77 and 4.2 K of isotactic polypropylene, preoxidized under controlled conditions, and of 2.6.8 trimethylnonane‐4‐one as a model compound of the inchain PP ketones CH2COCH2 is presented. The results show conclusively that the ESR spectra of low‐temperature PP photolysis reported in the literature arise from the decomposition of tertiary hydroperoxides, whereas the contribution by the Norrish I photolytic cleavage of ketones is of minor importance; the relative efficiency of radical production at 77 K (λ ≥ 300 nm) by both types of photoactive compound has been measured by ESR and found to be about 15 times greater for the hydroperoxides. The mechanism of solid‐state photolysis of PP hydroperoxides is dominated by the nearly complete decay of excited alkoxyls during the photolytic events that yield the chain end radicals CH(CH3)CH2· by β scission (87.8%) and the inchain radicals CH2C(CH3)CH2 by hydrogen abstraction (10.4%). The low yield of methyl radicals detected (1.8%) and their delayed appearance strongly suggest that these species are of secondary origin and that the decomposition of alkoxyls via CCH3 scission is of negligible importance. From the ESR anisotropy of the deliberately prepared peroxyradicals CH(CH3)CH2O2· and CH2C(CH3)(O2)CH2 evidence of the misalignment of terminal chain segments following scission of alkoxyls at 77 K was obtained. An unexpected result of the measurements at 4.2 K is represented by the identification of a clear signal by H atoms: the H atoms apparently are not trapped in perprotiated matrices, even at 4.2 K, because of their unusually high reactivity toward the hydrogen abstraction assisted by tunneling effects.
Poly(alkylene oxide) ionomers. X. Copolymerization of methyl ω‐epoxyalkanoates and characterization of the polymers
Authors: Muggee John , Vogl Otto 
Published: April 2003

AbstractSelected methyl ω‐epoxyalkanoates ranging from methyl 3,4‐epoxybutanoate to methyl 7,8‐epoxyoctanoate were copolymerized with a number of oxiranes and with oxetane. Tetrahydrofuran did not take part in the attempted methyl ω‐epoxyalkanote–tetrahydrofuran copolymerization, but acted only as the solvent. The oxirane copolymers had polymer compositions similar to the comonomer feed ratio. Oxirane comonomers used were propylene oxide (1,2‐epoxypropane), butylene oxide (1,2‐epoxybutane), 1,2‐epoxyhexane, epichlorohydrin, and phenylglycidyl ether. The initiator system used was triethylaluminum/water/acetylacetone (1.0/0.5/1.0) in about 5 mol %. In the copolymerizations using methyl 3,4‐epoxybutanoate as a comonomer, only small yields of polymer (in the range of 1 to 2%) were realized, while for methyl 4,5‐epoxypentanoate the yields were generally in the range of 20 to 60%. Methyl 7,8‐epoxyoctanoate copolymerized readily and gave yields of copolymers of 50 to 90%.
Poly(alkylene oxide) ionomers. XI. Polymerization and copolymerization of methyl ω‐epoxyundecanoate and characterization of the polymers
Authors: Bansleben Donald A. , Vogl Otto 
Published: April 2003

AbstractMethyl 10‐undecenoate was epoxidized in nearly quantitative yield with m‐chloroperoxy‐benzoic acid to methyl 10,11‐epoxyundecanoate. The functional epoxide monomer was polymerized by the reaction product of triethylaluminum/water/acetylacetone (1.0/0.5/1.0) to a high molecular weight elastomer having pendent carboxyl groups, and a molecular weight distribution near the most probable distribution. With the same initiator system, methyl 10,11‐epoxyundecanoate was copolymerized with ethylene oxide, propylene oxide, 1‐butene oxide, 1‐hexene oxide, phenyl glycidyl ether, epichlorohydrin, and 4,4,4‐trichloro‐1‐butene oxide. The copolymers were typically high in molecular weight, elastomeric, and had methyl 10,11‐epoxyundecanoate incorporations similar to the initial feed ratio of comonomers. The new family of functional polymers were characterized by their infrared and NMR spectra, dilute solution viscosity and thermal transitions.
Polyesters derived from 1,4‐oxathian‐2‐ones
Authors: Huffman K. R. , Casey D. J. 
Published: April 2003

Abstract1,4‐Oxathian‐2‐one (1a) was prepared in high yield by oligomerization of methyl(2‐hydroxyethyl)mercaptoacetate (3) followed by catalytic depolymerization in vacuo. A similar sequence starting with methyl(2‐hydroxyethyl)sulfonylacetate (5) afforded the corresponding sulfone, 1,4‐oxathian‐2‐one‐4,4‐dioxide (1c), however, 1,4‐oxathian‐2‐one‐4‐oxide (1b) could not be obtained by this procedure. Ring opening melt polymerization of 1a and 1c afforded low molecular weight crystalline polyesters 2a and 2c. Oxidation of 2a with m‐chloroperoxybenzoic acid produced the corresponding polyester 2b containing sulfoxide groups. Thermogravimetric analyses and visual observations indicated 2b to be thermally unstable relative to 2a and 2c.
Preparation of soluble and fusible poly(2,5‐dimethoxy‐1,4‐phenylene)
Authors: Mukai Katsuya , Teshirogi Takuma , Kuramoto Noriyuki , Kitamura Taku 
Published: April 2003

AbstractPoly(2,5‐dimethoxy‐1,4‐phenylene) was prepared by oxidative polymerization of p‐dimethoxybenzene with aluminum chloride and copper(II) chloride in nitrobenzene under reduced pressure. The polymers obtained were soluble in sulfuric acid and fusible at 320°C. The intrinsic viscosity of the polymer was ca. 0.07 in sulfuric acid. Demethylation of methoxy groups did not occur during the polymerization.
Polymeric catalysts. IX. Cobalt complexes of polyureas based on bipyridine pyridine and crown ether for aldol condensation
Authors: Zhang Keda , Kumar G. Sudesh , Neckers D. C. 
Published: April 2003

AbstractWe report herein studies of Co(OAc)2 and related transition metal compounds which serve as catalysts for aldol condensations when complexed with bipyridine, triphenyl phosphine, and crown ether. A comparison has been made with polymeric complexes of cobalt(II), which serve the same purpose. Cobalt complexes of built‐in polyureas based on bipyridine and crown ether as well as those immobilized to polystyrene by triphenylphosphine and poly(4‐vinyl pyridine) are also reported.
Synthesis of N‐substituted polyethylenimines with polarizable side chain pendent groups
Authors: Litt Morton H. , Kim Jinbaek , Rodriguezparada José M. 
Published: April 2003

AbstractTwo new N‐substituted polyethylenimines containing carbazole and acridone groups on the side chains were prepared. The polymers were obtained by cationic ring opening polymerization of the corresponding 2‐oxazoline monomers. The carbazole containing oxazoline was low melting and could be polymerized in bulk; however the acridone containing monomer had a high melting point and solution polymerization had to be used. This paper describes the synthetic procedures used to obtain these polymers.
Polychloroprene. I. Etude de la microstructure par RMN 1H
Authors: Petiaud Roger , Pham Quang Tho 
Published: April 2003

AbstractThe microstructure of polychloroprenes was studied by 1H‐NMR at high field (350 MHz). An examination with two solvents, CDCl3 and C6D6, was necessary to show all the addition modes. The complementary information obtained made possible the quantitative determination of head‐to‐tail, head‐to‐head, tail‐to‐tail, trans‐1–4, and cis‐1–4, 1–2, and 3–4 additions.
Direct synthesis of aromatic polyesters by use of a sulfonium salt derived from tosyl chloride and N‐methylimidazole
Authors: Higashi Fukuji , Ozawa Michihide , Chang Teh‐Chon 
Published: April 2003

AbstractA sulfonium salt derived from tosyl chloride and N‐methylimidazole was successfully used as an effective condensing agent for the preparation of high‐molecular‐weight aromatic polyesters by the direct polycondensation of aromatic dicarboxylic acids and bisphenols. Conditions for the formation of the sulfonium salt and of the reaction of the salt with dicarboxylic acids favorable for the polycondensation were examined. Thermal property of a polymer was investigated in terms of random sequences of monomer in the polymer backbone. Preparation of a polyamide and a polyesteramide was attempted with limited success.
Selective chemical modifications of dextran
Authors: Yalpani Manssur , Brooks Donald E. 
Published: April 2003

AbstractSpecific modification of the reducing end group of dextran has been achieved using the reductive amination procedure and solvent systems designed to optimize polymer reactivity. Dextran fraction (with Mw ranging from 10,000 to 500,000 daltons) were derivatized with [14C]‐octadecylamine in yields of up to 60% to afford the corresponding alkyl dextrans which are of interest as affinity ligands. Reactive dextran intermediates with terminal amine, carboxyl, and aldehyde functions were prepared using sodium cyanoborohydride and ammonium acetate, glycine, and glucosamine, respectively. The dextran glucosamine derivative was further modified by reductive amination with octadecylamine. Similarly, condensation of dextran with streptomycin produced a new type of cationic derivative bearing a terminal, branched saccharide residue. Other reducing‐end modifications included nitroxide‐spin labelling, covalent attachment to aminopropyl‐activated glass beads, and a carbodiimide‐mediated amidation of carboxyl—dextran. The reductive amination method was also applied to guar gum and locust bean gum.
Soluble magnesium–titanium catalysts for ethylene polymerization. I
Authors: Yano Takefumi , Ikai Shigeru , Shimizu Michimasa , Washio Katsutoshi 
Published: April 2003

AbstractA study has been made of a catalyst system comprising the heptane‐soluble magnesium and titanium compounds in combination with an organoaluminum compound for ethylene polymerization at a high temperature. The productivity for ethylene polymerization of the catalyst system, n‐butylethyl magnesium (BEM)‐2‐ethyl hexanol (C8H17OH)‐tetra‐n‐butoxytitanium[Ti(OBu)4]/diethyl aluminum chloride (DEAC) is higher than for MgCl2‐Cl2‐C8H17 OHTi(OBu)4/DEAC and much higher than MgCl2‐Ti(OBu)4/DEAC. The nature of the three different catalyst systems have been discussed in comparison with experimental data on polymerization behavior and the data of the elemental and x‐ray diffraction analysis of the solid products obtained from the reactions between the catalyst components.
Synthesis and polymerization of 4‐o‐vinylbenzyl‐2,2,6,6‐tetramethylpiperidine
Authors: Miyazawa Takeo , Endo Takeshi , Okawara Makoto 
Published: April 2003

AbstractSome hindered amine polymers containing 2,2,6,6‐tetramethylpiperidine structure were synthesized. A new monomer, 4‐O‐vinylbenzyl‐2,2,6,6‐tetramethylpiperidine, was homopolymerized and copolymerized with some vinyl monomers in the presence of AIBN as an initiator. The obtained amine polymers were oxidized with hydrogen peroxide to obtain the polymers having nitroxyl radical moiety.
Polymerization of methyl methacrylate by resin containing polyethylenepolyamine side chain–peroxide system
Authors: Nonaka Takamasa , Abe Takashi , Egawa Hiroaki 
Published: April 2003

AbstractMacroreticular resins (RST) bearing polyethylenepolyamine side chain were prepared by the amination of the chloromethylated macroreticular styrene—divinylbenzene copolymer beads. The polymerization of methyl methacrylate (MMA) was carried out in a water—organic solvent mixture containing hydroperoxide and RST. The polymerization of MMA proceeded smoothly in the presence of both hydroperoxide and RST. The presence of water was indispensable for this polymerization. 1,4‐Dioxane hydroperoxide showed a high activity for the polymerization of MMA. The polymerization of MMA by this system was greatly affected by the structure of the resins. It was especially accelerated by using macroreticular resins with appropriate porosities.
Thermal treatment, spectroscopic analyses, and electrical properties of poly(copper 2,3,9,10,16,17,23,24‐octacyanophthalocyanine)
Authors: Lin John W‐P. , Dudek Les P. 
Published: April 2003

AbstractThermal treatment of novel poly(copper 2,3,9,10,16,17,23,24‐octacyanophthalocyanine), PCOCP, has been carried out at different temperatures in an inert atmosphere. As polyacrylonitrile, the polymer can be thermally cyclized through the cyano groups to produce semiconductive and conductive materials. Polymeric copper octacyanophthalocyanine material with a conductivity as high as 5–8 (Ω cm)‐1 was prepared. Weight loss, electrical data, infrared, and photoacoustic results of the thermally treated copper octacyanophthalocyanine polymer are discussed.
Electropolymerization potential—FMO relations
Authors: Akbulut U. , Toppare L. , Türker L. 
Published: April 2003

AbstractElectroinitiated polymerizations can be carried out by direct electron transfer if the anodic (Ep,a) and cathodic (Ep,c) potentials of monomers are known. Peak potentials of various halostyrenes were measured by cyclic voltammetry in acetonitrile for the first time. Polymerizations were carried out at measured peak potentials, on Pt0 electrode versus Ag0/Ag+, in dichloromethane in which chain transfer is negligible. Frontier molecular orbital energies εm and εm+1 of monomers were calculated by Hückel molecular orbital considerations. Measured Ep,a and Ep,c values were correlated to calculated HOMO and LUMO energies, respectively. Linear equations have been developed for the above correlations as well as for Ep,a — Ep,c versus εm — εm+1.
An electrically conductive plastic composite derived from polypyrrole and poly(vinyl chloride)
Authors: De Paoli Marco‐A. , Waltman R. J. , Diaz A. F. , Bargon J. 
Published: April 2003

AbstractAn electrically conductive plastic material was obtained by the electrochemical polymerization of pyrrole in a poly(vinyl chloride) matrix. The transmission electron microscopy shows that polypyrrole is uniformly distributed in the matrix. The conductivity of the composites fall in the range of 5 to 50 S/cm, and their mechanical properties, as measured in a stress—strain test, are very similar to those of pure poly(vinyl chloride). These can be further improved by addition of poly(chloroprene) rubber as a plasticizer.
Polymer‐immobilized lipoamides—iron(II) system as a reducing catalyst for the reduction of nitrobenzenes to anilines by sodium borohydride
Authors: Kijima Masashi , Nambu Yoko , Endo Takeshi 
Published: April 2003

AbstractBased on a redox function of 1,2‐dithiolane ⇌ 1,3‐dithiol, lipoamide (LAm), and polymers having lipoamide structure were found to work as reducing catalysts for the reduction of p‐substituted nitrobenzenes to corresponding anilines with sodium borohydride in the presence of ferrous chloride in ethanol. Polyallylamine having lipoamide structure (PAA—LAm) showed a good reactivity for the reduction and was easily separated from the reaction mixture.
Direct mass spectrometry of polymers. XIII.. Thermal fragmentation processes in copoly‐α‐amino acids
Authors: Ballistreri Alberto , Giuffrida Mario , Maravigna Pietro , Montaudo Giorgio 
Published: April 2003

AbstractThe thermal fragmentation processes in L‐Proline—Sarcosine and in L‐Proline—L‐Alanine copolymers have been investigated by direct pyrolysis—mass spectrometry. The mass spectral data show that proline—sarcosine copolymers decompose in three steps, yielding cyclic oligomers. The first step is characterized by the presence of the Sar—Sar, Sar—Pro, and Pro—Pro cyclic dimers. In the second step the formation of several series of cyclic oligomers up to nonamers—decamers can be observed, while the third step of thermal decomposition process leads to the almost exclusive formation of Pro—Pro cyclic dimer. The proline—alanine copolymers, instead, show a single‐step thermal degradation process leading to the formation both of cyclic oligomers and compounds with olefin and nitrile end‐groups. Our results show that the thermal decompostion of alanine units is affected by the neighboring units along the polymer chain. Sarcosine units act as thermally labile probes, causing the selective thermal cleavage of the Pro—Sar copolymer.
Substitution and elimination reactions of poly(epichlorohydrin) and poly(2‐chloroethyl vinyl ether) using phase transfer catalysis
Authors: Iizawa Takashi , Nishikubo Tadatomi , Ichikawa Midori , Sugawara Yoshihiko , Okawara Makoto 
Published: April 2003

AbstractThe reactions of poly(epichlorohydrin) (PECH) and poly(2‐chloroethyl vinyl ether) (PCEVE) with various reagents were investigated using phase transfer catalyst (PTC) such as tetra‐n‐butylammonium bromide (TBAB), 18‐crown‐6 (CR6), and dicyclohexyl‐18‐crown‐6 (DCHC) is a solid—liquid two‐phase system. Although the reactions of these polymers hardly occurred without PTC in nonpolar solvents such as toluene and diglyme under mild conditions, the addition of PTC caused the reactions to proceed smoothly under the same conditions. In addition, the reactions of PECH and PCEVE with a strong base such as potassium hydroxide proceeded selectively through β‐elimination reaction to produce the polymers with pendant vinyl groups. These results suggested this method is useful for the syntheses of functional polymers. On the other hand, it turned out that quaternary ammonium salts such as TBAB have higher catalytic activity than crown ethers such as CRG and DCHE in these reactions. Furthermore, the catalytic activity of quaternary ammonium salts was strongly influenced by their chain length and the structure of the polymers.
Effect of carboxyl end groups on hydrolysis of polyglycolic acid
Authors: Huffman K. R. , Casey D. J. 
Published: April 2003

AbstractDye interaction analysis in hexafluoroisopropanol was used to determine end carboxyl groups in polyglycolic acid (PGA). The rate of heterogeneous hydrolysis of purified PGA in water at 37°C shows a first‐order dependence on carboxyl end group concentration at levels above 12 meq/kg. Reaction of molten PGA with a tetraarylorthocarbonate or a triarylketenimine gave end‐capped PGA with carboxyl levels as low as 1 meq/kg. These samples were somewhat more resistant to hydrolysis than untreated PGA despite an increased initial rate at the lower carboxyl levels.
Polymeric arylsulfonylnitromethane: A novel polymer reagent
Authors: Kamogawa Hiroyoshi , Sueki Toshiyuki 
Published: April 2003

Abstractp‐Vinylphenylsulfonylnitromethane (3) was synthesized by the reaction of sodium p‐styrenesulfinate with nitromethane. Free radical copolymerizations of 3 with styrene and N‐vinyl‐2‐pyrrolidone provided soluble copolymers. Conversions of RCH2X (X = Br, OAc) with the copolymers as reagents proceeded in a different manner from the corresponding lowmolecular‐weight compound, phenylsulfonylnitromethane, to afford RCOOH in addition to the expected RCH2CH2NO2 and RCH2COOH; no nitriles were formed.
Spectroscopic studies of poly(N‐acyldehydroalanines) containing asymmetric nucleic acid base derivatives as pendant groups
Authors: Brandt K. A. , Overberger C. G. 
Published: April 2003

AbstractWater‐soluble polynucleotide analogs having a poly(N‐acyldehydroalanine) {poly(α[–(N‐acylamino)acrylate])} backbone were studied by 360‐HMz1H‐NMR, UV, and CD spectroscopies. Significant UV hypochromicity values for the polymers versus monomer model compounds as well as peak shifts in the NMR spectra implied a high degree of base stacking in these systems. The CD spectrum of poly{(‐)‐2‐[2‐(thymin‐l‐yl) propanoamido] propenoic acid} (p(‐)TDHA), having an optically active side chain, was remarkably insensitive to the degree of neutralization of the polymer, but was very sensitive to the ionic strength of the solution. Continuous variation mixing experiments revealed no base‐pairing interactions between complementary charged polymers, and weak interactions between charged and uncharged polymers and model compounds. These results suggest that the polymers are conformationally restricted in solution.
The anionic polymerization of butadiene in the presence of dipiperidinoethane
Authors: Bywater S. , Mackerron D. H. , Worsfold D. J. , Schué F. 
Published: April 2003

AbstractThe polymerization of butadiene by lithium‐based initiators in aliphatic hydrocarbon solvents in the presence of dipiperidinoethane gives a highly 1,2 structure. This system was studied to determine the factors that govern the structure. The effect of this complexing agent on the kinetics of propagation, the microstructure of the polymer, and the ultraviolet spectrum of the active chain end was measured. The results suggest that more than one solvated species form, all giving highly 1,2 polymer structures, but that a solvate containing one chain end with one dipiperidinoethane molecule is the principal reacting species which gives close to 100% 1,2 structure. This reacting center has a high proportion of trans‐structure in the allyllic ion, únlike most complexed active chain ends, which are often highly cis. It is this transstructure in the ion that is thought to be responsible for the polymer structure.
Synthesis and cation‐binding properties of poly‐and bis(thiacrown ether)s
Authors: Oue Masatoshi , Ishigaki Akira , Kimura Keiichi , Matsui Yousuke , Shono Toshiyuki 
Published: April 2003

AbstractPoly‐ and bis(thiacrown ether) derivatives in which some oxygen atoms of benzocrown ether moiety are replaced by sulfur atoms have been synthesized. Their cation‐binding abilities were investigated by using the solvent extraction method. The poly‐ and bis(benzothiacrown ether)s showed great affinity for silver ion, being more excellent in the affinity than the corresponding monocyclic analogs. They, however, possess very poor cation‐binding ability for alkali and alkaline‐earth metal ions. The poly‐ and bis(thiacrown ether)s also bind mercuric ions effectively, whereas the corresponding monomeric analogs do not at all.