bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation and stabilization of high molecular weight polyethylene in solution
Authors: Chirinos‐Padrón Alfonso J. , Azócar José , Mun̄oz‐Escalona A. , Fuentes Alberto M. 
Published: April 2003

AbstractThe changes in the molar mass of high molecular weight polyethylene, in o‐dichlorobenzene, with time are examined using viscometry. The results show that the molar mass decreases with time and that the observed decay can be satisfactorily explained by a simple degradation model. Commercial antioxidants can inhibit the degradation process if the appropriate concentration is chosen. Thus, at very low concentrations a polynuclear phenol shows good antioxidant behavior but this decreases with an increase in concentration due to direct oxidation of the inhibitor. Conversely, zinc dimethyldithiocarbamate shows the best stabilizing activity which increases with concentration. The results are explained on the basis of the established mechanistic action of these compounds and show that viscometry is not an accurate method for measuring the molar mass of high molecular weight polyethylene samples unless the appropriate conditions are chosen. Even with the best inhibitor, some degradation is still observed.
Curing studies of a polyimide precursor. II. Polyamic acid
Authors: Brekner Michael‐Joachim , Feger Claudius 
Published: April 2003

AbstractThe cure of pyromellitic dianhydride–oxydianiline polyamic acid is compared with that of a model compound, diphenylcarbamido–dicarboxy–benzene, both having been synthesized in 1‐methyl‐2‐pyrrolidinone (NMP). Laser interferometry and thermogravimetric analysis showed that, analog to the diamic acid model compound, the polyamic acid forms complexes with NMP (repeat unit/NMP: 1/4 and 1/2). Thermal stability of these complexes was found to be similar to the ones of the diamic acid model compound as revealed by comparison of decomplexation temperature–heating rate curves. Activation energies of the decomplexation processes for the diamic acid are given. Anhydride formation, a reaction found in the cure of the model compound to compete with imidization, takes place also during the polyamic acid cure at fairly low temperatures. The molecular weight drop due to chain scission resulting from anhydride formation was followed by viscometry.
Polypyrazoles from aromatic dipropynones and aromatic dihydrazines
Authors: Connell J. W. , Bass R. G. , Sinsky M. S. , Waldbauer R. O. , Hergenrother P. M. 
Published: April 2003

AbstractTwo types of polypyrazoles, unsubstituted and phenylated, were prepared by a novel synthetic route involving the cyclopolycondensation of aromatic dihydrazines and aromatic dipropynones. The polymers had inherent viscosities as high as 1.05 dL/g and were soluble in N, N‐dimethylacetamide, chloroform (phenylated polypyrazoles only), and sulfuric acid. The polymers exhibited glass transition temperatures ranging from 202 to 266°C and polymer decomposition temperatures (10% weight loss) as measured by thermogravimetric analysis of 400–500°C in air and 465–512°C in nitrogen. The synthesis and characterization of several polypyrazoles are discussed.
Phthalonitrile‐based conductive polymer
Authors: Keller Teddy M. 
Published: April 2003

AbstractAn aromatic, diether‐linked phthalonitrile resin, prepared from 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl, can be converted into an environmentally stable, highly conductive material by thermal means. The conductivity of the pyrolyzed polymer can be varied and controlled as a function of both the pyrolytic temperature and annealing time. This allows the generation of a range of electrical behavior from an insulator to semiconductor and approaching metallic regions.
Synthesis of aromatic polyethers containing 2,6(7)‐dihydroxy [1,3,5(6),7(8)‐tetramethylanthracene] units
Authors: Percec Virgil , Tingerthal Jeanne Marie 
Published: April 2003

AbstractFriedel–Crafts copolymerization of 4,4′ bis(2,6‐dimethylphenoxy‐4‐Phenyl)sulfone with methylene chloride used both as comonomer and solvent leads to linear and soluble aromatic polyethers containing 2,6(7)‐dihydroxy[1,3,5(6),7(8)‐tetramethylanthracene] units. The polymerization proceeds by multiple electrophilic substitutions that lead first to diphenylmethane and then to dihydroanthrylene units, followed by dihydrogenation.
Binding of methyl orange and its homologs by powdered nylon 612: Peculiar temperature dependence on the binding
Authors: Takagishi Toru , Shibano Michihiro , Lim Yong Jin 
Published: April 2003

AbstractThe ability of powdered Nylon 612 to bind methyl orange, ethyl orange, propyl orange, and butyl orange was investigated at 5, 15, 25 and 35°C in an aqueous solution. The amount of binding of the dye is much higher with this polyamide than with powdered Nylon 66 reported previously,1 although the former polymer has fewer amide end groups. The Van't Hoff plots of the first binding constant for the binding of butyl orange and propyl orange by powdered Nylon 612 exhibit a bell‐shaped curve, whereas the plots for methyl orange and ethyl orange do not. Maximal binding occurs at approximately 15°C for propyl orange and at about 25°C for butyl orange. This is the first instance where the peculiar temperature dependence of the binding constant has been found in the binding of propyl orange, whose hydrophobicity is less than that of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic domains in powdered Nylon 612 and enhanced hydrophobic contributions in the binding process.
A polymer thin‐film technique to study the micromorphology of core/shell latexes
Authors: Shaffer O. L. , Dimonie V. L. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractA series of poly(styrene)/poly(styrene‐co‐acrylonitrile) core‐shell latexes were synthesized by seeded emulsion polymerization. The dried latex was dissolved in toluene and then cast on the surface of water to form a very thin film (60–90 nm). Phase separation in the thin film was studied by transmission electron microscopy (TEM). Electron micrographs of these thin films yielded fine structure and interesting morphology that was unattainable by ultramicrotoming of the corresponding compression‐molded specimens. Glass transition temperatures and percent grafted polystyrene were correlated with the TEM results. As grafting increases, mixing of the two phases improves, with the resulting Tg value being between the two Tg's of poly(styrene) and poly(styrene‐co‐acrylonitrile).
Effect of crystallinity and flexibility on the photodegradation of polyurethanes
Authors: Hoyle Charles E. , Kim Kyu‐Jun 
Published: April 2003

AbstractUsing fluorescence spectroscopy and gel content measurement, the photolysis of simple polyurethanes based on methylene 4,4′‐diphenyldiisocyanate (MDI) is shown to depend on both the flexibility and crystallinity of the polymer. Polyurethane films based on MDI and 1,12‐dodecanediol (MDI‐12) can be either annealed or quenched to yield a semicrystalline (as measured by DSC and X‐ray diffraction) or amorphous film, respectively. In the case of the quenched (amorphous) film, photolysis yields an ortho photo‐Fries product whereas the annealed (semicrystalline) film does not. Similarly, for a given photolysis time the annealed film generates a lower extent of crosslinked gel. In addition, photolysis of amorphous polyurethane films derived from MDI and ethylene oxide oligomers shows that for relatively inflexible polymers with only three ethylene oxide segments, little or no ortho photo‐Fries rearrangement products are generated upon photolysis. In contrast, photolysis of more flexible polyurethane films with approximately 13 ethylene oxide linkages yields the ortho photo‐Fries product. Apparently, for aromatic diisocyanate based polyurethanes, the extent and mechanism of degradation is directly dependent on the crystallinity and main‐chain flexibility of the polymer.
Synthesis of tailor‐made copolymers containing 1,3‐benzodioxole systems for selective flocculation of minerals
Authors: Bertini V. , Pocci M. , Picci N. , Lucchesini F. , Falbo A. , De Munno A. 
Published: April 2003

AbstractA general simplified model of the morphology of a polymeric flocculant based on only three types of chemical functions, that must be present in the polymer, is described and used for the preparation of tailor‐made selective flocculants for titanium minerals through the radical copolymerization of five new vinyl monomers (I–V) containing the 1,3‐benzodioxole system, with 4‐vinylpyridine, acrylic, methacrylic, and 4‐vinylbenzoic acids.
Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. III. 2‐vinyloxyethyl glycidyl ether: An epoxy‐functionalized vinyl ether
Authors: Sawamoto Mitsuo , Takeuchi Etsu , Hashimoto Tamotsu , Higashimura Toshinobu 
Published: April 2003

AbstractCationic polymerization of 2‐vinyloxyethyl glycidyl ether (VEGE), a vinyl ether with an epoxy group, was conducted with various initiators in CH2Cl2 in the temperature range from +15 to −78°C, and the possibility of its selective vinyl polymerization was investigated. BF3OEt2 polymerized both vinyl and epoxy groups of VEGE to yield polymers partially insoluble in organic solvents. HI/I2, iodine, and CF3SO3H gave soluble, low‐molecular‐weight oligomers with epoxy pendants. 1H‐NMR structural analysis of the oligomeric products showed that the epoxy/vinyl ratio of the pendants decreases in the order: 100% epoxy ∼ CF3SO3H > HI/I2 ∼ I2 ≫ BF3OEt2. Although HI/I2 or iodine mainly polymerized the vinyl group, the reaction of the vinyl ether‐type growing end with an epoxy group of VEGE took place during the polymerization, so that the monomer conversion leveled off at about 40%.
Studies in the formation of poly(oxazolidones). II. Selectivity of catalysts and kinetics in the synthesis of 2‐oxazolidone from butyl isocyanate and phenylglycidyl ether
Authors: Šehović Hajrija , Sendijarević Aiśa , Sendijarević Vahid , Frisch Kurt C. 
Published: April 2003

AbstractThe reaction of butyl isocyanate with phenylglycidyl ether was selected as a model reaction for the synthesis of aliphatic isocyanate‐based poly(2‐oxazolidones). The selectivity of different metal halides and aluminum trichloride/triphenylphosphine oxide (AlCl3 TPPO) and aluminum hexamethylphosphoramide (AlCl3 HMPA) complexes were investigated for oxazolidone formation. Both FTIR and mass spectrographic methods were employed for characterization of the reaction products. The kinetics of the model reaction was studied using AlCl3 TPPO in o‐dichlorobenzene at 120 and 140°C.
Preparation and properties of fluorine‐containing polyarylates from tetrafluoroisophthaloyl chloride and bisphenols
Authors: Kakimoto Masa‐Aki , Harada Shigeyuki , Oishi Yoshiyuki , Imai Yoshio 
Published: April 2003

AbstractFluorine‐containing polyarylates having inherent viscosities of 0.2–0.8 dL/g were prepared from tetrafluoroisophthaloyl chloride and various bisphenols by low temperature solution polycondensation in chloroform with triethylamine or by two‐phase polycondensation in a dichloromethane‐water or nitrobenzene‐water system with benzyltriethylammonium chloride as the phase transfer catalyst. These polyarylates were amorphous and were readily soluble in various solvents, including chloroform and N‐methyl‐2‐pyrrolidone. The glass transition temperature of the polymer derived from 2,2‐bis(4‐hydroxyphenyl) propane was 150°C. These polyarylates started to lose weight around 350°C in an air or nitrogen atmosphere.
Polymerization systems driven by aromatization energy: Anionic polymerization of 4‐allylidene‐2,6‐dimethyl‐2,5‐cyclohexadien‐1‐one and spiro[2,5]octadienone derivatives
Authors: Cho Iwhan , Kim Won‐Tai 
Published: April 2003

AbstractTo investigate the polymerization systems driven by aromatization energy, 4‐allylidene‐2,6‐dimethyl‐2,5‐cyclohexadien‐1‐one (Ia), 5,7‐dimethyl‐1‐vinylspiro[2,5]octa‐4,7‐dien‐6‐one (Ib), 4,7‐dimethyl‐1‐vinylspiro[2,5]octa‐4,7‐dien‐6‐one [Ic], 2‐vinyl‐2′‐methylspiro[cyclopropane‐1,4′‐(1′‐naphthalenone)] (Id), and 2‐phenyl‐2′‐methylspiro[cyclopropane‐1,4′‐(1′‐naphthalenone)] (Ie) were prepared and polymerized with sodium cyanide in N,N‐dimethylformamide. Monomer Ia was highly polymerizable even at −65°C. Monomers Ib–Ie also polymerized well, giving powdery polymers that were soluble in common solvents. All the polymerizations took place through the aromatization of the cyclohexadienone ring, suggesting that the aromatization energy is the driving force for the polymerization of these monomers.
Synthesis of new polydimethylsiloxane‐polyamide copolymers from phenylene‐bis‐5‐oxazolones and aminopropyl‐terminated polydimethylsiloxane oligomers
Authors: Policastro Peter P. , Hernandez Pamela K. 
Published: April 2003

AbstractAlternating polydimethylsiloxane‐polyamide block copolymers were prepared in dichloromethane or chloroform solution at room temperature from 3‐amino‐n‐propyl‐terminated polydimethylsiloxane oligomers and 2,2′‐p‐phenylenebis(4,4‐dimethyl‐5‐oxazolone). Solution and thermal properties of the polymers were characterized.
Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. II. p‐vinylphenyl glycidyl ether: An epoxy‐functionalized styrene
Authors: Hashimoto Tamotsu , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

Abstractp‐Vinylphenyl glycidyl ether (VPGE), a styrene derivative with an epoxy pendant, was polymerized by various cationic initiators, and its selective vinyl polymerization was investigated at low temperatures below −15°C. BF3OEt2 (a metal halide) and CF3SO3H (a strong protonic acid) polymerized both vinyl and epoxy groups of VPGE, and produced cross‐linked insoluble polymers. The HI/I2 initiating system and iodine, in contrast, polymerized its vinyl group in polar solvents (CH2Cl2 and nitroethane) highly selectively in the temperature range of −15 to −40°C to give soluble polymers with a polystyrene backbone and epoxy pendants; however, under these conditions, 10–15% of the epoxy groups of the polymers were consumed during the polymerization by the reaction with the growing species. The polymerization by HI/I2 in CH2CI2 involved a long‐lived propagating species, as indicated by a progressive increase in the molecular weight (M̄n) of the polymers with monomer conversion and their fairly narrow molecular weight distributions (M̄w/M̄n ∼ 1.6). The differences between the polymerizations of VPGE and p‐isopropenylphenyl glycidyl ether, an α‐methylstyrene‐type counterpart of VPGE, were also discussed with an emphasis on the effects of the α‐methyl group in the latter monomer.
Polyelectrolytes containing dihydronicotinamide. III. Fluorescence quenching by nicotinamide‐containing polymers in aqueous solution
Authors: Itoh Yoshihiro , Abe Koji , Senoh Saburo 
Published: April 2003

AbstractCharge‐transfer (CT) interaction of N‐benzyl‐1,4‐dihydronicotinamide (BNAH) and poly(sodium styrene‐p‐sulfonate) containing 6 mol % of BNAH groups (PNAH) with several types of nicotinamide‐containing polyelectrolytes in aqueous solution was investigated by fluorescence quenching. The experimental data were analyzed in terms of a kinetic model including both static and dynamic quenching. Hydrophobic association of BNAH with the polymers led to more effective quenching than the monomer [N‐benzylnicotinamide (BNA)] system. Electrostatic attraction of PNAH and BNA also resulted in the remarkably large value of apparent quenching constant (K′ = 1.4 × 104M−1). Further, the fluorescence of PNAH was quenched far more effectively by poly[N‐(p‐vinylbenzyl)nicotinamide] (PBNA) and poly(acrylamide)s containing nicotinamide (NA) groups (PAm) due to the formation of a polyelectrolyte complex (PEC). In this case, the K′ value depended on the BNA content in the copolymer, suggesting the structural matching effect of the interacting pair on the intermacromolecular interaction.
Magnesium chloride supported high‐mileage catalysts for olefin polymerizations. XVIII. Effect of hydrogen and lewis bases
Authors: Chien James C. W. , Hu Youliang 
Published: April 2003

AbstractHydrogen has been found earlier to increase the initial rate of polymerization by MgCl2/EB/PC/AlEt3/TiCl4‐AlEt3/MPT, CW‐catalyst (+Bi, +Be) (EB, ethyl benzoate; PC, p‐cresol; MPT, methyl‐p‐toluate), but decays more rapidly as compared to polymerizations in the absence of H2. In this study the effect of H2 was studied when either the internal Lewis base, EB Bi, or the external Lewis base, MPT Be, or both are deleted from the CW‐catalyst. H2 does not affect the stereospecificity of all the catalysts, but causes a slight increase of polymer yield, whereas the yield is virtually unchanged by H2 for the catalysts activated with Be. Unlike the catalyst (+Bi, +Be) where H2 increases active site concentrations [Ti*] about threefold, it affects [Ti*] negligibly when Be is absent. The rate constants of propagation is about the same with or without H2 for the CW‐catalyst (+Bi, –Be) or (–Bi, –Be); the same statement can be said about the rate constant of chain transfer with AlEt3 or with H2. Hydrogen increases the rate of catalyst site deactivation for the various catalysts in the order of(+Bi, +Be) > (–Bi, –Be) > (+Bi, –Be).
Syntheses and crosslinking reactions of self‐curable copolymers containing pendant cyclic iminoethers and carboxylic acid groups
Authors: Nishikubo Tadatomi , Iizawa Takashi , Takahashi Makoto , Tokairin Atushi 
Published: April 2003

AbstractSoluble copolymers containing both pendant cyclic iminoethers such as 4,4‐dimethyl‐2‐oxazoline or 4,4,6‐trimethyl‐4H‐dihydro‐1,3‐oxazine and carboxylic acid were successfully synthesized by radical copolymerizations of 4,4‐dimethyl‐2‐vinyl‐2‐oxazoline, 4,4‐dimethyl‐2‐isopropenyl‐2‐oxazoline, or 4,4,6‐trimethyl‐2‐vinyl‐4H‐dihydro‐1,3‐oxazine with methacrylic acid and styrene, methyl methacrylate, or ethyl acrylate using AIBN as an initiator in benzene or DMF at 60 or 80°C. The crosslinking reaction of the copolymers obtained did not occur by heating at 70°C. However, these copolymers quantitatively produced gel products by heating at 130°C. The rate of crosslinking reaction of the copolymer increased with increasing pendant cyclic iminoether and carboxylic acid groups. The rate of crosslinking was also affected by the molecular motion of the polymer chain.Our results show that the copolymers of more sterically hindered 2‐vinyl‐2‐oxazolines are more stable and so they can be crosslinked in a controlled manner and at higher temperatures than the previously studied polyoxaziline system.
Polymerization and conformational studies of poly(trans‐3‐ethyl‐D and L‐proline)
Authors: Tiba Omar , Overberger C. G. 
Published: April 2003

AbstractPoly(L‐trans‐3‐ethylproline), L‐PT3EP, and poly(D‐trans‐3‐ethylproline), D‐PT3EP, were prepared by ring opening polymerization of the corresponding N‐carboxyanhydrides (NCA) using triethylamine as an initiator. Using circular dichroism spectroscopy, it was shown that the incorporation of an ethyl group at the 3 position of the pyrrolidine ring caused a noticeable change in the conformational behavior of the polymer in solution. The ethyl group limited to some extent rotation of the polymer chain around the CCO bond and prevented the mutarotation between the two forms found in poly‐L‐proline polymers.
Poly(α‐amino acid)‐immobilized polymer adsorbents for optical resolution. IV. Elucidation of chiral recognition mechanism of poly(N5‐benzyl‐L‐glutamine)‐immobilized resin
Authors: Kiniwa Hideaki , Doi Yuka , Nishikaji Takashi , Ogata Naoya 
Published: April 2003

AbstractVarious investigations have been carried out in order to further elucidate the chiral recognition mechanism of immobilized poly(N5‐benzyl‐L‐glutamine) (PBLGN) for optical resolution. The shape and dimension of the chiral recognition site are determined by resolution of hydantoin derivatives, with substituents of varied bulkiness at the chiral center. The site of the hydrogen bonding association of the enantiomers responsible for chiral recognition is also elucidated. Several adsorbents with electron‐donating/withdrawing substituents incorporated into the PBLGN side chain phenyl are synthesized and evaluated for the resolution of (RS)‐5‐isopropylhydantoin in order to elucidate the association site of PBLGN. Based on the experimental evidences obtained, a most plausible mechanism of chiral recognition is proposed. Additionally, adsorbents with several other poly(α‐amino acid)s are also synthesized, and the effect of poly(α‐amino acid) side chain length is discussed.
Synthesis and esterolytic reactions of linear and cross‐linked asymmetric imidazole‐containing polymers
Authors: Tomono T. , Schiavone R. J. , Overberger C. G. 
Published: April 2003

AbstractAsymmetric linear and cross‐linked imidazole‐containing polymers were prepared from 1‐[2(S)‐methylbutyl]‐4‐vinylimidazole and 1‐[2(S)‐methylbutyl]‐5‐vinylimidazole. The esterolytic reactions of these linear and cross‐linked asymmetric polymers with the enantiomeric substrates (R)‐ and (S)‐4‐(3‐methylpentadecanoyl)‐3‐nitrobenzoic acid, (R)‐ and (S)‐S, were studied by measuring the pseudo‐first order kinetics of the solvolysis of these enantiomeric substrates in the presence of these asymmetric polymers. The linear homopolymers and copolymers of 1‐[2(S)‐methylbutyl]‐4‐ and 5‐vinylimidazole showed hydrophobic and electrostatic effects in the solvolysis of the enantiomeric substrates with these linear asymmetric polymers. Cross‐links were introduced into these asymmetric polymers to increase the rigidity and reduce the number of conformations available to the polymer. The reduced conformational mobility was expected to enhance any enantioselectivity in the solvolysis of the enantiomeric substrates with these polymers. Using these cross‐linked polymers, hydrophobic interactions were observed in the solvolysis of a series of substrates with increasing alkyl chain length. Also, on changing the polarity of the solvent, a bell‐shaped rate profile was observed in the solvolysis of the long chain substrate S. This effect was attributed to a combination of the coiling of the cross‐linked polymer chains and hydrophobic interactions with the substrate on changing solvent polarity. Even with the increased rigidity of these cross‐linked polymers, no significant enantioselectivity in the solvolysis of the enantiomeric substrates was observed. So, neither the linear nor the cross‐linked asymmetric polyvinylimidazoles showed enantioselectivity in the solvolysis of these enantiomeric substrates. In this case, the hydrophobic interactions and the reduced conformational mobility through crosslinking were not strong enough to bring about enantioselectivity in the solvolysis of these enantiomeric substrates.
Synthesis and characterization of polyesters containing heterocyclic thiaxanthone units
Authors: Reddy T. Ashok , Srinivasan M. 
Published: April 2003

AbstractSeveral polyesters containing thiaxanthone rings were prepared from 2,7‐dichloroformylthiaxanthone‐5,5′‐dioxide (IVa), 2,8‐dichloroformylthiaxanthone‐5,5′‐dioxide (IVb), and bisphenols by solution polycondensation. The 2,8‐diethoxycarbonylthiaxanthone‐5,5′‐dioxide (V) was prepared and characterized by spectral methods to confirm the formation of 2,8‐thiaxanthonedicarboxylic acid‐5,5′‐dioxide (IVb). Prior to polymer synthesis two model compounds,2,7‐diphenoxycarbonylthiaxanthone‐5,5′‐dioxide (MDE‐1) and 2,8‐diphenoxycarbonylthiaxanthone‐5,5′‐dioxide (MDE‐2), were synthesized and characterized by spectral methods. The polyesters were obtained in 62–78% yield and had inherent viscosities in the range 0.42–0.90 dL/g. The effect of thiaxanthone rings on solubility, crystallinity, and thermal stability of the polyesters are also discussed. The polyesters have decomposition temperatures in the range 372–438°C.