bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and pyrolysis studies of copolyesters
Authors: Vijayakumar C. T. , Ponnusamy E. , Balakrishnan T. , Kothandaraman H. 
Published: April 2003

AbstractRandom 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

AbstractNew 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.
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

AbstractRelatively 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

AbstractThe 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

AbstractSeveral 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractIt 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

AbstractIt 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

AbstractThe 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

AbstractThe 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

AbstractFour 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

AbstractIn 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

Abstract4,4′‐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.
Fluorescence of auramine O and its binding to poly(vinylbenzo‐18‐crown‐6) and to polyvinylbenzoglyme in water
Authors: Wong Kam‐Han , Kimura Keiichi , Smid Johannes 
Published: April 2003

AbstractBinding of the cationic dye auramine O (AuO) to the polysoap‐type polymers poly(vinylbenzo‐18‐crown‐6) (P18C6) and polyvinylbenzoglyme (PVBG) in water were studied by fluorimetry and dialysis. The quantum yield of P18C6‐bound AuO was found to be 0.028, the value being 0.018 for AuO bound to PVBG. The intrinsic binding constants were found to be 2.2 × 104M−1 (P18C6) and 1.2 × 104M−1 (PVBG), the respective first binding constants being 317 and 63M−1. Addition of crown‐ether‐complexable cations such as K+, Tl+, or Cs+ converts the neutral poly(crown ether) into a polycation, causing repulsion of the cationic dye and a strong decrease in the AuO fluorescence. AuO fluorescence was also studied in the absence of polymer in ether solvents, giving θ values of 0.011 and 0.018 in THF and dioxane. Traces of water rapidly form a nonfluorescent species. Solutions of AuO in water without polymer present exhibit very strong fluorescence on addition of BPh4 anions owing to formation of AuO+, BPh4− ion pairs and higher aggregates.
Anionic polymerization of lactones initiated by alkali graphitides. II. Changes in the KC24 structure during polymerization of lactones
Authors: Rashkov Iliya B. , Gitsov Ivan , Panayotov Ivan M. 
Published: April 2003

AbstractThe structural changes in the potassium graphitide KC24 in its interaction with ϵ‐caprolactone, γ‐butyrolactone and pivalolactone are examined by profilometric measurement and electron scanning microscopy. The interaction of KC24 with a nonpolymerizable lactone‐γ‐butyrolactone proceeds without delamination of the graphitide. The polymerization of ϵ‐caprolactone and pivalactone in the interlayer spaces of KC24 leads to destruction of the initiators structure. An increase in the temperature and monomer concentration enhances the delamination of the graphitide.
Friedel–crafts crosslinking methods for polystyrene modification. IV. Macromolecular structure of crosslinked particles
Authors: Barar Donald G. , Staller Kerry P. , Peppas Nikolaos A. 
Published: April 2003

AbstractCrosslinked polystyrene particles were prepared by Friedel–Crafts suspension crosslinking of polystyrene using 2,4‐dichloromethyl‐2,5‐dimethyl benzene as crosslinking agent. The polymer was dissolved in nitrobenzene and reaction occurred in a 70 wt % aqueous solution of ZnCl2 with poly(vinyl alcohol) as a suspending agent. The spherical particles produced were swollen in toluene, chloroform, and tetrahydrofuran to determine their equilbrium polystyrene volume fraction. Analysis of the crosslinked macromolecular structure gave values of number‐average molecular weight between crosslinks of M̄c = 900–5900 increasing as the nominal crosslinking ratio X decreased from 0.75 to 0.0625 mol of crosslinking agent per mole of polystyrene repeating unit. Porosimetric analysis contributed to the understanding of the importance of the pore structure for swelling behavior.
Macromers by carbocationic polymerization. IV. Synthesis and characterization of polyisobutenyl methacrylate macromer and its homopolymerization and copolymerization with methyl methacrylate
Authors: Kennedy Joseph P. , Hiza Misao 
Published: April 2003

AbstractThis article describes the synthesis and characterization of a new macromer, polyisobutenyl methacrylate (PIB‐MA), its free‐radical homopolymerization and copolymerization with methyl methacrylate (MMA) to afford the graft copolymer poly(methyl methacrylate‐g‐isobutylene) (PMMA‐g‐PIB), the characterization of these polymers, and some physical‐mechanical (stress‐strain) measurements of the graft copolymer. The key intermediate toward the synthesis of the target macromer was the preparation of polyisobutenyl chloride PIB‐Clt by the minifer technique. As shown by 1 H‐NMR spectroscopy, and independently by IR spectroscopy coupled with M̄n determination, the PIB‐MA macromer carries one terminal methacrylate function per polyisobutylene chain. The free‐radical homopolymerization of PIB‐MA to very high‐molecular‐weight product was achieved in bulk at 60°C. The free‐radical copolymerization of PIB‐MA with MMA also occurs readily and is a convenient route to PMMA‐g‐PIB. The reactivity of PIB‐MA is almost identical to that of MMA; however, in highly viscous systems its rate of diffusion to the reaction site is reduced.
Study of interpolymer complex formation of polyvinylpyrrolidone and poly(ethylene oxide) with phenolic polymers in nonaqueous media
Authors: Chatterjee S. K. , Sethi K. R. 
Published: April 2003

AbstractA study was made of interpolymer complex formation between polyvinylpyrrolidone (PVP) and poly(ethylene oxide) (PEO) with phenolic polymers (PPF) in an acetone–methanol mixture by several methods; for example, viscosity, potentiometry, conductometry, turbidity, and precipitate (complex) weight. A distinct stepwise complex formation between PVP and phenolic polymers was observed by these methods. As in polycarboxylic acid, however, PEO formed a 1:1 complex with phenolic polymers. Some of these observations have been interpreted in terms of the structure of the polymers, preferential solvation of the component polymers, and the probable change in conformation of the complex molecules in mixed solvents.
A kinetic method of reactivity ratio measurement in olefin copolymerization with Ziegler–Natta catalysts
Authors: Kissin Y. V. , Beach D. L. 
Published: April 2003

AbstractAn efficient kinetic method of reactivity ratio measurement for binary copolymerization of gaseous monomers4 that does not require the measurement of copolymer composition and can be applied to the data obtained in a single copolymerization run was modified and applied to olefin copolymerization with heterogeneous Ziegler–Natta catalysts. Estimated r1 and r2 values for pairs like ethylene‐propylene and propylene‐1‐butene agree favorably with published data.