bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible protection of oligomeric ethylene glycols by bis (2,4‐dinitrophenylation) and basic ethanolysis
Authors: Warshawsky Abraham , Shoef Nurit 
Published: April 2003

AbstractBis‐(2,4‐dinitrophenyl)glycols are stable in the presence of triethylamine but undergo ethanolysis in the presence of hydroxide ions. The quantitative removal of the DNP blocking group allows an integrated scheme to pure glycols from commercially available polyethylene glycol mixturesMixtures of ethylene glycol oligomers are obtained by anionic polymerization of ethylene oxide. See, for example, G. O. Curme and F. Johnston, Glycols, Reinhold, New York, 1953. They are commercially available (as PEG‐200, PEG‐400, etc., to indicate the average molecular weight of the major components).
by bis‐dinitrophenylation, chromatographic separation, and end‐group removal, using high performance liquid chromatography (HPLC) of the bis‐(2,4‐dinitrophenyl)glycols for purity monitoring. A facile synthetic method for the production of penta‐to dodecaglycols in a mixed, aqueous, dioxane solvent system, with fair yields, is also described. The bis‐(2,4‐dintrophenyl) protection of glycols is a reversible reaction that can be used as (1) a preparative method for pure glycols from readily available commercial polyethylene glycol mixtures; (2) a highly sensitive and accurate analytical methodA. Warshawsky, A. Tishbee, and N. Shoef, J. Liq. Chromatogr., submitted for publication.
coupled with HPLC.
Microstructures of polybutadienes prepared by anionic polymerization in polar solvents. Ion‐pair and solvent effects
Authors: Bywater S. , Firat Y. , Black P. E. 
Published: April 2003

AbstractThe microstructure of polybutadiene produced by anionic initiation in diethyl ether and tetrahydrofuran with counterions Li+, Na+ and K+ was determined by 1H‐ and 13C‐NMR. Ionization suppressing salts were added in tetrahydrofuran to ensure that only the ion‐pair reaction was studied. Results are compared with older published data. In general, the 1,4 content of the polymer increases with increasing counterion size but varies somewhat with solvent with a given counterion. The cis component of the 1,4 structures changes with temperature and counterion. It is suggested that this change reflects the proportion of cis and trans centers that carry the reaction.
Polymer‐bound flavins. I. Influence of polarity of the polymer chain on properties of bound flavin
Authors: Bootsma Jan P. C. , Challa Ger , Müller Franz 
Published: April 2003

AbstractThe preparation of flavin‐containing, water‐soluble terpolymers with varying contents of quaternary ammonium and neutral monomer units is described. The composition of the polymer, that is, the polarity of the polymer chain, affects the UV/VIS absorbance spectrum of the bound flavin moiety by influencing the flavin‐solvent interaction. Aerobic oxidation of 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) is accelerated as much as 17‐fold by polymer‐bound flavins, compared with free flavin. Depending on the ratio of polar/nonpolar groups in the flavin polymer and the 2‐propanol content of the aqueous reaction medium (pseudo) first‐order or Michaelis‐Menten type kinetics were observed as a function of substrate concentration. The influence of the polymer composition on flavin/BNAH complex formation (Km−1) and rate‐limiting hydride transfer step (k2) is discussed. Accumulation of the substrate in the polymer domain due to apolar interactions is one of the major factors that determine the observed rate enhancements.
Poly[(3‐hydroxypropyl) oxirane] and poly[(4‐hydroxybutyl)oxirane]: New hydrophilic polyether elastomers
Authors: Shih Jenn S. , Tirrell David A. 
Published: April 2003

AbstractPreparations of poly[(3‐hydroxypropyl)oxirane] and poly[(4‐hydroxybutyl)oxirane] are described. Three routes to poly[(3‐hydroxypropyl)oxirane] are discussed, each of which involves the methanolysis of a polymeric ester. (3‐Acetoxypropyl)oxirane, [3‐(m‐chlorobenzoyloxy)propyl]oxirane, and (3‐chloropropyl)oxirane were polymerized using the AIEt3/H2O/AcAc initiator system. Poly[(3‐acetoxypropyl)oxirane] and poly{[3‐(m‐chlorobenzoyloxy)propyl]oxirane} were converted directly to poly[(3‐hydroxypropyl)oxirane] by methanolysis, the former under either acidic or basic conditions only. Poly[(3‐chloropropyl)oxirane] was first converted to poly[(3‐benzoyloxypropyl)oxirane] by treatment with tetrabutylammonium benzoate; subsequent basic methanolysis then afforded poly[(3‐hydroxypropyl)oxirane]. Poly[(3‐hydroxypropyl)oxirane] is a colorless elastomer which can be cast into tough, clear films from water or methanol. Poly[(4‐hydroxybutyl)oxirane] was prepared from poly[(4‐chlorobutyl)oxirane] by benzoyloxylation and subsequent methanolysis. Poly[(4‐hydroxybutyl)oxirane] is insoluble in water, but is hydrophilic and can be cast into tough films from methanol or dimethylsulfoxide.
Anionic polymerization of lactones initiated by alkali graphitides. III. Polymerization of δ‐valerolactone initiated by KC24
Authors: Rashkov Iliya Bl. , Gitsov Ivan 
Published: April 2003

AbstractThe anionic polymerization of δ‐valerolactone initiated by KC24 in xylene or tetrahydrofuran was investigated. The influence of the polymerization conditions on the amount and composition of the oligomers fraction and high polymers formed was tested. Experiments were done with a potassium mirror and benzophenone‐potassium as initiators of the polymerization to check the influence of the layered structure of the initiator. It was found that the amount of the oligomers formed under comparable conditions increases in the order KC24 (9%), potassium mirror (22%), benzophenone‐potassium (56%). The highest yields of poly(δ‐valerolactone) (over 90%) and highest intrinsic viscosities (1.0 dL/g and more) were achieved by the KC24‐initiated polymerizations in xylene.
High‐strength fire‐ and heat‐resistant imide resins containing cyclotriphosphazene and hexafluoroisopropylidene groups
Authors: Kumar Devendra , Fohlen George M. , Parker John A. 
Published: April 2003

AbstractHigh‐strength fire‐ and heat‐resistant polymers were obtained by the thermally induced melt‐polymerization of maleimido‐phenoxy cyclotriphosphazenes linked by hexafluoroisopropyliden‐ediphthalimide groups. These polymers show good thermal stability and high char yields: 78–80% at 800°C in nitrogen and 60–68% in air at 700°C. Graphite‐fabric laminates did not burn in pure oxygen, even at 300°C (LOI = 100%), and were tested for shear, flexural, and tensile strengths. Two monomers were synthesized by reacting tris(4‐aminophenoxy)‐tris(phenoxy) cyclotriphosphazene with maleic anhydride and hexafluoroisopropylidenediphthalic anhydride. The triamine was synthesized by a stepwise reaction of hexachlorocyclotriphosphazene with phenol and 4‐nitrophenol to give tris(4‐nitrophenoxy)‐tris(phenoxy)cyclotriphosphazene and reducing the nitro groups. The structures of cyclic phosphazene‐trimeric precursors and the polymers were characterized by FT‐IR, 1H‐NMR, 31P‐NMR, and mass spectroscopy. The curing behaviors of polymer precursors were evaluated by differential scanning calorimetry and thermogravimetric analyses.
Phenothiaphosphine‐containing polyamides and polyesters
Authors: Kondo Hitoshi , Sato Moriyuki , Yokoyama Masaaki 
Published: April 2003

AbstractPhosphorus‐containing polyamides and polyesters, which had tricyclic fused rings (phenothia‐phosphine rings) in the main chain, were prepared and the properties of the resulting polymers were examined. These polymers were obtained at highly reduced viscosities in satisfactory yields by the polycondensation of 2,8‐dichloroformyl‐10‐phenylphenothiaphosphine 5,5,10‐trioxide with aromatic diamines or bisphenols. The polyamides and polyesters were soluble in polar aprotic solvents such as dimethylacetamide and N‐methyl‐2‐pyrrolidone; the polyesters were also soluble in chloroform. The polymers exhibited good heat resistance. The phenothiaphosphine‐containing polyamides and polyesters self‐extinguished immediately when flame was removed and were highly flame‐resistant. The polyester obtained from bisphenol A showed a limiting oxygen index value of 43.5.
New high‐yield, one‐step synthesis of polyglycolide from haloacetic acids
Authors: Pinkus A. G. , Subramanyam Ravi 
Published: April 2003

AbstractIn a new, one‐step synthesis, polyglycolide was prepared by the reaction of bromo‐ or chloroacetic acid with triethylamine in a nitromethane solution. It was discolored, by iodoacetic acid possibly as a result of iodine formed by the decomposition of triethylammonium iodide. The structure of polyglycolide was characterized by hydrolysis, 1H‐NMR and IR spectra, and x‐ray powder diffraction, which indicated partial crystallinity. A mechanism is proposed for the formation of polyglycolide. A lower limiting value of the number‐average molecular weight of 104 was determined by cryoscopy in 1,3‐dinitrobenzene for polyglycolide prepared from bromoacetic acid; the measurement was inaccurate because of the low solubility of the polymer. No significant effect of solvent (acetone, ether, or chloroform) on yield or melting point was observed; a higher yield was obtained in nitromethane. The polymer obtained with tri‐n‐propylamine and bromoacetic acid had properties similar to that obtained with triethylamine. No polymer was obtained with N,N‐dimethylaniline and bromoacetic acid or with triethylamine and bromoacetic acid in aqueous solution.
Direct mass spectrometry of polymers. X. Primary thermal fragmentation processes in totally aromatic polyesters
Authors: Foti Salvatore , Giuffrida Mario , Maravigna Pietro , Montaudo Giorgio 
Published: April 2003

AbstractThe thermal decomposition of a series of isomeric poly‐(oxphthaloyloxyphenylenes) (I–IV) and poly(m‐hydroxybenzoic acid) (V) was studied by Direct Pyrolysis–Mass Spectrometry. The results indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes, causing the formation of cyclic oligomers which are subsequently cleaved to open‐chain fragments. The size and relative abundance of the cycles produced appear to be strongly influenced by steric factors, i.e., by the structure (para or meta) of the repeating unit in each polymer. Remarkably, in the case of poly(m‐hydroxybenzoic acid) the formation of cyclic oligomers containing up to seven repeating units is observed.
Linear condensation polymers of aromatic 1,3‐diamines with 3‐pyridinealdehyde
Authors: Kharas G. B. , Litt M. H. 
Published: April 2003

AbstractIn the presence of one equivalent of acid, m‐phenylenediamine and 2‐methyl m‐phenylenediamine react with pyridine‐3 aldehyde with C alkylation to produce linear polymers, poly(4,6‐R‐methylene m‐phenylenediamine) and poly(4,6‐R‐methylene 2‐methyl m‐phenylenediamine). These were characterized by UV, IR, and NMR spectroscopy. Comparison with model compounds confirmed the above structures. A secondary reaction noted at 25°C and higher for the polymer was the oxidative coupling of two neighboring aromatic diamines to produce substituted 2,7‐diamino acridine groups along the chain.
Phase‐transfer reactions catalyzed by phosphonium salts bound to macroporous polystyrene supports
Authors: Tomoi Masao , Hosokawa Yasunori , Kakiuchi Hiroshi 
Published: April 2003

AbstractThe rate of reaction of alkyl halides with aqueous sodium acetate or cyanide catalyzed by phosphonium salts supported on insoluble polystyrene resins, and rates of ion‐exchange of the chloride ion in the catalysts against the acetate ion, were studied as a function of catalyst particle size, the percentage of ring substitution, the morphology of polymer support, and distance between active site and polymer backbone. Rates of 1‐bromooctane or benzyl chloride with macroporous, 7–25% ring‐substituted catalysts increased with increasing ring substitution. Rates with macroporous catalysts increased as a heptamethylene spacer was introduced between the active site and the polymer backbone. Rates of ion‐exchange with macroporous catalysts were facilitated with increasing ring substitution or by the introduction of the spacer chain. A relation between the catalytic activity of macroporous or microporous catalysts and ion‐exchange rates under triphase conditions was discussed.
Syntheses and electrical conductivity of polyamides containing tetrathiafulvalene moieties in the main chain
Authors: Watanabe Masayoshi , Iida Tadashi , Sanui Kohei , Ogata Naoya , Kobayashi Tadahiko , Ohtaki Zentaro 
Published: April 2003

AbstractNovel polyamides that contain tetrathiafulvalene (TTF) moieties were synthesized by direct polycondensation of Δ2,2′ ‐bi‐1,3‐dithiole‐4,4′(5′)‐dicarboxylic acid with aromatic diamines in the presence of triphenylphosphine, hexachloroethane, and pyridine. Complexes of these polyamides with bromine were TTF cation radical () salts which resulted from the charge transfer of TTF moieties to bromine. The electrical conductivity of undoped polyamides increased with a decrease in diamine length. By doping the bromine the conductivity of the polyamides was enhanced by 3–5 orders of magnitude and reached 10−5–;10−9S cm−1. Maximum conductivity was observed at the doping ratio of [Br]/[repeat unit] < 1. The electrical conduction in the bromine complexes may be attributed to the hopping of odd electrons of between TTF moieties.
Preparation and properties of aromatic polyesters and copolyesters containing phenylindane unit
Authors: Imai Yoshio , Tassavori Shahrzad 
Published: April 2003

AbstractAromatic polysters and copolyesters of high molecular weights with phenylindane units were prepared from combinations of 3‐(4‐hydroxyphenyl)‐1,1,3‐trimethyl‐5‐indanol and bisphenol A with isophthaloyl and terephthaloyl chloride by two‐phase polycondensation in a nitrobenzene‐water system with various phase‐transfer catalysts. The phenylindane‐containing polyesters and copolyesters were amorphous and readily soluble in a wide range of solvents that included chloroform, m‐cresol, tetrahydrofuran, and dimethylformamide. The glass transition temperatures of the phenylindane‐derived polyisophthalate and polyterephthalate were 235 and 253°C, respectively, which were higher than those of the corresponding bisphenol A analogs by some 50°C. These polymers began to lose weight around 400°C in air and nitrogen atmospheres.
Morphology of core‐shell latex particles
Authors: Muroi S. , Hashimoto H. , Hosoi K. 
Published: April 2003

AbstractThe progressive dissolution of carboxylated latex particles with increasing pH was utilized to investigate the internal structure of core‐shell latex particles, in comparison with that of copolymeric latex particles formed from the same monomers. The results indicated that in those latex particles which are formed when ethyl acrylate (EA) ‐methacrylic acid (MAA) or methyl acrylate (MA) ‐MAA mixture is polymerized in the presence of poly(MA‐MAA) or poly(EA‐MAA) seeds the shell is composed of the more hydrophilic poly(MA‐MAA) molecules relatively high in MAA content and the core is composed of both poly(MA‐MAA) and poly(EA‐MAA) molecules, regardless of the order of the stage feed, while the copolymeric latex particles are relatively uniform from surface to center in distribution of all components except MAA. Examination of the distribution of the carboxylic groups in all of the latex particles showed their concentration to be highest at the surface and to decrease with proximity to the center in accordance with other findings reported in the literature.
DTA studies on the thermal oxidation and crosslinking reactions of carboxyl‐terminated polybutadiene
Authors: Kishore K. , Pai Verneker V. R. , Dharumaraj G. Varghese 
Published: April 2003

AbstractStudies on the thermal oxidation of carboxyl‐terminated polybutadiene in the presence of antioxidants have been carried out by dynamic DTA. Bis‐thioacetylacetonato nickel(II) compounds are found to be effective in inhibiting the air oxidation reaction in the polymer. The crosslinking reaction of the polymer through the double bonds present in the polymer molecule is desensitized by the antioxidants and the effect is more with N‐phenyl‐1‐naphthylamine. An exothermic peak formed at 270°C in the presence of tris(2‐methylaziridinyl‐1) phosphine oxide has been identified as the curing reaction. The infrared spectra of CTPB in the presence of MAPO at various temperatures confirm the various stages of reaction.
Structure and electric conductivity of vapor deposition polymerization products of cyanoacetylene
Authors: Matsumura K. , Tsukamoto J. , Takahashi A. 
Published: April 2003

AbstractCyanoacetylene can be polymerized from the vapor state onto an inactive surface of substrate at a temperature as low as 200°C. The polymerization first occurs by way of the carbon–carbon triple bond. The reaction product obtained at 1000°C contains nitrogen at a concentration as high as 13.7%. At least some of this nitrogen is in naphtiridine ring or rings similar to it. The product obtained at 400°C is amorphous, while the product obtained at 1000°C has at least partly graphite‐like crystalline structures with an apparent crystallite size (Lc) of about 17 Å. The electric conductivities of the products obtained at 400, 700, and 1000°C are 7.7 × 10−2, 91, and 1600 S/cm, respectively. These values are extremely high compared to the pyrolized PAN treated at the same temperature. Electric conductivity of the product obtained at 400°C is well explained by the variable range hopping model in 3‐dimensional amorphous materials. With the products obtained at the higher temperatures, conductivity cannot be accounted for by the hopping model. This is probably due to the development of graphite‐like structure.
Linear polythioesters. VIII. Products of interfacial polycondensation of 1,4‐di(mercaptomethyl)‐tetramethylbenzene with isomeric phthaloyl chlorides
Authors: Podkoscielny Wawrzyniec , Kowalewska Wanda 
Published: April 2003

AbstractNew polythioesters by interfacial polycondensation of 1,4‐di(mercaptomethyl)‐tetramethylbenzene with phthaloyl, isophthaloyl, and terephthaloyl chlorides were obtained. To determine the optimal conditions of interfacial polycondensation the influence of the following factors on yield and value of reduced viscosity were studied: type of organic phase, the quantitative ratio of aqueous to organic phase, concentration of hydrogen chloride acceptor, molar ratio of reagents, rate of acid chloride addition, contribution of benzyltriethylammonium chloride as a catalyst, and the temperature of the reaction. The yield of all reaction products and the reduced viscosity of polythioesters which were soluble in the mixture of phenol‐tetrachloroethane were found. A thorough examination was carried out only for the polycondensation of dithiol with isophthaloyl chloride. The structure of all polythioesters obtained under the model conditions was determined by elementary analysis and infrared spectra. Initial decomposition temperature and maximum rate of decomposition temperature were defined from the curves of thermogravimetric analysis. Some mechanical and electrical properties of the polythioesters were determined. The molecular weight was not measured because of the low solubility of the obtained polythioesters.
Synthesis and characterization of MDI‐butanediol urethane model compounds
Authors: Hwang Kirk K. S. , Wu Guosheng , Lin Shaow Burn , Cooper Stuart L. 
Published: April 2003

AbstractHard‐segment model compounds containing one to five 4,4′‐methylene bis(p‐phenylisocyanate) (MDI) units extended with 1,4‐butanediol (BD) were synthesized. The ends of the model compounds were reacted with ethanol. The melting point (Tm) of the model compounds increased with the number of MDI units to an extrapolated value of 299°C for the homopolymer using Flory's equation accounting for chain end defects. The ΔH of fusion was 5.3 kcal/mol. Intrinsic viscosity measurements in DMA solutions revealed a Mark Houwink exponent of 1.43 suggesting that the hard‐segment model compounds are rodlike in solution. Wide‐angle X‐ray diffraction showed that the percentage of hard‐segment crystallinity decreased as the oligomer length increased. Infrared spectroscopy studies showed that the distribution of hydrogen bond distances between CO and NH groups became broader with increasing segment length.
Flame‐retardant epoxy resins based on phthalide derivative
Authors: Lo Jeelin , Pearce Eli M. 
Published: April 2003

AbstractThe phthalide‐containing epoxy resins are synthesized and characterized in comparison with the bisphenol‐A epoxy resins in terms of thermal properties. Although both resins contain comparable amounts of halogens, the resulting flame retardancy is higher in the phthalide‐containing resin. The char formation upon pyrolysis is also enhanced by the phthalide functionality.
Cationic oligomerization of bicyclic oxalactam
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi 
Published: April 2003

AbstractCationic oligomerization of bicyclic oxalactam, 8‐oxa‐6‐azabicyclo[3.2.1]octan‐7‐one [abbreviated as BOL (1)], was carried out at 0–60°C with trifluoromethanesulfonic acid and borontrifluoride etherate as catalysts to obtain the oligomer mixture at high yield. From the structural analysis of the isolated dimer, a N‐(2(e)‐carbamoyltetrahydropyran‐6(e)‐yl)‐8‐oxa‐6‐azabicyclo[3.2.1]octan‐7‐one, the oligomerization proceeded through the 5C‐6N scission in (1) but not through the 6N‐7C (amide group) scission as generally observed in common lactams. This peculiar oligomerization must result from the protonation to the oxamide unit in the BOL molecule.
Temperature dependence of the laser‐initiated polymerization of a thiol‐ene system
Authors: Hoyle C. E. , Hensel R. D. , Grubb M. B. 
Published: April 2003

AbstractThe laser‐initiated polymerization of a thiol‐ene photopolymerizable system was studied. The laser was operated in single‐ and multiple‐pulse modes to generate exotherms, which were measured in a modified differential scanning calorimeter. Arrhenius plots of the polymerization, obtained by measuring polymerization exotherms at various temperatures, showed positive and negative portions. Pseudoactivation energies for the thiol‐ene polymerization increased rapidly at low conversions (<50%) of the thiol and ene chromophores. The results were comparable to those obtained from photopolymerization of multifunctional acrylate monomers.
Kinetics of polymerization of methyl methacrylate initiated with cyclohexanone. Part I
Authors: Kaim A. 
Published: April 2003

AbstractThe kinetics of radical polymerization of methyl methacrylate were investigated in a dioxane solution with cyclohexanone as initiator. It was found that the overall rate of reaction initiated with cyclohexanone (Rp) is proportional to the concentration of monomer and to the square root of the concentration of the initiator. The effect of temperature on the Rp in the temperature range of 65–95°C was discussed. The Arrhenius activation energy Ea estimated for the temperature range of 65–75°C was 137 kJ mol−1.
Synthesis and characterization of graft copolymers from lignin and 2‐propenamide
Authors: Meister John J. , Patil Damodar R. , Field Larry R. , Nicholson John C. 
Published: April 2003

AbstractFree radical polymerization of 2‐propenamide in the presence of lignin, anhydrous calcium chloride, and cericion in photolyzed dioxane solvent produces a reaction product containing lignin‐(1‐amidoethylene) graft copolymer. Up to 49 weight percent of the product is poly(1‐amidoethylene) homopolymer. Photolysis products of dioxane and the presence of anhydrous calcium chloride are critical to the reaction. A maximum yield of polymer is obtained when the dioxane solvent is irradiated for 3 h in a Pyrex vessel and the reaction mixture contains 2.0 weight percent calcium chloride. Aqueous size exclusion chromatography of reaction products shows that the molecular size of the lignin‐(2‐propenamide) reaction product is significantly greater than that of unreacted lignin, that the side chain and the lignin backbone migrate as one unit through the column, and that mixtures of lignin and poly(1‐amidoethylene) are easily separated by the chromatographic column.