bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aromatic rigid chain copolymers. I. Synthesis, structure, and solubility of phenyl‐substituted para‐linked aromatic random copolyamides
Authors: Jadhav J. Y. , Preston J. , Krigbaum W. R. 
Published: April 2003

AbstractFour 2,5‐biphenylene based difunctional condensation monomers, such as 2,5‐diphenyldicar‐boxylic acid or phenylterephthalic acid (PTA), 2,5‐bis(carbonylimino‐4‐benzoic acid)biphenyl (2,5‐BCIBABP), 2,5‐diaminobiphenyl hydrochloride (2,5‐DABP.HCl) and 2,5‐bis(iminocarbonyl‐4‐benzoic acid)biphenyl (2,5‐BICBABP), have been synthesized and characterized. These monomers were polymerized in combination with terephthalic acid (TA) and p‐phenylenediamine (PPD) via the phosphorylation reaction to prepare a series of phenyl‐substituted random copolyamides having all amide groups attached to para‐positions of the benzene rings. All the copolyamides have been characterized by solubility, solution viscosity, and by differential scanning calorimetry (DSC). Some of these copolyamides have unusual solubility in organic solvents such as N,N‐dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidinone (NMP) containing dissolved lithium chloride. A few copolyamides were tested for lyotropic behavior and found to form anisotropic solutions at critical concentrations in organic solvents. A randomly distributed unsymmetrical phenyl substituent on the benzene ring of para‐oriented wholly aromatic polyamides dramatically changes the solubility and melting point. The phenyl substituent on a terephthalic acid unit is more efficient in decreasing melting point and increasing solubility in organic solvents of aromatic polyamides than the one on a p‐phenylenediamine unit. However, the former also introduces a more flexible link in the extended polyamide chain.
Radiation effects on silicon‐containing polyacetylenes
Authors: Tang Ben‐Zhong , Masuda Toshio , Higashimura Toshinobu , Yamaoka Hitoshi 
Published: April 2003

AbstractSi‐containing mono‐ and disubstituted polyacetylenes([CMeC(SiMe3)] n, [CHČH(nC5H11)SiMe3]n, etc.) underwent degradation in air; many of them exhibited relatively high yields of main‐chain scission (Gs > 1). The Gs values for the polymers having a long n‐alkyl group were usually large (ca. 2). In contrast, no polymer degradation occurred in vacuum, indicating that oxygen is necessary for the radiolysis. The polymers irradiated in air contained CO and SiO groups, and dissolved in polar solvents, which are nonsolvents of the starting polymers. From the radiation sensitivity and thermal degradability of these polymers, it is concluded that disubstituted polymers with high Si contents ([CMeC(SiMe3)]n, [CMeC(SiMe2CH2SiMe3)]n, etc.) are not only radiation‐sensitive but also thermally stable.
Polypyrazolinones from aromatic di(propynoic ester)s and aromatic dihydrazines
Authors: Andrews S. M. , Bass R. G. 
Published: April 2003

AbstractNovel polypyrazolinones with inherent viscosities ranging from 0.12 to 0.44 dL/g were prepared by the Michael‐type nucleophilic addition‐cyclization of various dihydrazines with 3,3′‐(1,3‐ or 1,4‐phenylene)bis(ethyl propynoate) (1,3‐ or 1,4‐PEP) and 3,3′‐(1,4‐phenylene)bis(phenyl propynoate) (1,4‐PPhP) in N‐methylpyrrolidone (NMP) solution at 25–110°C. The polymers exhibited moderate thermal stability with initial weight loss in air about 200°C and in nitrogen about 300°C (TGA). No apparent Tg′s were observed by DSC analysis. The synthesis and characterization of the polypyrazolinones is discussed.
Multitechnique surface spectroscopic studies of plasma modified polymers III. H2O and O2/H2O plasma modified poly(methyl methacrylate)s
Authors: Vargo Terrence G. , Gardella Joseph A. , Salvati Lawrence 
Published: April 2003

AbstractThe surfaces of poly(methyl methacrylate) (PMMA) films modified by O2H2O and H2O radio‐frequency glow discharge plasmas were studied using electron spectroscopy for chemical analysis (ESCA or XPS), low energy ion scattering (LEISS or ISS), Fourier transform IR spectroscopy (FTIR) with attenuated total reflectance (ATR) sampling, and critical surface energy from contact angle measurements. The extent and nature of modification with respect to promotion of a hydrophilic surface compared to the hydrophobic surface of the unmodified PMMA has been probed. Results show drastic decreases in C/O ratio at the near surface, which increases to that of the unmodified PMMA as deeper cross sections are analyzed. In addition peak fitting of ESCA data correlated with FTIR functional group information allows for the qualitative and quantitative analysis of the resulting bonding and structure of the modified layer. From these results combined with the polarity and surface energy differences obtained from contact angle measurements, the structural changes are discussed with respect to plasma reaction mechanisms and differences in the structure of the modified polymer films.
Cyclotrimerization of butyl and cyclohexyl isocyanate—catalysis and kinetics
Authors: Šehović Hajrija , Sendijarević Aiša , Sendijarević Vahid , Frisch Kurt C. 
Published: April 2003

AbstractThe cyclotrimerization of model aliphatic and cycloaliphatic isocyanates (butyl and cyclohexyl isocyanate) was carried out using an ammonium carboxylate and a salicylaldehyde‐potassium complex as catalysts. The kinetics of the cyclotrimerization of butyl isocyanate in both 2‐ethoxyethyl acetate and dimethylformamide (DMF) using the 2‐ethylhexanoate salt of trimethylaminopropanol‐2 was found to be of first order with respect to the isocyanate and also of first order with respect to the catalyst. The reaction rate in DMF was considerably greater than in 2‐ethoxyethyl acetate, as could be expected. Employing the salicylaldehyde‐potassium catalyst, the cyclotrimerization of butyl isocyanate followed second‐order kinetics with respect to the isocyanate and first order with regard to the catalyst. Due to the fact that the cyclotrimerization of cyclohexyl isocyanate was found to be slower than that of butyl isocyanate, the cyclotrimerization of this isocyanate was carried out only in DMF using the 2‐ethylhexanoate salt of trimethylaminopropanol‐2 as the catalyst. The kinetics of this reaction was found to follow second order with respect to the isocyanate and first order with regard to the catalyst. The products of the reactions were identified by IR, 1H‐NMR, and mass spectrometry.
Allylnadic‐imides: A new class of heat‐resistant thermosets
Authors: Renner Alfred , Kramer Andreas 
Published: April 2003

AbstractAllyl‐bicyclo‐(2,2,1)hept‐5‐en‐dicarboxylic(2,3)imides (allylnadic‐imides) are prepared by heating equivalent amounts of allylnadic anhydride and amines. Mixtures of isomers (1‐allyl‐endo, 6‐allyl‐endo and exo) were obtained, separated by flash chromatography and identified by 1H‐ and 13C‐NMR. A series of novel allylnadic‐imide monomers is described. Upon heating to 250°C oligomers are obtained. Diels—Aider rearrangement and “ene” type addition reactions seem to play a major role in oligomer formation. Bis‐ and tris‐allylnadic‐imides are viscous liquids resins or low melting solids, which are soluble in common solvents. Upon heating to 250°C insoluble, high Tg solids are obtained with good thermooxidative and environmental stability and with reduced burning rate. Cured allylnadic‐imide resins are excellent high temperature insulators and low permittivity dielectrics. Crosslinked copolymers with maleic‐imides and epoxy resins are described. Neat resin and carbon fiber composite properties are reported.
Syntheses of new thiazolium salt polymers and their catalytic activities
Authors: Yamashita Keiji , Tokuda Hiroyuki , Tsuda Kazuichi 
Published: April 2003

AbstractThiazolium salt polymers were synthesized for the purpose of obtaining a more efficient catalyst for the acyloin condensation. A new thiazolium salt, N‐methyl‐4‐vinylphenylthiazolium iodide was synthesized. However, this compound did not homopolymerize by radical initiator. Therefore, 4‐vinylphenylthiazole was polymerized and the obtained polythiazole was quarternized by methyl iodide. Poly(N‐methyl‐4‐vinylphenylthiazolium iodide) was examined as a polymer‐catalyst for the acyloin condensation of several aldehydes. This polythiazolium salt had an excellent catalytic activity in organic solvents, even in nonpolar solvents. Moreover, it was observed that the catalytic activity increases with the decrease of quarternization.
The block copolymers and polymer blends of nylon 6 with poly(4,4′‐diphenylsulfone terephthalamide). I. Preparation and thermal properties
Authors: Wang Huie‐Hsiung , Chen Wei‐Liang 
Published: April 2003

AbstractIn this study, the flexible nylon 6 was reinforced by the rigid‐chain aromatic polyamide, poly(4,4′‐diphenylsulfone terephthalamide) (PSA). Various high molecular weight block copolyamides were synthesized by solution polymerization using 4,4′‐diisocyanatodiphenylmethane (MDI) or p‐aminophenylacetic acid (p‐APA) as a coupling agent, respectively. Their thermal properties had shown that block copolyamides exhibited higher Tg and Tm, and better thermal stability, especially those using p‐APA as a coupling agent. Decrease in thermal stability of block copolyamides based on MDI coupling agent was due to its urea linkage which been explained and proved by the infrared spectra data. On the other hand, the PSA molecules could act as “nucleating agents” among the nylon 6 matrix in the polymer blends, and accelerated the growth rate of crystallization of nylon 6 molecules, even though high molecular weight of PSA was used.
Positron annihilation lifetime evaluation of thermal cycling effects in atactic polystyrene
Authors: Kasbekar Anand D. , Jones Phillip L. , Crowson Andrew 
Published: April 2003

AbstractPositron annihilation lifetime spectroscopy (PALS) was used to investigate the thermal cycling characteristics of two different molecular weight atactic polystyrene resins. Annealed compression molded samples were thermally cycled over the temperature range 253 K to 393 K with PAL spectra taken in 10 K increments upon both cooling and heating. The longest lived component lifetime and intensity, indicative of orthopositronium pick‐off, exhibit thermal dependencies that can be interpreted in a manner consistent with anticipated free volume changes associated with structural transitions.
FT–IR spectroscopic and thermal studies of poly(styrene‐co‐1‐vinyl naphthalene) and poly(vinyl methyl ether) blends
Authors: Kang Dong‐Pil , Ha Chang‐Sik , Cho Won‐Jei 
Published: April 2003

AbstractThe FT–IR spectroscopic analysis and the thermal behavior of the blends of styrene‐1‐vinyl naphthalene copolymers [P(S‐co‐1VN)] and poly(vinyl methyl ether) (PVME) were investigated in this work. The copolymers containing 23, 50, and 80% by weight of styrene were synthesized by radical polymerization. The blend films of the P(S‐co‐1VN) and PVME were cast from the mixed solvent of benzene/trimethylbenzene [50/50 (v/v)]. It was found from the optical clarity and the glass transition temperature behavior that the blends of PVME with P(S‐co‐1VN) of 80 wt % styrene and 20 wt % 1‐vinylnaphthalene (1VN) show miscibility below 50 wt % of the copolymer concentration and the concentration range to show miscibility becomes wider as the composition of 1VN decreases in the copolymers. From the FT–IR results, the relative peak intensity of the 1100 cm−1region due to COCH3bond of PVME and the peak position of 774 cm−1region due to the naphthyl ring of 1VN were sensitive to the miscibility of the P(S‐co‐1VN)/PVME blends. The frequency differences of the phenyl ring and the naphthyl ring in the P(S‐co‐1VN) from each frequency in the P(S‐co‐1VN)/PVME blends increase with increasing composition of styrene in the copolymers and with increasing concentration of PVME in the blends. A threshold energy exists to induce molecular interaction between the naphthyl ring of 1VN and the COCH3of PVME and to result in the miscible blends, regardless of the copolymer composition as well as the blend concentration. The threshold energy was estimated as about 3.689 × 10−21cal (779 cm−1) for the P(S‐co‐1VN)/PVME blend system. It can be concluded that the miscibility in P(S‐co‐1VN)/PVME blends is largely affected by the composition of the copolymers, and the blends become more miscible as the composition of styrene in the copolymers increases.
Solid‐state CP/MAS 13C‐NMR studies of naphthalene‐based thermotropic polyesters and model compounds
Authors: Kato Takashi , Kabir Gazi M. A. , Uryu Toshiyuki 
Published: April 2003

AbstractThermotropic aromatic polyesters based on 2,6‐naphthalenedicarboxylic acid and 4,4′‐dihydroxy‐1,6‐diphenoxyhexane 1a and ‐decane 1b have been synthesized by solution polymerization. The solid‐state structures of these polyesters have been examined by high‐resolution solid‐state CP/MAS (cross polarization/magic angle spinning) and solution 13C‐NMR. For precipitated original samples, alkylene spacers were generally in the all‐trans form in the solid state. For once‐melted samples, torsional gauche conformations were introduced to the spacers. The mesophase of the polyesters was identified as nematic. The temperature ranges of the nematic state of 1a and 1b were much wider than those of analogous polymers 2a and 2b based on terephthalic acid. For these polyesters, the substitution of the 2,6‐naphthalene ring for the benzene ring induced no appreciable change in the conformation of the diphenoxy alkylene units in the solid state and on the melting points. Thermotropic ester model compounds, i.e., bis(4‐butoxyphenyl) 2,6‐naphthalate 3a and bis(4‐butylphenyl) 2,6‐naphthalate 3b have been prepared and characterized by both solid‐state and solution NMR, which helped the interpretation of the solid‐state structures of the polyesters. These spectra were compared with those of terephthalate‐based related compounds 4a and 4b. The solid‐state spectra suggest that the butoxyphenyl group of 3a and the butylphenyl group of 3b formed almost the same conformations as those of 4a and 4b, respectively.
Polyimide–polyformal block copolymers
Authors: Grade M. M. , Verbicky J. W. 
Published: April 2003

AbstractIn an effort to combine and tailor the properties of thermoplastic resins we have investigated the synthesis of polyimide–polyformal block copolymers prepared by the condensation reaction of α,ω‐diamino functionalized polyformal oligomers with α,ω‐dianhydride terminated polyimide oligomers. Amino functionalized polyformal oligomers were synthesized by displacement condensation reactions of various bisphenols with methylene dihalides in the presence of base and aminophenols. Oligomeric aromatic polyformals having weight average molecular weights (MWw) of 7500 to 40,000 were obtained. Anhydride terminated polyimide oligomers with molecular weights (MWw) ranging from 10,000 to 15,000 were obtained by the condensation of bisphenol‐A–dianhydride and aromatic amines. Combining the polyimide oligomers with the polyformal oligomers in dipolar aprotic or nonpolar solvents afforded the desired block copolymers. The polyimide–polyformal block copolymers generally display two distinct glass transition temperatures by differential scanning calorimetry. The (AB)n block copolymers were evaluated by TGA in both air and N2 for thermal/oxidative stability.
Further polymers derived from bisazlactones and tetraamino compounds
Authors: Katritzky Alan R. , Sakizadeh Kumars , Swinson Joel , Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R. , Pathre Sadanand V. 
Published: April 2003

AbstractNew polymers containing benzimidazole in the polymeric backbone were obtained from the reaction of bis(oxazolones) with known and with a novel aromatic tetraamine. The polymers have inherent viscosities in the range of 0.1‐0.4 dL/g (in DMF 30°C).
Metallocene–methylaluminoxane catalysts for olefin polymerizations. IV. Active site determinations and limitation of the 14CO radiolabeling technique
Authors: Chien James C. W. , Wang Borg‐Ping 
Published: April 2003

AbstractThe initial active site concentrations, [C*]0, have been determined with CH3OT radiolabeling for the Cp2ZrCl2/MAO and CpZrCl3/MAO catalysts (Cp = η5 : cyclopentadienyl, MAO = methyl aluminoxane). Almost all the Zr are found to be catalytically active in 70°C ethylene polymerizations; [C*]0 = [Zr] and [C*]0 = 0.8[Zr] at Al/Zr ratios of 104 and 103, respectively. Lowering the temperature to 50°C and Al/Zr to 5.5 × 102 reduces [C*]0 to 0.2[Zr]. The rate constant of propagation at 70°C was calculated to be 1.6 × 103(M s)−1 for both catalysts at Al/Zr = 1.1 × 104; the values are decreased fivefold and tenfold, respectively, for the CpZrCl3 and Cp2ZrCl2 systems. The usage of 14CO to determine the propagating Zr–P species was investigated. With regard to the time of reaction of 14CO with the polymerization mixture, the initial phase is attributed to reversible CO complexation and reversible migratory insertion. The second slower phase may be due to the formation of enediolate. During the course of a batch polymerization the 14C radioactivity incorporated is small compared to the number of active sites found by CH3OT determination; it is only ca. 10% of [C*]0 at maximum rate of polymerization. Therefore, 14CO radiolabeling cannot be used to count C*.
Radiation induced radical reactions in poly(chloroalkyl methacrylate)s/triallylisocyanurate mixtures
Authors: Wuensche P. , Mueller S. , Lorkowski K.‐H. 
Published: April 2003

AbstractRadical generation after γ‐irradiation at 77 K and radical reactions during temperature increase are discussed for the polymers poly(2‐chloroethyl methacrylate) and poly(1,2,2,2‐tetrachloroethyl methacrylate), mixed with triallylisocyanurate (TAIC). After the radiation interaction radicals are generated in the ester alkyl side groups of the polymer by chlorine abstraction in both polymer/TAIC mixtures. Radical transfer to TAIC occurs during temperature increase to produce allyl radicals. Hence, the high radiation sensitivity of chlorine‐containing polymers is combined with the reactivity of allyl radicals of TAIC in such polymer–TAIC mixtures.
Electroninitiated polymerization of bis(trichlorophenoxo)‐tetramethylethylene diamine copper(II)
Authors: Sacak M. , Akbulut U. , Kisakurek D. , Turker L. , Toppare L. 
Published: April 2003

AbstractElectroninitiated polymerization of bis(trichlorophenoxo)‐N,N,N′,N′‐tetramethylethylene diamine copper(II) was achieved in acetonitrile at various peak potentials of the monomer. A constant potential approach was selected in polymerization reactions. Electrolyses were carried out under air, nitrogen, and oxygen atmospheres. Structural analyses of the polymers were done by 1H‐NMR and 13C‐NMR FT–IR spectroscopy. Molecular weights of the polymers were determined by vapor pressure (isopiestic) method.
Electron transport membrane: Preparation of polypeptide membrane with spacers between the polymer matrix and viologen moiety and their application to an electron transfer reaction
Authors: Ishikawa Kazunori , Nambu Yoko , Endo Takeshi 
Published: April 2003

AbstractPolypeptide membranes with several lengths of spacers [(CH2)n; n = 3, 6, 12] between the polymer matrix and viologen moiety as a functional group were prepared. Reduction of K3Fe(CN)6 with Na2S2O4 across the obtained membrane in aqueous media were carried out and reduction rate of K3Fe(CN)6 across the membrane of n = 6 was faster than that of n = 3. However, the reduction of the membrane (n = 12) did not proceed chemically and electrochemically at all.
Studies on acoustic behavior of praseodymium soaps
Authors: Mehrotra K. N. , Sharma Meera , Gahlaut A. S. 
Published: April 2003

AbstractThe CMC and various acoustic parameters of praseodymium soaps in 1‐pentanol have been determined by ultrasonic velocity measurements. The results show that the ultrasonic velocity, specific acoustic impedance, apparent molal compressibility, and molar sound velocity increase while adiabatic compressibility and intermolecular free length decrease with increasing concentration and chain length of soap.
Copolymerization of furan with maleic anhydride initiated by thioglycolic acid
Authors: Kuramoto Noriyuki , Suda Kaoru , Nagai Katsutoshi 
Published: April 2003

AbstractCopolymerization of furan (F) with maleic anhydride (MAH) initiated by thioglycolic acid (TGA) was studied in various solvents and temperatures in the presence of atmospheric oxygen. Copolymer between F and MAH was readily obtained by using thiol compounds as initiators. The atmospheric oxygen catalyses the copolymerization reaction. The rate of copolymerization is proportional to the concentration [TGA]0.55 at low concentrations (< 1.0 mol/L), at higher concentrations rates decrease gradually. The copolymerization rate increases with increase in copolymerization temperature and varies with the total monomer concentration as ([F] + [MAH])1.9. The overall energy of activation as calculated from the Arrhenius plot has been found to be 6.4 Kcal/mol within the temperature range of 25–50°C.
Preparation and properties of aromatic copolyamides from aromatic diisocyanates and aromatic dicarboxylic acids
Authors: Otsuki Toshihiro , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractWholly aromatic random copolyamides of high molecular weights were prepared by the high‐temperature solution polycondensation of an aromatic diisocyanate, 4,4′‐methylenedi(phenyl isocyanate) or 2,4‐tolylene diisocyanate, with a mixture of isophthalic acid and 4,4′‐oxydibenzoic acid. Glass transition temperatures of the polyamides and copolyamides were between 229 and 273°C; this depended on the combination of diisocyanates and dicarboxylic acids used. These aromatic copolyamides showed better solubility in various organic solvents and reduced crystallinity, compared to the corresponding homopolyamides. The copolyamides prepared from 2,4‐tolylene diisocyanate had greater solubility and higher glass transition temperatures than those obtained from 4,4′‐methylenedi(phenyl isocyanate).
Functionalization of PMMA by a functional “iniferter”: Kinetics of polymerization of MMA using N,N′‐diethyl‐N,N′‐bis(2‐hydroxyethyl) thiuram disulfide
Authors: Nair C. P. Reghunadhan , Clouet G. , Chaumont P. 
Published: April 2003

Abstractα,ω‐Dihydroxy‐terminated‐PMMA was synthesized by the bulk polymerization of methyl methacrylate in the presence of a functional “iniferter,” viz., N,N′‐diethyl‐N,N′‐bis(2‐hydroxyethyl)thiuram disulfide (DHTD). The kinetics of the polymerization were studied by determining the polymerization rate as a function of the “iniferter” concentration at 60, 70, 85, and 95°C. Evaluation of the data by a computerized multiple regression analysis led to calculation of the various kinetic parameters and the activation energies of the related phenomena. The maximum observed in the Rp–initiator concentration curve was found to shift to lower initiator concentration as the temperature increased. The formal reaction order with respect to the concentration of the initiator decreased with increasing temperature and concentration of DHTD. The chain transfer constants of DHTD with MMA were calculated from the molecular weights of the resulting polymers. The functionalities of the oligomers were calculated from the elemental analysis of the chain end groups. Thermogravimetric analysis revealed that the polymer chain ends were devoid of unsaturated groups and that the polymer underwent degradation only by random scission.
Polymerization of tetraallyl ammonium chloride
Authors: Matsumoto Akira , Mano Hisako , Oiwa Masayoshi , Butler George B. 
Published: April 2003

AbstractThe radical polymerization of tetraallyl ammonium chloride (TAAC) was carried out in water using azo‐initiator as compared to that of diallyl dimethyl ammonium chloride (DADMAC); the rate of polymerization was quite low for TAAC, around one‐third of DADMAC. Kinetic discussion revealed the importance of degradative chain transfer in the polymerization of TAAC. The cyclopolymerizability of TAAC was estimated kinetically as the ability of 5‐membered monocyclic radical to form a bicyclic ring, giving the cyclization constant of 21 mol/L at [M] = 2 mol/L. Gelation occurred at around 20% conversion.