bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of rare earth coordination catalyst for ethylene oxide and propylene oxide copolymerization
Authors: Shen Zhiquan , Wu Jian , Wang Guoping 
Published: April 2003

AbstractNeodymium tris(2‐ethylhexylphosphonate)‐triisobutylaluminum‐water system was investigated as a catalyst in ethylene oxide and propylene oxide copolymerization. Random copolymers of ethylene oxide and propylene oxide were obtained with high yield and high molecular weight in a short reaction time. The reactivity ratios of r1(EO) = 1.60 ± 0.04, r2(PO) = 0.45 ± 0.02 were determined. It was found that poly(propylene oxide) prepared with this catalyst system could initiate additional propylene oxide or ethylene oxide to form poly(propylene oxide) with higher molecular weight or propylene oxide‐ethylene oxide diblock copolymer. The microstructures of copolymers were studied by 13C‐NMR spectroscopy.
Synthesis and polymerization of a multimethacrylate
Authors: Jantas R. 
Published: April 2003

AbstractBy reacting poly(methacryloyl chloride) with 2‐hydroxyethyl methacrylate a multimethacrylate on a polymethacrylate template is obtained. Free‐radical polymerization of the multimethacrylate in dilute DMF solutions was investigated. The results obtained suggest that the polymerization process occurs along the template and results in partially ladder‐type polymers, containing unreacted double bonds. Based on the results of elemental analysis, IR, and 1H‐NMR spectra, structures of the multimethacrylate and the obtained polymer were proposed. The rate of disappearance of double bonds in the multimonomer during UV irradiation was examined. Thermogravimetric analysis of the multimethacrylate and related polymers was also performed.
Investigations of the chemical structure of sulfonated amino‐formaldehyde resins. I 13C‐NMR analysis of sulfonated urea‐formaldehyde resins
Authors: Pasch Harald , Dairanieh Issam S. , Al‐Tahou Baheeja 
Published: April 2003

Abstract13C nuclear magnetic resonance has been successfully used for the determination of the chemical structure of sulfonated urea‐formaldehyde resins. Model compounds (such as dimethylol urea and trimethylene diurea) were prepared and their NMR spectra were analyzed. The model compounds were then sulfonated and the additional signals that appeared were assigned to carbon atoms whose hydroxy groups were replaced by sulfonate groups. Urea‐formaldehyde and sulfonated urea‐formaldehyde resins were prepared and their spectra were compared and the sulfonate groups signals were identified. Using a semiquantitative approach, the relative concentrations of the main structural units were calculated and the effect of the monomer composition on the structure of the final resin was investigated.
Investigations of the chemical structure of sulfonated amino‐formaldehyde resins. II. Size exclusion chromatography of sulfonated urea‐formaldehyde resins
Authors: Pasch Harald , Dairanieh Issam S. , Khan Zahida H. 
Published: April 2003

AbstractThe liquid chromatographic behavior of sulfonated urea‐formaldehyde resins in aqueous eluents was investigated and a suitable molecular weight calibration was established at a column system, consisting of μ‐PORASIL 60 Å and μ‐BONDAGEL (linear). It was demonstrated, that in deionized water electrostatic interactions between the stationary phase and the resin molecules occurred and the separation according to size exclusion mechanism was disturbed. Ion exclusion was successfully eliminated, using aqueous sodium sulfate solution as the mobile phase. The molecular weight of the sulfonated urea‐formaldehyde resins was shown to be influenced by the ratio of the resin components. Increasing the formaldehyde to urea ratio resulted in an increase in the resin's molecular weight, whereas increasing the sulfite to urea ratio led to a decrease in the molecular weights. An explanation of this observation was presented.
Dielectric investigation of the effect of ethylamine on viscose rayon
Authors: Mansour A. A. , Shinouda H. G. , Rizk H. A. 
Published: April 2003

AbstractThe effect of treating viscose rayon by aqueous ethylamine of 73.5% w/w for different treatment times on two dielectric relaxation processes (γ and β) observed initially in viscose was studied. Thus, measurements of dielectric constants, ϵ′, and dielectric loss, ϵ″, at frequencies of 0.1–10000 kc/s over a temperature range of 298–333 K, were carried out on four treated samples for 0.5, 1, 2, and 4 h of immersion in ethylamine. Some physical properties were also determined a priori, namely, dissolution and ash content percentages, as well as accessibility toward water and iodine molecules by measurements of heat of wetting and iodine absorption, respectively. In comparison with viscose rayon, the following results were obtained: (i) The γ‐relaxation process was gradually removed by the action of ethylamine, and completely disappeared in samples treated for 2 and 4 h. For this process, the loss, magnitude of polarization, shape parameter, and relaxation frequency decreased with the increase of the time of treatment. (ii) The β‐relaxation process appeared in all samples investigated over the entire working temperature range. The loss maximum and magnitude parameter decreased with lengthening the time of treatment, whereas the shape parameter and the relaxation frequency increased, all tending toward limiting values over practically the same immersion period of 2–4 h. The results obtained from dielectric measurements, as well as those from other physical measurements, suggested that the viscose fiber obtained after treatment of 0.5 h in ethylamine had acquired some compact structure in the residual low fractions, in which the γ‐process was supposed to originate, and that further lengthening of the period of immersion resulted, however, in the development of a less‐closely packed structure in the amorphous regions of the fiber, where the β‐process originated. Based on the above, it was finally concluded that the treatment of viscose rayon with ethylamine of the above concentration resulted in several fractions, which vary in the degree of lateral order of arrangement of the chain molecules; i.e., in the relative arrangement of the polar groups in adjacent chains which govern the interchain forces and in turn the dielectric absorption. At the same time, the explanation of the results obtained in this work supports a previous interpretation suggested for the γ‐ and β‐relaxation processes in viscose.
29Si‐NMR studies of dimethyl and vinylmethyl containing oligodiorganyl cyclosiloxanes and linear copolymers
Authors: Ramarao M. , Packirisamy S. , Ravindran P. V. 
Published: April 2003

Abstract29Si‐NMR has been used to identify and analyze oligomeric mixtures of diorganyl cyclosiloxanes of the general formula FnDm−n (D = (CH3)2SiO, F = CH3(CH2CH)SiO, m = 3–5 and n = 0 −m). Chemical shift assignments were confirmed by comparing 29Si‐NMR and GC‐MS results for composition of the mixtures. The effect of vinyl group on the chemical shift of neighboring silicon atoms was estimated in terms of additivity parameters and good agreement was obtained between experimental and calculated chemical shift values. The distribution of dimethyl and vinylmethyl siloxy units in cyclosiloxanes is discussed. Pentad structures were observed in 29Si‐NMR spectra of poly(dimethyl‐co‐vinylmethyl)siloxanes and their intensities were found to be in confirmity with Bernoullian statistics.
Preparation of poly(amide‐imide)s by direct polycondensation with triphenyl phosphite. IV. Aliphatic‐aromatic poly(amide‐imide)s based on N,N′‐bis(ω‐carboxyalkyl)pyromellitimides
Authors: Hsiao Sheng‐huei , Yang Chin‐ping 
Published: April 2003

AbstractFour diimide‐diacids 3a‐d were synthesized from pyromellitic dianhydride and amino acids of the formula HOOC  (CH2)m  NH2, with m = 1, 3, 5, 10. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in N‐methyl‐2‐pyrrolidone (NMP)–pyridine solution in the presence of calcium chloride. The resulting poly(amide‐imide)s have an aliphatic‐aromatic structure and the relation between the general properties and the amount of the aliphatic part in the repeat unit was studied. IR spectroscopy, elemental analysis, and inherent viscosity measurements were used for the characterization. Studies of solubility, DSC traces, thermal stability, and crystallinity were also made.
Infrared analysis of metal chloride‐doped poly(vinylchloride) films
Authors: Seibles L. 
Published: April 2003

AbstractThe influence of metal chloride dopants (CoCl2, CuCl2, and FeCl3) on the infrared spectrum of solution‐grown thin films of poly(vinylchloride) was investigated using Fourier transform infrared spectroscopy. Detailed analysis and interpretation of the spectral data revealed that solvated metal chloride complexes and residual solvent (N, N‐dimethylformamide) entrained in the polymer films induced specific spectral changes. Extensive vacuum drying of the metal chloride‐doped films reduced the level of entrained solvent but no evidence was found for metal‐induced perturbation of the polymer CCl bans through formation of metal chloride–polymer complexes. Thus the observed spectral changes and a previously reported 106‐fold increase in the electrical conductivity of the polymer films, on doping with metal chlorides, do not appear to result from a specific metal–polymer interaction.
Controlled “living” anionic polymerization of glycidyl methacrylate
Authors: Leemans L. , Fayt R. , Teyssié Ph. , Uytterhoeven H. , De Winter W. 
Published: April 2003

AbstractThe living anionic polymerization of glycidyl methacrylate (GMA) in THF at low temperature initiated with diphenyl hexyl lithium, 9‐anthracenyl methyl lithium, and α‐methylstyryl lithium leads to well characterized homo‐ and block copolymers, with predictable \documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} and narrow molecular weight distributions and with all the oxirane groups intact. Broadening of the molecular weight distributions above a certain and very critical \documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} supported the idea that the living polymerization at low temperature might proceed in micelle‐like structures. Diffusional restriction of the monomer access towards the living centers, due to lesser solvation and increasing compactness of the polymer coils is thought to give rise to broadening of the molecular weight distribution of PGMA homo‐and block copolymers.
Synthesis and characterization of polyamides and polyureas with acyclic and cyclic bipyridinediyl diamino structures in the polymer backbone
Authors: Mamo A. , Finocchiaro P. , Bottino F. , Pappalardo S. 
Published: April 2003

AbstractA series of polyamides and polyureas containing cyclic (1b, 1c, and 1d) or acyclic (2b, 2c, and 2d) bipyridinediyl diamino units in the polymer backbone were prepared. By introducing aliphatic or aromatic comonomers, it was possible to influence the degree of rigidity of the resulting polymers. In the synthesis of the polymers 2c and 2d two new azamacrocycles 5 and 6, respectively, were also produced and they were isolated and characterized. 1H‐NMR and IR spectral data support the structure of the synthesized compounds. Thermal analysis data indicate that the polyureas posses lower PDT (polymer degradation temperature) values with respect to the corresponding polyamides.
Magnesium chloride supported high mileage catalysts for olefin polymerization. XX. Solid state NMR
Authors: Chien James C. W. , Dickinson L. Charles , Vizzini James 
Published: April 2003

AbstractMagic‐angle spinning cross polarization solid state NMR spectra and relaxation data have been obtained for the MgCl2/ethyl benzoate (EB)/p‐cresol (PC)/AlEt3 (TEA)/TiCl4 catalyst (CW) system following each stage of preparation. The change of chemical shifts of certain carbons in EB and their extremely short TH1 suggest strong complexation of EB with MgCl2 and that the EB is in a rigid physical state. The broad linewidths indicate dispersity in binding sites giving a range of chemical shifts. PC also forms a rigid complex with MgCl2 and has the effect of rendering the bound EB less rigid. Reaction between PC and TEA produces EtnAl (OC6H4Me)3‐n species. The ethyl carbons cannot be observed by cross polarization or by a simple π/2 carbon polarization. Treatment with TiCl4 removes most but not all of the PC moieties by extraction and conversion of the aluminum compounds to AlCl3. The 13C‐NMR of EB in the catalyst have chemical shifts like in MgCl2/EB.
New polymer syntheses. XLII. Thermotropic polyesters of hydroquinone and various aryloxyterephthalic acids
Authors: Kricheldorf Hans R. , Engelhardt Jürgen 
Published: April 2003

AbstractAryloxyterephthalic acids were prepared from dimethyl nitroterephthalate and phenol, 4‐fluoro, 4‐chloro‐, 4‐bromo‐, 4‐phenyl‐, 4‐cyclohexyl‐, 4‐phenoxy‐ and 4‐cumyl phenol. Polycondensations with hydroquinone or its derivatives gave the best results, when the aryloxyterephthaloyl chlorides were condensed with hydroquinone in pyridine or with silylated hydroquinone in the molten state. The resulting polyesters were characterized by elemental analyses, inherent viscosities, DSC measurements, microscopy under polarized light, WAXS measurements, and thermogravimetric analyses. All polyesters derived from hydroquinone are semicrystalline with melting points (Tm) in the range of 300–370°C and glass transitions (Tg) in the range of 80–110°C. Most of them form a nematic phase above their Tm; only the homopolyesters of napthyloxy and (4‐cyclohexyl phenoxy) terephthalic acid are isotropic above Tm. Yet the amorphous copolyester of both terephthalic acids and hydroquinone is nematic above Tg, like all copolyesters prepared from two differently substituted terephthalic acids.
The block copolymers and polymer blends of nylon 6 with poly(4,4′‐diphenylsulfone terephthalamide). II. Morphologies and mechanical properties
Authors: Wang Huei‐Hsiung , Chen Wei‐Liang 
Published: April 2003

AbstractThe relationship between the morphological structure and the mechanical properties of the block copolymers and polymer blends of nylon 6 with poly (4,4′‐diphenylsulfone terephthalamide) (PSA) was investigated by use of the mechanical model and optical observations. From features on the morphology, it demonstrated that the dispersed‐phase structures were observed in both of the polymer blends and the triblock copolyamides. Nevertheless, the multi‐block copolyamides exhibited a more homogeneous structure. Based on the experimental results of the crystallization isotherms, it had shown that thenvalue, according to the Avrami's equation, was 2.1 and 2.3 for polymer blends containing 3 and 5 wt % PSA, respectively. The mechanical properties had remarkedly indicated that multiblock copolyamides had a more significant reinforcing effect than the others. Based on the mechanical analysis of polyblends, it was found that the results were quite consistent with those of the Takayanagi's two‐phase mechanical model, except at high PSA. The optimum PSA content in the nylon 6 was considered to be 10–15 wt %.
A new one‐component anhydride‐cured epoxy with an aliphatic disiloxane dianhydride and metal‐coordinated lewis bases
Authors: Eddy Victoria J. , Hallgren John E. , Colborn Robert E. 
Published: April 2003

AbstractThe use of 1,3‐di(5‐[2,2,1]‐bicyclohexyl‐2,3‐dicarboxylic anhydride)‐1,1,3,3‐tetramethyldisiloxane, 1, as a curing agent in the presence of typical epoxy resins with Lewis bases as catalysts produces thermosets with HDTs of 320°C. The solubility of 1 in the epoxy resin allows for the preparation of a one‐component formulation. A latent catalyst was developed which employs amine complexes of cobalt bis(2,4‐pentanedionate). These formulations exhibit long term storage at ambient conditions, yet cure rapidly at 180–200°C.
Amidation of esters using trimethylsilylamines
Authors: Derosa Thomas F. , Jennejahn Rosemary 
Published: April 2003

AbstractTrimethylsilyl‐di‐n‐butylamine has been used to amidate methyl n‐propionate and polymethylmethacrylate (PMMA) in THF. Trimethylsilyl (N‐phenyl‐p‐phenyleneamine) amine was also prepared and used to amidate PMMMA and poly(ethylene‐co‐propylene)‐graft‐methylmethacrylate (OCP‐graft‐MMA) in THF and n‐hexane, respectively. Amidations were performed between 55 and 65°C. When trimethylsilyl‐di‐n‐butylamine was reacted with methyl propionate, less than 10% of the corresponding amide was generated because of a competitive aldol condensation. PMMA was smoothly amidated in excess of 60% using either trimethylsilyl(N‐phenyl‐p‐phenyleneamine)amine or trimethylsilyl‐di‐n‐butylamine without detectable competitive side reactions. OCP‐graft‐MMA was amidated in excess of 90% using a 5 M excess of trimethylsilyl(N‐phenyl‐p‐phenyleneamine)amine in n‐hexane.
Dispersion polymerization of styrene in polar solvents. IV. Solvency control of particle size from hydroxypropyl cellulose stabilized polymerizations
Authors: Paine Anthony J. 
Published: April 2003

AbstractChanging solvent has a dramatic effect on the outcome of HPC stabilized dispersion polymerization of styrene in polar solvents. In methoxyethanol/ethanol mixtures, particle size varies from essentially infinity for unstabilized reactions (below 30% ethanol) to about 3 microns in ethanol. In a series of n‐alcohols, there was a maximum in particle size at intermediate chain length: particle size increased from 2 microns in methanol to 8.3 microns in pentanol, then decreased again to 1 micron in octadecanol. These results were rationalized in terms of the three‐component Hansen solubility parameters. The largest particles were obtained in solvents with Hanson polarity and hydrogen bonding terms closest to HPC. The generality of the three‐component solubility parameter approach was examined by reactions performed in eight mixed solvents with the same values of all three Hansen terms. Seven of the eight solvents gave particles of similar size and molecular weight. The two critical effects of solvent on both particle size and molecular weight appear to be: (a) the solubility properties of the grafted HPC‐PS formed, and (b) the partitioning of monomer and initiator between solution and particle phases subsequent to nucleation.
Synthesis of sulfone‐containing polyamides by direct polycondensation with triphenyl phosphite
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping 
Published: April 2003

AbstractSeveral sulfone‐containing polyamides were prepared by the direct polycondensation reaction of 4,4′‐dicarboxydiphenyl sulfone (DCDPS) with various aromatic diamines by means of triphenyl phosphite in NMP‐pyridine solution containing 4 wt % LiCl. DCDPS was synthesized in two steps by the preparation of 4,4′‐dimethyldiphenyl sulfone (DMDPS) from toluene and chlorosulfonic acid and subsequent oxidation with an alkaline solution of potassium permanganate. The polyamides were obtained in 85–100% yield and had inherent viscosities in the range 0.42–1.65 dL/g. Their solubility, crystallinity, and thermal properties are also discussed.
Synthesis of polyethers containing viologen moiety and their application to electron‐transfer catalyst
Authors: Endo Takeshi , Kameyama Atsushi , Mambu Yoko , Kashi Yasuo , Okawara Makoto 
Published: April 2003

AbstractPolyethers containing viologen moieties were prepared by the reaction of tosylated polyethers with bipyridine. Viologen moieties of these polymers having  ((CH2)2O)n  chains were reduced into the cation radicals by sodium dithionite in dichloromethane, methanol, and benzene. The reduction of vicinal dibromide, ethyl 2,3‐dibromo‐3‐phenylpropionate using these polymers as electron‐transfer catalyst (ETC) was performed in dichloromethane to obtain ethyl cinnamate in good yield.
A study of novel heat‐resistant polymers: Preparation of photosensitive fluorinated polybenzoxazole precursors and physical properties of polybenzoxazoles derived from the precursors
Authors: Yamaoka Tsuguo , Nakajima Nobuko , Koseki Ken'ichi , Maruyama Yutaka 
Published: April 2003

AbstractA series of novel photosensitive polybenzoxazole precursors were prepared from polycondensation of 2,2‐bis(3,3′‐amino‐4,4′‐hydroxyphenyl)hexafluoropropane with photosensitive dicarboxylic acid chlorides such as p‐phenylenediacryloyl chloride and benzophenone‐4,4′‐dicarboxylic chloride. The precursors are soluble in common organic solvents owing to the presence of perfluoromethyl groups in the chain structure, and insolubilized in the solvents on irradiation with the light. Polybenzoxazole patterns with high resolution as well as high aspect ratio were reproduced by baking the precursor patterns at 300°C. The pattern shrinkage on the conversion to polybenzoxazole was slight. The polybenzoxazole films offered good heat‐resistance up to 400°C in addition to good electrical properties.
Controlled shrinkage polymers: Characterization of epoxy resins cured with spirobislactones
Authors: Sikes Allison M. , Brady Robert F. 
Published: April 2003

AbstractThe diglycidyl ether of bisphenol A (DGEBA) was cured with either an aliphatic or an aromatic spirobislactone using a tertiary amine catalyst. The products were characterized by FTIR, TGA, DSC, dilatometry, and single‐fiber adhesion measurements, and their performance was compared to that of DGEBA cured with acid anhydrides. Both aliphatic and aromatic bislactones are effective curing agents for DGEBA. FTIR and dilatometry confirm that both lactone rings open early in the curing reaction and initially offset shrinkage caused by polymerization. After the bislactone has been consumed, oxirane reactions proceed in a normal fashion. The final shrinkage of cured DGEBA polymers, with or without addition of bislactones, is 3.0–3.5%. Bislactone‐modified materials possess superior thermal properties, when compared to those of anhydride‐cured materials.
Kinetics and mechanism of emulsifier‐free emulsion polymerization. III. Styrene/nonionic comonomer (2‐hydroxyethyl methacrylate) system
Authors: Chen Show‐An , Chang Herng‐Show 
Published: April 2003

AbstractThe emulsifier‐free emulsion polymerizations of styrene in the presence of about 0.33–2.7% (relative to styrene) of the water soluble comonomer, 2‐hydroxyethyl methacrylate (HEMA), and of the initiator, potassium persulfate (KPS), were carried out. It was found that KPS plays a predominant role in the particle nucleation process, since the number density of polymer particles (Np) was dependent on the 0.97‐power of [KPS]. The nucleation ability of HEMA was weak, since Np was dependent only on the 0.17‐power of [HEMA]. The particle nucleation stage ceased quite early before 1% conversion, leading to nearly monodispersed polymer particles. The nucleation is suggested to be via the homogeneous nucleation mechanism. The particles grow via the core‐shell structure mechanism (shell region polymerization), since the particle size is rather large—from 1500 to 6000 Å. The amount of HEMA can affect the shell thickness and physical properties of the shell, such as the monomer swelling capacity and monomer diffusion rate.
Radical polymerization of N‐phenyl‐α‐methylene‐β‐lactam
Authors: Ueda Mitsuru , Mori Hideharu , Ito Hiroshi 
Published: April 2003

AbstractN‐phenyl‐α‐methylene‐β‐lactam (PML), a cyclic analog of N,N‐disubstituted methacrylamides which do not undergo radical homopolymerization, was synthesized and polymerized with α,α′‐azobis (isobutyronitrile) (AIBN) in solution. Poly (PML) (PPML) is readily soluble in tetrahydrofuran, chloroform, pyridine, and polar aprotic solvents but insoluble in toluene, ethyl acetate, and methanol. PPML obtained by radical initiation is highly syndiotactic (rr = 92%), exhibits a glass transition at 180°C, and loses no weight upto 330°C in nitrogen. The kinetics of PML homo‐polymerization with AIBN was investigated in N‐methyl‐2‐pyrrolidone. The rate of polymerization (Rp) can be expressed by Rp = k[AIBN]0.55[PML]1.2 and the overall activation energy has been calculated to be 87.3 kJ/mol. Monomer reactivity ratios in copolymerization of PML (M2) with styrene (M1) are r1 = 0.67 and r2 = 0.41, from which Q and e values of PML are calculated as 0.60 and 0.33, respectively.