bluuebunny/crossref_metadata_2025_split huggingface dataset:
Block copolymers derived from azobiscyanopentanoic acid. X. Synthesis of silicone–vinyl block copolymers via polysiloxane(azobiscyanopentanamide)s
Authors: Inoue Hiroshi , Ueda Akira , Nagai Susumu 
Published: April 2003

AbstractThe synthesis of silicone–vinyl block copolymers has been studied by the use of poly(azo‐containing siloxaneamide)s (abbreviated as PASAs), i.e., polysiloxane (azobiscyanopentanamide)s as macroazoinitiators. PASAs with number‐average molecular weight of 12000–31000 and with siloxane chain lengths of 250–9800 were prepared by the condensation of azobiscyanopentanoyl chloride and α,ω‐bis(3‐aminopropyldimethyl)polysiloxanes in equimolar feeds. Several kinds of silicone–vinyl block copolymers were synthesized by radical polymerization of vinyl monomers such as methyl methacrylate, styrene, and vinyl acetate, in the presence of PASA in homogeneous media. The block copolymers with siloxane contents up to 30 mol % were then characterized on the basis of infrared absorption, proton NMR spectra, and gel permeation chromatography.
Aqueous polymerization of acrylamide initiated by oxygenated cobalt(III) triethylenetetramine complex
Authors: Chen Chuh‐Yung , Kuo Jen‐Feng 
Published: April 2003

AbstractPolymerization of acrylamide was thermally initiated by the oxygenated cobalt(III) triethylenetetramine complex. Rate, conversion, and molecular weights obtained are favorable comparable to those initiated by K2S2O4 and K2S2O8 initiators. An induction period is about 3 mins. The value of Kdf at 60°C is 6.75 × 10−5 s−1, and the chain transfer to monomer constant is 1.2 × 10−5. The rate dependence obtained are a half order on the initiator concentration and a 1.38 order on the monomer concentration. The mole fraction of combination termination occurred in the overall termination reactions evaluated is 0.746.
Sulphur‐containing polyarylenequinodiimides
Authors: Sergeev V. A. , Nedel'kin V. I. , Arnautov S. A. 
Published: April 2003

AbstractDifferent synthetic approaches have been used for preparing some new polymers relating to sulphur‐containing polyarylenequinodiimides. The latter have been obtained both from quinodi‐imidedichloride and aromatic dithioles and directly from 1,4‐phenylenediamine and disulphenylchlorides. The mechanism of this process has been proposed on the basis of studying a model reaction of phenylsulphenylchloride with 1,4‐phenylenediamine. Polyarylenesulphonequinodi‐imides have been obtained by selective oxidation of polyarylenesulphoneamides with phenyliodozoacetate. Their structure has been proved by IR, PMR, and 13C‐NMR spectroscopies. Electrophysical properties of synthesized polymers have been studied.
Mass transfer of oxygen in poly(2‐hydroxyethyl methacrylate)
Authors: Parker J. W. , Cox M. E. 
Published: April 2003

AbstractThe diffusion coefficient of oxygen in poly(2‐hydroxyethyl methacrylate) has been explicitly measured using an optical technique based on fluorescence quenching. This measurement represents the first explicit determination of D in PHEMA. A diffusion coefficient of oxygen in PHEMA of 1.36 × 10−7 cm2/s at 20°C was obtained from this measurement. This value is shown to agree well with permeability data for PHEMA, the free volume theory of diffusion, and with values of D that have been explicitly measured in other methacrylate hydrogels.
Peroxide‐catalyzed grafting of maleic anhydride onto molten polyethylene in the presence of polar organic compounds
Authors: Gaylord Norman G. , Mehta Rajendra 
Published: April 2003

AbstractThe crosslinking of LDPE resulting from reaction with dicumyl peroxide at 180°C is increased in the presence of maleic anhydride (MAH). The presence of electron‐donating nitrogen‐containing compounds (amides, lactams, disubstituted aromatic amines, and amine oxides), phosphorous‐containing compounds (phosphites, phosphates, phosphonates, phosphoramides, and phosphine oxides) and sulfur‐containing compounds (sulfoxides, aryl disulfides, and thiazyl disulfides) which inhibit the homopolymerization of MAH but not that of methyl methacrylate, prevents crosslinking and yields soluble PE containing MAH units. Crosslinking, due to coupling of PE˙ macroradicals formed by hydrogen abstraction from PE by excited MAH, is prevented by electron donation from the additive to the MAH+ cation which is present in the MAH+−MAH excimer as well as in the excimer which is appended to the PE.
Molecular orbital analysis of the XPS spectrum of a fluorine containing polyimide: PMDA–BDAF
Authors: Silverman B. D. , Sanda P. N. , Clabes J. G. , Ho P. S. , Hofer D. C. , Rossi A. R. 
Published: April 2003

AbstractThe results of XPS measurements and molecular orbital calculations performed on the fluorine containing polyimide, PMDA–BDAF, are presented. The calculated carbon 1s (C1s) core energy level positions are compared with the level positions inferred from the XPS measurements. Within Koopman's approximation, the observed shape of the main XPS peak is consistent with the calculated distribution of C1s levels under this peak. Comparison of the magnitude of the carbonyl XPS peak intensity with the main peak intensity indicates a carbonyl C1s signal deficiency compared with that expected for “ideal bulk stoichiometry” i.e., for a polymer with no crosslinks or chain terminations. Comparison of data obtained from a grazing emission (surface sensitive) geometry with that obtained from a normal emission geometry, which probes more deeply into the bulk, indicates a signal enhancement of the C1s levels associated with carbon atoms of the CF3 groups as one nears the polymer surface. Such enhancement might be due to either actual differences in chemical composition, or to preferential structural ordering near the polymer surface.
Kinetics and mechanism of emulsifier‐free emulsion polymerization. II. Styrene/water soluble comonomer (sodium methallyl sulfonate) system
Authors: Chang Herng‐Show , Chen Show‐An 
Published: April 2003

AbstractThe emulsifier‐free emulsion polymerizations of styrene in the presence of about 1 wt% (related to styrene) of the water soluble comonomer, sodium methallyl sulfonate (NaMS), which has short hydrophobic group and strong hydrophilic ionic group, and of the initiator, potassium persulfate, are carried out. Under constant ionic strength, the number density of polymer particles (Np) is found to depend on 0.5‐power of the initiator concentration and shows a minimum in the comonomer concentration plot. Under constant concentration of monomer, comonomer and initiator, Np is found to depend on −1.1‐power of the ionic strength. In the earlier period, the presence of styrene oligomer having MW about 1000 and water soluble poly(NaMS) or copolymer with high NaMS content suggests a micellar nucleation mechanism, by which the styrene oligomer behaves as emulsifier and the poly(NaMS) can either stabilize or destabilize the existing particles, depending on its concentration in the aqueous phase. The particle size is rather uniform having an uniformity very close to 1 (ca. 1.001) throughout the entire process. It is much larger than that of the conventional emulsion polymerization or emulsifier‐free emulsion polymerization with the other comonomers by about 3 to 4 times in diameter or 27 to 64 times in volume, leading to that the average radical number in the particle could be much greater than 0.5. The (conversion)2/3 versus time plot is found to be linear from 6 to 50% conversion. During this period, for the conversion from 10 to 40% the polymerization rate increases twice but the particle volume increases four‐fold. In addition, MWD shows bimodal (excluding the styrene oligomer peak in the earlier period) during the growth period. But the lower MW peak shifts to higher MW and become larger, while the higher MW peak decreases, and finally the MWD becomes single mode after 58.6% conversion. These results suggest a “gradient polymerization” or “transition stage to core‐shell structure” in the earlier stage of particle growth and a “shell part polymerization” in the later stage.
The effect of flexibility on the photodegradation of aromatic diisocyanate‐based polyurethanes
Authors: Hoyle Charles E. , Chawla C. P. , Kim Kyu‐Jun 
Published: April 2003

AbstractThe photolytic degradation of 2,4‐TDI/aliphatic diol polyurethanes is directly dependent on the flexibility of the polymer backbone. The extent of photodegradation is accelerated above the glass transition temperature, indicating the role of chain flexibility and/or oxygen diffusion in the decomposition process. Photolysis of the model compound ethylN‐phenylcarbamate (EPC) in neutral host polymer matrices indicates that theparaphoto‐Fries toorthophoto‐Fries product ratio experiences an accelerated increase with temperature above the glass transition of the polymer matrix.
Polystyrenes with p‐oligo‐siloxane, silane, germanosiloxane, germane, or stannane as p‐substituents as materials for oxygen permeable membranes
Authors: Kawakami Yuhsuke , Hisada Hirofumi , Yamashita Yuya 
Published: April 2003

AbstractThe title polymers were synthesized and the oxygen permeation behavior through the polymer films were studied. The oligodimethylsilane‐substituted polystyrenes showed a little low Po2 compared with the oligodimethylsiloxane‐substituted polystyrenes. The important role of trimethylsiloxyl group in permeation was suggested.
Autoxidation kinetics of atactic polypropylene in bulk
Authors: De Andres Jaime , Aguilar Antonio , Domenech Jorge 
Published: April 2003

AbstractThe kinetics of the reaction between atactic polypropylene (APP) and oxygen in bulk at temperatures ranging from 170 to 210°C and oxygen partial pressures from 160 to 760 torr have been studied by thermal differential analysis. The reaction takes place in two successive steps, both giving hydroperoxide groups as product. Partial reaction orders with respect to APP and oxygen for the first step, which corresponds to the uncatalyzed attack of a CH tertiary bond to give a hydroperoxide, are one and two, respectively. In the second step, interpreted as another attack on a tertiary CH by oxygen, catalyzed by a neighboring hydroperoxide group, reaction orders are one and one‐half for APP and oxygen, respectively. Activation parameters have been determined and a reaction sequence is proposed. Hydroperoxidated APP subsequently decomposes via a zero‐order process giving methylketone groups as its main product. An interpretation of this process is also given.
Kinetics of reactions of methyl α‐eleostearate with cresols
Authors: Yoshimura Yukio 
Published: April 2003

AbstractThe kinetics of addition reactions between methyl α‐eleostearate which forms the main chain of tung oil and cresols when catalyzed by an acid, p‐toluene sulfonic acid, have been studied. The addition reactions, carried out with any one of the o‐, m‐, and p‐cresols were shown to be first order with regard to both methyl α‐eleostearate and cresol concentrations. The reactions were additions of two cresol molecules to one methyl α‐eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step in rate‐determining.

(E: methyl/α‐eleostearate, C: cresols)The apparent reaction rate constants (L/mol min) were found to be 0.046 for o‐cresol, 0.038 for m‐cresol, and 0.033 for p‐cresol. The apparent activation energies (kcal/mol) were found to be 0.95, 3.66, and 4.05, in the cases of o‐, m‐, and p‐cresols, respectively.
Cure of epoxy resins with cyanoacetamides
Authors: Renner Alfred , Moser Roland , Bellus Miriam , Fuhrer Hermann , Hosang Othmar , Szekely Gustav 
Published: April 2003

AbstractCyanoacetamides are a novel class of curing agents for epoxy resins. Since reaction products of epoxy compounds with cyanoacetamides have not yet been described, we investigated the reaction of phenyl‐glycidylether (PGE) and N‐isobutylcyanoacetamide (NICA) under the conditions of the epoxy cure (120–150°C). Twenty‐two fractions of the reaction product have been separated by preparative TLC and characterized by FD and MS mass spectroscopy. The structures of 10 reaction product have been elucidated by MS, NMR, and IR techniques. They belong to the classes of cyclic urethanes, spiro‐dilactones, cyclo‐oxa‐1‐hepten‐4‐one‐2, pyrimidones, aminocrotononitrile, and tertiary amine. This complex model reaction mixture does not enable us to propose a curing mechanism. However practical cure of Bisphenol A diglycidylether (BADGE) yields clear and tough solids with a glass transition temperature up to 200°C, good mechanical strength, and high adhesion to metal surface. Cyanoacetamides are latent hardeners requiring a curing initiator. Since N‐4‐chlorophenyl‐N′‐dimethylurea is a latent initiator, liquid, homogeneous, storage stable “one shot” systems can be formulated which harden quickly above 120°C. Heat aging properties of cured specimens are reported. A series of novel liquid, resinous, and crystalline cyanoacetamides and their potential as curing agent are described.
Morphology of block copolyurethanes. III. Effect of polyether molecular weight on the mechanical properties of solvent cast films
Authors: Benson R. S. , Lyman D. J. 
Published: April 2003

AbstractA homologous series of copolyether–urethane–ureas were synthesized with polypropylene glycol segments having molecular weights of approximately 200, 400, 700, 1000, 2000, and 3000. These copolymers were characterized using tensile measurements and dynamic mechanical spectroscopy. The dynamic mechanical measurements at low frequencies (≤ 1 Hz) showed evidence of the existence of an α‐relaxation process. This was attributed to constrained polyether segments located at the interfacial region between the hard urea segments and the soft polypropylene glycol segments.
Bis‐ or tetra‐maleimides of substituted s‐triazines chain‐extended by imide, amide, and urea groups for fire‐ and heat‐resistant applications
Authors: Mikroyannidis John A. , Melissaris Anastasios P. 
Published: April 2003

AbstractNovel phosphorylated bismaleimides and nonphosphorylated tetramaleimides containing substituted s‐triazine rings (chain‐extended by imide, amide, or urea groups) were prepared and polymerized. These polymer precursors were prepared by reacting 2,4‐bis(4‐aminophenoxy)‐6‐diethoxyphosphinyl‐s‐triazine or 2,4,6‐tris(4‐aminophenoxy)‐s‐triazine with maleic anhydride in combination with a bridging agent such as pyromellitic or benzophenone tetracarboxylic dianhydride, terephthaloyl chloride, and tolylene diisocyanate. The structure of polymer precursors was confirmed by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy and their curing behavior was investigated by differential thermal analysis (DTA). The phosphorylated bismaleimides were thermally polymerized at a lower temperature than did the corresponding nonphosphorylated tetramaleimides. Dynamic thermogravimetric analysis (TGA) showed that the nonphosphorylated and phosphorylated cured resins were stable up to 320–370 and 312–327°C, respectively, in nitrogen or air atmosphere. In addition, the latter afforded a relatively higher char yield. The relative thermal and thermooxidative stability of polymers with regard to the chemical structure of the bridging group was of the order imide > amide > urea. Upon isothermal aging the phosphorylated polymers exhibited a lower weight loss than did the corresponding nonphosphorylated polymers.
Investigation of the intramolecular structure of styrene–ethylmethacrylate copolymers by 1H‐ and 13C‐NMR: Reassignment of 1H‐NMR spectra
Authors: Tacx J. C. J. F. , Van Der Velden G. P. M. , German A. L. 
Published: April 2003

AbstractThe compositions and sequence distributions of homogeneous styrene (S)–ethyl methacrylate (E) copolymers, obtained by low conversion solution polymerization have been studied by 1H‐ and 13C‐NMR. A new set of peak triad assignments was proposed for the δ 2.1–4.2 ppm region in the 1H‐NMR spectrum, whereby the reactivity ratios of rS = 0.59 and rE = 0.50 were used to establish this new assignment. The EEE and SSS blocks, present in these copolymers, have a high degree of syndiotacticity (σEE = 0.23, σSS = 0.39), whereas the ESE units are exhibiting a slight tendency toward isotacticity (σES = 0.66).
Studies on some radical transfer reactions by entrapping the radicals as polymer endgroups. III. Reaction of ȮH radical with halide ions
Authors: Pramanick Dinabandhu , Sarkar Jyotish , Bhattacharyya Ramanath 
Published: April 2003

AbstractThe reactions of OH radical with Cl−, Br−, I−, and F− ions have been studied by entrapping the product radicals as polymer endgroup which have been detected and estimated by the sensitive dye partition technique. The rate constants of the reactions with Br−, Cl−, and F− ions have been determined to be 1.51 × 109, 1.32 × 109, and 0.92 × 109 L mol−1 s−1, respectively at 25°C and pH 1.00. Oxidation of I− ions liberates I, which inhibits the polymerization and the reaction could not be followed by polymer endgroup analysis. The observed order of reactivity Br− > Cl− > F− is in accordance with the electron affinities of the halide ions. The acidity of the reaction medium has a strong influence on the rate of reaction. With Br− ions, the rate constant of the reaction falls from 1.51 × 109 to 0.75 × 109 L mol−1 s−1 at 25°C as the pH is raised from 1.0 to 2.8. The method is simple and accurate and can be applied to study very reactive radicals.
Synthesis and properties of polysulfonamides containing thiophene links
Authors: Yi Mi Hie , Lee Sung Goo , Choi Kil‐Yeong , Jung Jin Chul 
Published: April 2003

AbstractIn order to study the synthesis and properties of polysulfonamides containing thiophene links, 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)propane [BCTP], 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)butane [BCTB], 1,1‐bis(5‐chlorosulfonyl‐2‐thienyl)cyclohexane [BCTC], and 2,4‐dichlorosulfonyl thiophene [DCST] were prepared and interfacial polycondensations with various aliphatic diamines were carried out. The resulting polymers had inherent viscosities in the range of 0.13–0.41 dL/g and showed high extent of moisture absorptions. Most of the polysulfonamides were soluble in electron‐donating solvents such as pyridine, DMF, DMSO, NMP, etc. These polysulfonamides exhibited relatively good thermal stabilities. The TGA data revealed 5% weight losses at 275–405°C and residual weights at 500°C were 13–40% under nitrogen. It was also found that dithienyldisulfonyl chlorides produced more thermally stable polymers than DCST, which were comparable to common polysulfonamides from aromatic disulfonyl chlorides.
Photoexcitable polymer membranes. Photoinduced membrane potential across poly(vinyl chloride) membrane doped with a photosensitive crown ether having lipophilic side chain
Authors: Anzai Jun‐Ichi , Hasebe Yasushi , Ueno Akihiko , Osa Tetsuo 
Published: April 2003

AbstractPhotoirradiation induced potential changes of 10–20 mV across the poly(vinyl chloride) membranes doped with a photosensitive lipophilic crown ether, p‐[3,4‐(1,4,7,10,13‐pentaoxatridecane‐1,13‐diyl)phenylazo]hexadecyloxybenzene was studied. The photoresponse of the membrane was highly improved, presumably due to the lipophilic nature of the crown ether. The photoresponse was explained in terms of the charge density change on the membrane surface. The electric double layer theory was applied to estimate the values of the photoinduced change of the charge density.
Graft copolymers having hydrophobic backbone and hydrophilic branches. III. Synthesis of graft copolymers having oligovinylpyrrolidone as hydrophilic branch
Authors: Miyauchi Noriyuki , Kirikihira Isamu , Li Xin , Akashi Mitsuru 
Published: April 2003

AbstractGraft copolymers were synthesized by the esterification reaction between acrylic copolymers and carboxyl group terminated vinylpyrrolidone oligomer using phase transfer catalysts. Acrylic copolymers were obtained by the radical copolymerization of β‐bromoethyl methacrylate, chloromethylstyrene or glycidyl methacrylate with methyl methacrylate. Hydrophilic oligomers were prepared by the radical oligomerization of vinylpyrrolidone using β‐mercaptopropionic acid as chain transfer agent. The degree of esterification increased with decreasing the molecular weight of oligomer and with increasing the number of potential grafting sites on polymer backbones. The water dispersibility of graft copolymers increased with increasing the nitrogen content and was therefore dependent on the branch oligomer content.
Synthesis of polybutadiene–polysulphide
Authors: Pujol J. M. , Brossas J. , Catala J. M. 
Published: April 2003

AbstractThe anionic synthesis of polybutadiene–polysulphide polymers from butadiene, elemental sulphur, and sodium was studied in a polar solvent (THF). The polycondensation results from the combination of three reactions: initiation of the monomer by the alkali metals, anionic propagation, and deactivation of the dianionic species on elemental sulphur. From the characterization of the resulting polymers it has been shown that the sulphur rank of the polymer can be adjusted by varying the ratio K = [sodium]/[sulphur]. The degree of polymerization of the organic chain can be controlled by changing the temperature or the monomer concentration. From the thiol content, it has been concluded that the polysulphide polymers are principally in a cyclic form. It was also observed that the formation of the 1,4‐structure for the butadiene unit is quantitative when the deactivation of the corresponding carbanions occurs on elemental sulphur.
Synthesis and polymerization of racemic and optically active substituted ß‐propiolactones. V. α‐methyl ß‐propiolactone
Authors: Hmamouchi Mohammed , Prud'homme Robert E. 
Published: April 2003

AbstractR(+) and S(−) enantiomers of α‐methyl β‐propiolactone (MPL) have been synthesized from the corresponding α‐methyl β‐hydroxymethylpropionates and racemic MPL from methyl methacrylate. The optical purity and absolute configuration of these lactones were determined using 1H‐NMR spectroscopy after complexation with a chiral compound: 2,2,2‐trifluoro‐1‐(9‐anthryl)‐ethanol. Optical purities of 100% were obtained for both the S(−) ([α0] = −10.4°, c = 1.3 g/dL in CHCl3) and the R(+) ([α0] = +10.5°, c = 1.0 g/dL in CHCl3) enantiomers. The corresponding racemic and optically active polylactones [poly(MPL)] were prepared by anionic polymerization, in bulk and in solution, as well as poly(MPL)s of intermediate optical purities. The polymers thus obtained are optically active ([α0] = 16.2° in CHCl3 for the optically pure polymer, S configuration) and exhibit significant differences. For example, the racemic poly(MPL) is soluble in several organic solvents such as tetrahydrofuran, benzene, CCl4, CH2Cl2, hexafluoroisopropanol, and CHCl3, whereas the optically active poly(MPL)s are soluble in CHCl3 and hexafluoroisopropanol only. Moreover, racemic poly(MPL) is amorphous whereas optically active poly(MPL)s are semicrystalline for optical purities larger than 51%. Melting temperatures and enthalpies of fusion of the semicrystalline polylactones vary with optical purity whereas glass transition temperatures remain invariant for all polymers, at about −28°C. The poly(MPL) of highest optical purity exhibits a melting temperature of 95°C and an enthalpy of fusion of 61 J/g.
Thermoxidative degradation of polypropylene
Authors: Vasile Cornelia , Odochian Lucia , Agherghinei Ion 
Published: April 2003

AbstractThe thermoxidative behavior of atactic and isotactic polypropylene under dynamical thermoxidative conditions has been studied. It has been established that, with the increase of the heating rate, the development of the oxidative processes are diminished and consequently a modification in the reaction mechanism takes place. One can notice at the same time that the oxidative processes are more intense in the case of the atactic polymer. The 5–15°C/min heating rates determine significant differences between the thermal behavior of the samples, permitting the elaboration of the standard curves useful in fast determination of the atactic content of the industrial products by routine analysis.