bluuebunny/crossref_metadata_2025_split huggingface dataset:
Singlet oxygen reactions with model compounds of cis‐ and trans‐polyisoprene containing one unit. Kinetic aspects
Authors: Tanielian C. , Chaineaux J. 
Published: April 2003

AbstractWe have studied the rose bengal‐sensitized photooxygenation of cis‐ and trans‐polyisoprene model compounds that contain one unit in methanolic solution, characterized the resulting monohydroperoxides, and determined their yield. We have also demonstrated the possibility of a second addition of singlet oxygen on the same unit and have undertaken a kinetic study to determine the rate constants of all the reactions of 4‐methyl‐4‐octene.
Functional monomers and polymers. XXXXI. Template polymerization of methacryloyl‐type monomers containing nucleic acid bases
Authors: Akashi M. , Takada H. , Inaki Y. , Takemoto K. 
Published: April 2003

AbstractIn due consideration of the specific base–base interaction that exists between nucleic acid molecules, the free radical polymerization of N‐β‐methacryloyloxyethyl derivatives of adenine, thymine, and theophylline initiated by azobisisobutyronitrile (AIBN) was studied in the presence of N‐β‐methacryloyloxyethyl‐type polymers which have complementary nucleic acid bases as template polymers. The rate of polymerization of N‐β‐methacryloyloxyethyladenine was accelerated when poly(N‐β‐methacryloyloxyethyluracil) or ‐thymine was present in the polymerization system. The effect of the stereoregularity of the template polymers, as well as polymerization temperature and the sort of solvents used on the rate of polymerization, was studied and discussed in some detail. The results suggest that the interaction between complementary bases plays a role in template polymerization behavior.
The radiation‐induced copolymerization of tetrafluoroethylene and styrene at high pressure
Authors: Brown Daniel W. , Lowry Robert E. 
Published: April 2003

AbstractThe radiation‐induced copolymerization of tetrafluoroethylene (A) and styrene (B) was studied in bulk and in perfluorotoluene at 22°C at autogenous pressure and 260 and 510 MPa. The reactivity ratio for addition to A‐ended radicals, rA, is effectively zero at the two lower pressures and is in the range 0.002–0.008 at 510 MPa. The other reactivity ratio, rB, is 6 at autogenous pressure and also at 260 and 510 MPa if the A content of the charge is less than 50%. If the A content is greater than 95%, rB appears to be 100 at pressures of 260 and 510 MPa. The apparent variation in rB cannot be explained by invoking a penultimate unit effect for B‐ended radicals. Polymerization rates scatter somewhat, but all rates are quite small when the A content of the charge is in the range 95–99.8%. Polymers containing as much as 66% A appear to be inherently benzene soluble but frequently contain some gel because of radiation‐induced crosslinking after their formation. No very high polymers were formed that contained more than a few percent A, even at high pressure. Features that complicated the study were immiscibility of the liquid monomers, extreme variation of the monomer—copolymer compatibility with charge composition, and freezing of B at high pressure.
Synthesis of polyamides from linear bisanhydrides and diamines
Authors: Ueda Mitsuru , Hara Osamu , Sato Akira , Imai Yoshio 
Published: April 2003

AbstractThe aminolysis of benzoic mesitoic anhydride was studied in a model system to select the reaction site by steric effect and was found to occur exclusively at the carbonyl group of the benzoic acid. Solution polycondensation of new linear bisanhydrides, terephthalic bis(mesitoic anhydride) and adipic bis(mesitoic anhydride), with aromatic diamines in polar aprotic solvents that contained lithium chloride at room temperature, afforded polyamides with high molecular weight. The interfacial polycondensation in a dichloromethane‐water system also successfully yielded polyamides from aliphatic diamines.
Synthesis of aromatic polyamides by 1‐hydroxybenzotriazole‐catalyzed polycondensation of active aromatic diesters with aromatic diamines
Authors: Ueda Mitsuru , Sato Akira , Imai Yoshio 
Published: April 2003

AbstractCatalytic actions of various additives were studied in the polycondensation of di(4‐nitrophenyl) isophthalate with bis(4‐aminophenyl) ether in N‐methyl‐2‐pyrrolidone, and 1‐hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high‐molecular‐weight polyamide. In addition to the polycondensation of the 4‐nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5‐trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt‐catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight‐membered transition state was proposed.
A study of the ring size in the copolymer of divinyl ether and maleic anhydride by H‐NMR spectroscopy
Authors: Butler George B. , Chu Y. C. 
Published: April 2003

AbstractThe well‐known alternating 1:2 cyclocopolymer of divinyl ether (DVE) and maleic anhydride (MA) possesses a wide spectrum of biological activities, including antitumor. Recent research on the structure of a variety of cyclopolymers has raised a question about the ring size of this cyclocopolymer. In this article we report on an extensive spectroscopic study of its structure. By use of deuterated monomers the H‐NMR peaks at δ 2.31, 3.47, 4.06, and 4.49 ppm with an area ratio of 2:1:1:1 were assigned to the hydrogens of methylenes, methines on the backbone anhydride unit, methines on the ring anhydride unit, and methines adjacent to oxygen on the cyclic ether ring, respectively. By examination of the possible isomeric structures of the bicyclic ring, the splitting of each peak group was further assigned for cis and trans disubstitutions on the anhydride unit. The splitting pattern from the 300‐MHz NMR spectrum of the DVE‐2,3‐dideuteriomaleic anhydride (DMA) copolymer confirmed the unsymmetrical ring structure. 13C‐NMR spectra were consistent with the conclusion from the H‐NMR spectra. A chair‐form, six‐membered ring with predominantly trans geometry in the anhydride ring was assigned to the structure of DVE–MA copolymer. On the basis of little or no change in the 13C‐NMR spectra of the copolymers prepared at different temperatures it was concluded that there was no significant change in structure with temperature. This led to the assignment of the energetically favored, six‐membered ring structure to the copolymer prepared under these conditions. A mechanism for cyclocopolymerization, based on the HOMO–LUMO interaction of the comonomers and the intramolecular radical addition on the preoriented double bond, was proposed. This mechanism leads to the formation of the six‐membered ring structure of the copolymer as the only product. A 13C‐NMR study of the structure of the copolymer prepared in chloroform by Kunitake and Tsukino is being published as a companion article.
The formation of polyethylene terephthalate in the presence of dicarboxylic acids
Authors: Chegolya A. S. , Shevchenko V. V. , Mikhailov G. D. 
Published: April 2003

AbstractThe process of polyethylene terephthalate (PET) formation in the presence of dicarboxylic acids has been studied. Certain amounts of terephthalic acid (TPA) have two‐ to threefold accelerating efficiency in the polycondensation process. To elucidate the causes of the acceleration the main reactions leading to PET formation in the presence of dicarboxylic acids have been investigated by the use of models. The evaluation of kinetic and equilibrium parameters obtained for model reactions made it possible to conclude that the influence of carboxyl‐containing additives on the apparent rate of polycondensation manifests itself in accelerating direct reactions and facilitating the liberation of the eliminated by‐product; that is, ethylene glycol (EG) from the polymer melt. Carboxylic acid acts as a catalyst on the ester interchange of 2‐hydroxyethyl ester end groups and thus increases the rate of polymer formation in this reaction 10–40 times. The parallel interaction between the 2‐hydroxyethyl ester end group and the carboxyl group of the added acid is also catalyzed by the acid and its rate constant is four times larger than that of the catalytic polycondensation of 2‐hydroxyethyl ester end groups. Unlike EG, the reaction water formed in the process is more readily removed from the reaction system and thus promotes the intensification of the process. In addition, the carboxyl groups react with the eliminated EG to decrease its amount and shift the equilibrium toward polymer formation. The investigation of the consequent parallel reactions on models made it possible to draw a conclusion about the higher reactivity of 2‐hydroxyethyl esters in the esterification processes. This fact has been explained by strengthening the nucleophilicity of the oxygen atom in the hydroxyl of a 2‐hydroxyethyl ester group compared with that of EG; for example, by the formation of an intramolecular cycle involving a hydrogen bond. Simultaneously, it has been found that in the system simulating PET polycondensation in the presence of dicarboxylic acids the reaction mechanism involves the catalysis by a proton formed during the carboxyl group dissociation and accepted by the 2‐hydroxyethyl ester group.
Photoinitiation. IV. The effect of lewis acid on the vinyl monomer polymerization photoinitiated by aromatic hydrocarbons
Authors: Capek Ignác , Barton̆ Jaroslav 
Published: April 2003

AbstractPolymerization of acrylonitrile photoinitiated by naphthalene, anthracene, phenanthrene, and pyrene is accelerated by an admixture of zinc (II) chloride, acetate, or nitrate. The effect of zinc (II) salts on the rate of pyrene‐photoinitiated polymerization of acrylonitrile leads to an increase in this rate in the order Zn/OCOCH3/2 < ZnCl2 < Zn/NO3/2. The maximum polymerization rate is achieved at the molar ratio [ZnCl2]/([ZnCl2] + [pyrene]) approximately 0.7. In contrast to the photoinitiated polymerization of acrylonitrile, the methyl methacrylate admixture of zinc (II) chloride exerts a smaller effect on the polymerization rate. In the pyrene‐photoinitiated polymerization of styrene an admixture of zinc (II) chloride retards the polymerization rate. Fluorescence of aromatic hydrocarbon in the system acrylonitrile–aromatic hydrocarbon is efficiently quenched by zinc (II) chloride. Stern–Volmer constants determined for pyrene (80 dm3 mole−1), phenanthrene (66 dm3 mole−1), and naphthalene (49 dm3 mole−1) are higher by about 2–3 orders of the Stern–Volmer constants for fluorescence quenching of aromatic hydrocarbons by acrylonitrile in the absence of ZnCl2. The fluorescence of anthracene in acrylonitrile is not quenched by ZnCl2. The acceleration effect of Zn (II) salts on the polymerization of acrylonitrile photoinitiated by aromatic hydrocarbons depends on two factors: an increase in the ratio of the rate constant of the growth and termination reactions, kp/kt, and an increase in the quenching constant of fluorescence of aromatic hydrocarbon, kq, by the complex {acrylonitrile…ZnCl2}. ZnCl2 thus influences both the growth and initiation reactions of the polymerization process.
Photoinitiation. V. Effect of medium polarity on the acrylonitrile polymerization photoinitiated by naphthalene
Authors: Capek Ignác , Barton̆ Jaroslav , Danciger Juraj 
Published: April 2003

AbstractThe heterogeneous polymerization of acrylonitrile photoinitiated by naphthalene is influenced by the polarity of the reaction medium. The rate of initiation increases with the increasing dielectric strength of the reaction medium. A similar trend is observable for Stern–Volmer constants of naphthalene fluorescence quenching by acrylonitrile. The ratio kp/kt1/2 of the rate constant for propagation and termination reactions is not influenced by a change in the polarity of the reaction medium. The effect of viscosity on the value of kp/kt1/2 known for polymerization in a homogeneous medium was not observed in the reaction systems studied.
Solvent resistance of a polymer chain chemically linked onto a solid surface
Authors: Papirer Eugène , Nguyen Van Tao , Donnet Jean‐Baptiste 
Published: April 2003

AbstractPolystyrene or polystyrene–polyisoprene copolymers have been grafted onto silica by an anionic procedure. The solvent resistance of the grafts has been examined. Linear relationships between the extractable amount of polymer and the solvent extraction temperatures are observed. The extrapolation of these lines leads to temperatures that are in close agreement with the ceiling temperatures of the grafted polymers.
Photoinitiated cationic polymerization by triarylselenonium salts
Authors: Crivello J. V. , Lam J. H. W. 
Published: April 2003

AbstractTriarylselenonium salts with complex metal halide anions such as BF, AsF, and SbF have been prepared and have been shown to be efficient photoinitiators of cationic polymerization. The photolysis rates of these compounds were studied and their quantum yields of photolysis were reported. Use of specific triarylselenonium salts in the polymerizations of cyclohexene oxide, epichlorohydrin, and 2‐chloroethyl vinyl ether are described.
Influence of the conformational state of polymethacrylic acid on the photophysical properties of pyrene in aqueous solution: A fluorescent probe and laser photolysis study
Authors: Chen T. S. , Thomas J. K. 
Published: April 2003

AbstractThe excited state of pyrene observed in fluorescence and pulsed laser techniques is used to show that pyrene is solubilized in the polymer coil of aqueous solution of polymethacrylic acid (PMA) at pH < 4–5. This leads to a decreased access of molecules such as I−, Tl+, CH3NO2, and O2 to excited pyrene in the polymer coil. The protection of the excited state by solubilization in the polymer is sufficient to enable 3‐bromopyrene phosphorescence to be observed at room temperature in these systems. Increasing the pH of the system uncoils the polymer and leads to increased accessibility of excited pyrene to CH3NO2; eventually, at pH >5, the pyrene is ejected into the aqueous phase of the system. In the presence of micellar solutions of surfactants increasing pH transports the pyrene from the polymer to the micellar aggregates. These fluorescence techniques are used to investigate the kinetics of expansion of the polymer coil. The system is suggested as a suitable model for the interaction of pyrene with biopolymers such as DNA.
Friedel–crafts reagents as charring agents in impact polystyrene
Authors: Brauman Sharon K. 
Published: April 2003

AbstractWe have screened various multifunctional Friedel–Crafts alkylation and acylation reagents for their charring ability in impact polystyrene. Only benzyl chloride reagents with Sb2O3–halogen catalysts promoted crosslinking; the result is increased char yields and decreased fuel production and thereby improved fire resistance. Selected systems were evaluated for ignition, extinction, flamespread, and smoke generation; chars were fully characterized.
Oligomeric benzimidazoles with reactive end groups
Authors: Brand Richard A. , Swedo Raymond J. , Marvel C. S. 
Published: April 2003

AbstractThe condensation of aromatic diamines with aromatic dinitriles and the subsequent conversion of the amidines formed to benzimidazole units has been adapted to the preparation of oligomeric benzimidazoles with nitrile and carboxyl end groups. These are promising new dibasic acids for the preparation of heat‐stable condensation polymers.
X‐ray photoelectron spectroscopy of an ethylene–tetrafluoroethylene copolymer
Authors: Pireaux J. J. , Riga J. , Caudano R. , Verbist J. , Gobillon Y. , Delhalle J. , Delhalle S. , Andre J. M. 
Published: April 2003

AbstractThe electronic structure of a clean copolymer of ethylene and tetrafluoroethylene is investigated by measuring the ESCA spectra of the core and valence levels. The chemical composition and alternating (>95%) structure of the copolymer, characterized separately by classical methods, is verified by analyzing the C 1s core‐level spectrum. The comparison of the experimental valence band with an original EHCO band‐structure calculation, and with similar data for a model of polymer with block structure, shows that the combined methods allow us to distinguish between the two compounds through their valence‐band spectra.
Polyimides derived from bismethylolimides. II. Polyamine‐imides from bismethylolimides and diamines
Authors: Kurita Keisuke , Itoh Hiroshi , Iwakura Yoshio 
Published: April 2003

AbstractCompounds in the N‐methylolimide group reacted smoothly with amines in the presence of water to yield the corresponding condensation products. Polycondensations of bismethylolimides, N,N′‐bismethylolpyromellitic diimide, and N,N′‐bismethylolbenzophenonetetracarboxylic diimide, with amines such as aromatic diamines, piperazine, and n‐butylamine, were carried out in DMAc that contained 1% water to produce linear polyamine‐imides. The polyamine‐imides assumed various colors, from very pale yellow to deep purple, and had inherent viscosities in the 0.07–0.37‐dl/g range. Most of these polymers were soluble in polar solvents such as DMAc and DMSO. The thermal stability of the polymers was examined by thermogravimetric analysis; decomposition started at 210–350°C and weight residue at 500°C was 22–85% in air.
Modification of properties of ion exchange membranes. VI. Electrodialytic transport properties of cation exchange membranes with a electrodeposition layer of cationic polyelectrolytes
Authors: Sata Toshikatsu , Mizutani Yukio 
Published: April 2003

AbstractWhen a cation exchange membrane is immersed in a cationic polyelectrolyte solution to form a thin layer on the membrane surface, the membrane properties are changed: permselectivity between cations with different electric charges (a relative transport number of the calcium ions to sodium ions, P), current efficiency, and electric resistance of the membrane. Here the more compact the cationic polyelectrolyte layer, the more outstanding the change in permselectivity. To make a more compact layer, an electrodeposition method was adopted and a change in the permselectivity of the resultant cation exchange membrane was investigated. By using the electrodeposition method a strongly basic polyelectrolyte with a larger molecular weight effectively changed the permselectivity of the cation exchange membrane: the P value dropped to about 0.3 from about 2.5 of the P of the untreated membrane during electrodialysis of the sodium chloride—calcium chloride system, and an increase in the electric resistance of the membrane (i.e., organic fouling) due to a cationic surface‐active agent could be prevented. It is noteworthy that by using the strongly basic polyelectrolyte with a larger molecular weight the electrodeposition method was effective, whereas the immersion method was ineffective. Furthermore, even with the electrodeposition method the cationic polyelectrolyte which had a relatively smaller molecular weight resulted in a more remarkable change in the P value than did that with a larger molecular weight. In the electrodeposition method the amount of polyelectrolyte cohered onto the membrane surface in creased with an increase in the concentration of the polyelectrolyte, and weakly basic polyelectrolyte, and weakly basic polyelectroyte (polyethyleneimine) was also available independent of its molecular weight.
Microstructure of the copolymers of methyl methacrylate with other methacrylates obtained by radical and anionic copolymerizations in tetrahydrofuran
Authors: Yuki Heimei , Okamoto Yoshio , Shimada Yoshiki , Ohta Koji , Hatada Koichi 
Published: April 2003

AbstractMonomer reactivity ratios r1 and r2 were determined in the copolymerizations of methyl methacrylate (MMA, M1) with 1, 1‐diphenylethyl (DPEMA), α,α‐dimethylbenzyl (DMBMA), tert‐butyl (t‐BuMA), diphenylmethyl (DPMMA), phenyl (PhMA), and 1‐naphthyl (NpMA) methacrylates (M2) in tetrahydrofuran (THF) by azobisisobutyronitrile (AIBN) at 60°C and butyllithium (n‐BuLi) at −78°C. The reactivities of the monomers were explained in terms of the polar effect of the ester groups in both copolymerizations. All the copolymers isolated in low yields were converted to PMMA either directly or by copoly(MMA—methacrylic acid) to determine the triad tacticities of the copolymers. Coisotactic parameters σ12 and σ21 were determined by assuming the terminal model statistics. The σ21 values always accorded to the σ21 values within experimental error, and in radical copolymerizations they were between isotactic parameters σ11 and σ22 of the homopolymerizations of MMA and M2 monomers. In anionic copolymerizations, however, the σ12 = σ21 values varied, depending on the M2 monomers. In copolymerization with DPEMA the values were less than both σ11 and σ22 with DMBMA they were between σ11 and σ22, with DPMMA, nearly equal to σ11, and with PhMA and NpMA, greater than both σ11 and σ22. The application of these parameters to copolymerizations performed at high conversion was also investigated.
Radiation‐induced grafting polymerization by the anionic mechanism
Authors: Kabanov V. Ya. , Aliev R. E. 
Published: April 2003

AbstractThe radiation‐induced grafting polymerization of phenylacetylene and 2‐methyl‐5‐vinylpyridine (2M‐5VPy) onto low‐density polyethylene has been investigated under strict identical conditions, using crude and thoroughly dried monomers. In the case of thoroughly dried monomers, the radiation‐induced grafting is performed by the combined (radical + anionic) mechanism. The kinetics of radical and anionic grafting of 2M‐5VPy are investigated in detail. The activation energies are 4.8 ± 0.3 and −2.7 ± 0.3 kcal/mole for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to the dose rate to the 0.47 ± 0.03 and 0.92 ± 0.03 power for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to monomer concentration to the 1.55 ± 0.05 and 2.1 ± 0.05 power for the radical and anionic grafting, respectively. These data conform to the contribution of the anionic mechanism in a thoroughly dried system. The mechanism of radiation‐induced anionic grafting is discussed.
Radiation‐induced addition reaction of carbon tetrachloride onto 1,2‐polybutadiene
Authors: Okamoto Hidemasa , Adachi Shoichi , Iwai Tadashi 
Published: April 2003

AbstractThe γ‐ray‐induced addition reaction of carbon tetrachloride onto syndiotactic 1,2‐polybutadiene film and liquid 1,2‐polybutadiene was carried out at room temperature. In the film gelation was pronounced and the rate of addition increased as the crystallinity of the polymer decreased. In the liquid gelation, which makes the polymer insoluble in carbon tetrachloride, did not take place, although a definite crosslinking reaction was noticed. In this case the appearance of the product changed from a viscous liquid to a white powder as the reaction proceeded. Its structure was compared with that of chlorinated 1,2‐polybutadiene. The addition of carbon tetrachloride to the vinyl group in liquid 1,2‐polybutadiene caused an anti‐Markownikoff‐type reaction and was accompanied by an unexpectedly large vinyl depletion in the polymer. The total decrease in the vinyl group was found to be much larger than that brought about by the addition of carbon tetrachloride. This discrepancy was attributed to a cyclization and crosslinking reaction ascribed to the vinyl group bound by the main chain. Cyclization and crosslinking were less noticeable in the chlorination than in the carbon tetrachloride.