bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of novel photodegradable poly(o‐nitrobenzaldehyde acetal) polymers
Authors: Petropoulos Constantine C. 
Published: April 2003

AbstractThe synthesis of novel photodegradable poly(o‐nitrobenzaldehyde acetals) is described. The polymers were prepared by condensing o‐nitrobenzaldehyde with a series of glycols. Polyesteracetals can also be prepared by first preparing the o‐nitrobenzaldehyde glycol acetal or polyacetal prepolymer and subsequent reaction with a diacid chloride. These polymers, although light sensitive, appear to be thermally stable since they were prepared in part by melt condensation techniques. The polymers are useful as positive working photodegradable polymers.
Polyurethanes. IV. Effect of poly(propylene glycol) tacticity on the properties of block copolyether‐urethanes
Authors: Shibatani K. , Lyman D. J. , Shieh D. F. , Knutson K. 
Published: April 2003

AbstractBlock copolyèther–urethane–ureas containing isotatic polypropylene glycols were synthesized and their dynamic mechanical properties compared to the analogous atactic structures. At poly(propylene glycol) molecular weights below 1000, tacticity appears to have little effect on the stress–strain properties of the block copolymers. At higher molecular weights, the ability of the isotatic polyglycol segments to crystallize under strain can effect cyclic deformation properties.
Anionic homopolymerization of ferrocenylmethyl methacrylate
Authors: Pittman Charles U. , Hirao Akira 
Published: April 2003

AbstractAnionic polymerization of ferrocenylmethyl methacrylate (FMMA) was investigated using high‐vacuum techniques. Initiators used included n‐butyllithium, sodium naphthalide, potassium naphthalide, Grignard reagents (both C2H5MgBr and C6H5MgBr), sodium methoxide, and lithium aluminum hydride. FMMA polymerization was readily initiated by each of the above initiators with the exception of sodium methoxide. The molecular weight of poly(ferrocenylmethyl methacrylate) could be controlled by varying the monomer‐to‐initiator ratio when lithium aluminum hydride was used in tetrahydrofuran (THF). In this system, poly(ferrocenylmethyl methacrylate), soluble in benzene or THF, was prepared with M̄n as high as 277,000 with a relatively narrow molecular weight distribution compared to samples prepared by radical‐initiated polymerization. The Mark‐Houwink values of K and a, determined in THF, were K = 4.94 × 10−2 and a = 0.53 (when M = M̄n) and K = 3.72 × 10−2 and a = 0.51 (when M = M̄w). It is clear that the polymer is moderately coiled in THF.
Cografting kinetics of styrene and ethyl acrylate onto polyethylene
Authors: Takahashi Tohru , Yasukawa Tamio , Murakami Kenkichi , Ohmichi Hideki , Sasuga Tsuneo , Araki Kunio 
Published: April 2003

AbstractKinetic studies of cografting reactions of styrene (St) and ethyl acrylate (EA) onto preirradiated polyethylene (PE) have been investigated by means of bromine labeling and infrared spectroscopy. Kinetic data obtained from these methods, that is, the percent grafting, the number of graft chains, and growing rates, were obtained at temperatures of 0, 20, 40, and 50°C. The graft percent was virtually influenced by the degree of swelling. At 0°C, the mixing ratio of ethyl acrylate and styrene monomer before the beginning of the reaction was equal to the existence ratio in the graft chains after the reaction. Therefore, this reaction is considered to be diffusion‐controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains after the reaction. Therefore, this reaction is considered to be diffusion‐controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains agreed with the theoretical curve calculated from monomer reactivity ratio. The number of active graft chains for given times were 3∼5 × 10−7 mole/g PE and it decreased with temperature; 0 > 20 > 50°C. While the total number of graft chains is 5∼15 × 10−7 mole/g PE and it increased with temperature; 0 < 20 < 50°C. The growing rate were 1∼5 monomer/site/sec for 0°C, 2∼15 for 20°C.
NMR studies on the reaction between methacrylonitrile and trimethylaluminum
Authors: Koma Yasuo , Iimura Kazuyoshi , Kondo Shoichi , Takeda Masatami 
Published: April 2003

AbstractThe reaction of MAN with AlMe3 was studied by the 13C‐ and 1H‐NMR spectral measurement. In the presence of an excess of AlMe3, it was found that a 1:1 complex of MAN and AlMe3 is initially formed and subsequently dimethyl(α‐methyl isopropylidene amino)aluminum is produced by the reaction of the complex with AlMe3. The isolated product was pale yellow crystal (mp 39–40°C). The kinetics of the reaction were also examined.
Novel solvent effects in the photopolymerization of methyl methacrylate by use of quinoline–bromine charge‐transfer complex as photoinitiator
Authors: Ghosh Premamoy , Mitra Partha Sarathi 
Published: April 2003

AbstractPhotopolymerization of MMA was carried out at 40°C in diluted systems by use of quinolinebromine (Q–Br2) charge‐transfer complex as the initiator and chloroform, carbon tetrachloride, chlorobenzene, dioxane, THF, acetone, benzene, toluene, quinoline, and pyridine as solvents. The results showed variable monomer exponents ranging from 1 to 3. For chloroform, carbon tetrachloride, and chlorobenzene, the monomer exponent observed was unity; for other solvents used, the value of the same exponent was much higher (between 2 and 3). Initiation of polymerization is considered to take place through radicals generated in the polymerization systems by the photodecomposition of (Q–Br2)–monomer complex (C) formed instantaneously in situ on addition of the Q–Br2 complex in monomer. The kinetic feature of high monomer exponent is considered to be due to higher order of stabilization of the initiating complex (C) in presence of the respective solvents. In the presence of the retarding solvents, very low or zero initiator exponents were also observed, depending on the nature and concentration of the solvents used. The deviation from the square‐root dependence of rate on initiator concentration becomes higher at high solvent and initiator concentrations in general. This novel deviation is explained on the basis of initiator termination, probably via degradative chain transfer involving the solvent‐modified initiating complexes and the propagating radicals.
Chemical changes in polymeric photodielectric media used in holographic recording
Authors: Freilich Y. L. , Levy M. , Reich S. 
Published: April 2003

AbstractPhotochemical response of two thick photodielectric holographic recording systems was studied by using a 488 nm argon laser line. These systems are made of poly(methyl methacrylate) or poly(methyl α‐cyanoacrylate) with p‐benzoquinone as sensitizer. It was found that in both systems, photochemically induced branching, followed by crosslinking of the polymeric chains provide the major effects that modulate the index of refraction of these materials. The change in polymer structure as measured by intrinsic viscosity was correlated to the change in index of refraction, by which the holographic recording process is accomplished.
Polymerization of ordered tail‐to‐tail vinyl stearate bilayers
Authors: Enkelmann V. , Lando J. B. 
Published: April 2003

AbstractThis study is a continuation of previous work done in this laboratory which has demonstrated the possibility of polymerizing built‐up monomer multilayers in the solid state. In the present work, the formation, structure, and solid‐state polymerization of multilayers of vinyl stearate which can be built up by the method of Langmuir and Blodgett were studied. A new technique to polymerize such films under the water surface was developed. This made possible the formation of poly(vinyl stearate) multilayers with different molecular orientations through bilayer polymerization. The mechanism of deposition and the structure and properties of head‐to‐tail and head‐to‐head, tail‐to‐tail poly(vinyl stearate) multilayers were investigated by using Fourier‐Transform infrared spectroscopy, x‐ray diffraction, and electron diffraction.
Hydrolysis of activated esters catalyzed by L‐histidine graft copolymers
Authors: Overberger C. G. , Dixon K. W. 
Published: April 2003

AbstractA graft copolymer of L‐histidine on polyethylenimine has been demonstrated to be an efficient catalyst for the hydrolysis of activated phenyl esters in aqueous systems. A lack of any significant cooperative effects between neighboring imidazoles or amines has been shown by a study of the catalytic solvolysis of p‐nitrophenyl acetate at varying pH. A similar study with 4‐acetoxy‐3‐nitrobenzoic acid has displayed a bell‐shaped pH‐rate profile indicative of electrostatic interactions between the catalyst and substrate. Hydrophobic interactions were also evident from an investigation of the hydrolytic rates of a series of 4‐acyloxy‐3‐nitrobenzoic acids. In an attempt to demonstrate stereospecific catalyzed reactions, the hydrolyses of optically active esters catalyzed by the optically active copolymer were studied.
Chloromethylation of polyphenylsiloxane prepolymers by silylation
Authors: Llauro M. F. , Bartholin M. , Guyot A. 
Published: April 2003

AbstractSilylation of nonequilibrated phenyl‐T‐siloxane polycondensates by dimethylchloromethylchlorosilane involves only a small part of the silanol groups present in these prepolymers. At room temperature, silylation and condensation of the silanol groups occur at the same time. This condensation can be either intermolecular only or both intermolecular and intramolecular, depending on the initial condensation state of the prepolymer. It seems that no condensation reactions take place when the reaction is carried out with reflux. In any case, and even with strongly reactive disilazanes, no more than 35% of the silanol groups are consumed. The results give some information about a polymer, the structure of which is (after all) rather badly known.
Study on wholly aromatic polyamides containing methyl‐substituted phenylene linkage
Authors: Takatsuka Ryozo , Uno Keikichi , Toda Fujio , Iwakura Yoshio 
Published: April 2003

AbstractIn order to study the influence of chemical modification on properties of polyamides, wholly aromatic polyamides have been synthesized from p‐phenylenediamine, its 2,5‐dimethyl and 2‐methyl derivatives, m‐phenylenediamine, its 2‐methyl and 4‐methyl derivatives, and terephthaloyl and isophthaloyl dichlorides by solution polycondensation at low temperature. The thermal stability and solubility of the methyl‐substituted polyamides were compared with those of unsubstituted ones. The introduction of methyl groups in a polymeric chain led to a decrease in their thermal stability to different degrees depending on the positions of methyl groups, accompanied by an increase in their solubility. The unsymmetrical introduction of methyl groups in benzene rings had a greater effect on the increase in solubility of polyamide than did symmetrical methyl groups.
Radical polymerization of muconic acid and ethyl muconate
Authors: Bando Yoshifumi , Dodou Takeshi , Minoura Yuji 
Published: April 2003

AbstractMuconic acid (Mu‐acid) was found to polymerize to trans‐1,4‐poly(Mu‐acid) with the use of azobisisobutyronitrile (AIBN) as an initiator. Similarly, a muconic acid derivative, ethyl muconate (EMu), was readily polymerized through a trans‐1,4 addition mechanism by the use of a radical or anionic catalyst, but did not polymerize when a cationic catalyst such as boron trifluoride etherate was used. Moreover, the copolymerization of Mu‐acid and EMu with various comonomers such as styrene, acryronitrile, and 2‐vinylpyridine was carried out and Q–e values of Mu‐acid and EMu are discussed. These substituted diene monomers always polymerized through trans‐1,4 addition with all catalysts and any comonomers.
Metal chelates in vinyl polymerization. I. Ferric dipivaloylmethide as an initiator
Authors: Prabha R. , Nandi U. S. 
Published: April 2003

AbstractThe behavior of the chelate, ferric dipivaloylmethide, Fe(DPM)3, in vinyl polymerization systems was investigated. The polymerization was found to be of free‐radical nature. The rate of polymerization was proportional to the square root of the concentration of the chelate. The monomer exponent was close to 1.5 for the Fe(DPM)3‐initiated polymerization of styrene and methyl methacrylate. The kinetic and transfer constants and activation energies for these systems have been evaluated. Spectral studies revealed the possibility of a complex formation between the chelate and the monomer. A kinetic scheme for the Fe(DPM)3‐initiated polymerization is derived based on this initial complex formation.
Metal chelates in vinyl polymerization. II. Mechanism of initiation by Fe(DPM)3
Authors: Prabha R. , Nandi U. S. 
Published: April 2003

AbstractThe nature of the interaction between the unsaturated monomer and the chelate, Fe(DPM)3, is studied in detail. The interaction is found to occur only in solution. The stoichiometry of interaction and the equilibrium constant are evaluated. With the help of spectral evidence, attempts are made to point out the specific sites of interaction.
Dielectric study of viscose rayon and viscose hydrocelluloses. I.
Authors: Shinouda H. G. , Hanna A. A. , Kinawi A. 
Published: April 2003

AbstractBoth dielectric and x‐ray results on viscose rayon and its hydrolysis residues show a rapid increase in the lateral order arrangement of the fiber chains in the earlier stages of hydrolysis. On the other hand, a divergence between the two measurements is found in the later stages of acid action. This is explained in terms of the role played by the fractions of molecular low dimensions which are in sensitive to x‐ray diffraction but contribute to the polarizability of the dielectrics.
Poly(vinyl chloride)–poly(ethylene oxide) block copolymers: Synthesis and characterization
Authors: Laverty John J. , Gardlund Zack G. 
Published: April 2003

AbstractPoly(vinyl chloride)‐poly(ethylene oxide) block copolymers have been synthesized in solution and emulsion. The polymers were made by first synthesizing macroazonitriles through the reaction of 4,4′‐azobis‐4‐cyanovleryl chloride with hydroxy‐terminated poly(ethylene oxide) of varying molecular weights. These macroazonitriles had molecular weights in the range of 3000–88,000 and degrees of polymerization from 5 to 24. Thermal decomposition of the azolinkages in the presence of vinyl chloride monomer yielded block copolymers containing form 2 to 20 wt % poly(ethylene oxide). The structures of the block copolymers were characterized by spectrometric, elemental and molecular weight analyses. The possibility of some graft polymerization occurring via free‐radical extraction of a methylene hydrogen from the poly(ethylene oxide) was considered. Polymerization of vinyl chloride with an azonitrile initiator in the presence of a poly(ethylene oxide) yielded predominately homopolymer with some grafted poly(vinyl chloride).
Determination of alternation in copolymers by the excimer fluorescence method
Authors: Alexandru L. , Somersall A. C. 
Published: April 2003

AbstractA novel method has been developed for the determination of the extent of alternation in copolymers in which one of the comonomers contains a fluorescent chromophore capable of intramolecular excimer formation. The ratio of excimer to monomer fluorescence intensity is linearly correlated with the fraction of adjacent fluorescent chromphores to isolated fluophores on the chain. The method is illustrated for the case of styrene‐acrylonitrile copolymers.
Functional monomers and polymers. XXXV. Oxidation of hydroquinone catalyzed by Cu(II)–polyelectrolyte complexes
Authors: Sato M. , Inaki Y. , Kondo K. , Takemoto K. 
Published: April 2003

AbstractOxidation of hydroquinone catalyzed by copper(II) complexes of poly‐1‐vinylimidazole, vinylamine‐vinylacetamide copolymer, and polyethyleneimine was studied in aqueous solution at 25°C. The rate of oxidation was determined spectrophotometrically over several pH values. The rate of copper(II) reduction was evaluated from copper(I)–cuproin complex formation, and the reoxidation of copper(I) to copper(II) was observed by visible spectroscopy. Among the copper(II) complexes, poly‐1‐vinylimidazole complex exhibited excellent catalytic activity, which amounted to over 20 times that of aqueous copper(II) ion solution, while the reduction of copper(II) in the former system was slower than that in the latter system. The reoxidation of copper(I) to copper(II) was found to be completed immediately in the presence of polymer ligands such as poly‐1‐vinylimidazole, while copper(I) ion was only slowly reoxidized. The discussion of the reaction mechanism emphasizes the importance of the reoxidation process.
Interaction between dyes and polyelectrolytes. VI. Metachromatic behavior of methylene blue induced by potassium poly(vinyl sulfate) and its homologs
Authors: Shirai Masamitsu , Nagatsuka Tatsuki , Tanaka Makoto 
Published: April 2003

AbstractEffect of structure of potassium poly(vinyl sulfate) and its homologs on the metachromatic behavior of methylene blue was investigated spectrophotometrically. The metachromatic behavior with addition of polyanions was followed by the changes in the molar extinction coefficient of the 664 nm band of methylene blue and in the wavelength of metachromatic band. Important factors for metachromasy were the number of anionic sites per polymer molecule, the degree of polymerization, and the flexibility of polymer chain. It was found that the amount of KCl or urea required to destroy the metachromasy was a useful measure for estimating the binding strength of methylene blue to polyanions.
Synthesis and properties of new potentially nonthrombogenic polymeric materials
Authors: Ferruti Paolo , Arnoldi Daniela , Marchisio Maria Antonietta , Martuscelli Ezio , Palma Mario , Riva Fernando , Provenzale Luciano 
Published: April 2003

AbstractA new family of block copolymers have been synthesized and characterized. These copolymers have a central block deriving from the polyaddition of N,N′‐dimethylethylenediamine to 1,4‐bis‐acryloylpiperazine, and lateral blocks of polystyrene. Preliminary biocompatibility tests have demonstrated that these new products show promise as long‐acting nonthrombogenic materials.
Nouvelle méthode de détermination des taux de réativité des copolymères par résonance magnétique nucléaire: Application aux poly(méthacrylate de méthyle–chlorure de vinylidène)
Authors: Chiang Ta Chi , Pham Quang‐Tho , Guyot Alain 
Published: April 2003

AbstractConstant‐composition copolymers of methyl methacrylate and vinylidene chloride produced by radical copolymerization are studied by 1H‐NMR at 60 and 250 MHz. The different methods of the literature for the derivation of reactivity ratios from either the copolymer composition or the sequence average lengths, or even the diad distribution, are applied but lead to rather dispersed results. A new graphical method is proposed, based on the use of peculiar values of the triad distribution functions. It allows us to detect a penultimate effect for the vinylidene chloride‐rich region. In the same range, a change in tacticity of the diads and triads on the methylmethacrylate sequences, as compared with homopolymers, is observed; it suggests that the anomaly is caused by the competition of the depropagation reaction.
Mechanism of emulsion polymerization of styrene in soap‐free systems
Authors: Goodall A. R. , Wilkinson M. C. , Hearn J. 
Published: April 2003

AbstractThe formation and growth of monodisperse polystyrene latex particles in the absence of added surfactant has been studied by sampling polymerization reactions at different times and determining the surface and bulk properties of the latex. A large number of nuclei in excess of 5 × 1012/ml were generated during the first minute of reaction, but this fell due to coagulation until a constant number (1011−1012/ml) was reached. The rate of polymerization per particle was then found to be proportional to the particle radius. Gel‐permeation chromatography has shown that the initial particles consist mainly of material of MW 1000 with a small amount of polymer up to MW 106, and the presence of this low molecular weight polymer, which in many cases can still be detected after 100% conversion, is taken as being indicative of particle formation via a micellization‐type mechanism involving short‐chain (MW 500) free‐radical oligomers. M̄n values determined for the latex particles throughout the course of reactions show that the molecular weight increases to a maximum of about 105 as the particles grow. The presence of anomalous regions within the particles has been confirmed by transmission electron microscopy, scanning electron microscopy, and gas adsorption studies. It has also been found possible to re‐expose these regions within apparently homogeneous particles by stirring with styrene monomer; this is indicative of a molecular weight heterogeneity within the latex particles. The presence of sulfate, carboxyl, and hydroxyl groups upon the latex particle surfaces has been determined by conductometric titration.
Cationic graft copolymerization of styrene onto poly(vinyl chloride) initiated by phosphorus trichloride
Authors: Taninaka Takumi , Iwamoto Kohji , Minoura Yuji 
Published: April 2003

AbstractThe effect of some organic halides on the cationic polymerization of styrene (St) initiated by phosphorus trichloride (PCl3) was studied to clarify the initiation mechanism on the cationic polymerization. Addition of organic halides caused an acceleration to some extent. Further, cationic graft copolymerization of St onto poly(vinyl chloride) and polychloroprene was carried out. In each case, grafting efficiency was lower than 10%. These results in the cationic polymerization of St by PCl3 in nitrobenzene support the assumption that the initiation step is caused by the dissociation of two molecules of PCl3 to ion pairs.
Studies of vulcanization with tetramethylthiuram disulfide and sulfur vulcanization accelerated by tetramethylthiuram disulfide of styrene–butadiene rubber in presence and absence of dicumyl peroxide
Authors: Das C. K. , Ghosh A. K. , Banerjee S. 
Published: April 2003

AbstractThe salient features of nonelemental sulfur vulcanization by tetramethylthiuram disulfide (TMTD) and elemental sulfur vulcanization promoted by TMTD both in presence and absence of ZnO and stearic acid have been studied. In stock containing TMTD, a higher rate constant value for dicumyl peroxide (DCP) decomposition was observed. TMTD decreases the crosslinking density due to DCP depending on its concentration. An entirely radical mechanism has been advanced in the absence of ZnO. ZnO or ZnO–stearic acid seems to alter the entire course of reaction. The rate of crosslinking increases in the presence of ZnO or ZnO–stearic acid. Moreover, crosslinks are formed additively (further supported from the activation energy data), and mixed crosslink formation has been confirmed by the methyl iodide test of the vulcanizates. Stearic acid has no effect on crosslink formation. An ionic chain mechanism has been postulated in the presence of ZnO, as suggested by British authors.
Binding of Cu(II) to poly(methacrylic acid)
Authors: Kolawole E. G. , Mathieson S. M. 
Published: April 2003

AbstractThe binding of Cu(II) ions to partly neutralized poly(methacrylic acid) (PMA) has been investigated by potentiometric titration and dialysis to determine the stoichiometry the Cu–PMA complexes formed. Partly ionized PMA was titrated with solutions of the metal ion to enable a large range of metal ion/polymer ratios to be studied. Combination of the results from these two techniques at ionic strength 0.1 indicates that at very low Cu(II)/polymer ratios, a 4:1 complex exists, but at higher ratios the complex breaks down to give a mainly 2:1 coordination with some 1:1 binding. Conductance titrations support these results. Viscometric titrations show strong interactions between the metal and polymer, preventing the full extension of the polyion at high degrees of ionization, and spectrophotometric titrations support the existence of at least two types of complexes in the solution.