bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trityl‐initiated copolymerizations of propylene oxide with tetrahydrofuran. VIII. Influence of reaction parameters
Authors: Blanchard L. P. , Gabra G. G. , Malhotra S. L. 
Published: April 2003

AbstractThe copolymerization of propylene oxide (PO) with tetrahydrofuran (THF) in dichloroethane (DCE) has been studied at −10, 0, +10, and +20°C. The reactions were initiated by triphenylmethyl cations associated with the following gegenions: PF6−, SbF6−, and AsF6−. The overall energies of activation (Eα of PO and Ea of THF) obtained with the three gegenions increase as one passes from PF6− to AsF6− then to SbF6−, though the magnitude of the increase in each case is not substantial. On the other hand, the associated frequency factors A show a considerable variation with the gegenion. The bimodal distributions of the molecular weights, obtained by GPC with the copolymer produced from reactions initiated with triphenylmethyl hexafluorophosphate, show that the proportions of the lower molecular weight component (L) decrease as the solvent is changed from DCE to toluene, and this is even more marked when bulk polymerization conditions are adopted. The proportions of the higher molecular weight component (H) however increase, as does its molecular weight. The GPC molecular weight distributions of the copolymers initiated with triphenylmethyl hexafluorophosphate in DCE to which water has been added, show that the molecular weight of component H decreases with increasing concentration of water, while that of component L remains practically unchanged at a value of 308. This corresponds to an average degree of polymerization (DP) of 4 to 5. The NMR and infrared spectra of copolymers prepared in the presence of still higher initial water concentrations indicate that the PO‐based polymer segments are present in excess of those required for a 1:1 copolymer.
Reaction of diisocyanates with alcohols. I. Uncatalyzed reactions
Authors: Anzuino G. , Pirro A. , Rossi O. , Friz L. Polo 
Published: April 2003

AbstractBecause diisocyanates are widely used raw materials in the production of urethane elastomers and foams, it is of particular interest, to know the contribution of secondary reactions to the overall reaction between diisocyanates and polyether glycols, because of the well known influence of crosslinks on the physicochemical properties of polyurethanes. A mathematical method is suggested to calculate rate constants for the primary and secondary reactions, the hypothesis being that the allophanate group is the main secondary product. The method has been verified with experimental data obtained by reacting models. In addition, the influence of the [NCO]/[OH] ratio and of temperature on the formation of the allophanate group has been studied. The method has been applied to the reaction of 4,4′‐diphenylmethane diisocyanate with poly(oxytetramethylene) glycol, a polyether glycol specifically designed for use in preparing polyurethanes. The results are in complete agreement with the experimental data.
Synthesis of polymaleamides by ring‐opening polyaddition reaction of N,N′‐disubstituted bisisomaleimides with diamines
Authors: Imai Yoshio , Ueda Mitsuru , Kanno Susumu 
Published: April 2003

AbstractThe ring‐opening polyaddition reaction of N,N′‐disubstituted bisisomaleimides with various diamines in N‐methyl‐2‐pyrrolidone at room temperature afforded polymaleamides having inherent viscosity up to 0.7 in almost quantitative yield. These polymers are a new class of homopolymaleamides and ordered alternating copolymaleamides. Almost all of the polyamides were soluble in a wide range of solvents such as dimethylsulfoxide, dimethylacetamide, m‐cresol, and formic acid. They did not show any melt temperature, and began to decompose at a temperature ranging between 200 and 300°C.
Preparation and addition polymerization of substituted 2‐oxazolines
Authors: McManus Samuel P. , Patterson William J. , Pittman Charles U. 
Published: April 2003

AbstractThe new oxazoline‐containing monomers, 4‐acrylyloxymethyl‐2,4‐dimethyl‐2‐oxazoline (AOMO), 4‐methacrylyloxymethyl‐2,4‐dimethyl‐2‐oxazoline (MAOMO), 4‐methacrylyloxymethyl‐2‐phenyl‐4‐methyl‐2‐oxazoline (PMAOMO), and the previously known monomer, 2‐isopropenyl‐4,4‐dimethyl‐2‐oxazoline (IPRO), were synthesized for addition polymerization studies. The monomers were homopolymerized in benzene using a free radical initiator and in aqueous media using emulsion techniques. Molecular weights of 8,000–15,000 (M̄w) were obtained for the homopolymers. Copolymerization studies were carried out with AOMO, MAOMO, and IPRO as M1, and methyl methacrylate (MMA), methyl acrylate (MA), styrene (STY), acrylonitrile (AN), and vinyl acetate (VA) as M2 for each case of M1. Relative reactivity ratios for the fifteen copolymers and Q and e values for the three oxazoline monomers were determined. The r1 values for AOMO and MAOMO copolymerizations indicated a lower value of k11 than expected, presumably because of steric effects. The r1 values in the IPRO copolymerizations were somewhat larger than expected. It was proposed that significant electron donation to the radical center of IPRO·by resonance effects occured.
Block and graft copolymers by selective cationic initiation. III. Synthesis and characterization of bigraft copolymers
Authors: Kennedy Joseph P. , Vidal Alain 
Published: April 2003

AbstractThe synthesis and characterization of new bigraft copolymers poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐styrene‐g‐α‐methylstyrene] (Nordel‐g‐PSt‐g‐PαMeSt) and poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐isobutylene] (Nordel‐g‐PSt‐g‐PIB) are described. The synthesis involves the use of a polyhydrocarbon backbone containing allylic chlorines and bromines (chlorobrominated Nordel) in conjunction with a suitable alkylaluminum compound to initiate selectively the polymerization of a monomer (generally styrene) from the chloride sites and subsequently to initiate the polymerization of another monomer (α‐methylstyrene or isobutylene) from the bromide sites. Conditions conductive to selective and sequential initiation have been worked out. The pure bigrafts are obtained by selective solvent extraction and their homogeneity (by gel permeation chromatography), overall composition (by nuclear magnetic resonance spectroscopy) and molecular weight (by osmometry) are determined.
Polymérisation anionique des diènes. III. Etude thermodynamique de la propagation du butadiène et de i'isoprène par les organo‐alcalins
Authors: Salle Robert , Essel Alain , Gole Jean , Pham Quang‐Tho 
Published: April 2003

AbstractThe present work is concerned with the influence of the polymerization temperature on the propagation mechanisms of polyisoprenyl‐ and polybutadienyl‐alkali metals. The thermodynamic parameters of the contact ion pairs and free ions propagations have been calculated. With Li+ in dioxane solvent, the vinyl propagation is stereospecific (for isoprene, the propagation is mainly 4–3). In comparison with benzene, the vinyl propagation of the polydienyl‐Li contact ions pairs should be due to complexation of Li+ by dioxane, an electron donor having a weak dielectric constant. In general, the stereospecificity of the propagation of contact ion pairs decreases with increasing counterion size; little difference has been observed with K+ and Cs+ ion pairs in dioxane and benzene media. For isoprene, the methyl substituant should have chiefly a steric effect in the propagation of free ions, whereas it should confer a polar character to the isoprene molecule in the presence of ions pairs.
Polymerizability of unsaturated monomers capable of forming stable radicals
Authors: Kato Masao , Takemoto Yutaka , Nakano Yasuhiko , Yamazaki Masahiro 
Published: April 2003

AbstractSome unsaturated monomers bearing hindered phenol and arylamine groups capable of forming stable radicals were prepared. Radical polymerizations of vinyl monomers having such groups were investigated with the use of azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide, and tetraethylthiuram disulfide as initiator. Polymerizations of these monomers went normally only when azobisisobutyronitrile was used as initiator. The other initiators inhibited polymerizations remarkably or completely. The results suggest that radicals resulting from benzoyl peroxide and cumene hydroperoxide or tetraethylthiuram disulfide abstract hydrogen of the phenol or the amine to produce the stable radicals, thereby inhibiting the polymerization. Meanwhile, carbon radicals resulting from azobisisobutyronitrile add selectively to the vinyl double bonds of the monomers to initiate the polymerizations. The vinyl derivatives as well as allyl derivatives and cinnamic acid derivatives copolymerize easily with conventional monomers such as styrene, maleic anhydride, and butadiene, again, only when azobisisobutyronitrile was used as initiator. Antioxidative properties for styrene copolymers and butadiene‐styrene copolymers incorporating the hindered phenol monomers were investigated.
Formation of free radicals in photoirradiated cellulose. III. Effect of photosensitizers
Authors: Hon Nyok‐Sai 
Published: April 2003

AbstractThe effect of several photosensitizers on the formation of free radicals in cellulose has been investigated. Radicals were generated with ultraviolet light, and examined by means of ESR techniques; irradiations were carried out at 77°K. On irradiation of the sensitized celluloses with light of λ > 3400 Å, samples treated with benzoyl peroxide, hydrogen peroxide, benzophenone, riboflavin, azobisisobutylonitrile, and metallic ions Cr2+ and Ni2+ exhibited single‐line spectra with line widths of 16 to 26 gauss. Samples treated with Pb2+ and Fe3+ exhibited three‐line and five‐line spectra, respectively. On irradiation with light of λ > 2537 Å, most of the sensitized samples exhibited five‐line spectra with different relative signal intensities. Among these, samples treated with Fe3+ manifested the most prominent spectra with the strongest relative signal intensities.
Polymerization of N‐vinylcarbazole by thionyl chloride
Authors: Biswas Mukul , Kamannarayana P. 
Published: April 2003

AbstractThe polymerization of N‐vinylcarbazole (NVC) initiated by SOCl2 in benzene and nitrobenzene solvents was studied at 32°C. Rp is first order with respect to SOCl2 concentration and also to NVC concentration up to a certain NVC concentration, after which it falls. Rate and the molecular weight increase with increasing dielectric constant of the medium. The rate and molecular weight are depressed by the addition of amines, thiophene, and water. The degree of polymerization is independent of SOCl2 and NVC concentration. A conventional cationic mechanism has been suggested, and a suitable kinetic scheme has been proposed in conformity with the findings.
Polymerization of ethylene oxide with potassium‐graphite inclusion compounds
Authors: Panayotov Ivan M. , Berlinova Iliyana V. , Rashkov Ilya B. 
Published: April 2003

AbstractThe polymerization of ethylene oxide (EO) in tetrahydrofuran (THF) initiated by inclusion compounds of potassium in graphite (C24K) at 50°C was studied. During the initial slow stage of the polymerization the catalyst efficiency increases, while during the second rapid stage the reaction proceeds at a constant concentration of the active centers. The influence of the catalyst and monomer concentrations on the concentration of the active centers and on the catalyst efficiency was studied. The existence of the slow stage is explained by diffusion of ethylene oxide between the graphite planes, where both initiation and initial chain growth take place. The diffusion of the growing chains from the catalyst into the solution brings about the formation of a necessary concentration of active centers in the solution, which ensures the rapid growth of the polymer chains under homogeneous conditions. An x‐ray study of the catalyst after polymerization shows a strongly disturbed crystal structure of the graphite. Poly‐(ethylene oxide) obtained at a higher degree of conversion, does not contain low molecular weight fractions.
Mass spectrometric investigation of polymers: Thermal degradation of truxillic and truxinic polyamides
Authors: Caccamese S. , Maravigna P. , Montaudo G. , Przybylski M. 
Published: April 2003

AbstractThe thermal degradation mechanism of four isomeric truxillic and truxinic polyamides were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact‐induced fragments. The results obtained have shown that the thermal degradation products are sensibly different for the head‐to‐head (hh) and head‐to‐tail (ht) polymers and that the predominant pyrolytic process is the cyclobutane ring cleavage. In the hh isomers, both symmetrical and asymmetrical cyclobutane ring cleavage was detected, while in the ht isomers only symmetrical cleavage occurs; this explains the noticeable difference found in the thermal stability of the two polymer types.
Study of radiation‐induced polymerization of vinyl monomers adsorbed on inorganic substances. III. Effect of p‐benzoquinone and ammonia on radiation‐induced polymerization of styrene adsorbed on silica gel
Authors: Fukano Kazuyuki , Kageyama Eiichi 
Published: April 2003

AbstractIn order to elucidate the mechanism of radiation‐induced polymerization of styrene adsorbed on silica gel, the effect of p‐benzoquinone and ammonia was investigated. The high molecular weight GPC peaks of both graft polymers and homopolymers decreased with increasing p‐benzoquinone concentration, while the low molecular weight peaks of both graft copolymers and homopolymers decreased with increasing ammonia concentration. The results indicate that the high molecular weight peaks of both graft and homopolymers are formed as a result of a radical mechanism and that the low molecular weight peaks of both types of polymers are formed by a cationic mechanism. In formation of both graft polymers and homopolymers both radical and cationic polymerization take place at the same time.
Polymers with a graphitic‐type structure. II
Authors: Kellman Raymond , Marvel C. S. 
Published: April 2003

AbstractFurther work has been done on the synthesis of a polymer from 1,4,5,8‐tetraaminoanthraquinone on 1,3,6,8‐tetraketo‐1,2,3,6,7,8‐hexahydropyrene which has a graphitic‐type structure. Improved purity of the starting materials, particularly of the tetraketone, has given a final product of better quality. The reaction conditions have been improved by lowering the temperature and increasing the time of the reaction.
Rigid rod‐random coil transformation, Mark‐Houwink constants, and Millich's intrinsic isoviscosity, [η]M, and isohydrodynamic volume, [η]MMM
Authors: Millich F. , Hellmuth E. W. , Huang S. Y. 
Published: April 2003

AbstractOn the basis of values of Mark–Houwink constants of rigid rod—polymer systems and their conformers a unique stage can be recognized which is common to all polymers of this type, independent of polymer conformation and solvent medium. The crude values derived for these polymer–solvent systems at 20–30°C. of Millich's intrinsic isoviscosity, [η]M, is 0.28 ± 0.04 dl/g, occurring at the coordinate molecular weight, MM, of 42,700, and produces a value of ca. 170 Å of Millich's isohydrodynamic polymer volume at this stage and temperature. Utility in the use of [η]MMM as a standard reference state, assuming reliable Mark–Houwink constants that obtain for strictly linear, monodisperse polymer samples, is indicated.
Thermal degradation of poly(tetramethyl‐p‐silphenylene) siloxane homopolymers and copolymers in nitrogen
Authors: Funt J. M. , Parekh R. D. , Magill J. H. , Shah Y. T. 
Published: April 2003

AbstractThe thermogravimetry (TGA) in nitrogen was measured for poly(tetramethyl‐p‐silphenylene)‐siloxane (TMPS) fractions with narrow molecular weight distributions and for block copolymers of TMPS and dimethyl siloxane (DMS) with varying composition. The measurements were made with the Perkin‐Elmer DCS IB‐TGA attachment which consists of a Cahn electrobalance and a wire‐wound furnace with programmable temperature controls. The weight loss curves for heating rates of 10, 20, and 40°C/min were analyzed using the method of Flynn and Wall. The analysis indicates that thermal degradation proceeds primarily by scission of the siloxane bond with an activation energy of 44 ± 3 kcal/mole for the uncatalyzed reaction and 13 ± 2 kcal/mole for the reaction occurring in the presence of residual catalyst. The thermal stability of the TMPS–DMS copolymer is impaired through increasing the concentration of the DMS component. Cyclic DMS trimer and TMPS monomer and dimer were observed by mass spectrometry which gave results consistent with the proposed mechanism of degradation.
Synthesis, characterization, and properties of block and bigraft copolymers
Authors: Kennedy Joseph P. 
Published: April 2003

AbstractThe syntheses of poly(styrene‐b‐isobutylene), poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐styrene‐g‐α‐methylstyrene], and poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐styrene‐g‐isobutylene] have been accomplished by using the principle of selective sequential initiation. This method makes use of the large differences in initiation rates that exist between labile organic chlorides and bromides when these halides interact with alkylaluminum compounds. Synthesis conditions have been worked out which allow composition control. These new AB blocks and bigrafts exhibit unusual mechanical and solubility properties, some of which will be described. For example, the Nordel‐g‐PSt‐g‐PIB bigraft exhibits only one low temperature transition (DSC, Rheovibron), suggesting an intimate aggregation of Nordel and polyisobutylene phases.
New developments in photochromic polymers
Authors: Smets G. 
Published: April 2003

AbstractNew developments on photochromic polymers have been obtained with systems containing spirobenzopyran derivatives. The importance of the chemical incorporation of the photochrome within the polymer backbone is stressed, and the influence of matrix orientation on the rate of fading is shown. Well known fatigue phenomena are illustrated on the basis of the changes of photostationary optical density on repeating the irradiation–dark recovery cycle. The photomechanical properties and characteristics of rubbery polyethylacrylates crosslinked with the photochrome bismethacrylate are considered in detail. Another principle of photochromism based on photodissociation phenomena is also discussed in the case of the photodissociation and photorecombination of anthracene derivatives and benzacridizinium tosylate, as well as in the case of the photodissociation and thermal recombination of benzpinacol groups incorporated in the polymer main chain. In these experiments in the solid state, it can be shown that the recombination involves always two successive steps: a rapid step corresponding to cage recombination and a second slow step related to diffusion and segment mobility (Tg) of the polymer.
Pyrolysis‐gas chromatography of polymers obtained by Friedel‐Crafts reactions of poly(vinyl chloride) with aromatic compounds
Authors: Cascaval C. N. , Schneider I. A. , Poinescu I. C. 
Published: April 2003

AbstractPyrolysis, in combination with gas‐chromatography technique, was used in the determination of the structure and study of the thermal degradation mechanism of the condensation polymers obtained by Friedel‐Crafts reactions of poly(vinyl chloride) with benzene, toluene, and naphthalene. The separation of the pyrolysis products was made using a column packed with chromosorb W (80–100 mesh) coated with 15% silicone SE‐52. The identification of the pyrolysis products resulted as a consequence of the thermal decomposition of condensation polymers and their semiquantitative estimation led to the final conclusion that the initial normal chlorine substitution in the macromolecular chain of poly(vinyl chloride) is followed by an important intramolecular cyclization reaction yielding 1,3‐methyleneindan units.
Block and graft copolymers by selective cationic initiation. IV. Physical properties of bigraft copolymers
Authors: Kennedy Joseph P. , Vidal Alain 
Published: April 2003

AbstractThe physical properties of bigraft copolymers, i.e., Nordel‐g‐polystyrene‐g‐poly(α‐methylstyrene) and Nordel‐g‐polystyrene‐g‐polyisobutylene, have been studied in terms of stress strain behavior, glass transition temperature, dynamic mechanical data, intrinsic viscosity versus temperature profile and solubility properties. These products are thermoplastic elastomers and show the presence of incompatible domains. Tg and dynamic‐mechanical data indicate an aggregation of the polystyrene and poly(α‐methylstyrene) phases.
Gamma‐ray induced polymerization of styrene in the presence of methanol
Authors: Beach T. J. , Burns C. M. , Huang R. Y. M. 
Published: April 2003

AbstractThe kinetics and molecular weight distributions (MWD) of the gamma‐ray induced polymerization of styrene in methanol were studied at 35°C, at low conversions and over a dose rate range of 2.76 × 103 to 2.74 × 104 rad/hr. The data obtained at low initial methanol content agreed with previously obtained results and the MWD of the polystyrene formed yielded a single unimodal peak with M̄n in the range of 35,000–480,000. However, at high initial methanol content and low dose rates, at least three peaks were clearly discernible over wide molecular weight distributions. The existence of these peaks is related to the kinetic data and the formation of three distinguishable regions in the polymerization system.
Maleimide polymers. III. Color reactions and kinetics
Authors: Haas Howard C. , Moreau Robert D. 
Published: April 2003

AbstractWe have shown previously that the free‐radical polymerization kinetics of maleimide can be explained by a scheme for retarded polymerization. The steps involve tautomerization of a growing maleimidyl chain to succinimidyl, the retarded addition of maleimide to the latter, and termination solely by resonance‐stabilized succinimidyl radicals. Combination termination is preferred, since this yields a very stable N,N′‐bisuccinimidyl structure. Other authors also invoke tautomerization to succinimidyl radicals which they believe terminate by disproportionation with growing maleimidyl chains to generate polymer with unsaturated endgroups. Free‐radical‐initiated polymaleimides are colored in the presence of base. Our measurements of the absorbance of polymaleimides at 387 and 500 nm in the presence of excess strong organic base show there is essentially no dependence on molecular weight. This suggests that the chromophoric groups are intramolecular and that color does not arise from the ionization of allylic protons associated with terminal double bonds. The near‐ultraviolet spectra of polymaleimides in slightly acidic media contain absorption bands at about 288, 320, and 360 nm. The structural impurities that account for these bands cannot be terminal unsaturation. We propose that the origin of these bands is pyrrolinone type structures which are formed by a retarded polymerization step through succinimidyl oxygen.
Synthesis of polypyrimidoquinazolinetetraones from N,N′‐bis(mesyloxy)pyromellitimide and aromatic diamines
Authors: Imai Yoshio , Ueda Mitsuru , Ishimori Motokazu 
Published: April 2003

AbstractA novel class of polypyrimidoquinazolinetetraones was synthesized by the polymerization of N,N′‐bis(mesyloxy)pyromellitimide with aromatic diamines in N‐methyl‐2‐pyrrolidone in the presence of triethylamine as an acid acceptor. The polymerization proceeded probably through the formation of ring‐opened adducts, followed by elimination and rearrangement yielding polyamide‐isocyanates, which in turn were cyclized to give polypyrimidoquinazolinetetraones. These polymers, which were soluble in strong acids, had inherent viscosities in the range of 0.17–0.27. Thermogravimetric analyses indicated that they began to decompose at around 450°C in air.