bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical polymerization of various alkyl methacrylates in liquid crystalline solvents
Authors: Tanaka Yoshio , Yamaguchi Fumio , Shiraki Masaru , Okada Akira 
Published: April 2003

AbstractThe polymerization of methacrylates of methyl, ethyl, butyl, hexyl, octyl, dodecyl, and octadecyl alcohols was studied with 2,2′‐azobisisobutyronitrile in the smectic, nematic, cholesteric, and isotropic liquid phases at 50–75°C. N‐(4‐Methoxyphenylmethylene)phenylamine, N‐(4‐ethoxyphenyl‐methylene)‐4‐butylphenylamine, cholesteryl octadecanoate, and benzene were used as the solvents. The viscosities of the polymers were enhanced in the mesomorphic solvents. The polymer was converted to the corresponding poly(methyl methacrylate) through hydrolysis and esterification. Tacticities of the resultant poly(methyl methacrylates) were determined by nuclear magnetic resonance spectroscopy. The isotacticities of the polymers obtained in the smectic and the nematic phases were basically the same and appeared to be larger than those of the polymers in the cholesteric and isotropic liquid states. The polymerization of the methacrylates of butyl and longer‐chain alcohols deviated from Bernoullian statistics and gave polymers more isotactic than those of methyl and ethyl methacrylates.
Effect of photooxidation of polystyrene on its dielectric properties. II. Use of dielectric loss measurements to study photooxidation
Authors: Weir N. A. 
Published: April 2003

AbstractDielectric loss measurements have been applied to study the short‐wave (λ = 254 nm) and long‐wave (λ > 300 nm) photooxidation of polystyrene which had been prepared using both free radical and anionic initiator. The high‐frequency loss peak, attributable to carbonyl products of oxidation is a sensitive monitor of the rate of oxidation, the sensitivity being greater than that of manometric measurements. The data are specific to carbonyl compounds and the technique is particularly suitable for studying the surfaces, on which most of the above photooxidation occurs with polystyrene. Effects of radiation intensity and oxygen pressure were also studied. The measurements have permitted a more detailed study of the long‐wave photooxidation process than has previously been undertaken, and the results emphasize differential reactivities of radically and anionically prepared polymers. Results are interpreted in terms of initiation by both impurities and charge‐transfer complexes.
Polymerization of aromatic nuclei. XVIII. Polymerization of benzene to poly‐p‐phenylene by aluminum chloride–air–water
Authors: Durham Judith E. , McFarland Kathryn N. , Kovacic Peter 
Published: April 2003

AbstractAlthough the reaction of benzene with aluminum chloride has been quite thoroughly examined by prior investigators, the present report is the first one on formation of poly‐p‐phenylene in this system. Optimum conditions, which gave low yields, involved 7 days at 49–51deg;C. The presence of oxygen (oxidant) and presumably water (cocatalyst) was necessary in order for polymerization to occur. Physical and chemical properties, e.g., behavior toward Br2 and H2O2–CH3CO2H, indicate that the polymer structure is slightly different from that of the material from C6H6–AlCl3–CuCl2. The polymer from C6H6–AlCl3 may possess a lower molecular weight and exhibits a greater degree of structural irregularity in the form of dihydrobenzene, p‐quinoid, or polynuclear regions. In the chemical studies, various compounds were used as models (tetrahydroquaterphenyl, triphenylene, and lower p‐polyphenyls).
General molecular weight‐lowering side reaction in the thermal condensation of aromatic methyl esters with aromatic amines and hydrazides
Authors: Flannigan Jerry E. , Mortimer George A. 
Published: April 2003

AbstractThe direct thermal condensation of aromatic methyl esters with aromatic amines and hydrazides was studied. Using model compounds, it was learned that N‐methylation of amines (both aromatic and aliphatic) and hydrazides is inherent at temperatures required for condensation polymerization. This side reaction prevents attainment of high molecular weight polyamides, polyhydrazides, or polyoxadiazoles from the corresponding difunctional aromatic monomers by heat alone. Reported catalysts for the condensation reaction do not prevent the side reaction.
Esterolytic activity of imidazole‐containing polymers. Hydrophobic influences in copoly[1‐alkyl‐4‐ or 5‐vinylimidazole/4(5)‐vinylimidazole]‐catalyzed hydrolysis of 3‐nitro‐4‐acyloxybenzoic acids
Authors: Overberger C. G. , Kawakami Y. 
Published: April 2003

AbstractWater‐soluble copolymers containing imidazole and N‐alkylated imidazole pendant groups have been synthesized in order to investigate the hydrophobic interactions between polymeric catalysts and long alkyl chain ester substrates. Copoly[1‐methyl‐4‐vinyl‐imidazole/4(5)‐vinylimidazole],copoly[1‐methyl‐5‐vinylimidazole/4(5)‐vinylimidazole], copoly[1‐ethyl‐5‐vinylimidazole/4‐(5)‐vinyl‐imidazole] and copoly[1‐propyl‐5‐vinylimidazole/4(5)‐vinylimidazole] were synthesized and their catalytic activity toward 3‐nitro‐4‐acyloxybenzoic acid substrates (Sn−) was determined in 28.5% ethanol–water and in water and compared with that of the mixtures of homopolymers. Hydrophobic interactions were important for rate enhancement of the hydrolysis of long‐chain ester substrates compared to that of short‐chain ester substrates. The copolymers catalyzed the hydrolysis of 3‐nitro‐4‐dodecanoyloxy‐benzoic acid (S12−) about two times faster than the mixtures at pH 7.11 in 28.5% ethanol–water. The hydrolysis of S12− by the copolymers was about five times faster in water than 28.5% ethanol–water.
Anionic polymerization with alkaline‐earth counterion. I. Preparation and characterization of dicarbanionic oligostyrylbarium and ‐strontium in tetrahydrofuran
Authors: Mathis Claude , Christmann‐Lamande Lydia , François Bernard 
Published: April 2003

AbstractDicarbanionic oligostyrylbarium or ‐strontium, PS=Ba++ and PS=Sr++, were prepared by reacting styrene with finely divided barium or strontium in THF or THP. The effects of reaction temperature, monomer, and metal concentration were described. Difunctionality of these living oligomers is confirmed from calculated and observed molecular weight data and also from conductivity measurements. λmax of carbanions is found to vary with DP. At 25°C it decreases from 368 nm for dimers to 359 nm for DP > 10. As observed for monocarbanionic polystyrylbarium (PS−)2Ba++, λmax of PS=Ba++ of high DP decreases with temperature, while λmax of PS=Ba++ of low DP increases with decreasing temperature. At −100°C the difference between the two extreme values is about 30 nm. Similar results are obtained with PS=Sr++. Such unusual spectral properties are interpreted, on the basis of excitation molecular theory, in terms of ring structures for the living oligomers.
Haloaldehyde polymers. IX. Polybromodichloroacetaldehyde
Authors: Lipp D. W. , Vogl O. 
Published: April 2003

AbstractBromodichloroacetaldehyde was synthesized by two methods. The first synthesis started from chloral, which was allowed to react with Ph3P and the resultant compound brominated and hydrolyzed to give bromodichloroacetaldehyde in an overall yield of 60%. Purification by repeated distillation from P2O5 gave polymerization grade bromodichloroacetabldehyde. Bromodichloroacetaldehyde could also be synthesized by bromination of dichloroacetaldehyde diethyl acetal. The yields of this synthesis were only 20–30%, and the aldehyde could not be purified readily to give polymerization grade monomer. Bromodichloroacetaldehyde could be homopolymerized at −30°C with anionic and also some cationic initiators to a polymer which was insoluble and did not melt but degraded to monomer above 200°C. The ceiling temperature of the polymerization was −15°C in 1M solution. Bromodichloroacetaldehyde could also be copolymerized with isocyanates, primarily aryl isocyanates, and also with chloral.
ESCA applied to polymers. XXI. Investigation of sample‐charging phenomena
Authors: Clark D. T. , Dilks A. , Thomas H. R. 
Published: April 2003

AbstractSample‐charging phenomena arising in the ESCA experiment have been investigated for a series of polymers. For samples studied as films or powders mounted insulated from the spectrometer probe and for gold under similar conditions it is shown that over a wide range of operating conditions, equilibrium charging shifts are characteristic of the sample and show a strong dependence on the theoretically calculated total photoionization cross sections. The surface sensitivity of the phenomenon has been demonstrated by monitoring changes in charging shifts as a function of hydrocarbon contamination. For polymer films mounted directly in contact with the spectrometer, the charging shifts exhibit time‐dependent behavior. The utility of studying sample‐charging shifts as an interesting phenomenon in its own right is demonstrated by reference to changes which occur consequent upon surface modification of an ethylene–tetrafluoroethylene copolymer system in RF plasmas excited in inert gases.
Charge‐transfer complexes as polymerization inhibitors. I. Amine–chloranil complexes as inhibitors for the radical polymerization of methyl methacrylate
Authors: Yassin Ahmady A. , Rizk Nadia A. 
Published: April 2003

AbstractCharge‐transfer complexes of N,N‐dimethylaniline (DMA) and triethylamine (TEA) with chloranil have been investigated as inhibitors for the sensitized polymerization of methyl methacrylate (MMA) in bulk and in solution. Complete inhibition is achieved by the complexes of both amines followed by retardation only in case of DMA. The higher inhibiting efficiency of the TEA complexes is attributed to their greater stability. The polymers formed in the presence of chloranil alone or its complexes with both amines are quinonoid and contain no combined nitrogen. The results support the idea that inhibition reaction involve electron transfer from the growing chains to the quinone, with formation of molecular complexes of polymeric cations and semiquinone anions. The latter are the actual inhibiting species, so that the efficiency of inhibiting depends on their concentration, which is determined by the stability of the molecular complexes formed. The inhibition reactions should accordingly be considered as oxidation–reduction processes in which the growing chains are the electron donors. The suggested mechanism affords an explanation for the great differences in the inhibiting power of a particular quinone for the polymerization of different monomers.
Polymerization of oriented monomers. II. Polymerization of 4‐vinylpyridine perchlorate in micellar aggregates
Authors: Paleos C. M. , Dais Photis 
Published: April 2003

AbstractPolymerization of 4‐vinylpyridinium perchlorate (I) is studied under isotropic and anisotropic conditions. Anisotropy or orientation of I may be achieved by micelle formation in concentrated aqueous or acid solutions, i.e., above the monomer's critical micelle concentration (CMC). Some properties of the isotropically and anisotropically obtained polymers are comparatively studied with the emphasis placed on the elucidation of their structure by 13C‐NMR spectroscopy. By the same spectroscopic technique the microstructure of 1,2‐polymer is further investigated in conjunction with the proposed polymerization model. It is concluded that polymer structure is affected by the organization of the monomers into micelles whereas their microstructure is not.
Thermal degradation of the polyurethane from 1,4‐butanediol and methylene bis(4‐phenyl isocyanate)
Authors: Grassie N. , Zulfiqar M. 
Published: April 2003

AbstractA polyurethane prepared from 1,4‐butanediol (BD) and methylene bis(4‐phenyl isocyanate) begins to evolve volatile degradation products at approximately 240°C. By a combination of thermal analysis methods (TVA, TG, and DSC) and examination of the volatile and involatile products by using a combination of GLC and infrared and mass spectrometric analysis, it is shown that the total reaction comprises a primary depoly‐condensation process in which the two monomers are formed, followed by the subsequent reaction of these monomers to form the volatile products, tetrahydrofuran, dihydrofuran, carbon dioxide, water, butadiene, hydrogen cyanide, and carbon monoxide and residual carbodiimide and urea structures. A mechanism, which accounts for all these products, has been formulated and tested.
Diffusion effects in the oxidative degradation of vulcanized rubbers. II. Transient rate of chain scission
Authors: Ono K. , Kaeriyama A. , Murakami K. 
Published: April 2003

AbstractThe effect of diffusion in the oxidative degradation of cis‐1,4‐polyisoprene vulcanizates was estimated by the analysis of the transient state of diffusion and oxidative degradation. An expression for the number of network chain scissions was obtained by solving the diffusion equation, which takes into account first‐order oxygen consumption as well as constant scission efficiency. A practical method was proposed to analyze the transient process, which makes it possible to estimate diffusion coefficient and first‐order rate constant independently. It was shown that the same analytical procedure would be applicable to the concentration jump method. The diffusion coefficient thus obtained was somewhat lower than the extrapolated value from the low‐temperature data which was obtained in the absence of oxidation. Possible reasons responsible for this discrepancy were discussed.
Constitution moléculaire d' α,ω‐difluoro‐μ‐oxo‐poly(méthylphosphanoxy diméthylsilanes): Mise en evidence d'une forte tendance à l'alternance régulière des centres siliciés et phosphorés à l'equilibre
Authors: Pace Simonne C. , Riess Jean G. 
Published: April 2003

AbstractThe purpose of this study was to gain a closer knowledge of the molecular constitution of the linear fluorine‐terminated oxygen‐bridged methylphosphanoxy/dimethylsilane polymers, for example, to find evidence for preferential sorting (or, on the contrary, for random scattering) of the substituents and building units. The title polymers were prepared by reaction of MeP(O)F2 with cyclic dimethylsiloxanes (Me2SiO)n (n = 3 or 4). An equilibrium is reached in the redistribution of fluorine vs. bridging oxygen atoms among the phosphorus and silicon‐based centers, and among the resulting building units, after about 2 months at 120°C. The excellent resolution of the 1H‐NMR spectra (Fig. 2), even at 60 MHz, allowed identification of seventeen different fragments (Table II). Nineteen equilibrated samples of varied overall compositions (R = F/(Si + P); R′ = P/(Si + P)) have been analyzed (Table IV), and their molecular constitution is described by a set of four basic constants. The fundamental features which govern the structure of these polymers are as follows. (a) The regular (Si‐O‐P) alternation of the two different centers, which is thermodynamically favored, as shown by the linkage constant K0 = [Si‐O‐Si][P‐O‐P]/[Si‐O‐P]2 ≃ 104, which describes the sorting of the silicon and phosphorus atoms on the bridging oxygens, and which deviates by four orders of magnitude from its random value of 0.25. (b) A somewhat surprising lack of preferential distribution of fluorine and oxygen between the two centers (KI = [MeP(O)F2][Me2SiO1/2]2/[Me2SiF2]‐[MeP(O)(O1/2)2]) differs little from (a), which contrasts with the preferential affinity of fluorine for silicon and oxygen for phosphorus (KI ≃ 107) that was found when F atoms and OCH3 groups were exchanged between the same centers. (c) The sorting of the fluorine atoms and oxygen bridges on each center, to give neso molecules and the terminal and medium building units, resulting in a slight preference for the formation of the terminal units, as expressed by
Bulk polymerization of methyl methacrylate electroinitiated by tetrabutylammonium salts
Authors: Pistoia Gianfranco , Ingo Gabriel Maria 
Published: April 2003

AbstractThe radical electroinitiated polymerization of methyl methacrylate has been performed in solutions of tetrabutylammonium salts. TBANO3 is by far the most efficient, because of the relatively low anodic potential required for the oxidation to the radical. The influence of factors such as temperature, current density, and salt concentration on yields and molecular weights has been examined. The absence of a gel effect allows the onset of a steady state in which the polymerization rate is first‐order with respect to monomer.
Study of gel formation in the polycyclotrimerization reaction as typified by polycyanate synthesis
Authors: Korshak V. V. , Pankratov V. A. , Ladovskaya A. A. , Vinogradova S. V. 
Published: April 2003

AbstractThe process of gel formation in the reaction of polycyclotrimerization of 2,2‐bis(4‐cyanatophenyl) propane has been studied as a function of the nature of solvent, monomer concentration, kind and concentration of catalyst, temperature of the process, and the way in which the reaction is conducted. The gel point and the dependence of the gel yield on the degree of the system conversion vary with the conditions of the process conduction and the solvent used. It was found also that the type of the catalyst affects the parameters indicated above only in certain solvents. A change in the monomer concentration has been found to affect differently the gel point of the system, depending on the nature of the solvent. The experimental data obtained have been compared with the results of the theory of gel formation developed for the process of polycyclotrimerization by Fukui and Yamabe. The dependence of the process kinetics on the type and concentration of catalysts has been investigated. No marked influence of temperature on the regularities of gel formation has been disclosed.
Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. I. γ irradiation
Authors: Yamamoto Fumio , Yamakawa Shinzo , Kato Yoshinori 
Published: April 2003

AbstractMutual irradiation of polyethylene (PE) in methyl acrylate vapor easily forms a poly(methyl acrylate) (PMA) homopolymer layer on the inner graft copolymer layer consisting of both PE and PMA components as a result of the rapidly increasing surface‐graft composition. This growth process of surface grafting has been found to provide some specific kinetic features different from those in other surface‐grafting systems. With formation of the surface homopolymer layer, low‐ and highdensity PE sheets give the same grafting rate, whereas both sheets give different rates in grafting stages or conditions in which the homopolymer layer is not formed. This result indicates that most monomers, penetrating across the surface, are entrapped or consumed in the surface homopolymer layer; accordingly the rate becomes independent of the type of PE sheets that have significantly different diffusion coefficients. The thickness of the inner graft copolymer layer, which is kept constant after homopolymer‐layer formation, increases with decreasing dose rate and with increasing monomer vapor pressure and temperature. This behavior can be qualitatively explained according to an equation for the initial steady‐state grafting depth.
Poly(carbon suboxide): A photosensitive paramagnetic ladder polymer
Authors: Yang N.‐L. , Snow A. , Haubenstock H. , Bramwell F. 
Published: April 2003

AbstractCarbon suboxide was found to give, on photo‐ and thermal‐polymerization, a photosensitive paramagnetic polymer. Studies of the kinetics of the ESR signal growth accompanying the polymerization process complement documented results obtained from monitoring the rate of polymer production and monomer disappearance. The spin concentration of the polymer increases with higher reaction temperature, reaching 2 × 1019 spin/g at a polymerization temperature of 105°C. The paramagnetism of poly(carbon suboxide) follows the Curie—Weiss law. Relaxation behavior at room temperature and g values for the spin systems have been obtained. The 105°C polymer shows a Weiss constant equal to 17°K and an extremely narrow ESR line width, ca. 10 mG, at 5°K. The 13C coupling constant from the selectively labeled polymer indicates π‐electron delocalization over the ladder polymer. The polymer paramagnetism can be further reversibly enhanced by visible light irradiation. The steady‐state concentration of the photo‐ESR signal is proportional to the square root of incident light intensity, with a quantum yield at room temperature for charge accumulation equal to 5% at an incident light level of 1015 photons/sec‐cm2. Fluorescence and excitation spectra of the soluble fraction of poly(carbon suboxide) are presented together with the quantum yield. The polymer has also been found to be an effective photopolymerization initiator at wavelengths longer than 340 nm.
Synthesis and property comparisons of random and alternating hybrid fluorocarbon–fluorosilicone copolymers
Authors: Riley M. O. , Kim Y. K. , Pierce O. R. 
Published: April 2003

AbstractThe synthesis of a number of random and alternating copolymers of a fluorosiloxane and a hybrid fluorocarbon‐fluorosiloxane are described, along with property comparisons. The random copolymers were prepared by silanol–chlorosilane condensation, while the alternating copolymer preparation involved the use of the novel silanol—silyl‐N‐methylacetamido condensation reaction, which was used to produce a high polymer, M̄n = 260,000. The physical properties of the two classes of polymers which were compared include: glass transition temperatures, reversion resistance, and thermal and oxidative weight loss. From these comparisons, it was possible to gauge the relative effects of backbone architecture, as well as monomer ratios, upon copolymer properties. Comparison of the thermogravimetric analysis (TGA) of both the random and alternating LS/FCS copolymer systems with the parent LS and FCS homopolymers indicates that the copolymer generally show little variation among themselves, but better thermal characteristics than either of the parents.
Particle nucleation in emulsion polymerization. I. A theory for homogeneous nucleation
Authors: Hansen F. K. , Ugelstad J. 
Published: April 2003

AbstractThis paper is the first in a series intended to clarify the particle nucleation mechanisms in emulsion polymerization. The theory for particle nucleation by precipitation of oligomeric radicals from the water phase is discussed and a model based on the diffusion, propagation and termination steps is presented. The physical factors that influence the capture rate of oligomers in particles are discussed, and qualitative expressions for the electrostatic repulsion and reversible diffusion are derived. These factors are shown to be able to explain the relatively slow absorption rate of oligomers in particles and micelles. A kinetic model for simultaneous particle nucleation and limited flocculation is presented. Numerical integration of this model shows that the particle number goes through a maximum and that simultaneous nucleation and flocculation of primary particles may take place after Interval I in an emulsion polymerization is finished.