bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemistry of fiber‐forming polymers. I. Acrylonitrile copolymers and fibers containing ketone groups
Authors: Alexandru L. , Guillet J. E. 
Published: April 2003

AbstractThe inclusion of minor amounts of methyl isopropenyl ketone in polyacrylonitrile and its copolymers with methyl acrylate and vinyl acetate causes the polymer to become sensitive to ultraviolet light in the 290–320 nm region. Both films and fibers show decreases in molecular weight on irradiation which are attributable to CC bond scission by the Norrish type II reaction. In addition to bond cleavage, decarbonylation occurs, presumably by a type I radical process which also leads to the formation of ketonitrile groups. Fibers spun from such polymers lose most of their tensile strength and elongation after a few months outdoor exposure to natural sunlight, whereas control samples not containing carbonyl groups will retain their strength for much longer periods. Quantum yields both for chain scission and for carbonyl loss in these systems are estimated to be of the order of 0.005.
Applications of ESCA to polymer chemistry. Part VI. Surface fluorination of polyethylene. Application of ESCA to the examination of structure as a function of depth
Authors: Clark D. T. , Feast W. J. , Musgrave W. K. R. , Ritchie I. 
Published: April 2003

AbstractMolecular core binding energies have been measured by ESCA for series of surface‐fluorinated high‐density polyethylene films. Detailed analysis of the results shows that the technique can be used to establish a comprehensive picture of the early stages of the surface fluorination process. Both the depth of fluorination, and stoichiometry and molecular structure as a function of depth, in the range 0–50 Å have been established. In addition, minor features such as oxidation, hydration, and hydrocarbon contamination at the surface are clearly revealed. Detailed consideration of the results allows a discussion of the dynamics of the overall fluorination process.
Kinetic study of early stages of heterophase polymerization of vinyl chloride initiated by radiation
Authors: Palma G. , Sebastiani L. , Tavan M. , Carenza M. , Brugnaro S. 
Published: April 2003

AbstractThe kinetics of the radiation‐induced bulk polymerization of vinyl chloride in the early stages was determined in the temperature range of −30 to 50°C and dose rates varying from 0.6 to 17 rad/sec by the dilatometric method. Some runs of polymerization of vinyl chloride added with different percentages of tetrahydrofuran were also carried out. The results were found to agree with those previously obtained with polymerizations carried out to high conversions. The results are discussed on the assumption of a decrease in the extent of swelling of the polymer by monomer with decreasing polymerization temperature. By comparison with the data of other precipitating polymerization systems the possibility of a generalized interpretation for the heterophase polymerization is examined.
Free‐radical polymerization of vinylferrocene. I. Kinetics
Authors: George M. H. , Hayes G. F. 
Published: April 2003

AbstractThe polymerization of vinylferrocene in benzene at 60°C in the presence of 2,2′‐azobisisobutyronitrile has been studied. Densities and apparent densities were determined and rates of polymerization measured dilatometrically. The results show that vinylferrocene does not obey normal vinyl polymerization kinetics. Thus the rate of polymerization is proportional to the mean monomer and mean initiator concentrations both raised to a power of 1.1, and the degree of polymerization is independent of the initiator concentration. The polymerization reaction also has a high overall activation energy of 139 kJ/mole. The unusual kinetics are due to a monomolecular termination of the polyvinylferrocene chain radical which is also intermolecular with respect to the chain radical. Termination occurs by an intramolecular electron transfer reaction from a ferrocene nucleus to the growing chain radical which deactivates the chain radical and produces a polymer molecule containing a high spin Fe (III) complex. The presence of this species has been confirmed by Möussbauer and ESR spectroscopy. The rate constant for termination is between 3 and 60 sec‐1. Intramolecular electron transfer has not been previously observed in vinyl polymerizations. The term “intralectran” is suggested to describe this new type of termination. Vinylferrocene readily undergoes transfer to monomer (with a transfer constant equal to about 8 × 10‐3) and to polymer, but not to benzene.
Molecular weight distribution studies. I. Radiation‐induced polymerization of liquid α‐methylstyrene
Authors: Chawla A. S. , Huang Robert Y. M. 
Published: April 2003

AbstractThe concentration of water in purified and BaO‐dried α‐methylstyrene was found to be 1.1 × 10−4M. The radiation‐induced bulk polymerization of the α‐methylstyrene thus prepared was studied in the temperature range of −20°C to 35°C. The polymerization rate varied as the 0.55 power of the dose rate. The theoretical molecular weights and molecular weight distribution were calculated from a proposed kinetic scheme and these values were then compared with those found experimentally. The agreement between these two was reasonably close, and therefore it was concluded that, from the molecular weight distribution point of view, the proposed kinetic scheme for the cationic polymerization of α‐methylstyrene is an acceptable one. The rate constant for chain transfer to monomer kf changed with temperature and was found to be responsible for the decrease in the molecular weight of the polymer with increase in temperature. kf and kp at 20°C were found to be 0.95 × 104 l./mole‐sec and 0.99 × 106 l./mole‐sec, respectively.
Formation of free radicals in photoirradiated cellulose. I. Effect of wavelength
Authors: Hon Nyok‐Sai 
Published: April 2003

AbstractFormation of free radicals in photoirradiated cellulose has been studied by means of ESR spectroscopy at 77°K. Three kinds of light sources with different wavelengths between 2500 and 4000 ÅR were employed. No radicals detectable by ESR were recorded when cellulose was irradiated with light of wavelength longer than 3300–3400 ÅR. Hydrogen atoms that generated a doublet spectrum (ΔH = 508 G) were observed when cellulose was irradiated with light longer than 2800 ÅR. Hydrogen atoms and formly radicals that generated doublet spectra with splitting constants of 508 and 129 G, respectively, were observed when irradiated with light shorter than 2800 ÅR. The scission of the polymer chain in cellulose is evident from decrease of the degree of polymerization, and the results of mass spectrometric analysis indicated H2, CO, CO2, and H2O to be the main volatile products of cellulose upon photoirradiation.
Thermal degradation of poly(parabanic acid)
Authors: Luongo J. P. , Schonhorn H. 
Published: April 2003

AbstractA variety of techniques were used to follow the thermal degradation of a poly(parabanic acid) (PPA‐M). The kinetic data associated with the weight loss as a function of time at elevated temperatures indicates a random initiation process followed by depolymerization. Infrared and mass spectral techniques further confirmed the kinetic data by showing the presence of isocyanate and amide groups in addition to CO, CO2, and nitric oxide gases being evolved. Incipient gelation occurs simultaneously with the formation of the amide. A reverse Hoffman rearrangement mechanism has been proposed which appears to be consistent with the available experimental data.
Monomer‐isomerization polymerization. XIII. Monomer‐isomerization polymerization of 1,4‐cyclohexadiene with Ziegler‐Natta catalyst
Authors: Yousufzai A. H. K. , Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

Abstract1,4‐Cyclohexadiene underwent monomer‐isomerization polymerization to yield poly(1,3‐cyclohexadiene) with a Ziegler‐Natta catalyst comprising TiCl4–Al(C2H5)3 catalyst with Al/Ti molar ratios of 0.5–3.0 at 60°C for 96 hr. Good yields of polymer were obtained (49.5% yield at Al/Ti = 3.0; [η] = 0.04 dl/g). The infrared and NMR spectra of the polymer were identical to those of poly‐(1,3‐cyclohexadiene), confirming that 1,4‐cyclohexadiene first isomerizes to 1,3‐cyclohexadiene and then homopolymerizes to give poly‐1,3‐cyclohexadiene. 1,3‐Cyclohexadiene polymerized without isomerization easily in the presence of TiCl3–Al(C2H5)3 catalyst at Al/Ti molar ratios of 0.5–3.0 at 60°C for 3 hr (76.3% yield at Al/Ti = 3.0; [η] = 0.06 dl/g).
Reaction of diisocyanates with alcohols. II. Catalyzed reactions
Authors: Anzuino G. , Pirro A. , Rossi G. , Friz L. Polo 
Published: April 2003

AbstractIn a previous work we reported a procedure to calculate rate constants for the primary and secondary reactions (urethane and allophanate formation, respectively) between isocyanate and alcohols. In the present paper the same procedure is applied to the catalyzed reaction, thus defining the selectivity for a series of catalysts.
Fragmentation in cationic olefin oligomerization
Authors: Larchance Pierre , Eastham Arthur M. 
Published: April 2003

AbstractThe dominant products from the polymerization of butene‐2 in CH2Cl2 at −25°C with BF3CH3OH as catalyst are C10, C12, and C14 olefins. Formed in lesser amounts are C9 and C13 olefins but C5–7 and C11 olefins have not been detected. The few products so far identified retain the basic butene‐2 structure suggesting that the anomalous products may not be formed in a typical carbonium‐ion‐type rearrangement reaction but perhaps arise in a fission process associated with the propagation and/or transfer steps in the polymerization. With propylene as monomer the normal oligomers are by far the most important products, but all fission products can be detected.
Redox polymerization of acrylonitrile. Kinetics of the reaction initiated by the redox system tartaric acid–V5+
Authors: Mohanty T. R. , Singh B. C. , Nayak P. L. 
Published: April 2003

AbstractKinetics of vinyl polymerization of acrylonitrile initiated by the redox system tartaric acid–V5+ have been investigated in aqueous sulfuric acid in the temperature range 30–40°C. The rates of polymerization and V5+ disappearance and the chain lengths of polyacrylonitrile were measured. From the results it is concluded that the polymerization reaction is initiated by an organic free radical arising from the V5+–tartaric acid reaction with termination by V5+ ions. A suitable kinetic scheme has been proposed, and the various rate and energy parameters were evaluated.
The kinetics of styrene emulsion polymerization
Authors: Piirma Irja , Kamath V. R. , Morton Maurice 
Published: April 2003

AbstractA study has been carried out on the kinetics of persulfate‐initiated emulsion polymerization of styrene in the presence of an anionic (oleate) or mixed anionic‐nonionic emulsifier. In both cases it appears that Smith‐Ewart kinetics are obeyed, i.e., there is a constant‐rate period up to 40–50% conversion, during which there is a concomitant constant molecular weight development. The sharp increases in molecular weight with conversion reported by Grancio and Williams appear to be an artifact resulting from the use of an impure emulsifier (Triton X‐100), which acts as a chain transfer agent to reduce the molecular weight by approximately an order of magnitude. Hence there does not appear to be any kinetic justification for assuming an inhomogeneous swollen latex particle (“core‐shell” morphology), and normal thermodynamic considerations should still apply to this swelling phenomemon.
Synthesis, mechanism, and property aspects of a new class of polyethers: Poly(1,4‐dichloro‐2,3‐epoxybutane)s
Authors: Vandenberg E. J. 
Published: April 2003

AbstractRing‐opening polymerization and copolymerization of the cis and trans isomers of 1,4‐dichloro‐2,3‐epoxybutane has let to an interesting 50% Cl. This family of polymers is expected to acquire commercial importance.
Effect of nonelectrostatic interactions on the macromolecular behavior of polyelectrolytes. III. Optical rotatory dispersion of PLL in water and aqueous‐organic mixtures
Authors: Beaumais Jacques , Fenyo Jean‐Claude , Muller Guy 
Published: April 2003

AbstractWe have investigated the optical rotatory dispersion of a stereo‐irregular polyelectrolyte when neutralized with alkaline and N‐tetraalkylammonium hydroxides, both in water and aqueousacetone mixtures.The variations of the optical activity properties during the neutralization can be well related to potentiometric and viscosity measurements. They are interpreted by assuming two kinds of solvation of the chiral centers located on the main chain, to which two partial optical rotary dispersions (ORD) of opposite signs are associated. The observed optical activity changes and specifically the discontinuity occurring in the neutralization range where a conformational transition between a compact structure and a more extended one is initiated, are thus accounted for in terms of the corresponding changes in the state of solvation of chains.
Photopolymerization of acrylonitrile in the presence of substituted triphenyl phosphites
Authors: Taninaka Takumi , Ogawa Takeshi , Minoura Yuji 
Published: April 2003

AbstractIt was found that acrylonitrile was polymerized at 30°C by ultraviolet irradiation in the presence of triphenyl phosphite and its derivatives, namely m‐CH3, p‐C2H5, and p‐CH3 substituted triphenyl phosphites under conditions where acrylonitrile alone did not polymerize and phosphites did not undergo photolysis. The rate of polymerization in the presence of triphenyl phosphite and tri‐p‐tolyl phosphite was found to be proportional to the monomer concentration, the phosphite concentration, and the light intensity. From these results, it was thought that a donor–acceptor complex formed between phosphite and acrylonitrile which absorbed light and initiated the radical polymerization. In the photopolymerization of acrylonitrile with substituted triphenyl phosphites, the rate of polymerization increased with an increase in electron‐donating ability of substituent. From the plot obtained by use of Hammett's equation (log Rp/Rp0 = ρσ), the ρ value was found to be −1.0.
Anionic polymerization initiated by lithium diethylamide in organic solvents. II. Investigation of the polymerization of isoprene
Authors: Angood A. C. , Hurley S. A. , Tait P. J. T. 
Published: April 2003

AbstractThe polymerization of isoprene, initiated by lithium diethylamide has been investigated in the presence of a number of additives. Kinetic results are interpreted on the basis of simultaneous initiation and propagation reactions. The effect of additives, particularly diethyl either, has a profound effect on both the rate of initiation and propagation. The active centers are believed to be ion‐pairs with the lithium counterions solvated by both ether and monomer molecules, and the actual propagation reaction is believed to involve a rearrangement of the monomer, complexed to the lithium, and the growing polymeric chain.
Effects of substituted triphenyl phosphites on the radical polymerization of acrylonitrile
Authors: Taninaka Takumi , Ogawa Takeshi , Minoura Yuji 
Published: April 2003

AbstractThe radical polymerization of acrylonitrile in the presence of nuclear‐substituted triphenyl phosphites (p‐Cl, H, p‐CH3, p‐OCH3) initiated by α,α′‐azobisisobutyronitrile at 50°C was investigated. It was found that the rate of polymerization decreased at low concentrations of phosphite, but after reaching a minimum the rate increased again with further increase in the phosphite concentration in the case of all substituted triphenyl phosphites. Formation of a weak complex between phosphite as donor and acrylonitrile as acceptor was confirmed from the change in chemical shifts of vinyl protons to higher magnetic fields on NMR spectroscopy. From the results of continuous variation method using NMR spectra, the complex was found to be of the 1:1 type. The effects of substituted triphenyl phosphite on the rate of polymerization and the chain‐transfer reaction to substituted triphenyl phosphites are discussed on the basis of these results.
Synthesis and properties of polycondensation polymers from compounds with asymmetric functional groups
Authors: Korshak V. V. , Vinogradova S. V. , Vasnev V. A. , Markova G. D. , Lecae T. V. 
Published: April 2003

AbstractThe effect of conditions of polycondensation on the structure of polymers formed from monomers with symmetric and asymmetric functional groups by nonequilibrium polycondensation has been studied for the system with acceptor‐catalytic polyesterification of β‐hydroxyethyl ethers of bisphenols and terephthalic acid chloride in the presence of triethylamine. Polymers with statistical or regular arrangement of diol residues in the chain can be produced in such systems, depending on the way in which starting compounds are introduced in the reactor. A difference in the reactivity of functional groups in an asymmetric monomer is not sufficient to produce polycondensation polymers with a regular structure. Gradual introduction of the symmetric monomer is essential to yield polymers with predominant “head‐to‐head” (“tail‐to‐tail”) configurations. Some properties of the resulting polymers have been studied. Polymers with ordered residues of the asymmetric monomers in the macromolecules have higher softening temperatures and an increased tendency for crystallization than the statistic polymers.
Synthesis of poly‐L‐naphthylalanine and its secondary structure
Authors: Ueno Akihiko , Nohara Masao , Toda Fujio , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractPolypeptides derived from L‐naphthylalanine and γ‐benzyl L‐glutamate were prepared. Conformational properties in solution were investigated by circular dichroism (CD) and infrared spectra on the soluble copolymers, and the copolymers were assumed to take the right‐handed α‐helical conformation. By the addition of trifluoroacetic acid, a transition of side‐chain arrangement is induced simultaneously with the conformational transition of the peptide backbone for the copolymer with the highest content of L‐naphthylalanine residues. Fluorescence spectra of the copolymers show no excimer emission, which is evidence for the rigid orientation of the side‐chain naphthyl groups. The infrared spectrum and x‐ray diagram of poly‐L‐naphthylalanine do not rule out the helical conformation in the solid state.
Graft polymerization of vinyl monomers onto cellulose in presence of soda lime glass. I
Authors: Mansour Olfat Y. , Nagaty Ahmed 
Published: April 2003

AbstractSodium bisulfite–soda lime glass has proved to be a good initiator for polymerization and graft polymerization onto cellulose of some vinyl monomers. A scheme dealing with the mechanism of initiation has been proposed assuming trapping of the bisulfite radical inside the glass frame‐work to form a so‐called sulfur‐impregnated solid. Such a solid has paramagnetic properties and acts on the vinyl monomers and cellulose as any free‐radical‐producing source thus leading to polymerization and graft polymerization onto cellulose. Other radicals containing sulfur, such as sulfite, sulfate, and persulfate failed to give such property with soda lime glass. With the sodium bisulfite–soda lime glass system the reactivity decreases in the order methyl methacrylate > ethyl acrylate > acrylonitrile which is inconsistent with the arrangement of acceptor monomers with decreasing electron‐donating ability. This may reflect interference of the addition reaction which may take place between the monomer and bisulfite and the rate of which may depend on the activation energy of the monomer.
Thermal and radiation‐induced dehydrochlorination of poly(vinyl chloride). II. Head‐to‐head structures
Authors: Mitani Katsuo , Ogata Takayuki , Awaya Hiroshi , Tomari Yasuo 
Published: April 2003

AbstractThe mechanism of dehydrochlorination of 2,3‐dichlorobutane and chlorinated polybutadiene which are model compounds of head‐to‐head poly(vinyl chloride) has been investigated by pyrolysis, thermal, and ultraviolet‐induced decomposition. The activation energy of dehydrochlorination for head‐to‐head poly(vinyl chloride) in nitrogen was 23 kcal/mole at temperatures of 150–190°C, which is slightly smaller than that (29 kcal/mole) for head‐to‐tail poly(vinyl chloride). The conjugated double bonds were formed by thermal and radiation decomposition of head‐to‐head poly(vinyl chloride), similar to head‐to‐tail poly(vinyl chloride). The probability of polyene formation by radiation‐induced dehydrochlorination is larger than that by thermal decomposition and is affected by the conformation and the molecular motion of the main chain. This may be due to the alternative mechanism of dehydrochlorination in the thermal and radiation decomposition. The amount of head‐to‐head linkage of poly(vinyl chloride) samples prepared with various catalysts is dependent on polymerization temperature rather than the kinds of catalyst. Commercial poly(vinyl chloride) has 6–7 head‐to‐head linkages per 1000 monomeric units.
Esterification of polymeric carboxylic acids
Authors: Cohen H. L. 
Published: April 2003

AbstractPolymers containing pendant carboxyl groups have been essentially completely esterified with little apparent change in molecular weight by the use of one of the following reagents: (1) trialkyl orthoesters, (2) dimethylformamide dialkyl acetals, (3) tertiary amines followed by alkyl halides, (4) quaternary ammonium hydroxide followed by alkyl halides. The use of some of these methods permits preparation of certain polymers that were previously not readily accessible.
Mechanism of oxidation at a copper–polyethylene interface. II. Penetration of copper ions in the polyethylene matrix
Authors: Allara D. L. , White C. W. , Meek R. L. , Briggs T. H. 
Published: April 2003

AbstractTwo surface analysis techniques (Rutherford backscattering and surface composition by analysis of neutral and ion impact radiation) have been applied to the study of interfacial copper transport in the oxidation of polyethylene films over copper surfaces. Analysis of films oxidized several thousand hours at 40, 57, and 87°C shows maximum concentrations of copper species in the polymer matrix of ∼0.1M extending to depths of several thousand angstroms. These results, together with previous infrared spectroscopic studies, allow some significant conclusions and hypotheses to be drawn as regards the roles of heterogeneous and homogeneous catalytic processes which occur in the thermal‐oxidative degradation of polyethylene–copper systems.
Emulsion copolymerization behavior of α‐methylstyrene with methacrylonitrile
Authors: Kenney J. F. , Patel P. J. 
Published: April 2003

AbstractThe emulsion copolymerization behavior of α‐methylstyrene with methacrylonitrile is described. The effects of polymerization temperature, potassium persulfate initiator concentration, sodium lauryl sulfate emulsifier concentration on copolymer yield, molecular weight, and rate of copolymerization are described. The copolymer was found to have an azeotropic composition at 43 mole‐% AMS. Reactivity ratios were determined to be 0.06 and 0.28 for AMS and MAN, respectively.