bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic polymerization of 9‐vinylanthracene
Authors: Michel R. H. 
Published: April 2003

Abstract9‐Vinylanthracene has been polymerized in a wide variety of cationic systems. Under these conditions of polymerization, the vinyl group and the center ring of the anthracene nucleus act as a 1,3,5‐triene system. Evidence for the structure of the product was obtained from infrared, ultraviolet, and particularly nuclear magnetic resonance spectroscopy. In the presence of trifluoroacetic acid, poly‐9‐vinylanthracene was converted to poly‐9,10‐dimethyleneanthracene.
Thermoelectric determination of polymer molecular weights
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F. 
Published: April 2003

AbstractAn apparatus is described for the determination of number‐average molecular weights, based on the thermoelectric method as proposed by Hill. With this improved instrument, temperature differences of down to approximately 5 × 10−5°C. can be recorded. This allows determination of molecular weights up to 40,000 for the case of coiled macromolecules in a poor solvent. The accuracy of measurements, for all molecular weights, has been established by using benzene solutions of polyisobutenes of narrow and defined molecular weight distributions.
Preparation and polymerization of 1,2‐epoxypropyl 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranoside
Authors: Gupta P. Das , Whistler Roy L. 
Published: April 2003

AbstractAllyl D‐glucopyranoside tetraacetate is prepared by reaction of acetobromo‐D‐glucose with allyl alcool. The glycoside is not readily polymerized by free radical mechanism but on conversion to the epoxide with peracids, polymerization is easily induced with triethylaluminum. The product with a D. P. of 250 is soluble in organic solvents. On alkaline deacetylation the hydrophylic polymer is water soluble but the aqueous solution possess comparatively low viscosity.
Copolymerizations in electron‐donor solvents with organolithium catalysts
Authors: Reich Leo , Stivala Salvatore S. 
Published: April 2003

AbstractA general scheme is postulated for copolymerizations in electron‐donor solvents with organolithium catalysts. The general mathematical expression obtained is simplified by utilizing two extreme conditions. The simplified equations are shown to be consistent with experimental evidence. While it is difficult to decide in favor of either solvation theory or O'Driscoll's concepts, the latter is favored based upon simplicity, plausibility and experimental evidence.
Redox polymerization of unsaturated polyester resins. II. Effect of copromoter metals on the redox polymerization activity of vanadium chelates
Authors: Svoboda Glenn R. 
Published: April 2003

AbstractOf a series of copromoter metal species investigated, it was found that several of these were strongly effective in synergizing the redox polymerization activity of vanadyl acetyl acetonate. Notable among these were Cu+2, Fe+3, Ti+3–Ti+6, Be+2, Al+3, and Th+4. Particularly notable was the effect of Ti+3–Ti+6, which strongly synergized the rate at which complete polymerization was obtained, eg., within 15 min. as compared to 20 hr. when vanadyl acetyl acetonate was used alone. Synergism with copromoter metal species was noted with as low as 2 mg. titanium used in conjuction with 2 mg. of vanadyl ion as the chelate. A minimal concentration for synergistic effect was noted for those metal species thus studied. This was found to range from 0.18 to 0.41 mmole of copromoter metal species per 100 g. of resin system. Advantage was taken of the peculiar effect of manganic acetyl acetonate to prolong gel times without affecting the rate at which complete polymerization was obtained. By using manganic acetyl acetonate in conjuction with vanadyl acetyl acetonate, it was possible to prolong the shelf‐life of a prepromoted resin from 17 to at least 110 days.
Preparation of polyconjugated systems by new reaction of dihydrohalogen polymerization
Authors: Paushkin I. M. , Nizova S. A. 
Published: April 2003

AbstractThe reaction of dihydrohalogen polymerization was suggested by the authors as a method for the preparation of polymers with conjugated double bonds on the basis of α,β‐dihalogen derivatives, oxides, and hydroxides. The reaction was carried out in an autoclave a t 200°C.; the reaction time was 6 hr. Polymers, obtained from α,β‐dibromopropylnitrile, α,β‐dibromopropyl alcohol, and α,β‐dibromoethylbutyl ether, are black and brown powders soluble in concentrated acids. The polymers show a sharp peak in EPR‐spectra characteristic of polyconjugated systems with concentration of paramagnetic particles of 1017–1019/g. The infrared spectra have characteristic absorption bands peculiar to polyconjugated systems.
Polymerization of isoprene with normal‐, iso‐, secondary and tertiary butyllithium
Authors: Kuntz Irving 
Published: April 2003

AbstractWhen isoprene (3.3M) in n‐heptane is polymerized at 23.1°C. by the different butyllithiums (0.004M), the times to reach 50% conversion to polymer are 3.5, 2.3, 2.0, and 2.2 hr. for the normal, iso, secondary, and tertiary butyllithiums, respectively. When the same experiment is carried out at an initiator concentration of 0.02M, the t0.5 for the same sequence of isomers is 3.1, 2.6, 1.4, and 1.3 hr., respectively. In these and other experiments, the inherent viscosity of the polymers prepared with tert‐butyllithium appears to be lower than those obtained with n‐butyllithium. The stereochemistry of the polyisoprene polymers obtained with the different initiators is identical. The results with n‐and isobutyllithium at 0.02M concentration seem to show the greatest deviation from first‐order kinetics. Using data from experiments at different initiator concentrations and constant isoprene concentrations, the kinetic order in tert‐butyllithium has been found to be 0.54 ± 0.17. These observations reflect differences in initiation rate for the varied butyllithiums. The kinetic order in initiator indicates that the growing isoprenyllithium chains are involved in dimer formation whose dissociation is the slow step in the propagation reaction.
Interaction of poly(methacrylic acid) and bivalent counterions. I
Authors: Mandel M. , Leyte J. C. 
Published: April 2003

AbstractThe calculation of formation curves of metal‐polyacid complexes from titration curves is discussed. The interaction of bivalent ions of Cu, Cd, Zn, Ni, Co, and Mg with poly(methacrylic acid) is investigated by this method. These metals seem to form complexes involving two carboxylate groups for each ion in a large domain of pH values. Formation constants for these complexes are given which decrease according to the order indicated above.
Effects of swelling on proton relaxation in vinyl polymers
Authors: Bonera G. , Chierico A. , Rigamonti A. 
Published: April 2003

AbstractPolystyrene and poly(methyl methacrylate) were swelled with the respective monomers and with suitable organic solvents. By means of a special experimental arrangement the spin‐lattice relaxation times of the protons of the swelling agent and of those of the swelled polymer were measured separately. Differences between the spin‐lattice relaxation time of the polymer during polymerization and that of the polymer swelled by the monomer are revealed and seem to point out a different degree of mobility in the polymer chains. In some instances an indication of differences in the motions that produce the relaxation is gained from the observed differences in the behavior of a polymer obtained through thermal polymerization and that of the same polymer obtained by ultraviolet radiation‐induced polymerization. With regard to the swelling agent there is also some experimental evidence pointing out the remarkable role taken by internal rotations of molecular groups in the mechanism of relaxation.
Effect of blending on the molecular weight distribution of polymers
Authors: Haward R. N. , Wright B. , Williamson G. R. , Thackray G. 
Published: April 2003

AbstractThe effect of blending polymers of different molecular weight on the Q value (Q = M̄w/M̄n) of the blend has been considered. A mathematical expression is derived, and its shows by a simple application to monodisperse systems that blending over a wide molecular weight range is necessary to give high Q values. These principles are then applied to the case of Ziegler and Phillips type high density polyethylenes having wide log‐normal molecular weight distributions. In this way it is shown that only blending over a very wide melt index range, e.g., 1000/1, can be expected to have a measurable effect on Q. A series of physical measurements on blended and homogenized Ziegler polyethylenes shows no significant differences between blends and directly produced polymers.
Copolymerization of propylene and styrene
Authors: Ashikari Nobuyuki , Kanemitsu Takayuki , Yanagisawa Kazuo , Nakagawa Kisaku , Okamoto Hiroshi , Kobayashi Shōgo , Nishioka Atsuo 
Published: April 2003

AbstractCopolymerizations of propylene and styrene were carried out with various Ziegler‐Natta type catalysts in order to find the catalytic activity, the monomer reactivity ratios, and some properties of the copolymer. The polymerization products were confirmed to be copolymers from the facts that special behaviors were observed in the infrared and NMR spectra and that the melting point dropped with increasing styrene content. Generally, copolymer produced with a AlR3–TiCl4 catalyst had low stereoregularity and comparatively low molecular weight. On the contrary, a copolymer produced with a AlR3–TiCl3 catalyst had high stereoregularity and high molecular weight (viscosity). In order to reduce the viscosity various additives were examined. Monomer reactivity ratios obtained by the catalysts areas follows: for Al(i‐Bu)3–TiCl3: r1 = 20.0 ± 3.5, r2 = 0.20 ± 0.13; for AlEt3–TiCl3: r1 = 20.5 ± 3.0, r2 = 0.30 ± 0.15; for AiEt3–VCl4: r1 = 7.2 ± 0.7, r2 = 0.16 ± 0.08. All cases show that the reactivity of propylene is much larger than that of styrene.
Thermodynamic parameters for isotactic and atactic poly‐l‐pentene
Authors: Krigbaum W. R. , Woods J. D. 
Published: April 2003

AbstractPrecipitation temperature measurements have been the exclusive source of thermodynamic parameters used for the comparison of polymers differing in tacticity. The Flory theta temperatures differ for the various tactic forms, although not in a manner which exhibits any obvious consistency. The precipitation temperature entropy parameters, on the other hand, have been larger for the isotactic polymer in every case but one. The theoretical treatment underlying the evaluation of ψ1 from precipitation temperature data is, unfortunately, not strictly valid. Thus, the interpretation of this behavior is in some doubt. We report the results of an osmotic study of isotactic and atactic poly‐l‐pentene in phenetole at three temperatures. For the isotactic and atactic modification the respective values found were Θ = 329.0 and 321.5°K., while for ψ1 the values were 0.45 and 0.72. The theta temperatures fall in the same order as those previously obtained for a closely related system, poly‐l‐butene–anisole, by precipitation temperature measurements. The osmotic ψ1 values are larger than those reported here‐tofore for other systems, but of more importance, they fall in the reverse of the order consistently obtained from precipitation temperatures. This suggests that the regular variation of the precipitation temperature ψ1 values can not have its origin in local pair interaction effects; instead, it must reflect some difference in the concentration dependence of the chemical potential for solutions of the various tactic forms.
Temperature coefficient of unperturbed dimensions from solution properties
Authors: Bianchi Umberto 
Published: April 2003

AbstractValues of d ln r02/dT, for polystyrene, poly(vinyl acetate), poly(methyl methacrylate), and polydimethylsiloxane recently obtained by different authors are compared. The large discrepancies among values reported are taken as an indication of the effects played by polymer–solvent interactions on unperturbed dimensions.
Thermochemistry of polymerization. Part I. Thermochemical aspects of copolymerization
Authors: Sawada Hideo 
Published: April 2003

AbstractA new theoretical relationship for the heat of copolymerization is described. The heat of copolymerization for low conversion copolymers can be related to the heats of homopolymerization, the polymer composition, and two parameters which characterize the alternation tendency in copolymerization.
Some considerations on nonstationary‐state kinetics of vinyl polymerization
Authors: Burkhart R. D. , Faucher J. A. 
Published: April 2003

AbstractWhen primary free radicals approach their stationary‐state concentration at a rate which is of the same order of magnitude as that with which chain radicals approach their stationary‐state concentration, the familiar nonstationary‐state equation relating the chain radical concentration to the time of reaction is no longer adequate. An accurate mathematical description of this situation has now been obtained which not only allows one to examine the dependence of chain radical concentration on the reaction time but also provides a basis for predicting under what conditions the primary radicals will be slow to approach a steady state. On the basis of these results the degree of error which is introduced into measurements of termination rate constants has been calculated and an experimental approach for measuring specific rate constants of chain initiation has been suggested.
Polyorganosilazanes
Authors: Krüger Carl R. , Rochow Eugene G. 
Published: April 2003

AbstractSince dialkyldichlorosilanes yield almost entirely the cyclic trimeric and tetrameric silazanes by ammonolysis, a method had to be found to convert these oligomers into polymers. This can be done by heating the cyclic compounds with a catalytic amount of ammonium halides, preferably ammonium bromide or ammonium iodide, at 160°C. or more over a period of 6–8 hr. at atmospheric pressure. During this time ammonia is evolved, and there remains an oily polymer containing some silicon–halogen bonds. These are converted into SiN bonds by treating the raw polymer in ethereal solution with gaseous ammonia, yielding colorless waxy polysilazanes after evaporation of the solvent. The structures, spectra, properties, and reactions of these new polymers are discussed.
Proton magnetic resonance study of sorption of water and alcohols by wool
Authors: Bradbury J. H. , Forbes W. F. , Leeder J. D. , West G. W. 
Published: April 2003

AbstractMeasurements have been made of the proton magnetic resonance spectra of water, methanol, and ethanol sorbed by wool. The line widths of the spectra are related to the freedom of movement (mobility) of the sorbate molecules within the protein structure. At any particular value of molar sorption it is found that the mobilities of water, methanol, and ethanol are approximately equal, but the increase in volume of the wool increases in this series in the approximate ratio of 1 : 2 : 3. Thus, when a comparison is made of the mobility of the three sorbates at equal values of the volume swelling it is found that the order of mobility is water > methanol > ethanol.
Graft copolymerization with styrene and methyl methacrylate in very viscous medium
Authors: Lazár M. , Pavlinec J. 
Published: April 2003

AbstractThe influence of the viscosity of the medium on the rate and efficiency of a chemically initiated graft copolymerization with styrene and methylmethacrylate was studied. The increase in viscosity was reached partly by formation of the respective homopolymers, partly by the atactic polypropylene. The transfer constant to the atactic polypropylene from growing polystyrene macroradicals and the ratio of the rate constants of reaction of primary radicals with atactic polypropylene and with styrene were determined. It was found that the total efficiency of grafting styrene to atactic polypropylene increases with increasing concentration of polypropylene in the initial mixture and that the conversion of monomer is not a major influence in this case. On the contrary, for grafting of methyl methacrylate to atactic polypropylene a decrease of total efficiency with conversion of monomer was observed. This indicates that the gel effect is not only a function of viscosity of medium but also of the character of polymers in the reaction mixture.
Stereoregular polymerization of vinyl alkyl ethers with metal sulfate–sulfuric acid complex catalysts
Authors: Lal Joginder , McGrath James E. 
Published: April 2003

AbstractThe polymerization of vinyl alkyl ethers at room temperature or above, to give crystallizable polymers is of considerable interest for both theoretical and practical considerations. The polymerization of these monomers has been studied with metal sulfate–sulfuric acid complex catalysts at 0°C. or above to give high molecular weight, isotactic polymers. Ferric hydrosulfate hydrate and aluminum hexahydrosulfate heptahydrate (AHS) were used as catalysts. The nature of the solvent employed during polymerization with these heterogeneous catalysts was found to be quite important from the point of view of polymerization rate and stereoregularity of the polymer. A vinyl ether having a linear alkyl group polymerizes considerably faster than a monomer having a branched alkyl group. The apparent first‐order rate constant values for the AHS‐catalyzed polymerization of vinyl alkyl ethers having n‐alkyl groups indicate the following sequence: ethyl > n‐butyl > n‐hexyl = n‐octyl. In the temperature range of 30–58°C. the overall activation energy for the polymerization of vinyl n‐butyl ether in heptane with AHS catalyst was found to be 9.7 kcal./mole. Vinyl n‐butyl ether was copolymerized with β‐vinyloxyethyl methacrylate (M2) using AHS catalyst. The average values of r1 = 0.82 and r2 = 0.004 were obtained.
Kinetics of polymerization of molten trioxane
Authors: Kučera Miloslav , Spousta Eduard 
Published: April 2003

AbstractConversion curves of molten trioxane polymerization at temperatures between 70 and 90°C. have been measured. Their analysis has established that the rate‐controlling step of the reaction
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is the addition of a trioxane molecule to the active center. Values of the rate constants k1 and k3k4/k2 as well as the rate constants of initiator deactivation ks have been determined. Initiator deactivation causes premature leveling off of the conversion curves, especially at lower temperatures of polymerization (70–80°C.). The activation energies of the rate constants have been determined.
Initiation of the bulk polymerization of trioxane
Authors: Kučera Miloslav , Spousta Eduard 
Published: April 2003

AbstractKinetic analysis of the induction periods of trioxane polymerization shows that although the interaction of the initiator with a trioxane molecule is slow, the reaction of the initiator with free formaldehyde (followed by the splitting of trioxane) is quick and yields active centers. Kinetic relations have been developed for the amount of free formaldehyde in the first stages of the reaction between the initiator and trioxane, for the rate of formation of active centers and for the time dependence of the conversion of trioxane during the induction period. Kinetic formulas are compared with experimental data.
Lattice modes of polyethylene
Authors: Enomoto S. , Asahina M. 
Published: April 2003

AbstractA modified Urey‐Bradley type force field was adopted to study the lattice modes of polyethylene by the GF matrices method with the intermolecular force constants which were estimated from the intermolecular potential function of methane. The frequencies of the modes were calculated at intervals of 30° for the phase differences along the a axis and the b axis. The elastic moduli of polyethylene crystal along both axes were also obtained from the intermolecular potential function.
The influence of molecular weight distribution on some properties of polystyrene melt
Authors: Ballman Richard L. , Simon Robert H. M. 
Published: April 2003

AbstractThe viscosities of a number of monodisperse polystyrene melts have been measured using a capillary rheometer. The materials covered a molecular weight range of 43,000–460,000. Shear rates of 1.54–1540 sec.−1 and temperatures of 350–450°F. were studied. The effect of molecular weight distribution of polydisperse polystyrene was also measured. It was found that while low shear viscosity was dependent on Mw, higher shear melt viscosities depended on averages between Mw and Mn until at 1000–2000 sec.−1, Mn controlled viscosity. Agreement with the 3.4‐power dependence of zero shear viscosity was good. Similar exponential relationships were found, with higher rates of shear, corresponding to smaller values of the exponent. Constant values of the exponent were found at constant shear stress but not at constant shear rate. Agreement with the constancy of the activation energy for viscous flow for various molecular weights and distributions at constant shear stress was good. However at constant shear rate, ΔE decreased as the molecular weight average increased and as the distribution broadened. Viscosity versus shear rate master curves were constructed by using the Buehe‐Harding procedure. All monodisperse polystyrenes showed excellent fit with the master curve. Other molecular weight distributions did not. Master curves also were constructed for measurements of dynamic viscosity versus frequency for monodisperse polystyrene. These curves when compared to steady state viscosities failed to confirm the correspondence of ηa to either |η*| or to η′.
Viscosity of amorphous polymers
Authors: Dibenedetto A. T. 
Published: April 2003

AbstractAn amorphous polymer is characterized as a homogeneous array of N identical, n‐center polymer segments which can be described in terms of four molecular constants. A mechanism for viscous flow (or self diffusion) is visualized as a positional exchange of two adjacent polymer segments in a hole the size of a segment‐pair. The activation energy for the viscous flow is the energy required to overcome the cohesive bonding to neighboring segments plus the work of compression required to form a hole of molecular dimensions. The effect of chain entanglement is estimated by using the theories of Bueche. An equation is derived for the viscosity in terms of a characteristic temperature, T0, a free volume expansion coefficient, β′, a fractional free volume for the glassy state fg0, an average segmental length, 2λn, and the four measurable molecular constants. This equation describes the lower limiting viscosity of polyisobutylene, polystyrene, and poly(vinyl acetate) over a viscosity range of up to a factor of 108 and for the whole temperature range of available data. It is shown that the characteristic temperature, T0, is close to the measured glass transition temperature, the free volume expansion coefficient, β′, is about 0.4 of the thermal expansion coefficient of the rubber and the fractional free volume fg0, is 0.1 for all the polymers. The size of the jumping unit in viscous flow is calculated to be about 0.1–0.3 of the size of an equivalent freely orienting segment.
Electron exchange polymers. XXII. Preparation and properties of poly‐2‐vinylphenothiazine
Authors: Kamogawa Hiroyoshi , Larkin Joel Marie , Tǒei Kyoji , Cassidy Harold G. 
Published: April 2003

AbstractA new electron exchange polymer, poly‐2‐vinylphenothiazine, was prepared from 2‐vinylphenothiazine by thermal polymerization in an acetylating solvent (acetic anhydride) to form poly‐2‐vinyl‐N‐acetylphenothiazine. This was hydrolyzed with alcoholic alkali to yield greyish white poly‐2‐vinylphenothiazine, which is soluble in pyridine, dimethylformamide, chloroform, dioxane, and tetrahydrofuran, but not in aqueous solvents. The polymer could be oxidized with air in the presence of light, and oxidation with ferric chloride or bromine in tetrahydrofuran could be followed spectrophotometrically. On treatment with bromine followed with aqueous dimethylamine, the polymer became soluble in 90% acetic acid, in which solvent it could be reduced with titanium trichloride and reoxidized with bromine.