bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular orbital considerations on the reactivities of vinyl compounds. III. Polarographic reduction
Authors: Fueno Takayuki , Asada Kameo , Morokuma Keiji , Furukawa Junji 
Published: April 2003

AbstractThe polarographic half‐wave reduction potentials E1/2 of several vinyl (including vinylidene) monomers were measured and were discussed on the basis of the molecular orbital theory. The current‐voltage curves were determined in a 0.05 M solution of tetra‐n‐butylammonium iodide in the mixture of dioxane and water (3:1 by volume). The values of E1/2 were read against the saturated calomel electrode. It was found that E1/2 is correlated with xiv by E1/2 = 2.33 xiv−0.80, where xiv stands for the root of the MO secular equation for the π‐electronic system of the vinyl monomer corresponding to the lowest vacant level. Some of the monomers could not be reduced in the range of the applied potential less negative than − 3.0 volt vs. SCE, which was reasonably explained by their relatively large values of −xiv. It was suggested that the polarographic reducibility of vinyl monomers is roughly parallel to their anionic polymerizability. Furthermore, the lowest vacant π‐orbital energies of vinyl compounds were calculated according to the first order perturbation method. The results obtained thus were in good accordance with those calculated directly from the secular equations. It was also shown that the first ionization potentials of vinyl compounds were roughly related to their highest occupied π‐electronic energies.
The effects of attenuation and secondaray scattering on the determination of the second virial coefficient by light scattering
Authors: Carpenter D. K. 
Published: April 2003

AbstractThe effects of attenuation and secondary scattering on the determination of molecular weights and second virial coefficients by light scattering are investigated. The correction to the molecular weight due to these effects is small unless the reference standard has a high turbidity. The correction to the second virial coefficient is negligible in good solvents but becomes relatively more important as the ⊖‐condition is approached. Determination of the ⊖‐temperature for a polymer‐solvent system by light scattering can be in error by as much as several degrees under certain conditions, viz., large cells, large values of the constant H = (32π3n20/3Naλ4)(dndc)2, and small values of the Flory‐Krigbaum entropy parameter ψ1.
Light‐scattering measurements on selected polyamides (nylons)
Authors: Beachell Harold C. , Carlson Douglas W. 
Published: April 2003

AbstractA series of polyamides (nylons) formed by polymerizing an aliphatic diamine with an aliphatic acid or by polymerizing an aliphatic amino acid has been investigated by light‐scattering techniques in the solvent 2,2,3,3‐tetrafluoropropanol with 0.1 N sodium trifluoroacetate, as added electrolyte. The series investigated consisted of nylon 6, nylon 66, nylon 610, and Zytel 61. The refractive index gradient (dn/dc) for these polyamides was found to be 0.190 cm.3/g., and the light‐scattering constant H was taken as 9.59 X 10−6 cm.2./g.2, both values being determined for 4358‐A. incident radiation. Molecular weights, second virial coefficients, and molecular dimensions have been determined for theses polymers.
The morphology of semicrystalline polymers. Part I. The effect of temperature on the oxidation of polyolefins
Authors: Hawkins W. L. , Matreyek W. , Winslow F. H. 
Published: April 2003

AbstractOxidation rates of several uninhibited polyolefins were determined in the temperature range 40–140°C. The logerithm of the induction period increased linearly with 1/T, no changes in slope being noted in the melting range with polythylene. At the lower temperatures branched polythylenes were more susceptible to oxidation than the linear types. In the solid statem, oxygen uptake of both modifications were substantially less than that observed for the molten polymer. The amount of oxygen reacting in the solid state was shown to be inversely proportional to the per cent crystallinity, which indicates that reaction with oxygen takes place only in the amorphous region of these semicrystalline polymers. Isotactic polypropylene was only slightly less reactive than the atactic form, and both were more reactive than polyethylene. The effect of temperature on the activity of several moderately effective anotioxidants in branched polythylene was measured. These data also conform to linear Arrhenius‐type plots. Activation energies were specific, however, for each antioxidant and varied considerably; thus, an antioxidant rated as relatively ineffective under accelerated testing conditions could be quite effective within the temperature range over which it would normally be used as a polythylene protectant. Carbon black, which is comparable with some to the less effective thermal antioxidants under accelerated test conditions, provided an unexpected high order of protection for polyethylene below the melting point. This increased protection in the solid state was attributed to the impermeability of the crystalline phase to oxygen and increased concentration of the bulky carbon (antioxidant) particles in the amorphous region.
Electron microscope observations on microgel and linear macromolecules of polyacrylonitrile
Authors: Heyn A. N. J. 
Published: April 2003

AbstractThe presence of microgel particles, which were expected on the basis of other indirect measurements to occur in polyacrylonitrile solutions, is directly demonstrated in these solutions with the electron microscope. The particles are spherical in shape and have a uniform size of about 500 A. These microgel particles are probably crosslinked or branched giant molecules. On the side of these particles linear molecular threads are observed. Their bundling together into microfibrils is also observed.
The effect of hydrogen bonding addends on the dilute solution viscosity of poly(acrylamide) and unionized poly(acrylic acid) and poly(methacrylic acid)
Authors: Eliassaf J. , Silberberg A. 
Published: April 2003

AbstractThe effect of various addends on the specific viscosity of dilute aqueous unionized poly(methacrylic acid) (PMA) solutions, unionized poly(acrylic acid) (PAA) solutions, and poly(acrylic acmide) (PAAm) solutions was investigated. The addition of sodium and lithium chloride decreases the specific viscosity of PMA and PAA but leaves PAAm unaffected. The addition of ethanol to aqueous unionized PMA causes a decrease in specific viscosity up to 15% of the addend and an increase at higher alcohol content. The specific viscosity of PAA is increased and that of PMA decreased by ethanol. Urea and acetic acid addition decrease the specific viscosity of PMA and increase that of PAA. Urea does not affect the specific viscosity of PAAm. Guanidine hydrochloride addition decreases the specific viscosity of PMA. Perfluorooctanoic acid addition increases and caprylic acid decreases the specific viscosity of PMA, whereas neither of them affects PAA. It is assumed that the specific viscosity is a measure of the degree of intramolecular bonding. The results are discussed on the basis of a model which considers separately the effect of the addend on the polymer and on water. It is shown that for intramolecular bonding to decrease, (fA/fW)exp {−(Δμ°A − Δμ°W)/kt} must be larger than unity. In this expression, which represents the effectiveness of addend in replacing water on the chain, fA and fW are the activity coefficients of addend and water, respectively, and (Δμ°A − Δ°W) is the free energy change when addend replaces water on the chain. Results from the literature are included in the discussion.
Birefringence in swelling crosslinked polymer beads
Authors: Gurnee Edward F. 
Published: April 2003

AbstractThe radial distribution of birefringence in a swelling polystyrene–divinylbenzene copolymer bead is measured from the optical patterns observed with a polarizing microscope. This birefringence arises from the restraining influence of the nonswollen core on the exterior shell of gel. It is found that the birefringence is negative in sign, and exhibits a sharp maximum at the gel‐core interface.
The thermal degradation of poly‐p‐xylylene
Authors: Schaefgen J. R. 
Published: April 2003

AbstractThe thermal stability of poly‐p‐xylylene prepared in solution by the Hofmann reaction has been measured by a viscometric method. The polymer decomposes by a first‐order random cleavage mechanism with an activation energy of 58 kcal./mole. The latter value is identified with the bond strength of the carbon‐carbon bond between methylene groups connecting benzene rings. The stability of this polymer is thus limited only by the strength of the weakest link along the chain. The polymer is shown to be more stable thermally and more soluble than polymer prepared from p‐xylene by the pyrolytic method. The effect of chain transfer agents on the thermal stability was investigated.
Polyolefin production with preformed solid catalysts
Authors: Harban A. A. , Field Edmund , Friedlander H. N. 
Published: April 2003

AbstractA broad range of plastic and elastomeric materials can be made from olefins by solid catalysts, either precipitated in situ or preformed with high surface area. Solid catalysts have been applied to polymer production in two basic processes: suspension and solution. In the suspension process, polymer is made below its softening point in a medium that dissolves neither catalyst nor polymer. In the solution process, polymer is made in solution with a solid catalyst dispersed in the solvent. The literature implies that suspension polymerization is always used with precipitated catalysts, and solution polymerization with preformed catalysts. However, the processes are independent of the catalysts. For example, a single family of promoted preformed catalysts can produce linear polyethylene of low melt index or polypropylene by a suspension process below 150°C., and linear polyethylene of normal melt index or copolymers of ethylene and α‐olefins by a solution process above 150°C. All these routes produce useful polymers with desirable properties. Suspension polymerization is used when the catalyst requires operation at low temperatures, when the product with desired properties can only be obtained at low temperatures, or when the molecular weight of the polymer is too high to give solutions of reasonable viscosity. Solution polymerization is used when the catalyst permits or requires higher temperatures of operation, when the desired product can be made at these temperatures, or when the molecular weight of the product is low enough to form solutions of viscosities that can be readily handled.
Radiation graft copolymerization in aqueous dispersion
Authors: Cooper W. , Sewell P. R. , Vaughan G. 
Published: April 2003

AbstractThe rates of polymerization of monomers in rubber in aqueous dispersion are higher than in the corresponding bulk polymerizations. The higher rates, which are independent of latex concentration over the range of concentration studied, have been attributed to the ingress of free radicals from a certain volume of the aqueous phase surrounding each particle. The γ‐radiation‐initiated graft polymerization of styrene with rubber is similar to that with methyl methacrylate, though the fraction of grafted polymer is lower. In the photoinitiated systems, styrene behaves differently from methyl methacrylate in that the rate of polymerization diminishes at higher monomer concentrations.
Electron resonance spectra of gamma‐irradiated polymers: Measurements at 77°K. on polymethacrylic acid and related compounds
Authors: Ovenall Derick W. 
Published: April 2003

AbstractThe electron spin resonance (e.s.r.) spectra of free radicals trapped in some addition polymers after gamma‐irradiation at 77°K. are described and discussed. When polymethacrylic acid is gamma‐irradiated at 77°K., the e.s.r. spectrum at this temperature consists of a symmetrical pattern of seven lines which may be due to dimethyl carboxy methyl radicals, (CH3)2C—CO2H. On warming to 300°K. this spectrum is replaced by the normal “five‐plus‐four line” spectrum, which has been attributed to trapped propagating radicals. When polymethacrylic acid freed from monomer is gamma‐irradiated at 77°K. the e.s.r. spectrum is a single line, probably arising from trapped ·CO2H radicals. A reaction scheme is put forward to account for the production of these radicals. Some observations on polymethyl, polyethyl, poly n‐butyl, and poly n‐hexyl methacrylates and polydimethyl itaconate are also reported.
Thioglycol polymers. I. Hydrochloric acid‐catalyzed autocondensation of thiodiglycol
Authors: Woodward F. N. 
Published: April 2003

AbstractThe possibility of including autocondensation of thiodiglycol in the presence of potential dehydrating catalysts has been investigated. Of the possible catalysts examined, hydrochloric and sulfuric acids were found to be the most effective. In the presence of 0.5–3.0% of the former at temperatures in the range 50–200°, low molecular weight, waxy, water‐soluble, solid polymers of the type HO[C2H4SC2H4O]nC2H4SC2H4OH were obtained in yields upto 67% in addition to some ring closure to give thioxane. The dimer (n = 1) was obtained in a pure state, and the next five members in the series (n = 2–6), in impure form. Evidence was obtained of the formation of the compounds with molecular weights up to about 1300 (n = 11).
Thioglycol polymers. II. Phosphorus pentoxide‐catalyzed autocondensation of thiodiglycol and 2,2′‐dihydroxydiethyl disulfide
Authors: Abrams J. T. , Andrews K. J. M. , Woodward F. N. 
Published: April 2003

AbstractThe study of the autocondensation of thiodiglycol initiated in Part I has been extended under conditions likely to give water‐insoluble polymers of higher molecular weight. The catalytic power of 27 compounds was first determined, and the rates of polymer production were assessed for reaction in the presence of those eleven compounds thus found to be most effective. On the basis of mean molecular weight (3300), solubility in benzene, yield, and appearance of the product, phosphorus pentoxide was chosen for more exhaustive tests. Heating thiodiglycol with P2O5 (2.0%) for 12 hr. at 140°/760 mm., followed by heating for increasing periods at 150°/40 mm., yielded products ranging from a viscous liquid (M.W. 2500; ηsp 0.067) to a rubbery dark‐brown wax (M.W. 6500; ηsp 1.061). The solubility in benzene, chloroform, and dichlorodiethyl ether decreased with increasing molecular weight. The catalyst tended to become exhausted: this was found to be due to chemical combination. 2,2′‐Dihydroxydiethyl disulfide was successfully autocondensed under similar conditions to give an elastic, insoluble polymer with some tendency to cold flow, presumably built up from C2H4OC2H4S2 units.
Polymerization of butene‐1 with Ziegler catalysts
Authors: Medalia A. I. , Orzechowski A. , Trinchera J. A. , Morley J. P. 
Published: April 2003

AbstractThe Ziegler polymerization of butene‐1 has been studied in detail, by means of the pressure bottle technique. Eight principal conditions of polymerization have been varied. The amount and properties of the polymer have been studied, with particular emphasis on the atactic polymer. The polymers are generally from 50 to 70% atactic. Yields of over 300 g. polymer per gram of triisobutyl aluminum and intrinsic viscosities of over 2.5 have been obtained. The rate of polymerization goes through a sharp maximum at a catalyst ratio (Al/Ti) of 1.5–1.7. The kinetics are first‐order in monomer, with a sharp drop in the rate constant after 1–5 hr. of polymerization.
Phenylene sulfide polymers. I. Mechanism of the macallum polymerization
Authors: Lenz Robert W. , Carrington William K. 
Published: April 2003

AbstractThe reactions used in the past for the preparation of phenylene sulfide and related polymers are reviewed. The Macallum polymerization is a polycondensation of an aryl halide and an inorganic sulfide or polysulfide in the absence of solvents. The monomer system studied most thoroughly is represented by the following, unbalanced equation:
The synthesis of aromatic divinylogs and aromatic halogenated vinylogs
Authors: Frisch K. C. 
Published: April 2003

AbstractTwo new higher homologues of p‐divinylbenzene, p‐allylstyrene (p‐allylvinylbenzene) and p‐1‐propenylstyrene (p‐1‐propenylvinylbenzene) were synthesized and characterized. Intermediates for the synthesis of difunctional aromatic vinylogs, p‐chloro‐allylbenzene was prepared for the first time and p‐bromostyrene was made by methods different from those reported previously for this material. The usefulness of anhydrous cobaltous chloride for the activation of vinyl bromide in the reaction with aromatic Grignard compounds was demonstrated in the synthesis of p‐allyl‐ and p‐bromostyrene. Rearrangement of the allyl to the 1‐propenyl group on treatment with activated alumina at 300° was shown in the synthesis of p‐1‐propenylstyrene and 1‐propenylbenzene. Peroxide‐initiated bulk polymerization of p‐divinylbenzene, p‐1‐propenylstyrene, and p‐allylstyrene established the following order of reactivity: vinyl > 1‐propenyl > allyl. Preliminary polymerization of 1‐propenylstyrene and copolymerization with styrene in bulk and in solution showed the former to be an efficient though slower crosslinking agent than p‐divinylbenzene. Molding of solid copolymers of styrene and p‐1‐propenyl‐styrene was carried out, resulting in the formation of thermosetting clear and brittle resins.
The stereoregular polymerization of isoprene with lithium and organolithium compounds
Authors: Stearns R. S. , Forman L. E. 
Published: April 2003

AbstractAll of the alkali metals catalyze the polymerization of dienes such as butadiene and isoprene. A stereoregular polymer is obtained when the polymerization of isoprene is catalyzed by lithium or organolithium compounds in the absence of oxygen contaning solvents. The polymer has molecular structure, configuration, and physical properties similar to Hevea rubber, and a microstructure comprised of 93–95% cis‐1,4 and 5–7% 3,4 addition. The polymerization appears to proceed by way of an homogeneous catalytic mechanism. Stereoregularity is a result of cis coordination between a monomer molecule with a carbon bound lithium atom and formation of a six membered, cyclic, activated complex. This complex owes its relative stability to the capability of the lithium atom to undergo hybridization and to behave as an atom with considerable divalent character. The observed effects of temperature, catalyst concentration, type of solvent, and effect of Lewis bases such as ethers on the microstructure of these isoprene polymers are consistent with the catalytic reaction mechanism advanced.
The polymerization and copolymerization of alkylvinylacetylene derivatives
Authors: Price Charles C. , McKeon Thomas F. 
Published: April 2003

AbstractWith the use of free radical initiators, homopolymers from vinylacetylene (I), 2‐ethyl‐1‐vinylacetylene (II), isopropenylacetylene (III), and 2‐ethyl‐1‐isopropenylacetylene (IV) have been prepared in which the ethynyl group was largely preserved. Copolymers of these monomers with methyl acrylate, methyl methacrylate, acrylonitrile, styrene, and 2‐vinylpyridine have also been prepared. The Q and e values were determined from 2‐vinylpyridine and acrylonitrile copolymers: Q = 0.50, e = −0.40 for vinylacetylene; Q = 0.44, e = −0.35 for 2‐ethyl‐1‐vinylacetylene; and Q = 0.35, e = −0.30 for isopropenylacetylene. The polymers absorbed oxygen and became crosslinked and insoluble on exposure to air, which complicated, the investigation of molecular weight and ultraviolet spectra.
Studies on the enzymatic synthesis of dextran
Authors: Braswell Emory , Stern Kurt G. 
Published: April 2003

AbstractThe molecular weight (determined by light scattering) of the dextran produced during the enzymatic synthesis increases while the intrinsic viscosity decreases throughout the course of the reaction. The size and spherical shape of the dextran molecule does not change significantly throughout the course of the reaction. The “branching ratio” (1,6‐links to non‐1,6‐links) as indicated by periodate titration increases with the degree of conversion. An increase in branching would explain the intrinsic viscosity decrease and the density increase with increasing molecular weight. Fructose, which accumulates as a byproduct in the reaction mixture, is not responsible for these effects. The molecular weight of the dextran resulting from purified enzyme is much greater than that produced from crude enzyme. Because of this it is difficult to make conclusions about the mechanism of synthesis from this kind of data.
Poly‐N‐lauryl methacrylate. V. Dilute solution properties by viscosity and light scattering
Authors: Chinai S. N. , Guzzi R. A. 
Published: April 2003

AbstractPoly‐n‐lauryl methacrylate, prepared by the emulsion technique, was fractionally precipitated to obtain nine sharp fractions. These fractions were studied in an ideal solvent, isopropyl acetate at 13°C., and in a nonideal solvent, n‐butyl acetate at 23°C., by the light scattering and viscosity methods. The principal relationships obtained are: in isopropyl acetate at 13°C. (theta solvent); [η]θ = 3.22 × 10−4 M, (r02)½ = 0.49 M; and the the good solvent, n‐butyl acetate at 23°C.; [η] = 8.46 × 10−5 M, (r2)½ = 0.35 M; for λ = 5460 A., A2 = 9.782 × 10−3 M and for λ = 4360A., A2 = 9.778 × 10−3 M. The effect of the size of the pendent groups on the degree of chain extension in ideal solvents is discussed. It was found that the degree of chain extension of the polymers thus far studied follows the order poly‐n‐lauryl methacrylate > poly‐n‐hexyl methacrylate > poly‐n‐octyl methacrylate > poly‐n‐butyl methacrylate > poly ethyl methacrylate ≥ polymethyl methacrylate.
Polyelectrolyte behavior of glycerol‐treated psoas fibers
Authors: Blum J. J. , Felauer E. 
Published: April 2003

AbstractGlycerol‐treated psoas fibers lengthen when transferred from distilled water to 0.01M barbital at pH 3.3. The addition of electrolyte then causes a considerable shortening, depending primarily on the charge of the anion. The effects of the ionic strength are reversible. The extraction of myosin from the fiber increases the pH at which length changes are observable.
The effect of polymer composition on radiation‐induced crosslinking
Authors: Witt Edward 
Published: April 2003

AbstractThe gelation induced by Co60 gamma radiation in butadiene‐styrene copolymers, homopolymers, and mixtures of these homopolymers was studied by use of random crosslinking theory. The number of crosslinks formed per 100 e.v. of energy absorbed by the polymer, G(X), was found to be 0.045 for polystyrene and 3.6 for polybutadiene. The behavior of styrene units in copolymers and physical mixtures of butadiene and styrene homopolymers was different for the two polymer systems. Gel measurements showed that in the copolymer system there was a transfer of radiation energy from butadiene to styrene units, whereas there was no energy transfer in mill‐ and latex–prepared physical mixtures. It was further determined that terpolymerization of methyl methacrylate with butadiene and styrene induces some chain scission within the polymer chain when it is irradiated, thereby lowering further the net crosslinking of the resulting polymer.