bluuebunny/crossref_metadata_2025_split huggingface dataset:
The branching reaction. III. Polymeric transfer constants of vinyl acetate with styrene and methyl methacrylate
Authors: Morton Maurice , Piirma Irja 
Published: April 2003

AbstractA study has been carried out to determine the polymeric transfer constants of poly(vinyl acetate), polystyrene, and poly(methyl methacrylate) in the polymerization of vinyl acetate, as well as the similar transfer constants of poly(vinyl acetate) in the polymerization of styrene and methyl methacrylate. As before, this was accomplished by polymerizing each monomer in the presence of varying amounts of the desired oligomer and separating the resulting polymers. The effect of oligomer endgroups was checked by using oligomers of different molecular weight (1000–5000). As found previously for styrene and methyl methacrylate, there was no noticeable effect of polymeric endgroups on transfer activity, hence the transfer constants found refer to the interior units in the chain. The values of the various transfer constants are given. As expected, the vinyl acetate radical showed a reactivity in hydrogen abstraction which was several orders of magnitude greater than that of the styrene radical, and at least one order of magnitude greater than that of methyl methacrylate. The absolute values of the activation energy for the transfer step were remarkably similar, the difference in transfer activity being largely due to the difference in activation energy of the propagation reaction, and also to steric considerations.
Aromatic polyimides
Authors: Bower G. M. , Frost L. W. 
Published: April 2003

AbstractAromatic polyimides were prepared in two steps. Pyromellitic dianhy dride was added to a solution of an aromatic diamine in a highly polar solvent, such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or N‐methyl‐2‐pyrrolidone, until a high molecular weight polypyromellitamic acid was obtained. The amount of pyromellitic dianhydride required was determined by the rate of viscosity increase with addition of the reagent, and it corresponded fairly closely to the stoichiometric quantity. Inherent viscosity of the polypyromellitamic acids in dimethylacetamide ranged from 0.54 to 3.22. Upon standing at room temperature, the viscosity of these solutions gradually declines. This viscosity decline is rapidly accelerated by an increase in temperature and is negligible at 0°C. Water and excess pyromellitic dianhydride result in a more rapid decline in viscosity. The polypyromellitimides were formed from the amide acids by heating. The solvent could be removed during the imidization step or earlier under vacuum at a lower temperature. Polypyromellitimides were prepared from m‐phenylenediamine, benzidine, 4,4′‐diaminodiphenyl ether, 3,4′‐diaminodiphenyl ether, 4,4′‐diaminodiphenyl sulfide, methylene dianiline, isopropylidene dianiline, several diaminobenzanilides, 4,4′‐diaminophenyl benzoate, and other amineterminated low molecular weight aromatic esters and amides. Polyimides cast in the form of thin films were for the most part clear, tough, flexible, insoluble, and infusible. Thick sections tended to be brittle and opaque. Several of the polymers in the form of films suffered less than 10% weight loss after aging 400 hr. at 325°C. in air. Most of these films were still intact and moderately flexible after this treatment.
Donor‐acceptor interaction in cationic polymerization. V. Influence of some alcohols on the molecular weight of polyisobutylene in polymerization catalyzed by aluminum trichloride
Authors: Zlámal Z. , Kazda A. 
Published: April 2003

AbstractAlCl3 in ethyl chloride at −78.5°C. forms with lower aliphatic alcohols (MeOH, EtOH, i‐PrOH, tert‐BuOH) complexes of the type 4ROH · AlCl3, 2ROH · AlCl3, ROH · AlCl3 and ROH · AlCl6. The existence of these complexes was established from the conductivity—composition graphs of corresponding ROH‐AlCl3 systems. These complexes are ionized to different degrees and their ability to catalyze the polymerization of isobutylene is proportional to the acidity of the alcohol forming the complex. Phenol differs somewhat in its behavior. The conductivity‐composition plot reveals the existence of complexes of the type 3C6H5OH · AlCl3, 2C6H5OH · AlCl3, and C6H5OH · AlCl3. The catalytic activity of complexes containing phenol and AlCl3 is considerably higher than that of complexes involving aliphatic alcohols. The dependence of the molecular weight of polyisobutylene on the composition of the active complex is a mirror image of the conductivity graph. The rate of termination reactions changes with both concentration and quality of anions present. The termination activity of anions derived from phenol and containing OC6H5 group is considerably higher than the termination activity of anions derived from aliphatic alcohols.
An application of the prigogine solution theory to intrinsic viscosities in polyisobutylene‐n‐alkane systems
Authors: Bataille P. , Patterson D. 
Published: April 2003

AbstractIntrinsic viscosities have been obtained for polyisobutylene in the series of n‐alkane solvents at −12, 24.3, and 57.9°C. Values of the χ parameter have been calculated using [η]/[η]ϑ = α2.43 and the Flory closed expression relating α to χ (as modified by Stockmayer): α5 — α3 = 2 × 0.49 CMM1/2 [(1/2) — χ]. The values found by the first method are in excellent agreement with an approximate expression for χ derived using the Prigogine theory of polymer solutions, viz. Rχ = ArA/T + BT/rA where rA is the number of segments in the solvent molecule. Values of the constants A and B compare well with those found from heats of mixing of polyisobutylene with the same solvents. Values of χ are also obtained using the more recently Kurata‐Stockmayer‐Roig expression for the α — χ dependence although reasons are advanced for preferring the Flory‐Stockmayer equation. Qualitative, but less good quantitative agreement is now found between the χ values and the Prigogine theory.
Monomers containing phosphorus. Part II. Copolymerization of diallyl phenyl phosphine oxide with n‐lauryl methacrylate
Authors: Beynon K. I. 
Published: April 2003

AbstractMonomer reactivity ratios have been measured for the copolymerization of n‐lauryl methacrylate with diallylphenylphosphine oxide at 80, 110, and 140°C. The n‐lauryl methacrylate is far more reactive in the copolymerization than the diallylphenylphosphine oxide. The reactivity ratios at 140°C. as calculated by the Mayo and Walling integrated equation vary with the composition of the starting mixture in the copolymerization, and the value of r2 is significantly negative. These effects are explained by the existence of a penultimate group effect produced by diallylphenylphosphine oxide.
Interactions of polyelectrolytes. A turbidimetric method for the estimation of ionized polymers
Authors: Josephs R. , Feitelson J. 
Published: April 2003

AbstractThe turbidity resulting from the interaction of protamine with negatively charged polymers in solution was adapted to the micro estimation of the latter. The influence of pH, salt concentration, and valency as well as protamine concentration and time dependence was investigated in the protamine—polymethacrylic acid system and the optimal conditions for turbidimetry were established. Amounts of down to 2 × 107−7 monomoles of polymer were conveniently measured. The method is usable over a wide pH range but is sensitive to the added salt or buffer concentration. The changes in turbidity as a function of the above mentioned variables are qualitatively explained in terms of polyelectrolyte interaction complexes and screeing of the aggregate charges by added electrolyte. The method was also tested for its applicability to the estimation of polyglutamic acid.
Coordination compounds of p‐nitrobenzeneazotyrosine
Authors: Mattison Louis E. , Phipps Martha S. , Alfred Lillian , Taylor Sally , Thompson John , Saul Barry 
Published: April 2003

AbstractIn continuation of earlier work, another chelating agent containing two different chelating systems in the same molecule (p‐nitrobenzeneazotyrosine) was synthesized. 2:1 coordination monomers of this molecule were made and characterized with divalent copper, lead, cobalt, nickel, uranyl, and zinc ions. From these compounds, two types of coordination polymers were synthesized and studied: those involving the ions of one metal bound with both chelating groups in the ligand, and those having two different metals bound in the same polymer chain. Thermal analysis data showed that (among the group under consideration) the bimetallic polymeric chelates have no exceptional stability.
Molecular properties of amorphous high polymers. I. A cell theory for amorphous high polymers
Authors: DiBenedetto A. T. 
Published: April 2003

AbstractA cell model is used to describe the structure‐insensitive properties of amorphous high polymers. An amorphous polymer is characterized as a homogeneous, one‐component phase containing N identical n‐center polymer segments. Each center is acted on by a cylindrically symmetric square well potential which is developed by assuming a 6–12 type interaction between point centers along the axis of the polymer chain. Molecular constants, p‐V‐T behavior, glass‐transition temperatures, and cohesion energy densities are predicted from a minimum of experimental data. A good agreement between theory and experimental data from various literature sources is shown for eight amorphous polymers.
Synergistic antioxidant combinations. Carbon black substitutes
Authors: Hawkins W. L. , Worthington M. A. 
Published: April 2003

AbstractAlkylated diphenoquinones form synergistic antioxidant combinations with sulfur and a variety of organosulfur compounds. In combination with thiols, reduction of the diphenoquinones to their corresponding diphenols occurs, and these phenols are also synergistic with sulfur compounds. Secondary amines including N,N'‐diphenyl‐p‐phenylenediamine and the diimine formed by its oxidation function similarly as do the polyacenes. Synergism with these antioxidant systems may result from regeneration of a phenol or a secondary amine as the active chain terminator. The effectiveness of these antioxidant combinations suggests, however, that additional stabilization reactions may occur involving the sulfur component.
Generalized approach to adhesion via the interfacial deposition of amphipathic molecules. II. Adhesion of polyethylene to aluminum
Authors: Schonhorn Harold 
Published: April 2003

AbstractOriented monolayer adhesives of radioactive stearic acid have been employed to bond polyethylene to aluminum. Bonding time, bonding temperature, and rate of peel are several of the parameters that were varied to determine their effect on the final peel strength. Techniques for maximizing the resistance to peel are discussed and incorporated in this communication. Peel strengths in excess of 100 lb./in. width are reported with stearic acid as the monolayer adhesive. The peel forces obtained in the present investigation are more than two orders of magnitude greater than those reported in the literature. The only limitation being the cohesive strength of the thermoplastic adhered. Kaeble's peel force theory is described and adapted to our experimental data. Reasonably good agreement is obtained for low peel strengths (≤25 lb./in. width).
Crystallization in starch: The role of ions in the lyotropic series
Authors: Khairy M. , Morsi S. , Sterling Clarence 
Published: April 2003

AbstractThe crystallization (retrogradation) of starch from solution has been investigated as a function of electrolyte composition and concentration. The anion effects follow a lyotropic series which causes retrogradation in the approximate descending order: CNS‐, (PO4≡, CO3=), I‐, NO3−, Br‐, Cl‐, C2H3O2‐, F‐, SO4=. Cations also tend to follow the lyotropic series of Ba++, Sr++, Ca++, K+, Na+, Li+. Increasing concentrations of most salts (except for NaF and MgSO4) result in decreased precipitation of starch. The descending order of ions in the lyotropic series is best explained in terms of the decreasing polarity and decreasing relative intensity of electric charge, due either to increasing ion symmetry or to increasing area of charge distribution as a result of resonance among several configurations. It is suggested that the polar, higher charge intensity in ions at the upper end of the series brings about charging of the starch molecule, which leads to solubilization because of (1) the repulsion of the similarly charged molecules and (2) the aggregation of a water mantle about each molecule.
Polyamides containing phosphorus. II. Structural effects on softening and glass transition temperatures
Authors: Pellon Joseph 
Published: April 2003

AbstractGlass transition temperatures as a function of structure for phosphorus‐containing polyamides and polyamides containing other heteroatoms are analyzed in terms of the effect of polarity, steric behavior, and bond flexibility differences. The side‐chain alkyl or aryl group carried by phosphorus was expected to increase chain mobility (lower glass transition temperatures) by separating chains and reducing intermolecular interaction. This general effect is offset by decreased mobility due to the greater polarity of the phosphorus groups, and the intramolecular steric hindrance to rotation caused by the alkyl or aryl group on phosphorus. Glass transition temperatures indicate the following order of bond flexibility: (CH2NCH2 ≈ CH2SCH2≈ CH2OCH2)> CH2P(R)CH2 ≈ CH2CH2CH2. The phosphorus‐to‐carbon bond showed no enhanced flexibility over a carbon‐to‐carbon bond.
Ultimate tensile properties of elastomers. I. Characterization by a time and temperature independent failure envelope
Authors: Smith Thor L. 
Published: April 2003

AbstractThe tensile stress at break (σb) and the associated ultimate strain (ϵb) of an elastomer depend on (1) the chemical and topological characteristics of the polymeric network, and (2) the test conditions under which rupture is observed. To separate these effects, the ultimate tensile properties can often be characterized by a “failure envelope” defined by values of σb and ϵb determined at various strain rates over a wide temperature range. Provided time—temperature superposition is applicable, such data superpose on a plot of log σbTϵ/T versus log ϵb, where T is the test temperature (absolute) and T0 is an arbitrarily selected reference temperature. The resulting failure envelope is independent of time (strain rate) and temperature and thus it depends only on basic characteristics of the polymeric network. To illustrate the characterization method, data on two styrene—butadiene gum vulcanizates, SBR‐I and SBR‐II, were analyzed. For SBR‐I, values of σb and ϵb obtained over extensive ranges of strain rate and temperature superposed to give a failure envelope. Data at elevated temperatures also gave a reliable value for the equilibrium modulus. For SBR‐II, data obtained at various temperatures under conditions of constant strain and constant strain rate yielded identical failure envelopes; this strongly suggests that the failure envelope is independent of the test method. A theoretical consideration of the time‐to‐rupture associated with different test methods showed that for given values of σb and ϵb the time‐to‐rupture from the following types of tests should increase in the order: constant strain < constant stress < constant strain rate < constant stress rate.
Random and block copolymers of poly(tetramethyl‐p‐silphenylene‐siloxane) and polydimethylsiloxane
Authors: Merker Robert L. , Scott Mary Jane , Haberland G. G. 
Published: April 2003

AbstractHigh molecular weight block copolymers having the structure [(CH3)2SiO]a[(CH3)2‐Si‐p‐C6H4‐Si(CH3)2O](b)n, can be conveniently prepared from the copolymerization of hydroxy end‐blocked dimethylpolysiloxanes and p‐bis(dimethylhydroxysilyl)benzene by use of essentially nonequilibrating catalysts, such as tetramethylguanidine di‐2‐ethylhexoate or n‐hexylamine 2‐ethylhexoate. The values of a and b above may be altered by employing hydroxy‐ended dimethylpolysiloxane of different degrees of polymerization or by preforming tetramethyl‐p‐silphenylene‐siloxane units. If the length of a segment is maintained at a constant value in the copolymers decreasing the mole ratio a/b results in higher tensile strengths and higher melting points which are manifestations of increased degrees of crystallinity. If the mole ratio a/b is held constant, increasing the length of the a and b segments leads to higher melting points and higher tensile strengths again reflecting an increase in the degree of crystallinity. High molecular weight copolymers [η] ranging from 1.0 to 2.1, possessing unstressed (unvulcanized) gum tensiles of 1000–2700 psi and elongations of 500–1000% can be readily obtained by the methods described.
Copolymerization of styrene. I. Copolymerization with styrene derivatives containing nitrile groups in the side‐chain
Authors: Kreisel Moshe , Garbatski Uri , Kohn David H. 
Published: April 2003

AbstractStyrene was copolymerized in bulk with cinnamonitrile, benzylidenemalononitrile, ethyl benzylidenecyanoacetate, and atroponitrile at 80°C. up to low conversions. The usual reaction scheme of copolymerization fitted only the pair styrene‐atroponitrile. The kinetic scheme of the other three pairs fitted the scheme proposed by Barb, taking into account the effect of the penultimate unit.
Mean square length of random polypeptide chains and the length of protein fibers
Authors: Crewther W. G. 
Published: April 2003

AbstractApplication of statistical mechanical theory gives the expression r2 = 27.9n − 20.3 relating the mean square end‐to‐end length, r2, of a random polypeptide chain in the trans‐form and n, the number of amino acid residues in the chain. The corresponding expressions for the cis and nonplanar forms are r2 = 8.6n − 0.8 and r2 = 15.5n − 4.8 rrespectively. The first of these equations has been used to obtain an expression for the fractional decrease in length of a crosslinked, aligned α‐helical structure when it is converted to the random coil form. The assumptions made are that the crosslinkages undergo little lateral displacement and that the volume remains constant. The expression so obtained is \documentclass{article}\pagestyle{empty}\begin{document}$l/l_{0} = {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } \mathord{\left/ {\vphantom {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } {1.5n}}} \right. \kern-\nulldelimiterspace} {1.5n}} $\end{document} where l is the supercontracted length of the polypeptide fiber, l0 is its original length and n is the number of amino acid residues between crosslinkages.
Crosslinkages in wool fibers and their relationship to the two‐stage supercontraction of wool fibers in solutions of LiBr
Authors: Crewther W. G. 
Published: April 2003

AbstractRupture of a large proportion of the disulfide bonds of wool by reduction and methylation has no effect on the extent of total supercontraction in solutions of LiBr at 98.5°C. Reduction and methylation of the disulfide bonds increases the extent of the first stage and decreases the extent of the second stage of supercontraction. No two‐stage phenomenon is then observed at the normal extent of the first stage of supercontraction. The relationship between the extent of the first stage of supercontraction and the content of residual disulfide bonds is that predicted by the statistical mechanical theory for a structure containing acid‐labile crosslinkages at equal intervals of about 35 residues and disulfide crosslinkages at equal intervals of about 20 residues along the α‐helices of the aligned structures. This is compared with the half‐cystine content of the low sulfur protein fraction of the wool; approximately 1 residue in 18. Conversion of the disulfide bonds of wool into SCH2CH2S crosslinkages causes a decrease in the extent of the second stage and total supercontraction but does not affect the extent of the first stage. The relationship between the extent of total supercontraction, and the content of dithioethylene crosslinkages is almost identical with that observed for the first stage and disulfide content in S‐methyl wool samples. The disulfide and sulfydryl contents of wool are not altered by supercontraction at pH 6. It is concluded that the first stage of supercontraction of wool fibers in solutions of LiBr is due to the conversion of aligned α‐helices into an elastomeric form, the extent of the first stage being restricted by disulfide and acid‐labile crosslinkages. Further contraction occurs during the second stage as a result of sulfydryl‐disulfide interchange reactions which eliminate the restrictive influence of the disulfide bonds. The final extent of supercontraction is limited by acidlabile crosslinkages.
Low temperature solution polycondensation of piperazine polyamides
Authors: Morgan Paul W. , Kwolek Stephanie L. 
Published: April 2003

AbstractA simple process is described for the preparation of condensation polymers from diamines and diacid halides, which comprises reacting equivalents of the intermediates at about room temperature in an inert solvent together with an acceptor for the by‐product acid. This first paper of a series discusses the formation of polyamides from piperazines and aliphatic and aromatic diacid chlorides. Examples are poly(sebacyl piperazine) and poly(terephthaloyl dimethylpiperazine). Such variables are discussed as types of acid acceptors, solvents, reactant balance, interfering reactions, and the mechanism of the reaction. Some of the polymers are described briefly in terms of melt temperature, solubility, and molecular weight‐viscosity relationships.
Amine acid‐acceptors for the preparation of piperazine polyamides by low‐temperature solution polycondensation
Authors: Morgan Paul W. , Kwolek Stephanie L. 
Published: April 2003

AbstractPolyamides from 2,5‐dimethylpiperazine and terephthaloyl and sebacyl chlorides, having high molecular weight, were prepared in a single solvent system in the presence of various amine acceptors. Strongly basic, hindered secondary amines were fair acceptors, but tertiary amines were preferred. The tertiary amines performed well when the pKa in water was equal to or greater than the pKa of the amine group on the end of a polymer chain. The polycondensations were affected adversely by acid chloride‐tertiary amine reactions, by precipitation of diamine salts, and under some conditions by precipitation of polymer.
Electron spin resonance of irradiated solution‐crystallized polyethylene
Authors: Salovey R. , Yager W. A. 
Published: April 2003

AbstractIf films containing oriented lamellae of solution crystallized polyethylene are rotated in the external magnetic field, marked anisotropy in electron spin resonance is noted. When the magnetic field is perpendicular to the chains the spectrum consists of ten lines with a hyperfine component separation of 15 gauss. When the magnetic field is parallel to the chains, the spectrum is a sextet with a splitting of 34 gauss. These splittings are in fairly good agreement with the studies of McConnell et al. on irradiated malonic acid single crystals. The high resolution and stability of electron spin resonance spectra of irradiated polyethylene crystallized from solution suggest greater perfection of crystalline order than in elongated fibers. Moreover, the results on solution crystallized polyethylene indicate that the alkyl radicals are formed at random in the crystalline matrix.