bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of Ziegler‐Natta polymerization of propylene and α‐d‐propylene
Authors: Overberger C. G. , Jarovitzky P. A. , Mukamal H. 
Published: April 2003

AbstractRates of propylene homopolymerization and α‐d‐propylene‐propylene copolymerization were determined by using constant‐pressure polymerization conditions. It could be demonstrated that the rate of propylene homopolymerization was constant under the conditions used. However, the initial rate of copolymerization was faster and decreased with time to the rate obtained for propylene homopolymerizations. The higher initial copolymerization rate was attributed to the stabilization of potentially active centers in solution when the deuterated monomer was present. These active centers are assumed to be formed by reactions of tetravalent titanium with monomer. These active centers, which are formed in solution, are said to be destroyed by isotopically controlled reactions, i. e., abstraction of the hydrogen or the α‐deuterium atom from these monomer‐alkylated species in solution or at the interface. These active centers are believed to be adsorbed and/or chemisorbed onto the precipitated catalyst surface and to be responsible for a polymer of considerably lower steric order. This scheme predicts a stereoregular polymer of high molecular weight produced by polymerization on a Ti(III) surface and a largely amorphous polymer of lower molecular weight produced by adsorbed and/or chemisorbed species. This prediction was verified by fractionation of the deuterated polymers into crystalline and amorphous portions.
Cyclopolycondensations. VII. Preparation of aromatic poly(ureido acids) by the low‐temperature solution polymerization and cyclodehydration to fully aromatic polyquinazolinediones
Authors: Tohyama Shunroku , Kurihara Masaru , Ikeda Kojuro , Yoda Naoya 
Published: April 2003

AbstractFully aromatic polyquinazolinediones (IV) of high molecular weight were obtained by thermal cyclodehydration of aromatic poly(uredio acids) (III) prepared by the polyaddition reaction of 4,4′‐diaminobiphenyl‐3,3′‐dicarboxylic acid (I) with aromatic diisocyanates (II). From the kinetic study of reactions of model systems (anthranilic acid with phenyl isocyanate) in the presence of a variety of basic catalysts, it was established that tertiary amines had the highest catalytic activity for the formation of ureido linkage. The optimum polymerization conditions were determined by the study of reaction variables such as monomer concentration, polymerization temperature, monomer ratio, and catalyst concentration. The effect of polarity and purity of organic solvents and reactants was also studied.
Alkyl vinyl esters of brassylic (tridecanedioic) acid
Authors: Chang Shu‐Pei , Miwa Thomas K. , Wolff Ivan A. 
Published: April 2003

AbstractBrassylic acid was partially esterified at 77°C. in toluene solution with ethyl, 2‐methylpentyl, or nonyl alcohol and with p‐toluenesulfonic acid used as catalyst. Half‐esters were isolated from the respective reaction mixtures in yields of 28, 34, and 32% after reaction times of 2,6, and 8 hr. Both recovered brassylic acid and byproduct dialkyl ester were successfully used as starting materials in subsequent esterifications. Consequently, conversion of starting materials to half‐ester would be increased in a process that involved continuous recycling of byproducts. Alkyl hydrogen brassylates were vinylated at 165°C. for 8 hr. with acetylene at 360 psig. The zinc salt generated in situ from zinc oxide served as catalyst and toluene as solvent. Yields were 80–88% and purities of products were 94–95%. Samples of 2‐methylpentyl vinyl brassylate and nonyl vinyl brassylate of much higher purity were obtained by preparative gas–liquid chromatography or molecular distillation. Physical properties and experimental conditions for gas–liquid chromatographic analyses of both the alkyl hydrogen and alkyl vinyl brassylates are reported.
Synthesis and polymerization of 1,3‐bis‐(2,3‐epoxypropylphenyl)tetramethyldisiloxanes and related compounds
Authors: Bilow N. , Lawrence R. E. , Patterson W. J. 
Published: April 2003

Abstract1,3‐Bis[p‐(2,3‐epoxypropyl)phenyl]tetramethyldisiloxane and its meta isomer were synthesized and subsequently cured with m‐phenylenediamine. Dielectric properties of the cured resin derived from the para isomer were measured between 25 and 100°C. The ambient temperature dielectric constant of the resin at 1 kc./sec. was 3.4, its dissipation factor was 0.01, and its volume resistivity was 1014 ohm‐cm. at 500 v. d.c. Several allylphenylsiloxanes were also prepared by the cohydrolysis of allylphenyldimethylethoxysilane with dimethyldiethoxysilane, bis(dimethylethoxysilyl)benzene, and methyltriethoxysilane. Preliminary epoxidation studies on these latter materials were also carried out.
Radiation‐induced polymerization of 1,1,2‐trichlorobutadiene
Authors: Matsuda Tatsuo , Fujii Shigetada 
Published: April 2003

AbstractThe γ‐ray‐induced polymerization of 1,1,2‐trichlorobutadiene, m.p. −48.5°C., was investigated in the temperature range from +55 to −196°C. In the liquid state, the following results were obtained: (1) the rate decreases with decrease of temperature (Ea = 8.0 kcal./mole); (2) the dose rate dependences of rate and of molecular weight are 0.49 and −0.25, respectively; (3) the reaction is inhibited by DPPH; (4) the structure of the polymer is predominantly 1,4 units. It was concluded that the liquid‐state polymerization proceeds by a radical mechanism, and the radical yield was found to be 19.7. In the solid state, the following results were obtained: (1) the rate is considerably higher than in the liquid state immediately above the melting point and gradually decreases with decrease of temperature (Ea = 0.34 kcal./mole); (2) the dependence of the rate on dose rate is unity while the molecular weight is independent of the dose rate; (3) the reaction rate is unaffected by DPPH and accelerated by dimethylformamide; (4) the structure of the polymer, 3,4 units, is completely different from that of the polymer obtained in the liquid‐state polymerization. The solid‐state polymerization is probably of a different nature and is not well elucidated.
Polynomial expansion of log relative viscosity and its application to polymer solutions
Authors: Palit Santi R. , Kar Indrajit 
Published: April 2003

AbstractSolomon and Ciuta's equation has been deduced from first principles and has been shown to be merely an algebraic consequence of the definition of intrinsic viscosity. Secondly, a consequence of this equation that [η]c should be linear with \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt {2\eta {\rm sp} - 2\ln \eta {\rm rel}}$\end{document}
with unit slope, is found to be fairly accurate when examined against literature and our own data, and so this equation is commended not only for single‐point determination of [η] but also for representing viscosity variation with concentration up to ηsp < 0.60. Thirdly, higher‐order approximations are found to be less suitable. Other consequences of Solomon and Ciuta's equation are discussed.
Arylene‐modified siloxanes
Authors: Breed L. W. , Elliott R. L. , Whitehead M. E. 
Published: April 2003

AbstractPolyarylenepolysiloxanes with varied structure can be obtained in condensation reactions of arylenedisilanols and N‐methylsiloxazanes. Molecular weights, viscometric properties, glass transition temperatures, and thermogravimetric analysis data are reported.
Endgroup study of chlorate–sulfite‐initiated acrylonitrile copolymer
Authors: Shibukawa T. , Sone M. , Uchida A. , Iwahori K. 
Published: April 2003

AbstractQuantitative determination of endgroups in an acrylonitrile–methyl acrylate (90:10) copolymer polymerized with NaClO3–Na2SO3 redox system in aqueous solution was carried out by conductometric and dyeing methods for SO3H incorporated into polymer, x‐ray analysis for S in polymer, and polarography for Cl in polymer. The number‐average molecular weight was measured by osmometry. Determination of endgroups was done on both unfractionated polymer and fractionated polymer. On the average, 0.95 mole S and 0.71 mole SO3H per molecule were found in unfractionated polymer. For fractionated polymer, 0.68 mole S and 0.69 mole SO3H per molecule were found. A small amount of Cl was also found in both unfractionated polymer and fractionated polymer. The difference between results for the two polymers and polymerization kinetics are discussed.
Polymerization of DL‐alanine NCA and L‐alanine NCA
Authors: Iwakura Yoshio , Uno Keikichi , Oya Masanao 
Published: April 2003

AbstractThe polymerization of N‐carboxy‐DL‐alanine anhydride and N‐carboxy‐L‐alanine anhydride were carried out in various solvents such as acetonitrile, dimethyl sulfoxide (DMSO), and nitrobenzene. The x‐ray diffraction diagram and the infrared spectra of the polymers of DL‐ and L‐alanine were obtained. The polypeptides obtained in acetonitrile and in nitrobenzene were in the α conformation, and the conformation of polypeptide obtained in acetonitrile was not influenced by its molecular weight. The polypeptide obtained in DMSO was essentially in the β conformation. It was observed that the α and β forms of polyalanine were altered on treatment of the polymer with m‐cresol, dichloroacetic acid, or formic acid.
Polymerization of acrylamide initiated by the persulfate–thiosulfate redox couple
Authors: Riggs J. P. , Rodriguez F. 
Published: April 2003

AbstractConversion–time data were obtained for the polymerization of acrylamide initiated by the redox couple persulfate–thiosulfate by using a dilatometer. A plot of initial rate as a function of thiosulfate concentration shows a well‐defined maximum and three distinct regions of behavior. In each region the shape of the conversion–time curves demonstrates the differences in apparent order with respect to monomer arising from changes in initiator concentration during an individual run. A reaction mechanism is proposed to explain the results, and a limiting form of the rate expression is derived for each of the three regions. The ranges of concentration studied are: persulfate, 9.5 × 10−4−4.7 × 10−2M; thiosulfate, 2 × 10−5−2 × 10−2M; initial monomer, 0.05–1.0M; and temperature, 30–50°C. Within these ranges the initial rate shows a halforder dependence on persulfate and a first‐order dependence on initial monomer concentration.
Association of polyacrylonitrile prepared by low‐temperature, solution polymerization with an organometallic catalyst
Authors: Chiang R. , Stauffer J. C. 
Published: April 2003

AbstractThe weight‐average molecular weights of polymers of acrylonitrile prepared by a free‐radical initiator and an organometallic catalyst have been determined by lightscattering measurements in N,N‐dimethylformamide, dimethyl sulfoxide, and dimethylacetamide at 25°C. and in dimethyl sulfoxide at 140°C. The apparent molecular weights of the polymers prepared with the NaAlEt3S(i‐Pr) catalyst in DMF at −78°C. (referred to as high‐melting polymers) changed from 54,800, 82,700, and 480,000 when measured in DMF at 25°C. to 36,000, 41,600, and 225,000 when measured in DMSO at 140°C., whereas the molecular weights of the free‐radical polymers remained unchanged. Furthermore, from results obtained in DMSO at 140°C., The intrinsic viscosity–molecular‐weight relationships were found to be identical for the high‐melting and the free‐radical polymer and in substantial agreement with an equation reported by Cleland and Stockmayer. The apparent decrease in molecular weight of the high‐melting polymer from 25 to 140°C. indicates rather clearly that the high‐melting polymers are associated in DMF at 25°C. The “aggregates,” even though present only at low concentrations, raised the weight‐average molecular weight markedly but affected the number‐average molecular weight only slightly, thus giving a high M̄w/M̄n ratio. It appears likely that when temperature and solvent are such that association does not occur, linear PAN's will have approximately the same intrinsic viscosity–molecular weight relationship (subject of course to slight change by polydispersity). The often reported abnormal molecular weight of samples prepared by solution polymerization especially at low temperatures, may be attributed to branching, or to an association, as reported here. The nature of association of PAN in dilute solution is also discussed.
Degradation of poly(ethylene oxide) by high‐speed stirring
Authors: Minoura Yuji , Kasuya Tanekazu , Kawamura Shinji , Nakano Akihiko 
Published: April 2003

AbstractDegradation of poly(ethylene oxide) (PEO) by violent stirring was studied in various solvents. The chain scission or the limit of the degradation was measured, and the effects of solvents, polymer concentration, stirring speed and degree of polymerization (DP) were investigated. It was found that the number of bonds broken per polymer chain was independent of the concentration but increased with the stirring speed and with decrease in the DP. The rate was much affected by the solvent used, being larger in a poor solvent. It was also found that the rate could be represented either by Jellinek's or Ovenall's rate equations, which have been applied to the ultrasonic degradation of polymers in solution.
General description of optical dichroic orientation factors for relating optical anisotropy of bulk polymer to orientation of structural units
Authors: Nomura Shunji , Kawai Hiromichi , Kimura Itzuro , Kagiyama Mitzuyasu 
Published: April 2003

AbstractThe relationship between the optical anisotropy of high polymeric materials in bulk and the orientation of structural units within the materials was described in general by using several types of mean values of the orientation distribution function of three Eulerian angles, i.e., the orientation factors, under some assumptions about the symmetry of the function being applicable for the most of the industrial products. A newly defined biaxial orientation factor, Fθηi = 〈sin2 θj cos 2ηj〉, where θj and ηj are the polar and azimuthal angles of the jth axis within the structural unit with respect to the bulk axes, may relate the biaxial orientation of the structural units to the dichroic orientation factors, which are measurable optical anisotropic indices of the bulk materials. Some applications of the results to the birefringence and infrared and dye dichroism are also discussed.
On the use of a random parameter in the theory of depolymerization of long‐chain molecules
Authors: Coyne Brian J. 
Published: April 2003

AbstractEquations for the time course of depolymerization of long‐chain polymers are derived by the method of randomization of a parameter for the case in which all bonds have equal probability of cleavage. This yields some gain in insight and avoids the necessity for solving systems of differential equations.
Sorption of organic vapors into drawn and undrawn polyethylene
Authors: Peterlin A. , Williams J. L. , Stannett V. 
Published: April 2003

AbstractDrawing of linear polyethylene at 60°C. to an extension ratio of ten drastically reduces the sorption and diffusion of n‐pentane, benzene, methylene chloride, and tetrachloroethylene. Methylene chloride was chosen for more detailed study. The sorption is of the normal Fickean type. It is also fully reversible in the temperature range between 25 and 45°C. if the sorbed amount is kept to below 0.5%. At higher concentrations the sample relaxes so that sorption irreversibly increases. The reversible sorption per gram of amorphous component is about 1/6 of that in undrawn polyethylene. The diffusion constant has a larger temperature and concentration dependence than in the undrawn material. At zero concentration the activation energy for diffusion is 34.4 kcal./mole and the diffusion constant at 25°C. is 8 × 10−11 cm.2/sec. as compared with 14.4 kcal./mole and 1.5 × 10−8 cm.2/sec. in undrawn PE. Cold drawing reduces the sorption sites without changing their energy content, but drastically cuts down diffusion and increases the activation energy. A smaller part of the increase of the latter is a consequence of the lower enthalpy of the amorphous material and a larger part is probably due to the increased distance between sorption sites.
Viscoelasticity of textile fibers at finite strains
Authors: Hall I. H. 
Published: April 2003

AbstractExperimental data obtained from stress–strain curves of five different textile fibers, at a series of different, constant strain rates covering a range of 61/2 decades have been used to study two methods of nonlinear viscoelastic analysis proposed elsewhere. According to the first of these, time and strain effects are factorizable so that stress σ, strain ε and time t are related by the equation σf1(ε)/ε = f(t),. This is shown to be unsatisfactory with the present materials, but an empirical modification to σf1(ε)/ε = f2(ε) + f(t) is satisfactory. According to the second, general nonlinear viscoelastic behavior can be described by an equation which reduces to the form σ/ε = F1(t) + εF2(t) + ε2F3(t) + when applied to extension at a constant strain rate. This series is shown to be strongly divergent except at fairly small stains. In fact, if it is truncated after about three terms, which are as many as can be estimated with any significance in the present experiments, it is applicable only to strains of about 3–4% and less. Numerical techniques which enable standard statistical procedures to be used have been devised to perform the above analyses and are described in detail.
Cationic polymerization of formaldehyde in liquid carbon dioxide. Part II: A kinetic study of the polymerization
Authors: Yokota Hisao , Kondo Masatsune , Kagiya Tsutomu , Fukui Kenichi 
Published: April 2003

AbstractThe kinetic behavior on the polymerization of formaldehyde with and without acidic catalyst, in liquid carbon dioxide, in the temperature range of 30 to 50°C. was investigated. In the polymerization without catalyst both the polymer yield and the degree of polymerization increased with reaction time and also with rising temperature. With acidic catalyst, such as acetic acid and dichloroacetic acid, both the polymer yield and the degree of polymerization increased more than that in the polymerization without catalyst. The overall rate of polymerization with and without acidic catalyst was expressed by the first‐order rate equation with respect to monomer concentration. From the results it was concluded that the polymerizations belonged to a type of successive polymerization with rapid initiation and no termination. The rate constant and the activation energy of each elementary process of polymerization were estimated on the basis of the results.
The synthesis of some optically active C‐methylated 2‐oxohexamethyleneimines
Authors: Overberger C. G. , Parker Gordon M. 
Published: April 2003

AbstractThree new, optically active, methyl‐substituted 2‐oxohexamethyleneimines were prepared by cyclization of the respective optically active C‐methylated 6‐aminohexanoic acids. The active forms of the amino acids used for the preparation of (−)‐3‐methyl‐2‐oxohexamethyleneimine and (−)‐7‐methyl‐2‐oxohexamethyleneimine were obtained by resolution of their diastereomeric quinine salts. s‐(+)‐5‐methyl‐2‐oxohexamethyleneimine was synthesized without racemization from optically pure 2‐isopropylidene‐5‐methyleyclohexanone (pulegone).
Chain transfer for vinyl monomers polymerized in N‐allylstearamide
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Wrigley A. N. 
Published: April 2003

AbstractApparent transfer constants have been determined for styrene, methyl methacrylate vinyl acetate, and diethyl maleate polymerized in N‐allylstearamide at 90°C. Regression coefficients for transfer were: methyl methacrylate, 0.301 × 10−3; styrene, with no added initiator, 0.582 × 10−3; styrene, initiated with benzoyl peroxide, 0.830 × 10−3; vinyl acetate, 62.01 × 10−3; and diethyl maleate, 2.24 × 10−3. Rates of polymerization were retarded for both styrene and methyl methacrylate. Vinyl monomer and comonomer disappearance followed an increasing exponential dependence on both initiator and monomer concentration. Although degradative chain transfer probably caused most of the retardation, the cross‐termination effect was not eliminated as a contribution factor. Rates for the vinyl acetate copolymerization were somewhat retarded, even though initiator consumption was large because of induced decomposition. The kinetic and transfer data indicated that the reactive monomers added radicals readily, but that rates were lowered by degradative chain transfer. Growing chains were terminated at only moderate rates of transfer. Unreactive monomers added radicals less easily, producing reactive radicals, which transferred rapidly, so that molecular weights were lowered precipitously. Although induced initiator decomposition occurred, rates were still retarded by degradative chain transfer. A simple empirical relation was found between the reciprocal number‐average degree of polymerization, 1/X̄n1 and the mole fraction of allylic comonomer entering the copolymer F2, which permitted estimation of the molecular weight of copolymers of vinyl monomers with allylic comonomers. This equation should be applicable when monomer transfer constants for each homopolymer are known and when osmometric molecular weights of one or two copolymers of low allylic content have been determined.