bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carborane polymers. II. Cyclic and polymeric formals
Authors: Green Joseph , Mayes Nathan , Kotloby Anatole P. , Cohen Murray S. 
Published: April 2003

AbstractCyclic and linear formals containing a unique polycycloborane named carborane were prepared. The treatment of carborane glycols with formaldehyde or dipropyl formal yielded cyclic formals, linear polyformals, a mixture of linear and cyclic formals or no formal product depending upon the reaction conditions and the particular carborane glycol used. It was demonstrated that two of the carborane diols have a great tendency to form cyclic formals in solution or bulk‐type reactions. In the reaction with 1,2‐bis‐(hydroxymethyl)carborane, the tendency to cyclize is greater than might be expected for a seven‐membered ring. This propensity to form cyclic structure has been attributed to the short carbon–carbon bond and the relatively acute external angle of the group attached to the carborane nucleus. The stability of these cyclics has been demonstrated by failure to open the formal cyclics to form linear polymer. Polymer was obtained with bis(2‐hydroxyethyl‐1‐carboranylmethyl) ether, however, neither cyclic nor polymer products were obtained with bis(2‐hydroxymethyl‐1‐carboranylmethyl) ether. The failure to obtain the desired products have been attributed to the steric requirements of the carborane group.
Evaluation of rate constants from thermogravimetric data
Authors: Fuoss Raymond M. , Salyer Ival O. , Wilson Harry S. 
Published: April 2003

AbstractA method has been derived whereby the characteristic constants of the rate equation may be derived directly from the thermogravimetric analysis curve. The method described, in contradistinction to previously described methods, does not require transformation to a time scale, nor pointwise graphical differentiation, and no mathematical approximations are made. The method is applicable to any reaction showing one or more successive thermogravimetric inflection points, requiring only that the location of the inflection point and the slope of the curve at that point be determined. It is demonstrated that the constants derived apply to the whole curve as well as the vicinity of the inflection point.
Packing density of polymer melts near the glass transition temperature
Authors: Bondi A. 
Published: April 2003

AbstractThe reduced or packing density ρ*  Vw/V of polymer melts coincides with a general curve of ρ* versus reduced temperature T* at high temperatures. However, the reduced density of the polymer melt is much higher than that of monomeric liquids as Tg is approached. The density information is converted to the number of external degrees of freedom per repeating unit frozen in as the polymer melt contracts. This loss of degrees of freedom begins at Tg* + 0.2, which is about the temperature below which the WLF shift relation becomes valid. The wide range covered by the numerical values Tg* and the relation of Tg to molecular structure is briefly discussed. The density data suggest that the fractional expansion volume (V − V0)/V(V0 = Vcryst. at T = 0°K.) at Tg is the only form of free volume as constant as required by the WLF relation.
Stereoregular diene polymerization with inorganic catalysts. I. cis 1,4‐Polymerization of 1,3‐butadiene with a cobaltous chloride–aluminum chloride complex
Authors: Scott Harvey , Frost Robert E. , Belt Roger F. , O'Reilly D. E. 
Published: April 2003

AbstractThe polymerization of 1,3‐butadiene with several catalytic CoCl2–AlCl3 compositions is described. Blue solid products of the reaction of CoCl2 with AlCl3 in which Co is coordinated in an octahedral configuration, are ineffective as stereospecific catalysts, unless they are treated with an aromatic hydrocarbon to yield a solution of a mixture of a green catalytic Co(AlCl4)2 complex, in which the Co coordination has a square planar configuration, and AlCl3 which is comparatively inert under polymerization conditions. This mixture forms regardless of the resulting (and frequent varying) molar ratio of Al to Co in solution, and regardless of whether the solid products contain AlCl3 that is not complexed with Co. Similar solutions result from the reaction of CoCl2 with AlCl3 in an aromatic hydrocarbon. In the absence of a modifier a benzene solution of a Co(AlCl4)2 complex catalyzes stereoregular and nonstereoregular polymerizations to about an equal extent. However, the addition of thiophene favors cis polymerization at the expense of the nonstereoregular polymerization, and a quantitative yield of polybutadiene with 94–99% of its unsaturation in the cis configuration and a sulfur content corresponding to one thiophene endgroup per polymer molecule was thereby obtained. Cis content and conversion reached a maximum at thiophene levels of 300 mole‐% based on AlCl3. At lower thiophene levels, conversion, unlike cis content, passed through a minimum before reaching a maximum. Polymers with a similarly high cis content were also obtained in the absence of thiophene by preparing oily catalyst compositions in toluene or xylene in the presence of traces of aluminum, magnesium or zinc powders which are believed to serve mainly as proton scavengers. The stereospecificity of the catalytic solutions was essentially independent of the ratio of Al to Co in solution. A possible mechanism consistent with polymerization data is discussed. It is suggested that stereoregular polymerization involves the attachment of thiophene and butadiene to one aluminum atom of the Co(AlCl4)2 complex in which Co is coordinated in a square planar configuration, by displacement of chloride ions from this aluminum atom to vacant coordination positions about the cobalt atom, resulting in an octahedral configuration about cobalt, followed by a cycloalkylation reaction between the coordinated thiophene and butadiene and subsequent insertion of butadiene into the polymer chain by a sequence of similar cycloalkylation reactions.
Stereoregular diene polymerization with inorganic catalysts. II. Magnetic resonance optical and x‐ray study of catalysts containing cobalt
Authors: O'Reilly D. E. , Poole Charles P. , Belt Roger F. , Scott Harvey 
Published: April 2003

AbstractComplexes formed between aluminum and cobaltous halides have been studied by means of nuclear magnetic resonance, electron paramagnetic resonance, optical spectra, and x‐ray diffraction. Solutions of aluminum chloride and cobaltous chloride in benzene exhibit two separate Al27 NMR signals: one arising from dissolved AlCl3 and another, shifted by 316 ppm to higher magnetic field, due to Al27 complexed with cobaltous chloride. Shifts and intensity changes in the Al27 resonance occurring upon the addition of LiAlCl4, thiophene, and butadiene to such solutions are described. EPR spectra of the cobalt aluminum complex at 77°K. were obtained and are interpreted by means of the theory of Abragam and Pryce. Optical spectra of cobaltous compounds in the visible and ultraviolet regions are given and related to the coordination symmetry of the compounds. X‐ray diffraction data on the fusion product of AlCl3 and CoCl2 indicate that a compound is formed with the composition Co(AlCl4)2 containing four molecules in a monoclinic cell unit. The results of the various methods are interpreted in terms of a complex of composition AlCl3·CoCl2·AlCl3 which forms charge‐transfer type compounds with butadiene and thiophene. A calculation of the chemical shift of Al27 in the model complex is given which is in good agreement with the experimental shift.
1,3‐Cyclohexadiene polymers. Part I. Preparation and aromatization of poly‐1,3‐cyclohexadiene
Authors: Lefebvre G. , Dawans F. 
Published: April 2003

AbstractPolymerization of 1,3‐cyclohexadiene was carried out in the presence of initiator systems such as titanium tetrachloride, organoalkali compounds, and Ziegler‐type catalysts. The best results as regards conversion rate and molecular weight, were those obtained with the use of organolithium compounds as initiators. When polymerization is performed in noncomplexing medium, all polycyclohexadienes are comparable, no matter what the initiator system used. They are composed mainly of 1,4‐substituted cyclohexene units and the double bond configuration is cis and trans. The cis–trans isomerization of the double bond seems to be independent of the polymerization mechanism. Complexing or highly polar reaction media favor the 1,2‐linking between cycles. The microstructure of the polymers was determined by infrared spectrometry and nuclear magnetic resonance analysis. Aromatization or partial dehydrogenation of polycyclohexadiene was achieved either by reaction with tetrachloro‐p‐benzoquinone or by bromination followed by dehydrobromination. An increase of the bromination temperature results in the direct formation of an aromatized polymer through the evolution of hydrogen bromide as soon as the bromine is fixed to the polymer. Infrared spectral analysis of the aromatized polymers give a further confirmation of two different types of substitution in polycyclohexadiene.
Homogeneous anionic polymerization. V. Association phenomena in organolithium polymerization
Authors: Morton Maurice , Fetters L. J. 
Published: April 2003

AbstractA study has been carried out of the association phenomena which occur during the polymerization of styrene, isoprene, and butadiene by organolithium initiation. This has been done by means of viscosity measurements of these systems after the conclusion of the polymerization reaction. It has been found that, in general, the polymerlithium species, in hydrocarbon systems, are associated in pairs. This applies to the styrene system in benzene and to the isoprene and butadiene systems in n‐hexane. In tetrahydrofuran solution, none of these systems show any polymer association. For the polyisoprenyl lithium in n‐hexane, the equilibrium constant for the dissociation of the associated pairs at 30°C. is of the order of 10−6, and the heat of dissociation is about 37 kcal./mole. By means of this viscosity technique, it has also been found possible to show that tetrahydrofuran forms a monosolvate with the polyisoprenyl lithium (RMiLi · THF) and that the heat of solvation is about 18 kcal./mole. These findings are in accord with the proposed mechanism in which the active species, in hexane, is represented by the unassociated polymer‐lithium, RMi,Li, while, in THF, it is the solvated species, RMiLi · THF. On this basis the following propagation rate constants have been deduced for isoprene polymerization: kp(hexane) = 3.4 × 103 exp {−4100/RT} = 8.9 at 60°C.; kp(THF) = 1.5 × 104 exp{ −6800/RT} = 0.4 at 60°C.
Cyclopolymerization of α,ω‐polymethylene diisocyanates
Authors: Iwakura Yoshio , Uno Keikichi , Ichikawa Kiyoshi 
Published: April 2003

AbstractThe study of polymerization of α,ω‐polymethylene diisocyanates, tetramethylene, trimethylene, ethylene, and methylene diisocyanate, was carried out by the use of basic catalysts and polar solvents. Soluble polymers were obtained. Structures of the polymers were determined on the basis of solubility, infrared absorption, x‐ray diffraction, and chemical reactions, especially aminolysis of the polymers. It was shown that these polymers contained heterocyclic recurring units (imidazolidone and imidazoline) in each polymer chain. Finally, a possible mechanism of this kind of cyclopolymerization is described.
Study of epoxy compounds. Part VI. Curing reactions of epoxy resin and acid anhydride with amine, acid, alcohol, and phenol as catalysts
Authors: Tanaka Yoshio , Kakiuchi Hiroshi 
Published: April 2003

AbstractThe curing reaction of an epoxy resin and acid anhydride with an amine and/or acid, alcohol, and phenol was studied kinetically by using commercial epoxy resins and acid anhydrides. No etherification reaction occurred at 70–140°C., even in the case of epoxide/acid anhydride/HA (acid, alcohol, or phenol) and of epoxide/acid anhydride tertiary amine/HA, and the initial reaction rate was proportional to the concentrations of epoxide, acid anhydride, and catalysts such as tertiary amine, acid, alcohol, and phenol. The apparent activation energy of the reaction system of Epikote 828/methyl‐bicyclo(2,2,1)heptene‐2,3‐dicarboxylic anhydride/triethanol amine/HA was obtained as about 14.7 kcal./mole, and the low frequency factors and large negative entropies of activation for the reaction might confirm that the curing reaction of epoxy resins and anhydrides belongs to the type of nucleophilic bimolecular displacement reaction. The effects of the substituents, R, of acid, alcohol, and phenol as cocatalyst on the curing reaction of epoxy resin/acid anhydride/tertiary amine/HA were studied. The reaction constants, p, obtained positively for HA's, indicate that electron‐withdrawing substituents of HA increase the rate of curing reaction of system of epoxide/acid anhydride/amine/HA. Differences in the catalytic and cocatalytic effects among benzoic acid, benzyl alcohol, and phenol in these reaction systems might be considered to depend on the donating power of hydrogen bond which is the important role rather than a general electrostatic interaction effect as solvent effects in nucleophilic substitution reactions. These results supported the proposed mechanisms reasonably.
Some aspects of thermal decomposition of polyoxymethylene and irradiated polyoxymethylene
Authors: Torikai Sadao 
Published: April 2003

AbstractThe thermal decomposition of polyoxymethylene and irradiated polyoxymethylene in vacuum was carried out and the kinetic aspects of thermal decomposition discussed. Although decomposition of low viscosity polyoxymethylene followed a pattern in which log (polymer residue) was roughly linear with decomposition time, the high‐viscosity polyoxymethylene which was obtained by the post‐polymerization of irradiated solid formaldehyde showed the two components different in stability. However the concentrations of the components depended on the decomposition temperature. After the thermal decomposition, the sample could not be further stabilized by acetylation, while this initial polymer could be highly stabilized by acetylation. The irradiated polymer also could not be thermally stabilized by acetylation, though the first component of the irradiated polyoxymethylene disappeared after acetylation. The components of the polymer irradiated at 100°C., ∼4 Mr (ηsp/c = 0.23) showed three components the concentrations of which are independent of decomposition temperature. In irradiation at room temperature, or in the case of irradiation by the electron beams from a Van de Graaf generator at a high dose rate, the evacuation at 100°C. of the irradiated sample after irradiation disclosed the clear dependence of formation of stable polymer on dose, and the formation of three components which are independent of the decomposition temperature.
Coupled vinyl and acetal ring‐opening polymerization
Authors: Goodman Murray , Abe Akihiro 
Published: April 2003

Abstract4‐Methylene‐1,3‐dioxolane and its derivatives were polymerized by cationic catalysts. Infrared and ultraviolet studies showed that the polymers of 2,2‐dimethyl‐ or 2‐methyl‐1,3‐dioxolane possess appreciable carbonyl content. This indicates that the polymerization takes place in such a manner that the carbon–carbon double bond opening is coupled with a concurrent acetal ring rearrangement in the propagation step to give “ketoether” sequences. 4‐Methylene‐1,3‐dioxolane, on the other hand, was found to polymerize mostly at the carbon–carbon double bond. Copolymerization of these monomers with acrylonitrile under ultraviolet irradiation was also studied.
Thermal decomposition of model compounds of polyvinyl chloride. II. Gaseous thermal decomposition of unsaturated chain end model compounds
Authors: Asahina Mitsuo , Onozuka Mitsuo 
Published: April 2003

AbstractThe gaseous thermal decomposition of model compounds with unsaturated chain ends which correspond to abnormal structures in polyvinyl chloride is studied. The allyl type chloride which is located in the main chain, but not at the end of polymer is more unstable than all kinds of abnormal structures present at the end of the polymer chain. Thus, it may be supposed that the sites of initiation of decomposition are formed during polymerization with chain transfer to polymer.
Dilute solution properties of partly urethanized polyvinyl alcohol
Authors: Sakurada Ichiro , Nakajima Akio , Shibatani Kyoichiro 
Published: April 2003

AbstractPartly urethanized polyvinyl alcohol samples, in a range of degree of urethanization up to about 10 mole‐%, were prepared by treatment of polyvinyl alcohol with urea. These were fractionated in a water–n‐propanol system into fractions, each having nearly the same nitrogen content. The degree of polymerization of the partly urethanized polyvinyl alcohol was estimated from the intrinsic viscosity of polyvinyl alcohol obtained by hydrolysis of the corresponding urethanized polymer. The effects of introduced urethane residue on solubility and dissolved state of polymer were investigated in water and theta solvents. Further, some thermodynamic parameters in water were discussed in relation to those of partly acetylated polyvinyl alcohol.
Radiation‐induced copolymerization of acrylonitrile with styrene
Authors: Tabata Yoneho , Hashizume Yoshio , Sobue Hiroshi 
Published: April 2003

AbstractRadiation‐induced copolymerization of acrylonitrile with styrene was carried out over a wide range of temperatures. It was found that the rate of copolymerization is proportional to the square root of the dose rate. An apparent activation energy of 6.90 kcal./mole was obtained for the copolymerization in an equimolar mixture of monomers. The rate of copolymerization increased with the molar concentration of acrylonitrile in the monomer mixture. Monomer reactivity ratios were determined as rAN = 0.03, rSt = 0.33 for the copolymerization at 15 and 0°C., rAN = 0.28, rSt = 0 at −20°C. in the liquid state of monomers. On the other hand, the monomer reactivity ratios were obtained as rAN ≃ 0 and rSt ≃ 0 for the copolymerization in the solid state at −78°C. It was concluded from these experimental results that there is a great difference between the liquid‐state and solid‐state copolymerizations, both in the polymerization mechanism and the structure of copolymers.
Determination of 1,2‐glycol units in polyvinyl alcohol
Authors: Harris Henry E. , Pritchard J. G. 
Published: April 2003

AbstractA titrimetric method, involving the determination of the periodate consumption by means of iodine and arsenious oxide, was applied to the determination of 1,2‐glycol units in polyvinyl alcohol by periodate cleavage. The method gave consistent results regardless of the molecular weight of the sample, and is believed to be accurate to ±0.05% glycol units. In contrast, it was shown that the well‐known Flory‐Leutner viscometric method gave results which were about 20% lower than those obtained by the first method for samples of molecular weight greater than about 40,000, and gave grossly unrealistic results for samples of much lower molecular weight. Details of the methods and sources of error are discussed.
Efficiency and frequency of grafting of methyl methacrylate to granular corn starch
Authors: Brockway C. E. 
Published: April 2003

AbstractPMMA content of graft copolymers with granular starch can be determined by acid hydrolysis with sufficient precision to allow reasonable estimates of efficiency and frequency of grafting. Preparation of the graft copolymer by initiation of methyl methacrylate with hydrogen peroxide and activators results in products containing long PMMA side chains attached to the starch at very infrequent intervals, but the length and frequency of attachment can be varied considerably by changes in the ratios of reactants. The highest frequency achieved was with PMMA of number‐average molecular weight of about 30,000, attached at a frequency of one chain per 230–250 glucose units in the starch. Under the more favorable conditions, oxidized starch yielded product of significantly more frequent grafting than did unmodified starch. Gradual addition of monomer, initiator, and activator to the starch slurry gave slightly higher frequency of grafting than did complete addition of all reactants at the start of the polymerization.
Statistical theory of the polymerization of polyepoxide monomers
Authors: Fukui Kenichi , Yamabe Tokio 
Published: April 2003

AbstractA statistical study of the ring‐opening polymerization of polyepoxides is made under the assumption of equal rates of initiation and propagation. The Poisson‐type distribution and the gel point formula are characterized by the following equations:

where p is the number of monomeric units, v is the number of propagating ends in a polymer, α is f[M]0/[I], p and pc are the fraction of reacted functional groups and its critical value, f is the number of functional groups on the monomer, and [I]0 and [M]0 are the initial concentrations of initiator and monomer, respectively.
Influence of catalyst depletion or deactivation on polymerization kinetics
Authors: Friedlander Herbert N. 
Published: April 2003

AbstractKinetic models based on the time dependence of the deactivation of catalyst sites have been fitted to data on reaction kinetics taken from the literature for polymerization of various olefins on a series of ionic and coordinate catalysts (both homogeneous and heterogeneous) for a variety of polymerization conditions. In clean coordinate polymerization systems where termination is unimportant, the propagation reaction plays a major role and is influenced by the number of active catalyst sites. The number of sites remains constant in some catalysts but varies in most. First‐order deactivation of catalyst sites leads to dead‐end kinetics similar to that described by Tobolsky for free‐radical polymerization with catalyst depletion by first‐order decomposition. Second‐order deactivation leads to kinetics linear in the logarithm of time. In heterogeneous polymerization, it is difficult to find a physical model for interaction of isolated sites required for higher‐order deactivation. The experimental data are fitted equally well by a mixed‐order model assuming sites of different stability exhibiting first‐order deactivation. At low conversions, the models are difficult to fit to experimental data in which monomer concentration is varing. Further experiments are required to test the models, obtain exact values for rates constants, and determine the influence of catalyst deactivation on molecular weight and molecular weight distribution.
Polymerization of the carbon–nitrogen double bond in carbodiimides
Authors: Robinson G. C. 
Published: April 2003

AbstractPolymerization of one of the carbon‐nitrogen double bonds in carbodiimides has been effected with n‐butyllithium catalyst in hydrocarbon solvents at 25°C. Monomers converted to polymer include diethylcarbodiimide, di‐n‐butylcarbodiimide, di‐n‐hexylcarbodiimide, diphenylcarbodiimide, diallylcarbodiimide, and methylisopropylcarbodiimide. Monomers which failed to polymerize were dicyclohexylcarbodiimide, diisopropylcarbodiimide, and methyl‐tert‐butylcarbodiimide. Thermal polymerization and depolymerization of diethylcarbodiimide was investigated and the polymers were characterized. Polymers with an inherent viscosity of 0.1–0.4 (formic acid solvent) were obtained in this work. The steric limitations on the nature of the substituents at the backbone nitrogen and the pendant nitrogen of the polymer chain were elucidated. The cis–trans isomerism possible at the pendant nitrogen is discussed. The failure of a solution of polydiethylcarbodiimide in aqueous acetic acid (presumably a polyelectrolyte) to behave on dilution as a polyelectrolyte is tentatively attributed to the stiff polymer backbone. Depolymerization of these polymers appears to be an unzipping.