bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probabilistic model for the structure of the microfibril of cellulose
Authors: Mejzler D. 
Published: April 2003

AbstractA probabilistic model is presented for the structure of an “ideal” microfibril of cellulose and the distribution of weak bonds along this microfibril is calculated. Exact and asymptotic formulas are derived for the number and weight distributions and for the corresponding averages. The relationship is examined between the model of Kuhn, accepted in theory of random degradation of chain polymers, and the probabilistic model which describes the structure of the ideal microfibril of cellulose.
Crystallization kinetics of high polymers: Isotactic polystyrene
Authors: Hay J. N. 
Published: April 2003

AbstractThe crystallization kinetics of a sample of isotactic polystyrene have been measured at various temperatures. Despite the presence of secondary crystallization sufficient accuracy can be attained to enable an Avrami relationship with a constant integral value of n to be assigned to most of the rate curves. The interpretation of the Avrami constants in terms of crystallization by growth of spherical entities, produced at fixed sites, is verified by microscope observations.
Correct determination of Staudinger's index (intrinsic viscosity) and of Huggins' constant
Authors: Ibrahim Fadel W. 
Published: April 2003

AbstractIntrinsic viscosities [η] and Huggins' constants k are generally determined by means of one of the following equations:

It was proven in an earlier paper that eq. (1) is an insufficient approximation of eq. (2) in the usual range ηr = 1.2–2.0. In this paper it is shown that eqs. (2) and (3) can lead to different Staudinger indexes (difference up to 30%). Huggins' constant k can vary from one equation to the other by as much as 300%. The experimental test of theoretical relationships between [η], k, and other molecular constants can lead to errors of the same magnitude. Values of [η] and k in pure and mixed theta solvents are discussed. It is moreover shown that eq. (2) is an inadequate approximation of eq. (3). Therefore eq. (3) is the only one which should be used.
Stress relaxation studies of chemically crosslinked gelatin films
Authors: Jopling D. W. 
Published: April 2003

AbstractStress relaxation, carried out in 85 : 15 methyl alcohol–water mixture at 60°C., of gelatin films crosslinked with oxystarch or difluorodinitrobenzene may be represented by the sum of three exponential rates of stress decay. Fresh formaldehyde‐crosslinked films relax rapidly and only require two such terms. The second term is shown to be due to the breaking of crosslinks. All excepting 10% of the broken crosslinks do not re‐form in unstressed positions as the formaldehyde is easily able to diffuse out of the layer. This 10% is suggested as being due to crosslinks involving a histidine residue. A large percentage of the broken oxystarch crosslinks do re‐form because the oxystarch is not easily able to diffuse out of the layer.
Polymerization of 1‐methylene‐4‐vinylcyclohexane by a cyclic polymerization mechanism,
Authors: Butler George B. , Miles Marion L. , Brey Wallace S. 
Published: April 2003

Abstract1‐Methylene‐4‐vinylcyclohexane was prepared by the following reaction sequence: (1) conversion of 4‐methylene‐cyclohexane methanol to the tosylate, (2) oxidation of the tosylate to 4‐methylenecyclohexane carboaldehyde by the method of Kornblum, and (3) reaction of the aldehyde with the ylide from triphenylmethylphosphonium bromide in a Wittig reaction to produce the diene. Polymerization of 1‐methylene‐4‐vinylcyclohexane was attempted with the use of free radical, anionic, cationic, and Ziegler‐type initiators. Polymers were obtained from the cationic (boron trifluoride) and Ziegler (titanium tetrachloride and triethylaluminum complex)‐initiated reactions. The polymer obtained by polymerization of this monomer with gaseous boron trifluoride as the initiator led to a solid polymer which was soluble in a number of organic solvents and had a softening temperature of 150°C. The infrared spectrum of this polymer gave absorption bands for terminal unsaturation. NMR analysis indicated that the unsaturation ratio was one double bond per two monomer units. The NMR analysis also indicated that this unsaturation was due to vinyl rather than methylene groups. Polymerization of this monomer by use of a Ziegler catalyst (titanium tetrachloride and triethylaluminum) led to a solid polymer of which 10% was soluble in a number of organic solvents. Although the infrared spectrum of this polymer indicated the presence of some terminal unsaturation, an NMR analysis indicated only an extremely small amount of residual unsaturation. The essential absence of unsaturation in this linear polymer supports an intramolecular interaction in this monomer, since Ziegler‐type initiators do not ordinarily initiate polymerization of the isobutylene type. These results can be interpreted as additional evidence for the nonbonded interaction concept as a driving force to cyclic polymer.
Properties of semicrystalline polyolefins. III. Plasticization and crystallization phenomena in sterically hindered polyolefins
Authors: Kirshenbaum I. , Isaacson R. B. , Feist W. C. 
Published: April 2003

AbstractIncreasing crystallinity and spherulite growth in rigid polymers can lead to increased resistance to deformation. Crystallization is facilitated by plasticization which, by increasing chain or segmental mobility, may promote both nucleation and the rate of crystal growth. Evidence points to the latter effect of increased rate of crystal growth being the more important when the plasticization is effected via sequential copolymerization techniques. In a number of copolymer systems, the increased extent of crystal growth more than compensates for the plasticization effects on molecular mobility and as a result, the “copolymers” show higher crystalline melting points, higher heat distortion temperatures, and increased modulus.
Field strength dependence of the electric birefringence of potassium polystyrenesulfonate solutions
Authors: Nakayama Haruo , Yoshioka Koshiro 
Published: April 2003

AbstractThe electric birefringence of potassium polystyrenesulfonate (KPSS) in water and dioxane–water mixtures is proportional to the square of the field strength for limiting low fields. Saturation of the birefringence is observed at higher field strength. This effect is the more pronounced, the lower the polyelectrolyte concentration. The specific Kerr constant decreases with increasing polyelectrolyte concentration and with increasing dioxane content. On the other hand, the electric birefringence of KPSS in glycerol–water and ethylene glycol–water mixtures is related to the field strength E by the equation, Δn/c = KEn, where c is the polyelectrolyte concentration, and K and n are constants. The exponent n changes from 1.05 to 1.70 in the range of the concentration studied (1.71 × 10−4−1.01 × 10−3 g./cm.3) in 50.9% glycerol–water. The deviation from the Kerr law is the more marked, the larger the fraction of glycerol. Alternatively the two‐term equation, Δn/c = AE + BE2, reproduces the data fairly well. The coefficient A decreases with increasing polyelectrolyte concentration in 50.9% glycerol–water, whereas B initially increases, reaches a maximum, and then decreases. The appearance of the first‐power term can not be explained by any existing theories of electric birefringence.
Coordinated polymerization of the bicyclo‐[2.2.1]‐heptene‐2 ring system (norbornene) in polar media
Authors: Michelotti Francis W. , Keaveney William P. 
Published: April 2003

AbstractNorbornene and a derivative have been polymerized to high molecular weight materials by use of the hydrated trichlorides of ruthenium, osmium, and iridium in alcoholic solvents. Structural studies on these polymers indicate that a major portion of the polymer repeating unit consists of cyclopentane rings linked in cis‐1,3 configuration with a predominance of trans double bonds.
Some low molecular weight polymers of d‐limonene and related terpenes obtained by Ziegler‐type catalysts
Authors: Modena Mario , Bates R. B. , Marvel C. S. 
Published: April 2003

Abstractd‐Limonene has been polymerized by use of Ziegler‐type catalysts to give a low molecular weight polymer which is identical in structure with those prepared by cationic initiation. The evidence indicates that the polymer has more than one type of recurring unit, at least one of which is bicyclic. α‐ and β‐pinene have also been polymerized by these catalysts. Data on optical activity and NMR spectra for all of the polymers are reported.
Unperturbed dimensions of polystyrene derivatives
Authors: Kuwahara Nobuhiro , Ogino Kazuyoshi , Kasai Akira , Ueno Susumu , Kaneko Motozo 
Published: April 2003

AbstractSeveral methods have been developed for estimating the unperturbed dimensions of polymer chains without measurements under theta conditions. Osmotic pressure and viscosity measurements have been performed to test the applicability of the methods of estimating the unperturbed dimensions. It has been observed that the Kurata‐Stockmayer and Stockmayer‐Fixman methods are applicable to poly‐p‐methylstyrene and poly‐p‐chlorostyrene in nonpolar and polar solvents. The effect of halogenation at the para position to internal rotation has been given by a comparison of the unperturbed dimensions for poly‐p‐methylstyrene and poly‐p‐chlorostyrene.
Solvent effects in anionic copolymerization
Authors: O'driscoll Kenneth , Patsiga Robert 
Published: April 2003

AbstractThe monomer pair styrene–p‐methylstyrene has been anionically copolymerized in the presence of benzene and tetrahydrofuran. The results of these copolymerizations lead to the proposal of a comprehensive mechanism which is consistent with these and other known facts of anionic propagation in both vinyl and diene polymerizations. The essence of the proposed mechanism is that solvent or monomer can complex the positive counterion. Another monomer can then add to the complex or, in the case of the monomer‐complexed counterion, a rearrangement can occur which incorporates the complexed monomer into the chain as the last unit.
Spherulitic crystallization. Part I. “odd‐even” polyamides: Nylon 56 and nylon 96
Authors: Magill J. H. 
Published: April 2003

AbstractNylon 56 and nylon 96 polymers have been shown to crystallize in a number of spherulitic forms which are primarily dependent on the crystallization temperature. A variety of structural types have been reconciled within a general pattern of spherulitic crystallization behavior peculiar to “odd‐even” polyamides. Spherulite growth rates and spherulite morphology presented for most of these structures follow a consistent pattern. Crystalline platelets exhibiting single‐crystal properties have been grown from the melts of these polymers. The morphology of these platelets and spherulites is discussed in relation to the “transition stage” between single crystals and spherulites.
Branching in poly(butadiene‐co‐styrene). I. Branching determined by viscometry and ultracentrifugation
Authors: Blachford J. , Robertson R. F. 
Published: April 2003

AbstractA sample of poly(butadiene‐co‐styrene), SBR, was divided into twelve fractions by precipitation from a dilute benzene solution. The intrinsic viscosities [η] and weights of all the fractions were measured, and the sedimentation coefficients s0 were determined for the nine fractions of highest molecular weight. From the values of [η] and s0 the number of crosslinks per molecule m, was calculated for each fraction. The results indicated that only the four fractions of highest molecular weight contained crosslinked molecules. The number of crosslinks per weight‐average primary (prior to crosslinking) molecule for the entire sample, δ0, was obtained from the weights of the fractions and the values of m. By use of various theories, values of δ0 of 0.78, 0.56, and 0.38 were obtained. From the values obtained for [η] and s0 and the pycnometric partial specific volume of the polymer in benzene, the molecular weights M of the nine fractions of highest [η] were calculated. The molecular weights of the remaining fractions were calculated from the relation between M and [η] obtained by others. A molecular weight distribution curve was established and used to obtain δ0 ≤ 0.36.
Kinetics of styrene polymerization catalyzed by rhenium pentachloride
Authors: Kamachi Mikiharu , Miyama Hajime 
Published: April 2003

AbstractPolystyrene of high molecular weight was obtained in a good yield by the polymerization of styrene catalyzed by rhenium pentachloride in benzene or benzene—ethylene dichloride solution. The mechanism of this polymerization reaction was studied by kinetic and spectroscopic measurements. Experimental results were well explained by assuming that a π‐complex between rhenium pentachloride and monomer initiates the cationic polymerization in the case of benzene solution and that +CH2CH2Cl initiates the cationic polymerization in the presence of ethylene dichloride.
Effect of temperature on ozone cracking of rubbers
Authors: Gent A. N. , McGrath J. E. 
Published: April 2003

AbstractThe rates of growth of single ozone cracks have been measured for vulcanizates of a series of butadiene–styrene copolymers, over a temperature range from −5°C. to 95°C. The rates appear to be determined by two mechanisms. At low temperatures, near the glass transition temperature, they are quantitatively related to the segmental mobility of the polymer. The principal rate‐controlling step in this case is concluded to be movement of the polymer chains after scission to yield new surface. At high temperatures the rate approaches a limiting value of 10−3 cm./sec./mg. of ozone/l. This is about 1/1000 of the maximum possible value when instantaneous reaction of one incident ozone molecule causes scission of one network chain.
Poly(chloroaldehydes). I. Polychloral stabilization
Authors: Rosen Irving , Hudgin D. E. , Sturm C. L. , McCain G. H. , Wilhjelm R. M. 
Published: April 2003

AbstractPolychloral diol, unlike polyoxymethylene diol, is not readily capped in the presence of alkali catalysts. Polychloral is capped under acid conditions by acid anhydrides and chlorides and does not appear to undergo degradation during the process. Evidence for end‐capping is provided by infrared analysis in the case of the low DP polychloral, metachloral. End‐capped polychlorals possess good stability towards hot dimethylformamide and good stability at elevated temperatures (255°C.). From the melting points of copolymers, polychloral itself is estimated to have a melting point of about 460°C. The high melting point is consistent with the rigidity of the polymer chain. A means of estimating the DP of the polymer is proposed, based on a form of endgroup analysis. By this technique, metachloral is estimated to have a DP of about 50.
Polybenzothiazoles. I. Synthesis and preliminary stability evaluation
Authors: Hergenrother Paul M. , Wrasidlo Wolfgang , Levine Harold H. 
Published: April 2003

AbstractCompletely aromatic polybenzothiazoles possessing superior oxidative and thermal stability have been prepared from aromatic bis(o‐mercaptoamines) and aromatic dicarboxylic acids and benzothiazole forming derivatives thereof. The condensations were performed in N,N‐diethylaniline and polyphosphoric acid. The former solvent gave meltable, low molecular weight prepolymers which were advanced to high molecular weight polybenzothiazoles by heating in the solid state. The course of the reaction was follwed by removing samples periodically and determining the polymer melt temperature, inherent viscosity, specific extinction coefficient and observing changes in the infrared spectrum. In polyphosphoric acid, relatively high molecular weight polybenzothiazoles were obtained after a short reaction period. The polybenzothiazoles exhibited average TGA weight losses of 6% to 600°C. in static air. The maximum glass transition temperature obtained for poly‐2,2′‐(m‐phenylene)‐6,6′‐bibenzothiazole was 910°C. Most of the polybenzothiazoles were soluble in concentrated sulfuric acid and 0.3% solutions exhibited inherent viscosities as high as 1.51.
Elemental organic compounds. Part XIV. Polymerization of diene with organotransition metals
Authors: Tsutsui Minoru , Ariyoshi Junji 
Published: April 2003

AbstractThe polymerization of 1,3‐butadiene by using organotitanium catalysts, e.g. tetramethyltitanium (classified as a radical‐type catalyst), gave rubberlike polybutadiene in low yield which was rich in the trans‐1,4‐stereoisomer, while the polymerization of 1,3‐butadiene by use of organotitanium catalysts, e.g., tetravinyltitanium and tetraphenyltitanium (classified as a π‐type catalyst) gave polybutadiene rich in the 1,2‐configuration in high yield. Titanocene dichloride and bisbenzenechromium iodide were each used individually to catalyze the polymerization of 1,3‐butadiene with methyl Grignard reagent. In both cases polybutadienes rich in the 1,4‐configuration were obtained in quite low yield. These results were interpreted to be due to the lack of availability of 3d orbitals in the above‐mentioned catalyst. Organic chromium, iron, cobalt, and nickel compounds were also investigated as catalysts for the polymerization of 1,3‐butadiene. Viscous, low molecular weight products were obtained in all cases. When the chromium catalysts were used, a mixture of polymers, namely 1,2‐and trans‐1,4‐polybutadiene, was obtained in high yield. On the other hand, low product yields were observed with the use of the other catalysts; however, trans,trans,trans‐1,5,9‐cyclododecatriene was found in each case. The configuration of polybutadiene was also dependent upon the number, odd or even, of organic groups on a transition metal atom.
Morphology of deformed polypropylene. Quantitative relations by combined x‐ray, optical, and sonic methods
Authors: Samuels Robert J. 
Published: April 2003

AbstractThe submicroscopic morphology of uniaxially deformed isotactic polypropylene films has been examined by x‐ray diffraction, infrared dichroism, birefringence, sonic modulus, small‐angle light scattering, density, and electron microscopic techniques. Several new theoretical relationships and techniques have been developed. These include (1) a two‐phase sonic modulus theory which makes possible the determination of the amorphous orientation function and the intrinsic sonic moduli of the polymer, (2) a general relationship for the quantitative determination of the infrared transition moment angle and for the quantitative determination of the crystal orientation function from infrared dichroism measurements only, (3) the determination of the extension ratio of spherulites from the small‐angle light‐scattering patterns of deformed films, (4) a technique for the experimental determination of the intrinsic birefringence of the crystal and amorphous regions of isotactic polypropylene, (5) correlation of the polarizability difference determined from solid‐state measurements with that determined from solution measurements, and (6) other techniques for the rapid determination of orientation functions. Morphological information about uniaxially deformed isotactic polypropylene films, obtained as a consequence of these developments, is reported.
Dynamic mechanical properties of poly(n‐butyl methacrylate) near its glass transition temperature
Authors: Meyer H. H. , Mangin P.‐M. F. , Ferry John D. 
Published: April 2003

AbstractThe storage and loss shear compliances (J′, J″) of poly(n‐butyl methacrylate) (number‐average molecular weight 320,000) were measured at frequencies between 0.08 and 1.0 cycle/sec. in the temperature range of 18–33°C., encompassing the glass transition. Data were obtained both at voluminal equilibrium and as a function of time during the slow isothermal contraction which follows a quench to a temperature near the transition. The latter data were supplemented by dilatometric measurements on similar samples to determine the magnitude of the volume contraction. Correlation of the dependences of J′ and J″ on temperature and on elapsed time (at constant frequency) indicated that the relaxation mechanisms are controlled primarily by free volume. The method of reduced variables was successfully applied to the dependence of J′ on temperature and elapsed time using shift factors aT,t calculated from the modified Doolittle equation and the magnitudes of volume contraction measured dilatometrically. The dependence of J″ on both temperature and elapsed time was more complicated, indicating a change in the shape of the retardation spectrum with free volume. The behavior is qualitatively very similar to that of poly(vinyl acetate), previously studied, except that the magnitudes of J′ are considerably larger and the thermal expansion coefficient of the free volume is smaller.
Copolymerization of allylureas with lauryl methacrylate
Authors: Beynon K. I. , Hayward E. J. 
Published: April 2003

AbstractMonomer reactivity ratios have been measured for the copolymerization of lauryl methacrylate and allylureas at 100°C., benzoyl peroxide being used as catalyst: lauryl methacrylate–monoallylurea, r1 = 29.9 ± 1.2, r2 = −0.22 ± 0.06; lauryl methacrylate–N,N‐diallylurea, r1 = 27.4 ± 0.8, r2 = 0.014 ± 0.05; lauryl methacrylate–N,N′‐diallylurea; r1 = 14.5 ± 0.7, r2 = −0.12 ± 0.04. The reactivity ratio r1 is of lauryl methacrylate relative to the allylurea molecule as a whole and the monomer reactivity ratio r2 is of the allylurea molecule relative to lauryl methacrylate. The values of the monomer reactivity ratios of lauryl methacrylate relative to a single allyl group in each of the allylureas have been calculated. It appears that the allyl groups in all of these molecules have similar reactivity for copolymerization with lauryl methacrylate. The monomer reactivity ratios provide evidence for cyclic propagation reactions in the copolymerization involving N,N‐diallylurea.
Dye‐sensitized photopolymerization. V. Polymerization of acrylamide in deaerated systems
Authors: Chen Catherine S. Hsia 
Published: April 2003

AbstractThe photopolymerizations of acrylamide sensitized by thiazine dyes and eosin Y in deaerated aqueous and ethylene glycol systems were investigated. The removal of most of the dissolved oxygen resulted in higher rates and higher quantum yields of polymerization. Linear per cent polymerization–time relationships were obtained. The induction period was eliminated or reduced, depending on the structure of the dye. The rate of polymerization and the molecular weight of the polymers were proportional to the 1.5 power of the monomer concentration in water and to the first power in ethylene glycol. The presence of an appropriate reducing agent was essential. In the absence of an added reducing agent, no polymerization took place in ethylene glycol and in aqueous solutions of pH ≤7. At pH >7, when hydroxyl or other anions were present as the reducing species, polymerizations took place at lower rates than in systems where a reducing agent was added. The polymerization was dependent on the nature of the buffer as well as the pH of the solution. The effectiveness of the reducing agent was also pH‐dependent. In aqueous polymerization, no enhancement in rate was observed when an appropriate combination of a cationic and an anionic dye was used as the sensitizer. The initiation mechanisms were probably different for deaerated systems and for systems under ambient atmospheric conditions. In anaerobic polymerizations, where oxygen was completely removed, enhanced rates were observed when both methylene blue and triethanolamine were used as the sensitizer. In the absence of triethanolamine polymerization took place at pH >7 but only very slowly.