bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of monolayers. V. Tacticity of the insertion poly(methyl methacrylate)
Authors: Blumstein Alexandre , Malhotra Shadi. L. , Watterson Arthur C. 
Published: April 2003

AbstractInsertion poly(methyl methacrylate) (PMMA) formed within a monolayer of monomer adsorbed on montmorillonite was studied by means of NMR spectroscopy and shown to be composed of short stereosequences with a predominant isotactic component. The stereospecificity of the insertion PMMA can be understood in terms of the organization of the monomer adsorbed on the surface of the mineral. The monolayer of monomer is assumed to be composed of monads and isotactic diads due to dipole‐ion interactions between the molecules of methyl methacrylate and exchangeable cations. Results of experiments relating factors such as temperature, density of ion population of the surface, and the nature of ions are discussed. It is shown that the populations of isotactic and syndiotactic triads Pi and Ps determined experimentally in the insertion PMMA are in a reasonable agreement with values calculated from the model. It is shown, furthermore, that Pi increases with increase in the density of the ion population, in agreement with the equations derived from the model.
Effect of pressure on dissociation of poly(methacrylic acid) in aqueous solution
Authors: Suzuki Keizo , Taniguchi Yoshihiro 
Published: April 2003

AbstractThe effect of pressure (up to 6300 atm) on the electrical conductivity of poly(methacrylic acid) (PMA) in aqueous solution was investigated in the concentration range 0.001M to 0.1M (in equivalents of carboxyl groups) at 30°C. The degree of ionization α calculated from the conductivity data increased linearly with pressure. From dilatometric measurements of volume changes when PMA was partially neutralized with NaOH, a conformational transition was confirmed to take place above α = 0.12, and the volume change accompanying the dissociation of the side chain groups (carboxyl groups) was found to be − 12.5 ml/H+. It may be inferred from the values of α at each polymer concentration and from the dilatometric data that there is no conformational transition from a compact structure to the coiled form below at least 6,000 atm in the absence of Na+ counterions.
Crystallization of isotactic polystyrene from solution
Authors: Keith H. D. , Vadimsky R. G. , Padden F. J. 
Published: April 2003

AbstractDifficulties previously encountered in the growth of chain‐folded single crystals of isotactic polystyrene suitable for study by electron microscopy and electron diffraction have been overcome using very poor solvents (including atactic polystyrene of low molecular weight). The hexagonal lamellar crystals produced are relatively stable under electron bombardment and, as a consequence, dark‐field moiré patterns produced by double diffraction from overlapping layers are easy to study. These patterns show no evidence of differences in lattice spacing between fold and nonfold planes such as have been reported in single crystals of several other polymers. Such differences were attributed to congestion at fold surfaces and their absence in polystyrene, for which the surface energy of fold surfaces is small, supports this interpretation. A comparison of crystallization kinetics of polystyrene crystals grown from good and from poor solvents reveals differences in growth rates of three or more orders of magnitude at comparable supercoolings. This disparity cannot be accounted for by acceptable adjustments of thermodynamic parameters in current theories of crystallization with chain folding. The role of molecular conformation in solution appears to exert an unexpectedly large influence on crystallization rate.
The polymeric nature of selenium crystallization. I. Morphology and thermodynamic considerations
Authors: Crystal Richard G. 
Published: April 2003

AbstractThe morphology of selenium has been studied in light of present concepts of crystallinity in crystalline organic polymers. Spherulitic crystallization and resultant morphology were examined as a function of temperature by transmission and replication electron microscopy, electron diffraction, and optical microscopy. Evidence is given for polymer chain folding during crystallization of trigonal selenium. Theoretical thermodynamic calculations presented yield several thermodynamic values including an equilibrium melting point of 219.2°C, a fold surface energy of 337 ergs/cm2 and a lateral surface energy of 9.8 ergs/cm2.
Melting behavior of drawn films from polyethylene single‐crystal mats
Authors: Maeda Masahiko , Miyasaka Keizo , Ishikawa Kinzo 
Published: April 2003

AbstractDrawing of mats of linear polyethylene single crystals prepared from dilute solution is possible at temperatures above about 90°C. The structure and properties of the drawn specimens are much different from those ordinary drawn bulk polymer. Drawn mats have been investigated by differential scanning calorimetry. The characteristic experimental results are: (a) a broad melting curve, (b) considerable superheating depending on the rate of heating, (c) constancy of the melting point and the heat of fusion with annealing, (d) deviation from the relation between the heat of fusion and the density obtained for the drawn bulk specimens, (e) appearance of two melting peaks in samples annealed at temperatures above about 130°C. These results imply that the structure of the drawn mat is characterized by a larger number of the tie chains connecting the neighboring crystals (the structure postulated in earlier papers) than is the case in ordinary drawn bulk polymer. It can be concluded that the transformation of a fringed micellar type of structure to the folded lamellar structure may be difficult during annealing unless crystals melt and then recrystallize during cooling.
Viscoelastic properties of blends of “entangled” polymers
Authors: Prest W. M. 
Published: April 2003

AbstractThe effect of molecular weight distribution on the viscoelastic properties of “entangled” polymers has been examined with blends of narrowly distributed polystyrene and broadly distributed polydimethylsiloxane. It is shown that blending laws established for nonentangled polymers do not apply to high molecular weight systems. The steady‐state shear compliance of a blend is examined as a function of its molecular weight and the molecular weight of its components, and an approximation is given for the longtime viscoelastic response of entangled blends.
Thermal history and melting behavior of poly(ethylene terephthalate)
Authors: Nealy D. L. , Davis T. G. , Kibler C. J. 
Published: April 2003

AbstractLow molecular weight poly(ethylene terephthalate) samples were crystallized isothermally at 120–245°C from both the amorphous state and the melt. Isothermal annealing of these polymers at 215°C provided polymers which exhibited multiple melting peaks in thermal analysis, referred to as form I and form II, as assigned by Bell and Dumbleton. In these samples the peak temperature of the form II melting endotherm and the average crystallite size are dependent on the temperature of initial crystallization. This result requires a mechanism for retaining some structural feature during the conversion from morphological form I to form II. DSC thermograms obtained at varying heating rates on samples showing only form II endotherms support the assignment of superheating as the cause of the shift to higher peak temperatures with increasing heating rate.
Alternating copolymerization of carbonyl sulfide with aziridines
Authors: Yokota Hisao , Kondo Masatsune 
Published: April 2003

AbstractThe copolymerization of carbonyl sulfide with aziridines such as ethylenimine, propylenimine, and N‐ethylethylenimine was studied in various organic solvents. The copolymerizations occurred easily without the addition of any catalyst and gave white powdery crystalline copolymers. The copolymers produced were insoluble in many organic solvents, but soluble in p‐chlorophenol and dimethyl sulfoxide. The elementary analyses and the infrared spectra showed that alternating copolymers which have a thiourethane structure were produced. In the copolymerization of carbonyl sulfide with ethylenimine, both the polymer yield and the molecular weight of the resulting polymer increased with the use of a solvent having a higher dielectric constant, and also with an increase in the ratio of carbonyl sulfide to imine in the feed. The rate of copolymerization of carbonyl sulfide with aziridines was in the order of ethylenimine > propylenimine > and N‐ethylethylenimine. Irradiation of the copolymers improved their thermal properties and increased their melting point.
Polymers containing polyhedral borane rings I. Condensation polymers
Authors: Schaefgen J. R. , Miller H. C. , Sauer J. C. , Sharkey W. H. 
Published: April 2003

AbstractThe preparation and properties of a unique new class of polymers containing polyhedral borane cages as part of the backbone polymer chain are described. The synthesis of polyamides, polyesters, polyureas, and polyurethanes proceeds from suitably chosen B10 and B12 polyhedral borane dicarbonyls, diols, and diisocyanates by typical condensation polymer techniques. Each complementary monomer may be a borane compound, but more often higher molecular weight products are provided when one monomer is a conventional organic reagent such as an aromatic diisocyanate. The polyamides prepared from 1, 12‐B12H10(CO)2 and organic diamines were crystalline and soluble, but molecular weight were limited because the amidation reaction was reversible and/or the amide linkage could be split by nucleophilic attack by some solvents. The polyurethanes prepared from Na2B12H10(OH)2 and aromatic diisocyanates were high molecular weight and relatively more stable. Clear, colorless, tough films were prepared. These polymers were soluble in many polar solvents and exhibited typical polyelectrolyte behavior.
Influence of free and copolymerized triplet quenchers on the photolysis of poly(vinyl phenyl ketone) in solution
Authors: Lukáč Ivan , Hrdlovič Pavol , Maňásek Zdeněk , Belluš Daniel 
Published: April 2003

AbstractThe influence of free, diffusion‐control quenchers of triplets (naphthalene, biphenyl, 2,5‐dimethyl‐2,4‐hexadiene) on the photolysis of poly(vinyl phenyl ketone) in benzene solution has been investigated. The Stern‐Volmer plots for quenching of main‐chain scission were linear, and the quenching constants were independent of the macroviscosity of the solutions. Copolymers of vinyl phenyl ketone with 1‐vinylnaphthalene and 2‐vinylnaphthalene containing as much as 10% (by weight) vinylnaphthalene were prepared. The photolysis of the copolymers was compared with the photolysis of poly(vinyl phenyl ketone) in the presence of free naphthalene. It was found that the quenching efficiency of found naphthalene units was about 21 times higher. The possibility of migration of the absorbed energy along the polymer chain is discussed. The relation between average‐number molecular weight Mn and intrinsic viscosity [η] has been determined osmometrically. For unfractionated poly(vinyl phenyl ketone) in benzene at 30°C, the relation [η] = 2.82 × 10−5 Mn0.84 has been found.
Effects of pulses of current on the cationic electropolymerization of isobutylvinylether
Authors: Funt B. L. , Blain T. J. 
Published: April 2003

AbstractThe cationic electropolymerization of isobutyl vinyl ether was induced and controlled by sequences of pulses of current of various lengths and of similar or opposite polarity. A remarkable degree of control over the rate of the reaction was demonstrated for a system that is subject to “flash” polymerization by conventional chemical initiators. The mechanism is shown definitively not to correspond to the electric field effects proposed by Tanaka, Ise and Sakurada as applicable to all such electropolymerizations.
Cationic polymerization of 1‐ethoxy‐1,3‐butadiene
Authors: Fueno T. , Tsunetsugu T. , Arimoto K. , Furukawa J. 
Published: April 2003

Abstractcis‐ and trans‐1‐Ethoxy‐1,3‐butadienes were polymerized by a variety of cationic agents in various solvents at −78°C. The trans ether, which is the more stable isomer, was found to have greater polymerizability than the cis ether. The trans monomer gave polymers predominantly of the trans‐1,4 type, whereas the cis monomer showed a tendency toward the formation of polymers having the microstructure of the 1,2 type. It was concluded that, in the cis ether, the carbon atom which is the most vulnerable to the attack of carbonium ions is the one at the 2‐position, whereas, in the case of the trans isomer, the terminal 4‐carbon is the most reactive center. The conclusion was confirmed from the results of acetal addition reaction catalyzed by boron trifluoride etherate. The marked contrast in the mode of reaction of the two isomeric ethers toward carbonium ions was interpreted in terms of the difference in the degree of bonding in the transition state.
Cationic copolymerization of tetrahydrofuran with epoxides. I. Polymerization mechanism in the presence of a glycol
Authors: Hammond J. M. , Hooper J. F. , Robertson W. G. P. 
Published: April 2003

AbstractPolymerization of several epoxides and their copolymerization with tetrahydrofuran have been studied. The polymerizations were carried out by use of BF3·O(C2H5)2 as catalyst in the presence of 1,4‐butanediol. Variations of catalyst and 1,4‐butanediol ratio and concentration affect polymerization rate, molecular weight, and the formation of cyclic oligomers. The latter is also influenced by monomer fed ratio in the case of the copolymerizations. These effects are discussed, and some observations are made concerning the mechanism, particularly with respect to the role of the 1,4‐butanediol. Mayo‐Lewis monomer reactivity ratios were determined. The ratios found differed from previously published figures.
Syntheses and properties of photochromic polymers of the mercury thiocarbazonate series
Authors: Kamogawa Hiroyoshi 
Published: April 2003

AbstractPhotochromic vinyl polymers of the mercuric thiocarbazonate series were synthesized via the three sequences: (1) synthesis of p‐(meth)acrylamidophenyl mercuric acetate(II) by the reaction of (meth)acrylyl chloride with p‐aminophenyl mercuric acetate, followed by polymerization to afford corresponding polymers(III) and subsequent reaction with diphenyl‐ or di‐β‐naphthyl‐thiocarbazone, (2) alternative preparation of III by the reaction of (meth)acrylyl chloride polymers with p‐aminophenyl mercuric acetate, and (3) reaction of N‐hydroxymethyl (meth)acrylamide polymers with p‐amidophenyl mercuric thiocarbazonates. The photochromic behavior of these polymers was investigated to provide data which might indicate the effect of steric conditions on the isomerization of the photochromic components in polymers both under illumination and in dark recovery.
Reduction of composite NMR spectra by using an analog computer
Authors: Mochel V. D. , Claxton W. E. 
Published: April 2003

AbstractAn analog computer program has been devised to resolve complex composite curves such as might be encountered in various forms of spectroscopy or chromatography. Seven Gaussian or Lorentzian curves, or any combination of seven curves, can be used and displayed simultaneously to resolve the composite curves. Various degrees of skew and truncation, as well as slanted and curved baselines, can be introduced. The peak amplitude, width and position can be determined from potentiometer settings. The integrated relative area of each of the peaks is read out on a digital voltmeter with a reproducibility of about ±0.1%. The utility of the technique is demonstrated by resolving highly overlapped peaks in NMR spectra of butadiene–styrene copolymers. It is necessary to use as many as eight curves to resolve the styrene aromatic proton resonance. This analysis yields styrene‐centered distributions and styrene sequence distributions from the NMR spectra of butadiene–styrene copolymers. In addition, it is shown that a distinction can be made between short styrene sequences, which contain two and three styrene units, and long styrene sequences, which include all sequences longer than three units.
Sequence distribution of poly(ether)urethane elastomer
Authors: Suzuki Hajime 
Published: April 2003

AbstractPoly(ether)urethane elastomers (PEUE) having different sequence distributions can be synthesized by the reaction of p‐phenylene diisocyanate, poly(oxytetramethylene glycol), and hydrazine by four different routes. The degree of the sequence distribution of PEUE was determined by high‐resolution NMR spectroscopy. The sequence distribution of PEUE synthesized by the prepolymer method in solvent (method 1) was found to coincide with the sequence distribution calculated from the reactivity ratio of two isocyanate groups in p‐phenylene diisocyanate. On the other hand, the sequence distribution of PEUE obtained by the prepolymer method without solvent (method 2) was found to deviate from that expected from the reactivity ratio. The degree of the distribution of monomers in PEUE having the same composition ratio corresponded to the infrared absorbance ratio at 1720 and 1700 cm−1.
Some studies on a polymer from urea
Authors: Bandyopadhyay Pranab C. , Das Asoke K. 
Published: April 2003

AbstractA polymer having the structure of guanidinopolyhydroxynitrile has been produced by heating an equimolar mixture of urea and anhydrous ZnCl2 in nitrogen at 300°C and 27 atm. The structure has been established from elemental analysis, percentage of nitrogen as primary amine, and ultraviolet and infrared spectra of the polymer and its derivatives. A mechanism of the polymerization based on some experimental evidence has been suggested. Its physical properties have been attributed to its skeletal structure and ring closure by hydrogen bonding. Thermograms reveal that it is stable to 150°C, after which it decomposes slowly till a 75% weight residue is obtained at 575°C with a constant weight plateau extended to 680°C. In acid solvents, protonation occurs at the NH2 group or the azomethine nitrogen atoms, producing polycations. The polyelectrolytic character in acids has been confirmed by viscometric and osmotic studies and the molecules tend to be both coiled up and associated in solutions. [n] in anhydrous formic acid is 0.3636 dl/g. The molecular weights of the polymer and its various fractions range between 39,500 and 25,900. Dielectric constants, dielectric losses, and conductivities of the polymer have also been measured as functions of frequency and temperature and it has been proved that the dispersion is due to dipole polarization. The average energy of the dipole is 1.73 × 10−2 eV/°K, the intrinsic activation energy for conduction is 0.186 eV, the conductivities being of the order of 2 × 10−6 to 7 × 10−7 mho‐cm−1. The polymer is therefore a semiconductor. The number of charge carriers is 2.12 × 1016/cm2, which agrees reasonably well with the value, 6.66 × 1016, obtained from spin‐density calculations from ESR signals.
Chemorheological treatment of crosslinked EPT
Authors: Murakami Kenkichi , Tamura Saburo 
Published: April 2003

AbstractStress relaxation mechanisms were investigated on three types of (EPT) ethylene–propylene terpolymers in air at 109°C. These polymers differe only by the structure of the crosslinkage in which there is a carbon–carbon bond, a polysulfide linkage (S◯) or a monosulfide linkage (S). All the stress relaxation of peroxide‐cured EPT polymer was not due to the oxygen‐induced cleavage of the main chain but to a physical flow. In the case of sulfur‐cured EPT polymer, the relaxation curve is divided into three straight lines when the procedure X is used and log f(t)/f(0) is plotted linearly with time. It was concluded that this graph was in agreement with an interchange reaction of the polysulfide linkage by an oxidative cleavage of the monosulfide linkage. On the other hand, a TT‐cured EPT polymer gave a plot with a straight line. This stress relaxation could be explained by an oxidative cleavage of the monosulfide linkage.
Radiation‐induced polymerization of tetraoxane in the solid state
Authors: Nakase Yoshiaki , Yoshida Masaru , Ito Akihiko , Hayashi Koichiro 
Published: April 2003

AbstractThe radiation‐induced polymerization of tetraoxane in the solid state has been investigated in air and in vacuo. The polymerization rate was higher in air than in vacuo, whereas the molecular weight of the polymer obtained at high conversion in air was considerably lower than in vacuo. A large decrease in the molecular weight with increasing polymer yield observed in air may be explained mainly by degradation during polymerization.
Polymerization of propylene by the three‐component system comprising titanium(III) chloride, ethylaluminum sesquichloride, and sodium sulfate
Authors: Matsumura Kiichiro , Atarashi Yuji , Fukumoto Osamu 
Published: April 2003

AbstractSodium sulfate increases the polymerization activity of the titanium(III) chloride (AA)–ethylaluminum sesquichloride system for the polymerization of propylene. The reaction of ethylaluminum sesquichloride with sodium sulfate at mild conditions isolates diethylaluminum chloride, which is responsible for the polymerization activity. The reaction of these components at severe conditions forms an organometallic compound containing sulfate, (C2H5)4Al2SO4, and this compound is a powerful activator for titanium(III) chloride.
Polymerization of asymmetric polyfunctional monomers. III. Ionic polymerization of acrylic and methacrylic esters of 2‐allylphenol
Authors: Solomon O. F. , Corciovei M. , Gabe I. , Beral E. 
Published: April 2003

AbstractThe polymerization of acrylic and methacrylic esters of 2‐allyphenol with different anionic, cationic and coordination catalysts was studied. The polymerization occurs exclusively or predominantly through (meth)acrylic CC double bonds in all the studied cases. With anionic catalysts the allylic groups are not polymerizable and the polymers have linear structure. Polymerization with catalysts based on dialkylaluminum chloride (alone or associated with some metal salts) yields soluble or partially crosslinked polymers, depending on the reaction conditions. The crosslinking is due to the participation of allylic groups in the polymerization reactions. Copolymers of acrylic and methacrylic esters of 2‐allylphenol with styrene, acrylonitrile, methyl methacrylate, N‐vinylcarbazole and 1,3‐pentadiene were synthesized by copolymerization in the presence of anionic catalysts and of systems based on dialkylaluminum chloride.
Collision between polymeric radicals for termination rate constants
Authors: Ito Katsukiyo 
Published: April 2003

AbstractThe motion of each polymeric radical during a collision between the polymeric radicals with the same radius is treated as completely random motion. The result obtained is: kt = 0.250ks (where kt is the chain‐termination rate constant and ks is the reaction rate constant between radical chain ends). On taking the motion of the primary radical during a collision between a primary radical and a large polymeric radical to be completely random, the result obtained is: kti = 0.250ksi (where kti is the primary radical termination rate constant and ksi is the reaction rate constant between primary radical and radical chain end). On substituting ks for ksi in the second equation, the rate constant obtained becomes the chain termination rate constant between the very small polymeric radical and the very large polymeric radical, and identical to the former equation. This identity indicates that the effect of the difference of the size of the polymeric radicals on the collision process relating to the chain termination rate constant should not be large.