bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and reactivity of α,β‐unsaturated ethers. V. Cationic copolymerizations of ring‐substituted phenyl vinyl ethers
Authors: Fueno T. , Okuyama T. , Matsumura I. , Furukawa J. 
Published: April 2003

AbstractPhenyl vinyl ether (M1) has been copolymerized with its various ring‐substituted derivatives (M2) in toluene at −78°C with stannic tetrachloride as catalyst. The substituents investigated include p‐CH3O, m‐CH3O, p‐CH3, m‐CH3, p‐Cl, and m‐Cl. The course of copolymerization was followed by gas chromatographic determinations of residual monomers, and the monomer reactivity ratios were evaluated by use of the integral form of the Mayo‐Lewis copolymerization equation. Except for the unusual case of the m‐CH3O derivative, the observed values of log (1/r1) were found to be linearly correlated with Hammett's σ constants, the reaction constant being ρ = −1.76 with the correlation coefficient r = 0.990. Comparisons of these results with the existing data for the styrene copolymerizations have enlightened the behavior of the oxygen atom in transmitting the electronic effects of ring substituents onto the reaction center.
Termination rate constant in radical polymerization
Authors: Ito Katsukiyo 
Published: April 2003

AbstractOn the basis of the assumption that the primary radical immerses into a polymeric radical, the rate constant of primary radical termination was derived. By applying and developing further the same treatment, the rate constant of chain termination was derived. This rate constant was experimentally confirmed. It was found that the rate constant of chain termination for the polymerization of some methacrylates depends on the distance of translation of radical chain end per collision, solvent viscosity, and the Taft polar constant for ester group.
Interfacial syntheses of polyphosphonate and polyphosphate esters. I. Effects of alkaline medium
Authors: Millich F. , Carraher C. E. 
Published: April 2003

AbstractThe effects on polymer yield and viscosity in the interfacial condensation of hydroquinone with phenylphosphonic dichloride as a function of the pH of the aqueous medium are reported. Reactions competing with polymer formation are discussed. The beneficial advantages in the use of soluble buffers or bases of limited water solubility to control pH are contrasted with results of conventionally used sodium hydroxide. The results of investigations of other comer pairs for which reaction conditions have not been optimized are also reported; desoxyribose and the diols: thymidine, resorcinol, 2,5‐dichlorohydroquinone, 1,3‐dihydroxyacetone, 1,4‐butanediol, tartaric acid, ethylene glycol, and 2,2‐dimethyl‐1,3‐propanediol are tabulated.
Relation of the chemical structure of polycyanurates to thermal and mechanical properties
Authors: Nakamura Yoshiro , Mori Kunio , Tamura Kosaku , Saito Yoshiko 
Published: April 2003

AbstractForty polycyanurates were prepared by the interfacial polycondensation of 2‐substituted 4,6‐dichloro‐s‐triazines with various aromatic diols. Nitrobenzene was used as a solvent, aqueous sodium hydroxide as an acid acceptor, and a cationic emulsifier as an accelerator. The rate of reaction was largely increased by ultrasonic irradiation. The polymer yield was in the range 57–91%, and the reduced viscosity was 0.41–3.5. The polymers were soluble in chloroform, nitrobenzene, and o‐dichlorobenzene but insoluble in common organic solvents such as alcohol, acetone, and hydrocarbons. A clear film was obtained from the chloroform‐soluble polymers after evaporation of the solvent. The softening temperature and the thermal stability of each polycyanurate was significantly related to the substituent on the s‐triazine nucleus as well as to the diol component in the molecular chain. Polymers of favorable properties were derived from 2‐substituted 4,6‐dichloro‐s‐triazines with R = C6H5, N(C6H5)2, N(C6H11)2, N(C6H5)(SO2C6H4CH3), or carbazyl and aromatic diols such as 4,4′‐dihydroxybenzophenone, Bisphenol A, or phenolphthalein. These polymers showed tensile strength of 500–670 kg/cm2, elongation at break of 2.9–6.0%, and a minor weight loss at 300–350°C.
Differential thermal analysis of polyethylene under high pressure
Authors: Davidson Theodore , Wunderlich Bernhard 
Published: April 2003

AbstractThe design of a differential thermal analysis apparatus for use at elevated pressure is described. Experiments on melting and crystallization of folded‐chain crystals of polyethylene and poly(ethylene–butene‐1) copolymer, and melting of extended‐chain polyethylene crystals have been conducted at pressures up to 4200 bars. The precision in transition temperature measurement was ±1°C. The Clausius‐Clapeyron equation predicts the melting point increase with pressure at atmospheric pressure to be 32.0°C/kb. The melting point depression due to copolymerization remained constant over the complete pressure range analyzed on the poly(ethylene–butene‐1) used in this study. Crystallization of polyethylene is retarded at elevated pressures, and a 50% larger degree of supercooling is necessary at 5000 bars to give a crystallization rate equal to that observed at atmospheric pressure. The difference in melting point between folded‐chain and extended‐chain polyethylene increases from 8.4°C at 1 bar to 25.6°C at 3000 bars.
Statistical models in the study of stereospecific polymerization
Authors: Shelden Ronald , Fueno Takayuki , Furukawa Junji 
Published: April 2003

AbstractTriad tacticity data obtained by NMR analysis have previously been interpreted in terms of two basic statistical models in order to elucidate the stereospecific polymerization mechanism. In this paper the characteristics of these two basic models for stereospecific polymerization, the enantiomorphic‐sites (EMS) model, and the polymer‐end control (PEC) model, are examined and compared. The tacticity values accessible to the two‐parameter EMS model, which includes the influence of the chain end unit, are shown to be highly restricted. Only about 20% of the isotacticity versus syndiotacticity plot is accessible to this model. To this extent the consistency of a set of triad tacticity data with the model can be tested. No such tacticity limits are exhibited by the two‐parameter PEC model, which includes the influence of the penultimate unit. Any set of tacticity values which can be interpreted in terms of the two‐parameter EMS model can also be interpreted in terms of the two‐parameter PEC model.
Bond rupture in highly oriented crystalline polymers
Authors: Peterlin A. 
Published: April 2003

AbstractThe strength‐limiting process in the fracture of semicrystalline fibers and highly oriented films is the rupture of tie molecules connecting the folded chain lamellae in the machine direction. This view is supported by the data on stress and temperature dependence of lifetime of fibers under load and on radical formation during the fracture experiment. The observed tensile strength, however, is about 10 times smaller and the number of fractured chains between 100 and 1000 times larger than expected on the basis of the known number of tie molecules in the fracture plane. This discrepancy is a consequence of the inhomogeneity of the micromorphology of fiber structure, which causes a much larger stress concentration on the most unfavorably located tie molecules than the average value one would expect in the case of perfectly uniform stress distribution on identical tie molecules. The fluctuation of amorphous layer thickness, of number and length of tie molecules, produces such a high stress concentration on some tie molecules throughout the sample that they rupture long before the average stress concentration is sufficient for chain fracture. By accumulation of damage caused by gradual chain rupture the weakening of the sample locally proceeds so far that at the maximum damage concentration, microcracks start to form, and the fiber breaks.
Surface energy effects for small holes or particles in elastomers
Authors: Gent A. N. , Tompkins D. A. 
Published: April 2003

AbstractExpansion of a small spherical hole in a highly elastic solid is treated theoretically. Both elastic and surface energy terms are considered; the corresponding surface forces are assumed to be additive. The surface energy of the elastomer is assumed to be similar to that of simple liquids. Pressures or triaxial tensions required to inflate pre‐existing holes to an indefinitely large size are calculated. Small holes require extremely large pressures, of the order of 1000 atm for holes of 10 Å radius. These results suggest a means of determining the distribution of hole sizes in elastomers and account in principle for experimental observations of cavitation processes. Detachment of the elastomer from a small rigid inclusion is treated in a similar way. The general absence of dilation or cavitation on stretching carbon black‐filled elastomers is thus accounted for solely in terms of the small size of these filler particles.
Transition temperatures and structural correlations for cellulose triesters
Authors: Klarman A. F. , Galanti A. V. , Sperling L. H. 
Published: April 2003

AbstractSix homologs of the cellulose triester series were found to exhibit, in general, three second‐order transitions as determined dilatometrically. A parallel study of torsional modulus versus temperature revealed one glass–rubber transition, which allowed molecular assignment of one of the above. The dependence of the remaining two transition temperatures on length of the ester group permits some speculation with regard to their origin. The glass–rubber and secondary transitions exhibit an inversion for cellulose trivalerate and higher homologs, the two secondary transitions occurring at temperatures higher than the glass–rubber transition. A possible explanation for this anomaly in terms of side‐chain crystallization is discussed.
Plastic deformation of poly‐4‐methylpentene‐1 crystals
Authors: Woodward A. E. , Morrow D. R. 
Published: April 2003

AbstractThe plastic deformation of poly‐4‐methylpentene‐1 (P4MP1) crystals on a unidirectionally drawn substrate has been investigated by electron microscopy. In addition to cracks spanned by fibrils and buckling perpendicular to the stretch direction, both features found in deformation studies of other polymers, a unique slip mechanism leading to sectorization of P4MP1 crystals is observed; deformation was also found to occur by means of localized lamellar thinning. The exact type of plastic deformation occurring in P4MP1 crystals is found to depend on the orientation of the lamellae with respect to the tensile axis. Some evidence for a periodicity on the fibrils studied is given.
Extended‐chain crystals. V. Thermal analysis and electron microscopy of the melting process in polyethylene
Authors: Prime R. Bruce , Wunderlich Bernhard , Melillo Louis 
Published: April 2003

AbstractDifferential thermal analysis and electron microscopy of partially molten, extended‐chain polyethylene crystals, grown under elevated pressure, was performed. It could be shown that melting peaks on the low temperature side of the main melting peak are due to narrowly distributed, low molecular weight polymer segregated in extended‐chain crystals. Superheating of crystals before melting increased with molecular weight and chain extension. The melting mechanism of extended chain crystals was shown to be a successive peeling off of chains which leaves the chain extension constant up to melting of the last crystal trace.
Electrochemical anionic polymerization of 4‐vinylpyridine in pyridine
Authors: Bhadani S. N. , Parravano G. 
Published: April 2003

AbstractThe preparation of poly‐4‐vinylpyridine (poly‐4VP) by electrochemical polymerization of 4‐vinylpyridine (4VP) in pyridine containing sodium tetraphenylboron (NaBPh4) is described. Information on the influence of monomer concentration, current density, polymerization rate, molecular weight, and electrochemical efficiency is presented. The polymerizations were performed under conditions of constant electrolysis current. Polymer formed in the cathodic compartment only, where a red‐orange solution developed after about 15 min of electrolysis time. The optical absorption spectra of these colored solutions were studied. Cyclic voltammograms of 4VP in pyridine and NaBPh4 are also reported, and the influence of the scan rate upon peak current is described. The results indicate that the polymerization was anionic and nonterminating. The characteristics of the electrochemical polymerization of 4VP in pyridine are compared with those of the same monomer in liquid NH3. In the former case, the catholyte was homogeneous, and polymer growth occurred in the liquid phase, while in the latter growth took place in a heterogeneous environment. Kinetic consequences of these physical differences are pointed out. Suggestions for the mechanism of this electrochemical initiation are advanced.
Hydrolytic polymerization of caprolactam. II. Vapor–liquid equilibria
Authors: Giori C. , Hayes B. T. 
Published: April 2003

AbstractThe system water–caprolactam–polymer at equilibrium is regarded as a solution consisting of two solvents (water and caprolactam) and one solute (polymer). The activities of water and caprolactam in equilibrium at 270°C in the range of 2–10 wt‐% total water content have been determined by vapor‐pressure measurements. Water shows large negative deviations from Raoult's law, as a consequence of the different size of water and polymer molecules. The partial molar free energies of mixing are compared with the expressions derived from the Flory‐Huggins theory of polymer solutions; the results are not conclusive, but seem to indicate a qualitative agreement with the theory. The increase in vapor pressure during polymerization in sealed systems and the water dependence of the polycondensation equilibrium are discussed and explained in terms of water activity changes.
Synthesis of poly‐2‐oxazolidones from diisocyanates and diepoxides
Authors: Dileone R. R. 
Published: April 2003

AbstractPoly‐2‐oxazolidones of high molecular weight have been synthesized from diisocy anates and diepoxides. The synthetic method was first developed for the model compound 3‐phenyl‐5‐phenoxymethyl‐2‐oxazolidone prepared from phenyl isocyanate and phenyl glycidyl ether. Conditions found most suitable for a high yield involve slow addition of isocyanate to a solution of epoxide and catalyst, temperatures of 160°C or higher, and a catalytic amount of n‐butoxylithium in 1‐butanol. The same procedure was used to prepare high molecular weight poly‐2‐oxazolidones. The polymer structure was confirmed by infrared spectroscopy and elemental analysis. All polymers prepared were of sufficient molecular weight to be compression molded. The bulk mechanical properties characterize poly‐2‐oxazolidones as potentially useful engineering thermoplastics. A mechanism for oxazolidone formation is proposed.
γ‐ray and ultraviolet graft copolymerization of maleimide by vapor‐phase method
Authors: Hayakawa Kiyoshi , Yamakita Hiromi , Kawase Kaoru 
Published: April 2003

AbstractGraft copolymerization of maleimide onto ethyl cellulose and polyethylene films by using its sublimation vapor was carried out under γ‐ or ultraviolet irradiation. When polyethylene film was used as a backbone polymer the grafting reaction proceeded without a perceptible sorption of monomer, while a considerable amount of monomer was captured into ethyl cellulose film and grafting of the sorbed monomer was observed. The monomer seemed to be monomolecularly dispersed in this film. The presence of air retarded the reaction. The grafted films were characterized by strong infrared absorption bands due to polymaleimide branching. The fractions assigned to the graft copolymer were isolated from the grafted films by selective elution. The grafted branches were supposed to be very short, judging from the polymaleimide contents of those fractions.
Influence of microstructure on the tensile behavior of acrylic copolymers
Authors: Majerus John N. , Pitochelli Anthony R. 
Published: April 2003

AbstractUniaxial tensile properties were determined for two series of copolymers: ethyl acrylate–acrylic acid and butyl acrylate–acrylic acid. The comonomer ratio was varied from 85/15 to 95/5 and various molar ratios of a difunctional carboxylate epoxy crosslinker were used. The master modulus curves indicated that increasing the amount of crosslinker and/or increasing the number of crosslink sites per chain caused both the equilibrium modulus and the transition temperature to increase while increasing the bulk of the side groups decreased both the modulus and transition temperature. All the master ultimate strain curves exhibited a maximum value corresponding to some value of reduced time τc and exhibited a shape analogous to a lognormal distribution function with nonzero asymptotes. The maximum ultimate strains were found to be a nonlinear function of the crosslink density and to occur at higher values of temperature and/or lower values of strain rate when either the amount of crosslinker or the relative frequency of the crosslink sites increased. Replacing the pendant ethyl group with a butyl group caused the maximum ultimate strains to occur at temperatures about 60°F lower than the corresponding ethyl acrylate copolymer. This replacement also decreased the magnitudes of the maximum ultimate strains associated with the same crosslink density. It was concluded that the chemical efficiency of the crosslink sites decreases with decreasing relative frequency of the crosslink sites along the prepolymer. Furthermore, the crosslink efficiency decreased as the length and flexibility of the nonreactive side groups increased. The dependency of the actual crosslink density was found to be critically influenced by the chemical crosslink efficiency. A molecular model involving both chain entanglements and chemical corsslinks is postulated which explains qualitatively the observed behavior of the master ultimate strain data.
Polymerization of sodium 2‐sulfoethyl methacrylate in aqueous solution
Authors: Kangas D. A. 
Published: April 2003

AbstractThe rate of sodium 2‐sulfoethyl methacrylate (SEMΘNa⊕) polymerization in aqueous solution was measured as a function of temperature, ionic strength, K2S2O8, and SEMΘ‐Na⊕ concentration. The ratio of rate constants, kpkt−1/2(fkd)1/2, increases with decreasing ionic strength. Because SEMΘNa⊕ is itself an ionic salt, the ratio of polymerization rate constants increases with decreasing monomer concentration. The change in ratio of rate constants as a function of ionic strength can be described by an equation derived from the limiting form of the Debye‐Hückel theory. The value of the effective ionic charge on the polymeric growing radical is 3, as calculated by means of the derived equation.
Etude par RPE des radicaux libres daus le tétraoxane irradié
Authors: Saito E. , Cannavo C. , Hayashi K. 
Published: April 2003

AbstractThe free radicals induced in tetraoxane at liquid nitrogen temperatures by 60Co γ‐rays have been studied by ESR. The powder spectrum as well as he spectra of the single crystal rotated around the b axis have been studied through their modifications from −196°C up to + 80°C. These spectra show that at low temperatures two radicals exist conserving the cyclic nature of the parent molecule. During the course of annealing, starting at −140°C and towards −85°C they are gradually replaced by radicals with a linear structure, this being the first step in the post‐polymerization process of tetraoxane. Further increase in temperature leads to radical sites situated on the polymer chains. At low temperatures evidence has also been found for the formyl radical, radical pairs, and a photo‐sensitive radical.
Use of carbon suboxide to obtain block and graft copolymers. II. Grafting of carbon suboxide on polyethylene
Authors: Bukowski Andrzej , Porejko Stansislaw 
Published: April 2003

AbstractExperiments have been carried out on grating of carbon suboxide on nonactivated polyethylene films and on films previously activated by ultraviolet irradiation and by γ‐irradiation. The experiments gave a grafted copolymer. A grafted copolymer was also obtained on grafting carbon suboxide in solution on polyethylene films preactivated by means of ozonization at 70°C. Examination of the copolymer indicated its structure to be cross linked. It has been proved that below 50°C single molecules of carbon suboxide react with polyethylene. The polyethylene thus modified is then easily surfacedyed.
Thermal degradation of copolymers of styrene and acrylonitrile. I. Preliminary investigation of changes in molecular weight and the formation of volatile products
Authors: Grassie N. , Bain D. R. 
Published: April 2003

AbstractBy the use of thermal volatilization analysis (TVA), 292°C was chosen as a suitable temperature for a preliminary experimental survey of the thermal degradation of styrene–acrylonitrile copolymers. TVA also indicated that there is no fundamental change in reaction mechanism as the acrylonitrile content of the polymer is increased from zero to 33.4% although there is a progressive increase in the rate of volatilization. The increase in the rate of volatilization over that of polystyrene is directly proportional to the acrylonitrile content of the copolymer. From the changes in molecular weight which occur during the reaction it is clear that the primary effect of the acrylonitrile units on stability is to cause an increased rate of chain scission, but there is a small proportion of “weak links” which are associated with the styrene units and which are broken instantaneously at 292°C. The number of monomer molecules liberated per chain scission, the zip length, is about 40 for polystyrene in the initial stages of degradation and decreases only to the order of 20 even in copolymer containing 24.9% acrylonitrile. Thus the unzipping process is not severely affected by the acrylonitrile units; this is borne out by the fact that acrylonitrile appears among the products in very much greater concentrations than from pure polyacrylonitrile. The proportion of larger chain fragments (dimer, trimer, etc.) also increases with acrylonitrile content.
High‐resolution NMR spectrum of deuterated and undeuterated poly(propene sulfone)
Authors: Ivin K. J. , Navrátil M. 
Published: April 2003

Abstract100 MHz spectra have been obtained for DMSO‐d6 solutions of poly(propene sulfone) made from propene (I), propene‐1,1,3,3,3‐d5 (II), propene‐cis‐1,2‐d2 (III) and propene‐2‐d1 (IV) by copolymerization with sulfur dioxide; also by oxidation of poly‐(propene‐2‐d1 sulfide)s of different tacticities.The following chemical shifts and coupling constants were determined: τA = 6.06, 6.12, 6.19; τB = 6.43, 6.51; τC = 6.05; τCH3 = 8.44; J = 6.5 Hz; JAB = 14.0 Hz.
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Both the A and B protons are sensitive to tacticity, giving rise to five lines in the methylene spectrum of III and ten lines, consisting of four overlapping AB quartets, in the methylene spectrum of IV. From a consideration of the relative intensities of the peaks in the spectra of poly(propene‐2‐d1 sulfone)s of different tacticities the following assignment to triad structures has been made: τA: 6.06 hi, 6.12 i and s, 6.19 hs; τB: 6.43 hi and i, 6.51 s and hs. The proportions of the four triad‐structures correspond to a single‐parameter model for chain growth in which the probability of an isotactic placement σ is 0.50 for the free‐radical copolymerization of propene and sulfur dioxide, 0.55 for the ZnCO3‐initiated polymerization of propene sulfide and 0.64 for the CdCO3‐initiated polymerization of propene sulfide. The spectrum of III shows that for polymer made at −90°C, one mode of addition is preferred. By analogy with other systems it is assumed that this is trans addition. For polymer made at 60°C, both trans and cis addition occur in nearly equal proportions. Assuming that cis addition occurs via the inversion of the intermediate alkyl radical, the activation energy for inversion is found to exceed that for addition of sulfur dioxide by 2.7 kcal/mole (11 kJ/mole). This appears to be the first reported case of a preferred mode of addition to an ethylenic bond in a free radically initiated polymerization.