bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of n‐octadecene‐1 with catalysts derived from titanium tetrachloride and triethylaluminum
Authors: Aubrey D. W. , Barnatt A. 
Published: April 2003

AbstractThe effects of variation in Al/Ti mole ratio, catalyst concentration, reaction time, and temperature on the yield and some physical properties of polymers of n‐octadecene‐1 obtained with the use of Ziegler catalyst systems derived from titanium tetrachloride and triethylaluminum have been investigated. Results show many features similar to those obtained by other workers with lower olefins. In general, the yield of polymer shows a distinct maximum at an Al:Ti mole ratio of 2.8:1 and total catalyst concentration (at the stated mole ratio) of 4%, based on monomer; the yield increases sharply with polymerization temperature to a maximum at about 40°C. and with time up to about 12 hr. at 25°C. Polymer intrinsic viscosity also shows a strong dependence on Al:Ti mole ratio and catalyst concentration, increasing between Al:Ti mole ratios of 2.0–3.4, and showing a maximum at catalyst concentration of 3.5% on monomer. Polymer intrinsic viscosity shows a decrease with increasing reaction temperature and an increase with time of polymerization. The polymer densities, melting points, and fraction soluble in hexane (at 25°C.) appear to show much less dependence on the variables under consideration, and no firm conclusions are drawn. An important reaction concurrent with polymerization is the formation of a trans nonterminal isomer of octadecene. This certainly affects the yield (the nonterminal isomer not being polymerizable under the same conditions); the effect of the presence during polymerization of isomerized monomer on the physical characteristics of the polymer is less clear, and further work is proceeding.
Polymerization of cyclic ethers in the presence of maleic anhydride. Part I. Polymerization of trioxane and 3,3‐bis(chloromethyl)oxetane by γ‐rays, ultraviolet light, and benzoyl peroxide
Authors: Takakura Koichi , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractCyclic ethers such as trioxane and 3,3‐bis(chloromethyl)oxetane have been polymerized easily in the presence of maleic anhydride by the irradiation of γ‐rays and ultraviolet light. The polymer formed is a homopolymer of cyclic ether. The rate of polymerization is accelerated by suitable amounts of oxygen which is required to form some active species at the initiation step. The polymerization is inhibited by the addition of a small amount of radical scavenger, thus suggesting a radical initiating mechanism. In addition, the polymerization is easily initiated by benzoyl peroxide even in vacuo at or above 50°C. Diaroyl and diacyl peroxides are also effective, and polymerization also proceeds in the presence of chloromaleic anhydride, exactly in the same manner as in maleic anhydride. On the other hand, it is well known that polymerization of these cyclic monomers rarely occurs with radical catalysts and easily with cationic catalysts in the absence of maleic anhydride. From these results, it may be concluded that the polymerization is brought about by means of a radical–cationic species.
Study of the mechanism of formation of transparent polyacrylonitrile
Authors: Shavit N. , Oplatka A. , Levy M. 
Published: April 2003

AbstractThe kinetics of bulk polymerization of acrylonitrile, leading to a transparent polymer, was studied. The reaction was followed by a dilatometer specially designed for high degrees of conversion and for continuous supply of monomer during the reaction. The last stages of polymerization were followed by density determinations. It was found that the kinetic scheme did not show any irregularities, and that the major condition for obtaining a transparent polymer is a continuous supply of monomer to fill up the gaps formed by the contraction during the polymerization process.
Homopolymerization of 2‐alkyl‐ and 2‐aryl‐2‐oxazolines
Authors: Tomalia D. A. , Sheetz D. P. 
Published: April 2003

Abstract2‐Aryl‐ and 2‐alkyl‐2‐oxazolines have been polymerized to poly‐(N‐aroyl)aziridines and poly(N‐acyl)aziridines, respectively, in the presence of boron trifluoride. The polymers obtained were glassy, light yellow resins with molecular weights ranging from 3500 to 7500 (35–50 oxazoline units per chain). The polymerization rates have been determined for several of these monomers. A polymerization mechanism is proposed.
Electron spin resonance studies on Ziegler‐Natta type catalyst systems
Authors: Ono Yoshio , Keii Tominaga 
Published: April 2003

AbstractElectron spin resonance spectra of Ziegler‐Natta type catalyst systems (titanium trichloride and alkyl aluminums) have been studied. When triethylaluminum was added to titanium trichloride, an absorption with a g value of 1.96 was observed from the solid phase of the system. The number of spins of this signal is equal to that of the active centers for propylene polymerization. The solid phase from the mixture of titanium trichloride and diethylaluminum chloride also gives the same signal, which suggests the identity of the action of two alkyl aluminums on titanium trichloride surface. The signals obtained from the liquid phase of the both systems are all ascribed to the reaction products of the reaction of alkyl aluminum with titanium tetrachloride occluded in solid.
Theoretical studies on the degradation of ladder polymers
Authors: Tessler Martin M. 
Published: April 2003

AbstractThe random degradation of four‐ and six‐membered ring ladder polymers was simulated on a digital computer by utilizing a Monte Carlo model. The degradation was compared with that of a single‐chain linear polymer undergoing an identical degradation reaction. Significant differences in the change in molecular weight as a function of time were noted between the ladder polymer and the single chain polymer. Similar studies were conducted with imperfect ladder polymers which had occasional missing bonds in the ladder structure. These imperfections produced a marked drop in molecular weight at a given time compared with the perfect ladder polymer.
Studies on polymers containing functional groups. VI. Kinetics of the polymerization and copolymerization behaviors of o‐hydroxystyrene
Authors: Kato Masao , Kamogawa Hiroyoshi 
Published: April 2003

AbstractSome kinetic studies were made of the homopolymerization of o‐hydroxystyrene and its copolymerization behavior with styrene and methyl methacrylate in tetrahydrofuran using azobisisobutyronitrile as initiator were done. The rate of polymerization experimentally obtained is given by Rp = K[M][I]0.72. Accordingly, it is likely that the growing chain radicals are terminated not only by mutual termination but also by a chain‐transfer mechanism, the latter occupying a considerable portion. The latter is mostly attributed to the transfer to monomer, i.e., Cm for o‐hydroxystyrene was 1.3 × 10−2. Some transfer mechanisms were assumed, although it is difficult to elucidate the mechanism in detail, owing to its complexity. Effects of solvent on the rate of polymerization were examined, dioxane, methyl ethyl ketone, ethanol, and tetrahydrofuran being used. However, no differences were found among the solvents. The apparent activation energy of polymerization was found to be 21.5 kcal./mole. Monomer reactivity ratios and Alfrey‐Price Q–e values for o‐hydroxystyrene were determined. The Q–e values (Q = 1.41, e = −1.13) are rather similar to those of p‐methoxystyrene. Thus, the e value for o‐hydroxystyrene is more negative than that for styrene.
Model compounds and polymers with quinoxaline units
Authors: Jadamus Hans , De Schryver Franz , De Winter Walter , Marvel C. S. 
Published: April 2003

AbstractTetra‐ and heptanuclear N‐heterocycles, their dimers and their polymers have been prepared by condensation of o‐phenylenediamine or 3,3'‐diaminobenzidine with 2,3‐dihydroxyquinoxaline, 2,3,2,3'‐tetrahydroxy‐6,6'‐bisquinoxaline, or 2,3,7,8‐tetrahydroxy‐1,4,6,9‐tetraazaanthracene in polyphosphoric acid, or with the O‐phenyl derivatives of the latter three compounds in phenol. The condensation products are highly colored compounds with characteristic absorption spectra. The polymers show good thermal stability.
Deviations from topotaxy in trioxane polymerization
Authors: Adler George 
Published: April 2003

AbstractIt is shown by photomicrographic techniques that the polymer does not always form in a unique crystallographic direction in the solid‐state polymerization of trioxane. The polymerization in these instances cannot therefore be considered topotactic in the usually accepted sense. The crystallization of the polymer is attributed to factors which are, in a sense, secondary to the actual reaction mechanism.
Polymerization of butadiene sulfone
Authors: Minoura Yuji , Nakajima Shigemitsu 
Published: April 2003

AbstractPolymerization of butadiene sulfone (BdSO2) by various catalysts was studied. Azobisisobutyronitrile (AIBN), butyllithium, tri‐n‐butylborn (n‐Bu)3B, boron trifluoride etherate, Ziegler catalyst, and γ‐radiation were used as catalysts. Butadiene sulfone did not polymerize with these catalysts at low temperatures (below 60°C.), but polymers were obtained at high temperature with AIBN or (n‐Bu)3B. The polymerization of BdSO2 initiated by AIBN in benzene at 80–140°C. was studied in detail. The obtained polymers were white, rubberlike materials and insoluble in organic solvents. The polymer composition was independent of monomer and initiator concentrations and reaction time. The sulfur content in polymer decreased with increasing polymerization temperature. The polymers prepared at 80 and 140°C. have the compositions (C4H6)1.55‐ (SO2) and (C4H6)3.14(SO2), respectively, and have double bonds. These polymers were not alternating copolymers of butadiene with sulfur dioxide. The polymerization mechanism was discussed from polymerization rate, polymer composition, and decomposition rate of BdSO2. From these results, the polymerization was thought to be “decomposition polymerization,” i.e., butadiene and sulfur dioxide, formed by the thermal decomposition of BdSO2, copolymerized.
Acid–base Properties of Ion‐exchange Resins. Dissociation and Swelling of Resin Copolymers of Methacrylic Acid, Methyl Methacrylate, Divinylbenzene, and Ethylvinylbenzene
Authors: Mathieson A. R. , Shet R. T. 
Published: April 2003

AbstractThe dissociation, capacity, swelling, and water content of crosslinked methacrylic acid—methyl methacrylate resins have been measured. Resins were prepared with different degrees of crosslinking for the same carboxylate content, and vice versa. The ionic strength of the external solution was also varied, and the behavior of commercial resins compared with that of the laboratory resins. Potentiometric titration curves were obtained, and curves were also obtained by back‐titration of the salt form of the resins with acid. The capacities showed that almost all carboxyl groups are accessible in resins containing 2.5% or 4.0% divinylbenzene, but not in those containing 8% or 12%. For these highly crosslinked resins the back‐titration curves differed from the forward curves. Apparent dissociation constants pK′a = pH + n log [(1 − α)/α] decreased with increased ionic strength, increased with increased crosslinking, and showed no trend with carboxylate content. Swelling is decreased by increased salt concentration, particularly for lightly crosslinked resins. Maximum swelling is achieved at about 80% dissociation. The reciprocal of the swollen volume is proportional to the per cent of divinylbenzene. Commercial resins showed much lower swelling than laboratory prepared resins ostensibly having the same composition. The Gibbs‐Donnan theory of resin dissociation was applied to calculate the intrinsic dissociation constant (pK′0). Assuming a model of randomly kinked chains dissolved in the sorbed solution, good agreement with the expected value of 4.85 was found (calcd. pK′0 = 4.81 = 0.14), except for the most highly crosslinked resins. For polyampholyte resins, agreement was found by using a model having a uniform potential distribution throughout the resin (pK′0 = 4.9).
A New, General Synthetic Method for the Preparation of Linear Poly‐p‐xylylenes
Authors: Gorham William F. 
Published: April 2003

AbstractA new, general synthetic route to poly‐p‐xylylene and substituted poly‐p‐xylylenes is described. The key intermediate in the new process is di‐p‐xylylene [(2,2)p‐cyclophane]. It has been found that di‐p‐xylylene is quantitatively cleaved by vacuum vapor‐phase pyrolysis at 600°C. to two molecules ofp‐xylylene.p‐Xylylene spontaneously polymerizes on condensation to form high molecular weight, linear poly‐p‐xylylene. The conversion of di‐p‐xylylene to poly‐p‐xylylene is quantitative. The process is adaptable to the preparation of a wide variety of substituted poly‐p‐xylylenes by pyrolysis of ring‐substituted di‐p‐xylylenes and polymerization of the resultant substitutedp‐xylylenes. Many of these polymers are not attainable by any other route. All are linear and free of crosslinking. Evidence supporting the proposed mechanism of pyrolytic cleavage of every molecule of di‐p‐xylylene to two molecules ofp‐xylylene is presented. Tough, transparent polymeric films are obtained from the process when the polymerization of thep‐xylylenes is conducted on glass or metal surfaces. Outstanding combinations of physical, electrical, and chemical properties are displayed by poly‐p‐xylylene, polychloro‐p‐xylylene, and other substituted polymers. A comparison of the relative merits of the original Szwarc route and the new di‐p‐xylylene route to poly‐p‐xylylenes is presented.
Mechanism of Polymerization of α‐Olefins on Oxide Catalysts
Authors: Miesserov K. G. 
Published: April 2003

AbstractThe polymerization of ethylene on a chromic oxide catalyst with and without a solvent has been studied. It was found that the active catalyst surface is formed exclusively as a result of its interaction with ethylene. This interaction is accompanied by the formation of products which poison the surface of the catalyst when they are sorbed on it in the absence of a solvent. A catalyst which contains no Cr+6 atoms as a result of reduction by alcohol is inactive. On the other hand, a catalyst which contains only Cr+6 atoms becomes active only after it has been partially reduced. The most probable product of this reduction is trivalent chromium atoms. The results obtained have given grounds for the assumption that the active complex contains Cr+6 and Cr+3 atoms. A possible mechanism of the reaction is discussed. Owing to the oxidative action of CrO3 on the ethylene molecules, part of the Cr+6 is reduced to Cr+3, and the trivalent chromium becomes alkylated. The monomer molecule is added at the Cr+3—C bond thus formed. A strong Lewis acid, CrO3, lowers the electron density on the Cr+3 atom. This increases the strength of the Cr+3—C bond and the ability of the Cr+3 atom to coordinate with the monomer molecule. The monomer molecule enters the chain at the moment when the strength of the Cr−3—C bond is weakened due to coordination of this molecule with the Cr+3 atom.
Some viscoelastic properties of siloxane polymers during irradiation
Authors: Jenkins R. K. 
Published: April 2003

AbstractThe dynamic moduli, E′ dyn, and loss tangents, tan δ, of polydimethylsiloxane and polydimethyldiphenylsiloxane polymers have been investigated by an in situ technique during γ‐irradiation. These viscoelastic properties were calculated and plotted as a function of irradiation exposure time by measuring the free end displacements and resonance frequencies of polymeric cantilever reeds. The reeds were swept through a small frequency range from about 20 to 100 cycles/sec. The moles of effectively elastic chains per unit volume (v) of the two unfilled polysiloxahes were calculated from in situ modulus data and compared to values obtained utilizing the swelling technique. The approximate molecular weights between entanglements, Me, of these unfilled polymers were determined by extrapolation of moduli data to zero radiation exposure. The addition of a large silica filler, SiO2, into the polymers did not alter the crosslinking rates, and the filler did not enter into polymer—filler bonding.
Tensile strength of oriented polymers below the glass transition temperature
Authors: Prevorsek Dusan C. 
Published: April 2003

AbstractA theory of tensile strength, based on the observation of cracks in specimens strained to breaking, is formulated. The treatment involves the assumption that a crack grows to a critical size by a nucleation process. When this critical size is exceeded the crack becomes unstable and propagates spontaneously to produce rupture. By comparing the predicted and measured strength, one can estimate the magnitude of the stress concentration factor in fibers. An interpretative analysis of experimental data obtained at various strain rates indicates that the resulting changes in tensile strength are due primarily to the changes in modulus.
Effect of birefringence on light scattering from oriented systems
Authors: Stidham S. N. , Stein R. S. 
Published: April 2003

AbstractThe effect of birefringence on the intensity of polarized scattered light from an oriented polymer film is analyzed on the basis of a model in which the scattering element is imbedded in a homogeneous birefringent matrix. The scattering intensity is shown to depend upon the polarizer and analyzer angles, the scattering angles, the sample birefringence and thickness, and the scattering coefficients for the four polarization combinations. Computer calculations for reasonable values of these parameters indicate that these corrections can be quite appreciable.
X‐ray diffraction studies of diisotactic polymers of cis‐ and trans‐2‐butene oxides
Authors: Barlow Malcolm 
Published: April 2003

AbstractCrystalline polymers derived from cis‐ and trans‐2‐butene oxides were studied by x‐ray diffraction methods. X‐ray fiber and powder photographs of poly(trans‐2‐butene oxide) were indexed by an orthorhombic unit cell with the dimensions a = 13.72 A., b = 4.60 A., and c (chain axis) = 6.90 A.; the space group is P212121. The crystal structure of this polymer has been determined in projection. The chain has an erythro‐diisotactic structure with ‐dl, dl‐ carbon sequences. The polymer has a nonplanar zigzag backbone with carbon and oxygen atoms of alternate monomer units lying nearly in a plane. Two chain molecules pass through the unit cell. The unit cell of poly(cis‐2‐butene oxide) is orthorhombic with lattice constants a = 11.20 A., b = 10.44 A., c (chain axis) = 7.01 A. The polymer has a threo‐diisotactic structure with ‐dd,dd‐ or ‐ll,ll‐ carbon sequences. Four chain molecules pass through the unit cell. The crystal lattice is body‐centered but the space group has not yet been established. The polymer has an almost fully extended zigzag chain configuration. Polymers prepared by either metal halide catalysts (FeCl3, SnCl4) or organometallic catalysts were essentially identical; the latter catalysts did, however, yield more highly crystalline polymers.
Application of dn/dc data for the determination of partial specific volumes of dissolved macromolecules
Authors: Heller Wilfried 
Published: April 2003

AbstractThe principles of a method are outlined whereby one can determine the partial specific volume of a solute, V̄, by means of measurements of dn/dc using a suitable pair of equations and a simple graphical interpolation procedure. The method yields V̄ data which compare well with densitometrically obtained V̄ data if the polarizability of both solvent and solute molecules is unaffected by the solution process. It is tested successfully on solutions of polystyrene in various solvents. The method appears to be particularly attractive for measurements of the change of V̄ with temperature and also for conveniently following the time rate of changes in ‐ such as during the coil → helix transition.
Mechanism of fracture in glassy polymers. III. Direct observation of the craze ahead of the propagating crack in poly(methyl methacrylate) and polystyrene
Authors: Kambour Roger P. 
Published: April 2003

AbstractObservation of optical interference fringes at the tip of a crack in a glassy polymer allows the construction of the configurations of the crack tip and the craze that precedes it. The craze extends 25 μ beyond the crack tip in poly(methyl methacrylate) and 550 μ beyond the tip in the polystyrene studied. The craze at the crack tip in PMMA may be seen to deform elastically as much as 100% under stress before crack propagation recommences. Such deformation is estimated to account for as much as 40% of the nominal Griffith energy of crack propagation.
Solution properties of polyoxymethylene
Authors: Stockmayer Walter H. , Chan Lock‐Lim 
Published: April 2003

AbstractLight scattering and viscosity have been measured at 25°C. for dilute solutions of six unfractionated polyoxymethylene samples in the mixed solvent hexafluoroacetone–water (mole ratio 1/1.7) slightly buffered with triethylamine. Dialysis equilibrium through porous Vycor glass thimbles indicates that the polymer is strongly solvated by the hydrate (CF3)2C(OH)2, and this must be taken into account in evaluating weight‐average molecular weights from the light‐scattering data. Over the molecular weight range 23,000–185,000, the intrinsic viscosities (in deciliter per gram) follow the relation

The corresponding unperturbed dimensions are σ = 2.3 ± 0.2 or r02/nl2 = 10.5 ± 1.5.
Light scattering of polar chain molecules subjected to an electrical field
Authors: Wallach M. L. , Benoit H. 
Published: April 2003

AbstractEquations previously developed for the light scattering of polar chain polymers subjected to orientation by an electrical field are extended to the case where the elementary dipoles have arbitrary direction with respect to the chain contour. As an illustration of the theory, measurements were made of the light scattering of nitrocellulose solutions as a function of the angle of observation, the field strength, the direction of the field, and the frequency of the field. The principal results obtained were: the molecules are deformed by the electrical field; orientation is due primarily to a permanent electric moment whose component per chain segment is of the order of 4 Debye; and the relaxation times for molecular orientation are of the order of magnitude predicted by the theory of Stockmayer and Baur.
Frequency and temperature dependence of the dynamic mechanical properties of poly‐4‐methylpentene‐1
Authors: Penn Robert W. 
Published: April 2003

AbstractThe dynamic mechanical properties of poly‐4‐methylpentene‐1 have been measured in torsion in the temperature range from 25 to 160°C. at frequencies from 10−3 to 10 cps. Two transitions are found. The first, with a peak at 40°C. at 1 cps, appears as a normal glass transition. A broad high temperature peak appears at 130°C. The dynamic compliance‐frequency data can be superposed by the conventional method of reduced variables for temperatures up to 100°C. The temperature dependence of the shift factors follows the WLF equation. Above this temperature, superposition can be achieved by applying horizontal and vertical shifts to both components of the dynamic compliance. When the vertical shift is permitted, the range of applicability of the WLF equation is extended to 160°C.
Effect of molecular weight upon the heterogeneous nucleation of crystallization in polypropylene
Authors: Beck H. N. 
Published: April 2003

AbstractThe effect of basic aluminium dibenzoate upon the supercooling of polypropylene fractions of molecular weight 9.2 × 103‐1.25 × 106 was determined by differential thermal analysis. The response to heterogeneous nucleation within the precision of the method used appears to be only slightly dependent, if at all, upon the molecular weight of the polymer.