bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of olefin oxides and of olefin sulfides
Authors: Lal Joginder
Published: April 2003

Two new catalyst systems, sulfur–diethylzinc and 98% hydrogen peroxide–diethylzinc, have been investigated for polymerizing propylene oxide. The sulfur–diethylzinc catalyst system has a broad range of sulfur/zinc atomic ratio for polymerizing propylene oxide heterogeneously to high molecular weight materials in high yields. The highest polymer yield is obtained at the sulfur/zinc atomic ratio of 3–3.5. Like the water–diethylzinc system, the hydrogen peroxide–diethylzinc system has a narrow range of hydrogen peroxide/diethylzinc molar ratio in the vicinity of 0.57 for optimum polymer yield. Crystallinity measurements by x‐ray diffraction of a few polymers prepared with these three catalyst systems showed that they are fairly similar in the extent of their crystallinity. A plot of the per cent of polymer insoluble in acetone against inherent viscosity of the original polymer also showed that the polymers prepared with sulfur–diethylzinc and hydrogen peroxide–diethylzinc catalyst systems have similar amounts of crystallinity. Data are given for the polymerizability of ethylene oxide, 1,2‐butene oxide, styrene oxide, propylene sulfide, 1,2‐butene sulfide, and a vulcanizable copolymer of propylene oxide and allyl glycidyl ether with the sulfur–diethylzinc catalyst system. The polymers from the olefin sulfides had lower inherent viscosities than the polymers from the corresponding olefin oxides. Aging of the sulfur–diethylzinc catalyst (S/Zn atomic ratio = 3.5) improved the yield of poly(propylene oxide). The yield was essentially unchanged when propylene oxide was polymerized in six different solvents. The formation of C2H5SxZnSC2H5 and C2H5SxZnSyC2H5 (x and y are integers between 2 and 8) and possibly C2H5SxZnC2H5 as the catalytically active species is postulated during the reaction of sulfur and diethylzinc.
Untersuchung der Bildung von Polyesteramiden aus Dicarbonsäure‐anhydriden und Oxazolidinonen‐2
Authors: Burckhardt S. , Reichert K.‐H. , Hamann K.
Published: April 2003

The well‐known reaction of dicarboxylic acid anhydrides with epoxides, catalyzed by bases and yielding linear polyesters, has been extended by a variation of the reactants. The reactions of succinic and phthalic anhydrides with N‐substituted oxazolidinones‐2, which by their tendency to split off CO2 may be regarded as ethyleneimine derivatives, give in the presence of a few mole percent of LiCl at 200–220°C. within 5–10 hr. polyester amides of molecular weights up to 3.500 in nearly quantitative yield. The polymer yield corresponds to the CO2 evolution indicating an equal consumption of oxazolidinone and anhydride in the reaction. The experimental activation energies of 22.8 and 20.2 kcal./mole for the reaction of 3‐phenyl oxazolidinone‐2 with succinic and phthalic anhydrides, respectively, fairly agree with earlier values reported for the corresponding reactions of the cyclic carbonates.
Polymerization of 1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose and 1,2‐O‐isopropylidene‐α‐D‐glucofuranose
Authors: Whistler Roy L. , Seib Paul A.
Published: April 2003

A new method for preparing D‐glucose polymers is described. Isopropylidene derivatives of D‐glucofuranose, particularly the 1,2‐mono‐O‐derivative, are treated with Lewis acids, such as boron trifluoride, to eliminate acetone and produce a highly branched polymer with a molecular weight of 12,700. Approximately one isopropylidene unit remains, possibly on the potential reducing end of the glucan. Up to 95% of the polymer units are D‐glucopyranoside units indicating that ring expansion occurs during the condensation.
Polymerization of α‐halogenated p‐xylenes with base
Authors: Gilch H. G. , Wheelwright W. L.
Published: April 2003

Various α‐halo‐p‐xylenes have been polymerized with base yielding p‐xylylene polymers. The reaction involves a 1,6‐dehydrohalogenation to give a xylylene which then polymerizes. α,α′‐Dichloro‐p‐xylene forms poly‐α‐chloro‐p‐xylylene and polymers containing stilbene units; α,α,α′,α′‐tetrachloro‐p‐xylene gives poly‐α,α,α′‐trichloro‐p‐xylylene; alkyl, aryl, and halogen ring‐substituted α‐chloro‐p‐xylenes give the corresponding ring‐substituted poly‐p‐xylylenes. The more halogens in the α positions (up to five), the weaker the base necessary for dehydrohalogenation. Sodium hydroxide in methanol will polymerize tetrachloro‐p‐xylene, while potassium tert‐butoxide in refluxing p‐xylene is necessary to polymerize α‐chloro‐p‐xylenes. Stilbenes are formed when α‐halo‐p‐xylenes are reacted with potassium tert‐butoxide in polar solvents such as dimethyl sulfoxide.
Chemistry of polybutadiene—iron carbonyl systems
Authors: Berger M. , Manuel T. A.
Published: April 2003

The treatment of polybutadienes with iron carbonyls results in formation of polymers containing tricarbonyl(conjugated diene)iron units [C8H12Fe(CO)3] and also results in geometrical isomerization of free double bonds. Heating of the iron carbonyl‐containing polymers gives ferromagnetic products with enhanced thermal stability. The incorporation of iron carbonyl groups into the polymer is favored by basic solvents and high temperatures, the geometrical isomerization by acidic solvents and low temperatures. Steric factors are powerful in determining the rate of isomerization.
Polymerization of n‐octadecene‐1 with catalysts derived from titanium tetrachloride and triethylaluminum
Authors: Aubrey D. W. , Barnatt A.
Published: April 2003

The 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

Cyclic 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

The 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

2‐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

Electron 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

The 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

Some 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

Tetra‐ 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

It 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

Polymerization 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

The 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

A 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

The 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

The 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

A 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

The 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

Crystalline 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

The 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

Observation 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

Light 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

Equations 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

The 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

The 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.
Persistent polarization in polymers. I. Relationship between the structure of polymers and their ability to become electrically polarized
Authors: Miller M. L.
Published: April 2003

The ability of various polymers to acquire persistent polarization (i.e., to become electrets) was investigated. Polarization was induced in the polymers by two methods: (a) by cooling under a voltage drop and (b) by cooling with flow under pressure. There was found to be an optimum temperature for electret formation by either method. This optimum temperature was roughly 37°C. above Tg when polarization was produced by application of a voltage drop and roughly 57°C. when polarization was produced by flow under pressure. Crystallinity and the nonhomogeneities present in blended polymers were harmful to electret formation, but a small critical amount of ionic impurity was helpful.
Molecular structure of polyethylene. XIII. An improved cryoscopic method for determining number‐average molecular weight of polyethylene
Authors: Newitt E. J. , Kokle V.
Published: April 2003

The determinations of the number‐average molecular weight of polyethylene by cryoscopy has been improved, permitting precise measurements with both linear and branched polyethylenes in the molecular weight range 4,000–30,000. Improvements include a cryometer of new design, a lower‐melting cryoscopic solvent containing a nucleating agent to control supercooling and rate of crystallization of the solvent, and more precise measurement of freezing point depression. Polyethylene samples are dissolved in hexamethylbenzene admixed with 0.1% of cadmium iodide, and steady‐state freezingpoint depressions are measured with a thermistor to a maximum sensitivity of 5 × 10−5°C. Molecular weight measurements are reproducible to within ±10%. The cryoscopic apparatus and procedure are described in detail, and results obtained with samples of linear and branched polyethylene are presented and discussed.
Structure of pressure‐crystallized polypropylene
Authors: Kardos J. L. , Christiansen A. W. , Baer Eric
Published: April 2003

The structure of polypropylene crystallized at pressures up to 5000 atm. has been studied. Upon slow cooling from the melt at 320 atm., the γ modification, previously found only in low molecular weight and stereoblock fractions, begins to appear in small amounts in addition to the normal α monoclinic form. As the pressure is increased further, a larger proportion of the sample crystallizes in the γ form until, at 5000 atm., only the γ modification is present. X‐ray and DTA studies show that the γ form of polypropylene transforms to the normal α modification at a temperature only slightly below the γ melting point. Evidence is presented which favors the occurrence of a solid‐state transition as a model of transformation to the α form. Results from isothermal crystallizations at low supercoolings and annealing experiments under high pressure show that the melting point of the γ modification of polypropylene is very sensitive to crystallite perfection.
Fibrous/lamellar microstructure in polyethylene
Authors: Williamson R. B. , Novak R. C.
Published: April 2003

A shish‐kebab microstructure consisting of both fibrillar and lamellar crystals has been observed with transmission electron microscopy in polyethylene crystallized from the melt. The parallel fibrillar crystals are aligned at right angles to closely spaced lamellar crystals. The lamellar crystals were grown epitaxially on a few fibrillar crystals obtained by shearing a solution which preceded the creation of the thin melt film. The fibrillar/lamellar microstructure revealed by dissolving a paraffin diluent illustrates two aspects of oriented structures not reported previously: (a) a high density of intercrystalline links parallel to the original nucleating fiber connecting the lamellar crystals, and (b) a connectivity between lamellar crystals growing on different nucleating fibers. The samples are observed to have a continuous two‐dimensional crystalline superstructure.
N‐Alkyl‐substituted polyamides and copolyamides having long methylene chain units
Authors: Saotome Kazuo , Komoto Hiroshi
Published: April 2003

N‐Alkyl‐substituted polyamides and copolyamides have been prepared from N,N′‐dialkyl p‐xylenediamine and N,N′‐dialkyl hexamethylenediamine with long‐chain aliphatic dicarboxylic acids. Crystalline N‐alkyl polyamides were obtained by the use of dicarboxylic acids higher than C16. The melting point versus composition curves for the crystalline N‐alkyl copolyamides which were prepared from a mixture of diamine and the corresponding N‐alkyl diamine with α,ω‐octadecanedioic acid showed convex type plots. X‐ray examination of N‐alkyl copolyamides revealed that all the systems behaved in the same basic manner, the second component was always present without dissolving in the lattice of the first. Dilatometric curves showed two inflection points, corresponding to the melting points of the N‐alkyl and unsubstituted polyamides respectively. From these results, a block copolymer structure was suggested for the N‐alkyl copolyamides. The mechanisms for the formation of the block structure were also discussed.
Polyurethanes and polyureas having long methylene chain units
Authors: Saotome Kazuo , Komoto Hiroshi
Published: April 2003

Polyurethanes and polyureas containing long methylene chain units have been prepared from the following six series of monomer combinations; aliphatic diisocyanates with aliphatic glycols or diamines, methylene bis(4‐phenyl isocyanate) with aliphatic glycols or diamines, and p‐xylylene diisocyanate with aliphatic glycols or diamines. A good linear relationship was noted between the polymer melting points of each series against the concentration of functional groups. Both polyurethanes and polyureas from p‐xylylene diisocyanate showed higher melting points than those from methylene bis(4‐phenyl isocyanate) with corresponding aliphatic monomers. The relations between the melting points of these polymers with long methylene chains, including polyamides which were previously reported, and the chain components were discussed. The higher melting points of polymers containing p‐xylylene group are attributed to the high rigidity of this group.
NMR study of poly(vinyl formate)
Authors: Ramey Kermit C. , Lini David C. , Statton Gary L.
Published: April 2003

The high resolution nuclear magnetic resonance spectrum of poly(vinyl formate), yielded, upon examination at 100 Mc./sec., and under the conditions of decoupling, information on the three tactic forms present. The normal and decoupled spectra indicate that only the CHO resonance is sensitive to the stereochemical configuration. The three components of the CHO resonance are tentatively assigned to isotactic (i), heterotactic (h), and syndiotactic (s) triads with increasing field strength, respectively. This assignment was made on the basis of poly(vinyl alcohol) and poly(vinyl acetate) derived from poly(vinyl formate). The results show that the tacticity is slightly dependent upon the temperature of free‐radical polymerization.
High‐pressure reactions. II. γ‐Ray polymerization of acrylamide
Authors: Prince M. , Hornyak J.
Published: April 2003

The post‐irradiation effect of high pressure on the γ‐ray‐initiated solid‐state polymerization of acrylamide has been described. Polymer conversion was found to increase significantly with applied pressure. The molecular weight of polymer increases with pressure.
Kinetics of nonequilibrium methylsiloxane polymerization and rearrangement
Authors: Adams Frederick P. , Carmichael Jack B. , Zeman Ronald J.
Published: April 2003

Nonrandom reactions were demonstrated experimentally during the polymerization of (CH3)3SiOSi(CH3)3 plus [(CH3)2SiO]4 and the rearrangement of (CH3)3SiO[(CH3)2SiO]5Si(CH3)3 or (CH3)3SiO[(CH3)2SiO]8Si(CH3)3, using sulfuric acid‐treated Fuller's earth as catalyst. Cyclic and linear reaction products were analyzed by gas–liquid chromatography. A four‐step polymerization mechanism was proposed to account for the approach to equilibrium from either the forward or reverse direction. Reaction rate expressions for this mechanism were reduced to a finite set of nonlinear ordinary differential equations. These were solved by using a fourth‐order Runge‐Kutta numerical integration on a Burroughs B5500 computer. The calculated molecular weight distributions thus obtained were found to agree at all times with the distributions from polymerization and rearrangement experiments.
Determination of kinetic parameters for pyrolysis of cellulose and cellulose treated with ammonium phosphate by differential thermal analysis and thermal gravimetric analysis
Authors: Akita K. , Kase M.
Published: April 2003

Activation energy E, pre‐exponential factor k0, and reaction order n for the pyrolysis of α‐cellulose and cellulose modified with dihydrogen ammonium phosphate were determined by means of TGA and DTA. The results obtained are E = 53.5 kcal./mole, k0 = 1018.8 min.−1, n = 1 for α‐cellulose and E = 32 kcal./mole, k0 = 1012 min.−1, n = 1 for modified cellulose. A new theory of DTA was also developed. This theory, in which it is concluded that the peak value of DTA curve coincides with the maximum rate of reaction, may be used not only for the present work but is generally applicable to DTA studies. Detailed procedures of experiment and theory are described.
Poly‐1,6‐Diselenahexamethylene, 1,2‐diselenane, and their effects on vinyl polymerizations
Authors: Brown J. R. , Gillman G. P. , George M. H.
Published: April 2003

Poly‐1,6‐diselenahexamethylene has been prepared, and some of its properties and those of its depolymerization product, 1,2‐diselenane, have been studied. Depolymerization probably occurs by a free‐radical mechanism. The effects of these organoselenium compounds on the thermal polymerization of styrene, methyl methacrylate, vinyl acetate, and acrylonitrile at 60°C. in the presence and absence of 2,2′‐azobisisobutyronitrile and on the direct photopolymerization of these vinyl monomers at 25°C. has been examined. Various reaction mechanisms are suggested to explain the experimental results.
Kinetics of free‐radical polymerization of p‐vinylbenzyl methyl ether: Crosslinking by initiator free radicals
Authors: Symcox Robert O. , Cotman John D.
Published: April 2003

Kinetics of polymerization of p‐vinylbenzyl methyl ether at low conversion either in bulk or in benzene have been found to be quite similar to those of the unsubstituted monomer styrene. Rates of polymerization initiated by peroxides or α,α′‐azobisisobutyronitrile over the temperature range 50–70°C. have been found to be proportional to [Monomer][Initiator]1/2 with an activation energy difference Epropagation – 1/2 Etermination ≈ 6 kcal./mole. Azo initiation leads to essentially unbranched poly(vinyl‐benzyl methyl ether) even at very high conversions, whereas initiation of undiluted monomer by diacyl peroxides results in some crosslinking at high conversion. Use of biacetyl as a photoinitiator of polymerization over the temperature range 0–60°C. with either bulk monomer or monomer solutions in benzene has been found in each instance to yield crosslinked, insoluble polymers at low degrees of conversion. Benzene solutions of soluble polymer have been converted to high molecular weight branched polymers by free radicals generated by photolysis of biacetyl, and a substantial preference of methyl free radicals to abstract benzyl hydrogens of poly(p‐vinylbenzyl methyl ether) rather than add to solvent benzene has been observed.
Copolymerization of 4‐cyclopentene‐1,3‐dione with p‐chlorostyrene and vinylidene chloride
Authors: Winston Anthony , Li George T. C.
Published: April 2003

The copolymerization of 4‐cyclopentene‐1,3‐dione (M2) with p‐chlorostyrene and vinylidene chloride is reported. The copolymers were prepared in sealed tubes under nitrogen with azobisisobutyronitrile initiator. Infrared absorption bands at 1580 cm.−1 revealed the presence of a highly enolic β‐diketone and indicated that copolymerization had occurred. The copolymer compositions were determined from the chlorine analyses and the reactivity ratios were evaluated. The copolymerization with p‐chlorostyrene (M1) was highly alternating and provided the reactivity ratios r1 = 0.32 ± 0.06, r2 = 0.02 ± 0.01. Copolymerization with vinylidene chloride (M1) afforded the reactivity ratios r1 = 2.4 ± 0.6, r2 = 0.15 ± 0.05. The Q and e values for the dione (Q = 0.13, e = 1.37), as evaluated from the results of the vinylidene chloride case, agree closely with the previously reported results of copolymerization with methyl methacrylate and acrylonitrile and confirm the general low reactivity of 4‐cyclopentene‐1,3‐dione in nonalternating systems.
Poly(chloral‐1,3‐dioxolane diol)
Authors: Dietrich Heinz J. , Karabinos Joseph V. , Raes Maurice C.
Published: April 2003

Chloral and cyclic formals were copolymerized in the presence of acidic catalysts and controlled amounts of water to diols of varying compositions and molecular weights. Cyclic oligomers were formed irreversibly as by‐products from the monomers and were also obtained by depolymerization. Condensation of the diols with diisocyanates yielded linear polyurethanes of improved flame resistance.
Radiochemical determination of low unsaturations in polyisobutene. Stoichiometry of the reaction between chlorine and branched double bonds
Authors: McGuchan R. , McNeill I. C.
Published: April 2003

In a previous paper, the radiochemical determination of low unsaturation in polyisobutene was effected by reacting radiochlorine with the double bonds. The reaction is one of substitution rather than addition, and the derivation of true unsaturation values required an assumption to be made regarding the number of chlorine atoms (one or two) incorporated per double bond. In this paper the assumption is tested by examining the stoichiometry of the chlorination of suitable model compounds of known or measurable unsaturation under the experimental conditions used previously. It is found that reaction leads to a monochloro product rather than the dichloro product previously assumed. Conclusions regarding the chain termination process in isobutene polymerization are re‐examined in the light of this result.
Stress–strain behavior of swollen polymeric networks
Authors: Rijke A. M. , Taylor G. L.
Published: April 2003

The network parameters of swollen, solution‐crosslinked polymer filaments can be collected from deswelling measurements in solutions of nonpermeating polymer or, as shown in this paper, from the stress–strain relation when in equilibrium with the surrounding solvent. The degree of swelling, at which the partial molar free energy of elasticity equals zero, is found to vary with solvent power in agreement with earlier findings on other systems. Comparison with results of studies on rubber networks crosslinked in the absence of diluent show that previously observed discrepancies between theory and experiment can be attributed to the deficiency of the single term involving the one‐third power of the volume fraction of polymer in the swollen network to describe the contribution of the partial elastic free energy.
Studies on tacticity of polyacrylonitrile. II. High‐resolution nuclear magnetic resonance spectra of 2,4‐dicyanopentanes
Authors: Murano Masao , Yamadera Reizo
Published: April 2003

The NMR spectra of 2,4‐DCNP were measured in CCl4, NaCNS–D2O, DMSO‐d6, and other solutions. The spectra of the meso form show no significant change with the solvent, but the racemic form shows two kinds of spectra, one of which is observed in a solvent for PAN and the other in a nonsolvent. In the solution, the meso 2,4‐DCNP is considered to have two equivalent conformations, TG and G'T, which are the mirror images with each other. The racemic 2,4‐DCNP, however, might have predominantly either the TT or GG conformation in CCl4, pyridine, and benzene, while it has the two conformers with almost equal probability in NaCNS–D2O and DMSO‐d6. The results obtained from the calculation assuming appropriate constants are in fairly good agreements with the observed spectra of the 2,4‐DCNP isomers. The values of chemical shifts and coupling constants used in the calculation correspond to those of PAN which were obtained previously from the analysis of the NMR spectra.
A study of the molecular weights of tetrahydrofuran–propylene oxide copolymers by gel permeation chromatography and other methods
Authors: Blanchard L. P. , Baijal M. D.
Published: April 2003

The cationic copolymerization of tetrahydrofuran and propylene oxide was studied in a batch system. Boron fluoride ethyl ether and 1,2‐propanediol were used as catalyst—co—catalyst system. Number‐average molecular weights M̄n of various copolymers were determined by vapor‐pressure osmometry (VPO) and hydroxyl endgroup analysis (OH). The VPO and OH molecular weights differed considerably. To explain the differences, several copolymers were analyzed by gel permeation chromatography (GPC). The chromatograms obtained showed for each copolymer analyzed two peaks, one located in the high molecular weight region, the other in the low molecular weight region. An attempt is made to correlate the results and to show the usefulness of GPC in the characterization of THF—PO copolymers.
Polymerization of styrene with VOCl3–aluminum alkyls
Authors: Anand L. C. , Deshpande A. B. , Kapur S. L.
Published: April 2003

The polymerization of styrene with VOCl3 in combination with AlEt3 and with Al(i‐Bu)3 in n‐hexane at 40°C. has been investigated. The rate of polymerization was found to be second order with respect to monomer in both systems. With respect to catalyst the rate of polymerization was first order for VOCl3–AlEt3 and second order for VOCl3‐Al(i‐Bu)3 systems. The activation energies for VOCl3–AlEt3 and VOCl3–Al(i‐Bu)3 systems were 7.37 and 11.25 kcal./mole, respectively. The molecular weight of polystyrene in the AlEt3 system was considerably higher than that in the Al(i‐Bu)3 system. The valence of vanadium obtained by a potentiometric method showed that the catalyst sites in the AlEt3 system are different in nature from those in the Al(i‐Bu)3 system. The effect of diethylzinc as a chain‐transfer agent in the AlEt3 system was also studied.
Free‐radical polymerization of vinyl ferrocene
Authors: Baldwin Mart G. , Johnson Kenneth E.
Published: April 2003

The results of quantitative studies of the rates of free‐radical polymerization of vinyl ferrocene indicate that the latter has polymerization characteristics similar to those of styrene. The rates of homopolymerization of these two monomers in benzene at 70°C. were measured with the use of azobisisobutyronitrile as catalyst. The rate constants (k = Rp/[M][I]1/2) are kVF = (1.1 − 1.8) × 10−4, kSTY = 1.65 × 10−4. Small amounts of vinyl ferrocene and styrene have similar effects on the rates of polymerizations of methyl methacrylate and ethyl acrylate and on the molecular weights of the resulting polymer. Polystyrene and poly(vinyl ferrocene) with similar molecular weights are isolated from polymerizations carried out under identical conditions. The rates of copolymerization of vinyl ferrocene—methyl methacrylate, vinyl ferrocene—styrene, and styrene—methyl methacrylate were determined by following the disappearance of monomers by means of gas chromatographic analyses. The relative reactivity for vinyl ferrocene is slightly lower than that for styrene.