bluuebunny/crossref_metadata_2025 huggingface dataset:
Diisocyanate‐linked polymers. II. Mechanical and swelling properties of some polyurethane elastomers
Authors: Smith Thor L. , Magnusson Alan B.
Published: April 2003

A study was made of the mechanical and equilibrium swelling properties of five series of polyurethane elastomers prepared from polyoxypropylene glycol 2025, dipropylene glycol, trimethylol propane, and either toluene diisocyanate (TDI) or hexamethylene diisocyanate (HDI). The study included the dependence of the properties on the ratio of isocyanate to hydroxyl groups, the concentration of urethane groups, [U], and the triol concentration; the triol concentration and [U] were varied independently in four series of elastomers. It was found that the glass transition temperature for both the TDI elastomers and HDI elastomers increased linearly with [U]. For elastomers having a constant [U], the quasi‐equilibrium elongation at a given value of T − Tg increased linearly with the reciprocal of the number of effective chains per unit volume, but the tensile strength depended only slightly on this quantity. For elastomers having the same triol concentration, the ultimate properties over a wide temperature range were compared at equal values of T − Tg and were found to depend on [U], especially for elastomers having the largest [U]‐values. Several factors that might contribute to this behavior are considered. No major differences between TDI and HDI elastomers were observed except in Tg values. The equilibrium swelling ratios in benzene were used along with equilibrium modulus data to calculate the polymer–solvent interaction parameter χ1. This parameter was found to be independent of crosslinking density, but it increased with [U] and was slightly less for the HDI elastomers than for the TDI elastomers.
The initiation of polymerization of methyl methacrylate by the poly(methyl methacrylate) anion
Authors: Graham Roger K. , Dunkelberger David L. , Cohn Elizabeth S.
Published: April 2003

Addition of methyl methacrylate monomer to poly(methyl methacrylate) which has been polymerized with fluorenyllithium or sodium‐naphthalene in tetrahydrofuran at −78°C. produces high conversion of monomer to polymer. By a comparison of the number‐average molecular weights before and after the addition of the second monomer, it is demonstrated that no new polymer chains are formed on polymerization of the second monomer, so that the polymerization is initiated by the poly(methyl methacrylate) anion. Styrene is shown to be an inert diluent in these systems. The technique is also applied to additions of styrene and of methyl methacrylate monomer to polystyrene initiated with sodium‐naphthalene; the new polymer is demonstrated to be initiated by the polystyrene anions.
Interaction constants for the system isoprene–cis‐1,4‐polyisoprene (synthetic)
Authors: Cunningham Robert E.
Published: April 2003

Values of the interaction parameter χ1 for the system isoprene–(synthetic) cis‐1,4‐polyisoprene have been determined over a range of compositions and temperatures, from results of vapor pressure measurements and the Flory‐Huggins equation. At constant temperature χ1 decreases as V2 increases. At V2 ≈ 0.95, χ1 decreases also with increasing temperature. Densities of the monomer and polymer were also determined.
Organic peroxides. I. Initiation of styrene polymerization
Authors: Lowell A. I. , Price J. R.
Published: April 2003

The relationship between peroxide activity for several aliphatic and aromatic peroxides, as given by the respective decomposition rate constants (kd), and their influence on the polymerization of styrene at 70°C. is reported. Particular emphasis was placed on studying the role of these peroxides in determining rates and degrees of polymerization (DP) and the “efficiency” of these peroxides in the initiation of polymerization. A correlation of peroxide activity could best be made with rates of polymerization. Most of the peroxides studied did not exhibit chain transfer activity, and the DP was a function of the propagation and termination characteristics of the monomer‐polymer radical system. Two chlorinated benzoyl peroxides had considerable chain transfer activity, but this could not be correlated with their decomposition rate constants. Although there was no relationship of peroxide activity to efficiency of initiation, some of these efficiency values appeared to be unreasonably low. The major uncertainty appeared to be the use of published peroxide kd values which were not determined under conditions suitable for use with polymerization data to calculate efficiencies. Where necessary, kd values were redetermined and the final results gave a more suitable basis for comparison of peroxide activities and their influence on polymerization. The use of infrared analysis for determination of peroxide decomposition rate constants is described.
Determination of degree of crosslinking in natural rubber vulcanizates. Part VI. Evidence for chain scission during the crosslinking of natural rubber with organic peroxides
Authors: Moore C. G. , Scanlan J.
Published: April 2003

The possible scission of natural rubber chains during their crosslinking by organic peroxides at 140°C. has been examined: (1) by comparing the kinetics of crosslinking and of peroxide decomposition and (2) by measuring the relaxation in stress of an extended sheet of a peroxide vulcanizate subjected to further crosslinking by di‐cumyl peroxide in nitrogen. The former method is too insensitive to establish the occurrence of chain scission, but the latter method indicates that degradation of the primary network occurs during the formation of the secondary network, an effect which is ascribed to the unimolecular scission of polysoprenyl radicals competing with their bimolecular combination to from crosslinks. Under the reaction conditions prevaling in (2) it is calculated that degradation of the primary network occurs equivalent to about 10% of the new elastically effective crosslinks formed. These findings suggest that minor revision of the existing calibrations1,4 relating the physical and chemical degrees of crosslinking of a natural rubber vulcanizate is necessary, since the basis of the original chemical estimate1 was that the sole fate of polyisoprenyl radicals, derived from the reaction of natural rubber with alkyloxy‐, aralkyloxy‐ and methyl radicals, is bimolecular combination. However, the available data, coupled with the present status of stress relaxation theory, are inadequeate to permit precise corrections of the existing calibrations to be made at this stage.
Radiation crosslinking of rubber. III. Chain fracturen
Authors: Mullins L. , Turner D. T.
Published: April 2003

Purified natural rubber has been exposed in vacuo to the 4‐M.e.v. electron beam from a linear accelerator and attempts have been made to estimate the ratio of fractures of the main chain of carbon atoms to crosslinks, using three different methods. Measurements of the sol fraction (S) as a function of the radiation dose (R) did not conform to a linear relationship between S + S1/2 and R−1 reported by Charlesby and Pinner for a number of other polymers. It appeared that in the present experiments there was little consummated random fracture, and it was found that the sol fraction tended towards zero at radiation doses above about 50 Mrad. The stress in rubbers maintained at constant elongation decreased continuously on irradiation, and it was found that rigorous exclusion of traces of air and impurities was of critical importance. Deficiencies of previous analyses of stress‐relaxation data are discussed and an attempt made to provide an internally consistent treatment of the data. In one treatment which made no allowance for the possible contribution of chain entanglements a value for β of 0.18 was obtained. In another treatment an attempt was made to allow for entanglements and a much lower value for β of 0.03 was obtained. This very low value may be due to the inadequacy of the assumption made that fracture inevitably releases entanglements under conditions where a much higher rate of concurrent crosslinking may serve to lock them into the network. Further work is required to establish a reliable basis for the interpretation of stress‐relaxation data. In a third method stress‐strain measurments of irradiated rubber provided estimates of the number‐average molecular weights of both (1) the chain segments between adjacent crosslinks and (2) the primary molecular chains. Comparison with similar data for vulcanizates prepared by thermal decomposition of di‐tert‐butyl peroxide gave a value for β of 0.11. This value was calculated on the assumption that no fracture occurs on formation of the peroxide vulcanizates and is, therefore, likely to be an underestimate. The nominal G(X) value of 0.9 is increased to 1.05 when an allowance is made for fracture.
Linear phenol–formaldehyde polymers. Synthesis of partially substituted polymers
Authors: Burke W. J. , Short Glen A. , Higginbottom Harold P.
Published: April 2003

Reaction of 2,6‐bis‐(chloromethyl)‐4‐chlorophenol withp‐cresol provided a convenient synthesis of 2,6‐bis‐(2‐hydroxy‐5‐methylbenzyl)‐4‐chlorophenol. Condensation of formaldehyde with this trimer alone and in the presence of controlled amounts ofp‐cresol made possible the synthesis of linearp‐cresol–p‐chlorophenol–formaldehyde polymers having 1,2, and 4p‐chloro substituents per 12 phenolic residues. Treatment with sodium in liquid ammonia gave the corresponding dehalogenated polymers. Crosslinking of the latter with hexamethylenetetramine was studied. Both series of polymers were characterized by infrared spectra.
Vulcanization of butadiene/styrene rubber in a thermal neutron field
Authors: Anderson Herbert R.
Published: April 2003

Vulcanization of butadiene/styrene rubber in a thermal neutron field is described. Tread type vulcanization produced from highly ionizing particles resulting from the nuclear reactions B10(n, α)Li7* and Li6(n,α)H3 (where Li7* denotes Li7 left in excited state to yield ultimately a 0.4 m.e.v. gamma ray) have negligible residual radioactivity and possess physical properties comparable with those produced by other means, e.g., gamma rays and peroxides. Swelling and stress‐strain properties indicate that the response of the tread type compound to analogous nuclear reactions have pronounced differences. The vulcanizates also differ markedly. Values of G, the crosslinking efficiency of energy utilization, of the tread‐type compound in a helium atmosphere was found to have an average value of 3 for promotion by lithium methoxide and 0.9 in the case of boron nitride. Such values decrease 30% with lithium methoxide promotion and increase by a factor of 2 for boron nitride promotion when air is substituted for helium as an irradiation atmosphere.
Infrared spectra of crystalline polysaccharides. IV. The use of inclined incidence in the study of oriented films
Authors: Liang C. Y. , Marchessault R. H.
Published: April 2003

The infrared spectra (tilting spectra) obtained with the incident beam inclined to oriented films are discussed. Various experimental settings for obtaining the tilting spectra are studied. It is pointed out that quantitative interpretations (to determine the direction of the transition moment of a normal mode) of the tilting spectra are not possible at present. Qualitative interpretations, however, are usually possible. The tilting spectrum of a uniaxially oriented film of chitin crysallites at various settings is presented for the purpose of demonstrating different tilting effects. The tilting spectra of 101 and 101 uniplanarly oriented films of cellulose I materials and of doubly oriented films of cellulose I and cellulose II crystallites are presented. A number of interesting tilting effects in these spectra are discussed in terms of crystal structure.
Polymerization of α‐piperidone by alkali metal and certain acyl compounds
Authors: Yoda Naoya , Miyake Akihisa
Published: April 2003

It has been shown that the resonance‐stabilized, six‐membered lactam, α‐piperidone, is polymerized by alkali metal and acyl compounds to form poly‐5‐valeramide, melting point 259°C., [r] = 0.25, d = 1.243. A mechanism is proposed for the polymerization of α‐piperidone with alkali metal and acyl compound which involves chain propagation by the stepwise addition of piperidone ring at the end of the molecules leading to the formation of poly‐5‐valeramide. This mechanism is supported by experimental results obtained in the presence of alkali metal salts of α‐piperidone, data on deuterium exchange reactions, and infrared analytical evidence. The conditions for polymerization have carefully been investigated. A maximum conversion of 76% was obtained. As the concentration of alkali metal and acyl compound increases, the conversion increases. On the other hand, the conversion decreases when the concentration of alkali exceeds 3.0 mole‐% and the concentration of N‐acetyl piperidone is over 1.0 mole‐%. As the reaction temperature increases, both conversion and the degree of polymerization diminish. Furthermore, the polymerization with other useful catalysts has been reported.
Hydrogen bond chains and dielectric relaxation of polyvinyl alcohol
Authors: Kurosaki Shigehiko , Furumaya Toshihiko
Published: April 2003

The dielectric constant ϵ′ and the loss factor ϵ″ of untreated and heat‐treated polyvinyl alcohol and of a deuterated polyvinyl alcohol were observed over the frequency range of 30–106 cycles/sec. at several temperatures. For comparison, ϵ′ and ϵ″ of two normal long‐chain alcohols were also measured. Polyvinyl alcohol has its ϵ″ peak at a frequency of 104−105 cycles/sec., and activation energies E* for dielectric dispersion are quite small (6–18 kcal./mole), despite the large relaxation time. This finding cannot be explained by the theory of restricted rotation of dipoles, but can be explained by the use of the concept introduced by Sack of the chain mechanism of dielectric relaxation in hydrogen‐bond chains. It is concluded that hydrogen‐bond chains in the amorphous regions of polyvinyl alcohol have a mean length of about 1350 A. and are shortened only very slightly by deuteration.
Theory of viscoelasticity of amorphous polymers. III. Dispersion of dynamic bulk modulus
Authors: Nakada Osamu
Published: April 2003

The origin of the relaxation phenomena associated with volume deformation in amorphous polymers is attributed to the configurational relaxation of the three‐dimensional extension of the chain molecule. A diffusion equation of chain configuration is formulated with the use of the model of a chain molecule which is composed of beads connected by Hookian springs. A dynamic relation between varying pressure and volume is derived by integration of the diffusion equation for sinusoidal pressure change, and thus the real and imaginary parts of the bulk modulus are calculated. The dispersion of bulk modulus is specified by two characteristic time constants, τβ and τΓ, the former relating to the rubberlike elasticity of a chain, and the latter to the elasticity of the energetic nature which comes from the distorsion of chemical bonds and also from the change of cohesive energy. A preliminary comparison of the theory with experiment is made.
Isotope effects in polymerizations of carbon‐14‐labeled styrenes
Authors: Hodnett Ernest M. , Jensen Arnold W.
Published: April 2003

Styrene‐β‐C14 has been polymerized (1) thermally at 99°, (2) with benzoyl peroxide at 51°, and (3) with stannic chloride at 25°. The C14‐labeled monomer was found to react (1) 91.8%, (2) 91.5%, and (3) 95.0% as fast as the nonradioactive styrene under these conditions. When styrene‐α‐C14 was polymerized (1) thermally at 99° and (2) with stannic chloride at 25°, the radioactive monomer reacted 97.0% and 100% as fast as nonradioactive styrene. These results are interpreted in terms of the propagation step of the reaction.
The kinetics of the polymerization of methyl methacrylate. I. The bulk reaction
Authors: Hayden P. , Melville Harry
Published: April 2003

A thermocouple method of following the nonstationary state of chemical reactions has been used to study the changes which occur in the velocity coefficients and energies of activation for the propagation and termination reactions over the whole range of the conversion of methyl methacrylate to polymer. After about 10% conversion the rate and lifetime of the kinetic chain increase as conversion proceeds. These changes are accompanied by a decrease in the overall energy of activation and an increase in the temperature coefficient of the reciprocal of the lifetime. During this stage of the reaction, the intensity exponent falls from an initial value of 0.5 to 0.25. These results are believed to be due to an increase in the activation energy for the diffusion of polymeric radicals in the increasingly viscous medium. Beyond 40% conversion the activation energy for the propagation increases while the corresponding velocity coefficient decreases, possibly due to the monomer addition step becoming diffusion controlled. Simultaneously the intensity exponent increases toward unity.
On the thermodynamical interpretation of osmotic and of Donnan equilibria in salt‐containing polyelectrolyte solutions. Part I
Authors: Alexandrowicz Z.
Published: April 2003

A formal treatment is proposed for the interpretation of Donnan and osmotic equilibria in a three component solution which consists of a polyelectrolyte, a simple salt, and a solvent. To this end a scheme is outlined for the measurement of the activity coefficients of the permeating components; namely the salt and the solvent. According to this scheme, these coefficients are measured in a way which facilitates their graphical differentiation in respect to the concentration of the polyelectrolyte and of the salt. As a second stage, the use of a thermodynamical cross relation and of the Gibbs‐Duhem equation leads to the evaluation of the partial derivatives, in respect to the above mentioned variables, of the activity coefficient of the polyelectrolyte itself. The numerical integration of the latter is also discussed. The above calculation of the various activity functions provides a complete thermodynamical description of the three component system. Such a description suffices to correlate in a formal way, without the introduction of any theoretical models, the results of various methods of measurement (e.g., osmotic pressure, light scattering, the transport phenomena). Since it is considered that the socalled “osmotic concentration method” (a previously described differential osmotic technique) is best adapted for the execution of the requisite measurements, the calibration of this method is given for solutions which contain a freely permeating salt.
Apparent activation energy of hydrolysis of some cellulosic materials
Authors: Nelson Mary L.
Published: April 2003

Apparent activation energies for heterogeneous acid hydrolysis of four samples of cellulose which differed in crystallinity were calculated separately for the amorphous and crystalline regions, from data obtained under drastic hydrolytic conditions. Some approximate activation energies were also calculated for hydrolysis of the amorphous fraction of cotton and a viscose rayon, using data obtained with a range of dilute acid concentrations. These values are discussed in relation to hydrolytic conditions. The relations between the hydrolysis rate, the acidity function (H0), and the hydrogen‐ion concentration, as well as the values of activation entropy were examined for evidence with respect to reaction mechanism. Data from the literature were used to show that the activation energy probably is temperature dependent.
Calculation of nonbonding forces as applied to stereospecific polymerization
Authors: Ferstandig L. L. , Goodrich F. C.
Published: April 2003

The nonbonding interactions were calculated for four models resembling types of propylene polymerization. The calculations predict syndiotactic polymerization for a radical or carbonium ion model and suggest isotactic polymerization for anionic‐type reaction.
A kinetic study of the oxygen‐initiated polymerization of ethylene
Authors: Ehrlich Paul , Pittilo Robert N.
Published: April 2003

The kinetics of the oxygen‐initiated polymerization of ethylene show some features previously unrecorded in vinyl polymerizations. Preceding formation of polyethylene, there is an induction period which depends strongly on temperature and pressure but only slightly on oxygen concentration. During the induction period the rate of oxygen consumption increases exponentially with time and approximately one‐half of the oxygen is consumed prior to polymerization which can take place only if certain critical conditions depending primarily on pressure and oxygen concentration are exceeded (critical boundary). A formal reaction mechanism with degenerate kinetic chain branching is postulated from which the most important experimentally observed relations can be deduced. The induction period for polymerization then becomes the reciprocal branching factor for the oxidation of ethylene and the critical boundary a kinetic limit familiar in hydrocarbon oxidations with degenerate branching. The shape of the critical boundary can be derived by postulating, in addition, a sequence of reaction steps similar to those frequently used to represent the low temperature oxidation of hydrocarbons. Under the conditions investigated, the initiation mechanism dominates the polymerization, and an interpretation of the propagation and termination steps cannot be made.
Crystal structure of d,l‐poly(propylene oxide)
Authors: Stanley E. , Litt M.
Published: April 2003

Powder and oriented fiber photographs of crystalline poly(propylene oxide) were taken and indexed. An orthorhombic unit cell with space group P212121 of dimensions a = 10.40 A., b = 4.64 A., and c = 6.92 A. was found. The polymer has a sinuous, zig‐zag backbone, with the methyl group falling between the oxygen and methylene groups of the neighboring chain. The oxygen and methylene groups are almost interchangeable, and it is possible that both optically active and d,l unit cells are present at the same time.
Copolymerizability of vinylpyridines
Authors: Tamikado Takashi
Published: April 2003

The copolymerizations of 2‐vinylpyridine (2‐VP), 4‐vinylpyridine (4‐VP), and 5‐ethyl‐2‐vinylpridine (5‐Et‐2‐VP) with styrene (St), methyl methacrylate (MMA), and methyl acrylate (MA) have been investigated. The copolymer compositions have been determined by visual titration with crystal violet indicator of the copolymers in the 20:80 glacial acetic acid‐acetonitrile mixture with N/10‐perchloric acid in glacial acetic acid. It has been proved that this titration method is consistently successful. The monomer reactivity ratios, r1 and r2, were calculated for the systems St‐2‐VP (0.56 ± 0.02 and 0.9 ± 0.2, respectively), MMA–2‐VP (0.439 ± 0.002 and 0.77 ± 0.02, respectively), MA–2‐VP (0.168 ± 0.003 and 1.58 ± 0.05, respectively), St–4‐VP (0.54 ± 0.03 and 0.7 ± 0.1, respectively), MMA–4‐VP (0.574 ± 0.004 and 0.79 ± 0.05, respectively), MA‐4–VP (0.22 ± 0.01 and 1.7 ± 0.2, respectively), St–5‐Et‐2‐VP (0.79 ± 0.03 and 1.2 ± 0.2, respectively), MMA–5‐Et‐2‐VP (0.395 ± 0.003 and 0.69 ± 0.03, respectively), and MA–5‐Et‐2‐VP (0.179 ± 0.006 and 1.16 ± 0.08, respectively). The alternating tendencies of the pyridines with the comonomers measured by the reactivity ratio products have been discussed in connection with styrene and, further, the Q‐e values have been calculated. On the basis of these data, it has been concluded that the pyridyl groups of these monomers act as electron donors to the double bond, as does the phenyl group in the styrene molecule; these groups show comparable resonance stabilization to styrene, and thus the copolymerizabilities of these vinylpyridines are analogous to that of styrene.
The effect of network flaws on the elastic properties of vulcanizates
Authors: Scanlan J.
Published: April 2003

A treatment is given of the effect of network flaws due to the finite chain length of the primary elastomer molecules on the elastic properties of rubber vulcanizates. In this treatment full allowance is made for the elastically inactive material which exists either as sol or as loose ends of the network. The cases of linear primary molecules with either a random distribution of lengths or with uniform lengths are considered, and the results are compared with those of earlier theoretical treatments.
Melt viscosity of polymers: Effect of polydispersity
Authors: Bueche F.
Published: April 2003

The author's theory for the melt viscosity of high polymers is extended to include the effect of molecular weight polydispersity. It is found that if one describes the viscosity by the relation η = (const.)Mt3.5, the molecular weight average appropriate for Mt lies between the weight and z average. For molecular weight distributions with Mw/Mn less than about two, Mt is best represented by Mw. Above that value, Mz is a better approximation. These latter statements are not precise because of the fact that Mt appears sensitive to the exact form of the distribution. Reasonable agreement with available experimental data is found.
Molecular weight of ethyl cellulose
Authors: Scherer P. C. , Tanenbaum A. , Levi D. W.
Published: April 2003

Light‐scattering and viscosity measurements were made on six ethyl cellulose fractions in methanol at 25°C. The relation [η] = 5.23 × 10−4M̄w0.65 was found to hold over the molecular weight range of 0.98 × 105 to 4.10 × 105. Second virial coefficients for this system were found to be essentially zero at 25°C. The dependence of dielectric dispersion of ethyl cellulose solutions on molecular weight was confirmed.
Poly(2‐ethylbutyl methacrylate). VI. Dilute solution properties by viscosity and light scattering
Authors: Didot F. E. , Chinai S. N. , Levi D. W.
Published: April 2003

Poly(2‐ethylbutyl methacrylate) was prepared by emulsion polymerization and fractionated. Light‐scattering and viscosity techniques were used to study eight fractions in a good solvent, methyl ethyl ketone, and in an ideal solvent, isopropanol. Relations between viscosity and molecular weight are shown. The effect of the size of pendant groups on the degree of chain extension of a series of alkyl methacrylate polymers in ideal solvents is discussed. It was found that the degree of chain extension of the polymers thus far studied follows the order: poly(n‐lauryl methacrylate) > poly(n‐hexyl methacrylate) > poly(2‐ethylbutyl methacrylate) ≥ poly(n‐octyl methacrylate) > poly(n‐butyl methacrylate) > poly(ethyl methacrylate) ≥ poly(methyl methacrylate).
Proton magnetic resonance in irradiated and unirradiated polyvinyl alcohol
Authors: Fujiwara Shizuo
Published: April 2003

Crystalline and amorphous components in PVA were investigated by the analysis of the line shapes of the NMR spectra of several samples being different in the degree of polymerization and in the forms. Measurements of the temperature dependence of the line shape, the line width, and the second moments were also performed for the irradiated and unirradiated samples. In the samples bombarded in the air by the deuteron beam, marked irradiation effects were observed by the measurements of the humidity dependence of the NMR intensity of the motional component, of the temperature dependences of the line shape and the second moment, and of the behavior of the line shapes at the higher temperature range, suggesting the occurrences of the destruction of the amorphous part, the degradation of the less‐motional part, and the crosslinking of the amorphous part with the less‐motional one. Investigations were also made with the samples irradiated by gamma rays in vacuum. The NMR features of the gamma‐irradiated samples showed the optimum point of about 106 rad, which would refer to thedestruction of the amorphous component and the initiation of crosslinking.
Dynamic mechanical measurement of M̄n
Authors: Cox W. P. , Isaksen R. A. , Merz E. H.
Published: April 2003

A procedure is described for the measurement of number‐average molecular weight M̄n on a specimen in bulk form, utilizing a dynamic torsion pendulum. For both atactic and isotactic polystyrenes it has been found that the minimum value of the damping logarithmic decrement, δm, (above the glass temperature) is related to an measured osmometrically in dilute solution by M̄n = δ × 105. The M̄v/M̄n ratio can also be estimated directly from the δ vs. temperature curve. A four‐element spring‐and‐dashpot model yields similar 6 vs. T curves when the Williams‐Landel‐Ferry temperataure dependence is assigned to the viscosity of the dashpots.
Oxidation and grafting of benzyl and ethyl cellulose
Authors: Gleason E. , Stannett V.
Published: April 2003

The preparation of graft copolymers of benzyl and ethyl cellulose was attempted through the initiation of vinyl polymerization by the cellulose ether hydroperoxides. The benzyl and ethyl cellulose ether hydroperoxides were prepared in solution by oxidizing with air. The polymer underwent severe chain degradation concurrently with hydroperoxide formation. The relative rates of these reactions differed for the benzyl and ethyl cellulose ether and also depended on the nature of the solvent. As a result, the hydroperoxide content of the polymer could be increased by lengthening the oxidation time, but the number of hydroperoxide groups per chain increased much more slowly. With the use of ethyl cellulose hydroperoxide as initiator, a kinetic study of styrene polymerization was made. Rates of hydroperoxide decomposition were also measured so that the efficiency as initiator could be determined. These rate data indicated an efficiency of 60–90% and considerable chain transfer to the hydroperoxide groups. In the preparation of graft copolymer the amount of actual graft was determined to be very small. Poor yields of graft copolymer were attributed to an unfavorable competition in the reactions of initiation and chain transfer and to the degraded chain length of the cellulose ether hydroperoxide. Substantiating evidence for the occurrence of nongrafting initiation and transfer reactions came from an infrared study of low molecular weight polystyrene initiated with α‐isobutoxyethylhydroperoxide.
On the mechanism of emulsion polymerization of styrene. II. Polymerizations in soap solutions below and above the critical micelle concentration and some remarks on the kinetics of emulsion polymerization
Authors: Van der Hoff B. M. E.
Published: April 2003

Emulsion polymerizations of styrene were carried out at different phase ratios. The initial soap concentration was varied from below to above the critical micelle concentration (CMC). Above the CMC the number of particles formed agrees with values calculated from the Smith‐Ewart theory. As the soap concentration is reduced below the CMC the number of particles decreases sharply. In this concentration range the number of particles is independent of the amount of initiator but depends strongly on soap concentration. Kinetic features suggest a similarity between particle formation in these polymerizations and in homogeneous precipitation of inorganic insoluble salts. The coefficient of variation of particle diameter distribution below the CMC is about 2.5% and at high soap concentration about 15%. Bimodal distributions are obtained when the initial soap concentration is near the CMC. The initiation efficiency of persulfate is calculated from the rate and degree of polymerization and also from the number of particles formed. The efficiency increases from 0.2 to 0.6 with decreasing persulfate concentration. When the particles are smaller than about 0.12 μ, polymerization kinetics follow the Smith‐Ewart theory. Values are reported for the monomer concentration in the particles and for the constant of propagation. Larger particles exhibit a gel effect, i.e., more than one radical can coexist in a particle for a significant lenght of time. From polymerization rate data and molecular weight measurements the rate constants for the transfer reaction to monomer and for termination are calculated. The latter constant is found to be two to three orders of magnitude smaller than values obtained in solution polymerization. The difference is attributed to the high viscosity of the interior of the particles which causes the termination reaction to be diffusion‐controlled.
Pyrolysis of polyolefins
Authors: Wall Leo A. , Straus Sidney
Published: April 2003

The differences in thermal decomposition behavior previously observed between linear and branched polyethylenes have been explored experimentally by investigating and comparing the rates of volatilization of a series of twenty polymers. Similar differences were observed between linear and branched polypropylenes. The linear material in both cases exhibited behavior characteristic of a random decomposition, while the branched material did not. Other materials studied included high pressure polyethylene; low pressure copolymers of ethylene with propene, butene, and pentene‐1; and polymers and copolymers prepared from diazoalkanes. Systematic deviations from random theory were found to occur with branching. The greater the branching, provided that the branches were longer than one carbon atom, the greater was the rate of decomposition and the more it was at variance with random theory. No quantitative theory accounting for these results is yet available. However, it seems that polymer branching enhances intramolecular transfer at the expense of intermolecular transfer. This is evidenced by the observed rate‐conversion curves, which are of a type similar to that found for polymers that decompose mainly into monomer.
The effect of molecular weight distribution on the rheological properties of polystyrene
Authors: Rudd John F.
Published: April 2003

Melt viscosities were measured on 25 narrow molecular weight distribution (anionically polymerized) and 7 broad distribution (isothermally polymerized) polystyrenes ranging in molecular weight from 50,000 to 570,000. Measurements were made at temperatures between 200 and 250°C. and at shearing stresses of 120,000–1,400,000 dynes/cm.2 using a capillary‐type viscometer. Zero shear viscosity and non‐Newtonian constant was found to depend upon weight‐average molecular weight while high shear viscosity was found to depend upon some molecular weight between weight average and number average. Analysis of flow curves for two materials having the same zero shear viscosity but different weight average‐number average ratios indicated that the narrow distribution material had a higher high shear viscosity than the broad material pointing to lessened ease of fabrication. From flow data at different temperatures, apparent activation energies were calculated. Apparent activation energy was found to be independent of molecular weight above a molecular weight of 50,000 and to decrease slightly with increasing M̄w/M̄n ratio. The effects of plasticization and blending upon flow properties were also studied using samples to which 1% mineral oil had been added and blends of high and low molecular weight narrow distribution polymers.
Crystalline polyvinylcyclopropane, polyvinylcyclopentane, and polyvinylcyclohexane
Authors: Overberger C. G. , Borchert A. E. , Katchman A.
Published: April 2003

Vinylcyclopropane was polymerized with a catalyst of triisobutyla luminum and titanium trichloride and yielded crystalline polyvinylcyclopropane. The reaction of crystalline polyvinylcyclopropane with hydrogen bromide yielded an amorphous, bromine‐containing polymer. A bromine‐modified polyvinylcyclopropane, which was also amorphous and several other modified polymers were prepared. The pyrolysis of both 1‐ and 2‐cyclopentylethyl acetates yielded vinylcyclopentane, which was polymerized with catalysts of triisobutyl‐aluminum and titanium tri‐ and tetrachloride. Vinylcyclohexane was polymerized, and the properties of crystalline polyvinylcyclohexane were compared with those of the crystalline five and three‐membered pendant ring polymers.
Osmotic pressures of aqueous polyvinylpyrrolidone solutions
Authors: Cerny L. C. , Helminiak T. E. , Meier J. F.
Published: April 2003

The osmotic pressures of six well‐fractionated samples of polyvinylpyrrolidone were measured in aqueous solution in a Lucite‐block type osmometer. The molecular weights and interaction parameters were determined by employing the theory proposed by Maron for osmotic pressure. It was shown that for all of the fractions, a linear relation existed for ψ and y as predicted by the theory. This new method for expressing osmotic pressure data is compared with the more commonly used expression:

It was found that the molecular weights and T2 are in satisfactory agreement. However, the value ofg was not a constant equal to 0.25, but varied with the molecular weight. The expression for the osmotic pressure given by Maron's theory appears to be an accurate and rapid method of converting osmometric data to molecular weights.
The mechanism of polyvinyl chloride stabilization by barium, cadmium, and zinc carboxylates. II. Radioactive tracer studies
Authors: Frye Alfred H. , Horst Raymond W.
Published: April 2003

Polyvinyl chloride deteriorates primarily by a zipperlike elimination of hydrogen chloride from the polymer and the concomitant formation of a colored and easily ozidizable polyene chain. Baum and Wartman have shown that the elimination is initiated by the rupture of certain especially labile carbon‐chlorine bonds. In Part I of this series, we presented infrared evidence to show that the barium, cadmium, and zinc salts of 2‐ethylhexanoic acid, when milled into polyvinyl chloride, react with the resin by an esterifying displacement of chlorine, and proposed that their stabilizing action arises, at least in part, from substitution of certain labile chlorine atoms with more stable carboxylate groups. In the present work we have prepared the barium, cadmium, and zinc salts of radioactive 2‐ethylhexanoic acid and have shown that when these salts are milled into polyvinyl chloride, and the films heat‐treated and then subjected to repeated dissolution in tetrahydrofuran and precipitation with methanol, the precipitated resin shows an effectively constant retention of radioactivity. Hence, the proposed esterifying displacement is unequivocally proved. We have also shown that the amount of radioactivity which is retained by the precipitated resin varies with the particular salt, the temperature, and duration of heat treatment, and that it qualitatively parallels the intensity of the 5.75‐μ band observed in Part I. Finally, we have shown that one function of the organic phosphites (frequently components in commercial stabilizers) is to render innocuous the chlorides of barium and cadmium, which otherwise exert a very deleterious action upon the resin, but which are inevitably generated by the interaction of eliminated hydrogen chloride upon the metal carboxylates.
Copolymers of vinyl chloride and some vinyl esters of acids derived from pinene
Authors: Marvel C. S. , Shimura Yukio , Magne F. C.
Published: April 2003

Homopolymers of terpene‐derived vinyl monomers and copolymers of these with vinyl chloride incorporating varying amounts of the terpene‐derived monomers have been described. Copolymers incorporating 24–26% of terpene‐derived monomer were screened as rigid plastics. None of these comonomers resulted in an internally plasticized film when incorporated in the copolymer. A homopolymer‐copolymer blend exhibited limited compatibility. The use of an external plasticizer with these copolymer compositions appears to have merit.
Blue solutions of potassium in ethers as initiators of anionic polymerization
Authors: Dainton F. S. , Wiles D. M. , Wright A. N.
Published: April 2003

It is shown that freshly prepared, filtered, blue solutions of potassium in 1,2‐dimethoxyethane (DME) or in tetrahydrofuran (THF) initiate the rapid polymerization of styrene. For the K—DME system 100% yields of living polymer are obtained, whereas for the K—THF system, fractional yields of nonliving polymer are formed. By the application of rapid mixing and quenching techniques, minimum values of the rate constant of anionic propagation are obtained for the K—DME system at —78, 0, and 25°C. and for the K—naphthalene—THF system at 0°C. The true initiator in these blue solutions is considered to be a solvated, spin‐coupled, electron pair. The difference between the two systems and the probable kp values are discussed.
Expansion of copolymerization theory (influence of neighboring units on radical reactivity with monomers)
Authors: Ham George E.
Published: April 2003

Equations are presented which allow for the first time a thorough definition of the detectable influence of all neighboring units on radical reactivity in copolymerization. These effects are expressed in terms of reactivity ratios involving the competition of two monomers for characteristic terminal chain sequences.
Application of an expanded copolymerization equation to the system styrene–fumaronitrile
Authors: Ham George E.
Published: April 2003

Application of the equations developed in the previous paper shows that the copolymer system styrene‐fumaronitrile obeys the equation:

where r1 = K—aaa/K—aab = 0.8, r1′ = K—baabaa/K—baabab = 0.3, and r1″ = K—babaa/K—babab = 4.0.
Polymerization with redox initiators. II. The system styrene–benzoyl peroxide–dimethylaniline at elevated temperatures
Authors: O'Driscoll K. F. , Schmidt J. F.
Published: April 2003

Kinetic measurements have been made on the bulk polymerization of styrene at 30 and 60°C. in the redox system dimethylaniline–benzoyl peroxide. From these measurements it has been ascertained that the kinetic behavior of this system at higher temperatures is the same as that at lower temperatures. The decomposition rate constant and the efficiency in initiating polymerization were determined. It has also been shown that neither the amine nor the products of the amine‐peroxide reaction affect the propagation of the polymerization.
Shear degradation of vinyl polymers in dilute solution by high‐speed stirring
Authors: Johnson William R. , Price Charles C.
Published: April 2003

The degradation of polyisobutylene and polystyrene resulting from high‐speed stirring of their dilute solutions has been investigated. Maximum degradation was obtained in “poor” solvents, at low temperatures and at highest possible rates of shear. The lower limit of the intrinsic viscosity reached for polyisobutylene in benzene solution was 1.30 as measured in cyclohexane at 30°. For polystyrene the lowest molecular weight attained is represented by an intrinsic, viscosity of ca. 0.75 in methyl ethyl ketone at 25°. The polymers were sheared in the presence of iodine and the amounts of iodine incorporated into the polymers measured radiochemically. The amounts of iodine incorporated during shear were of the same order of magnitude as the number of chain scissions calculated on the basis of the decrease in intrinsic viscosity.
Synthesis of optically active vinyl polymers by asymmetric induction. II
Authors: Schmitt George J. , Schuerch Conrad
Published: April 2003

Maleic anhydride and l‐α‐methylbenzyl vinyl ether were copolymerized by a free radical mechanism in homogeneous solution to yield a levorotatory copolymer. Upon removal of the original asymmetric center by photobromination and hydrolysis, a dextrorotatory copolymer was produced. This reversal of the sign of rotation can be attributed only to an excess of one configuration in the chain backbone induced during the propagation step of the polymerization.
Branching in polymers. I. Network defects
Authors: Case L. C.
Published: April 2003

The problem of inactive chains in a polymer network is considered in this paper. It is shown that the previous treatment is only approximate. More rigorous treatments are derived here for random crosslinking of polymers which are initially either geometrically distributed in molecular weight or are monodisperse. The new treatments give values for active chain concentrations which are lower than those calculated by the approximate method. At high crosslink densities and for chains of molecular high weight initial, all methods yield approximately identical values.
Reaction kinetics and tacticity of macromolecules. I. Methacrylic acid—ester copolymers
Authors: Smets G. , De Loecker W.
Published: April 2003

Three different samples of polymethyl methacrylate of different tacticities were prepared, the first by the conventional method in the presence of benzoyl peroxide as initiator (conventional polymer), the second by a pseudo‐ionic method with phenylmagnesium bromide in toluene solution (polymer A), the third photochemically at −20°C. in toluene in the presence of benzoin (polymer B). On the basis of their infrared spectra, polymer A corresponds to a syndiotactic structure, while polymer B must be considered as a mixture of conventional and isotactic polymers. These polymethyl methacrylate samples were hydrolyzed in concentrated sulfuric acid up to different degrees of hydrolysis by heating up at 60°C., isolated, and purified. The kinetics of the hydrolysis of the corresponding acid—ester copolymers were studied; the reactions were carried out in buffered aqueous solution at different degrees of neutralization. Polymer A hydrolyzes about four to five times faster than the conventional polymethyl methacrylate, while polymer B hydrolyzes very slowly and must contain configurations which are resistant to acid hydrolysis in these experimental conditions; this configuration is probably the isotactic one.
Polymer NSR spectroscopy. III. The rates of the propagation steps in the isotactic and syndiotactic polymerization of methyl methacrylate
Authors: Bovey F. A.
Published: April 2003

By measurement of peak areas in the α‐methyl region of the NSR spectra of 15% chloroform solutions of methyl methacrylate polymers prepared by free radical initiation over a 178° range of polymerization temperatures, it has been found that syndiotactic propagation becomes increasingly dominant as the polymerization temperature is decreased and that propagation tends toward randomness as the polymerization temperature is increased. We report the first experimental measurement of the difference in activation enthalpies and entropies for syndiotactic and isotactic monomer placement. It is found that there is no difference in the activation entropies of these processes, but that isotactic placement requires an additional activation enthalpy of 775 ± 75 cal./mole.
Studies on polyoxypropylene glycols. Part II. Derived thermodynamic functions for the systems: Polyglycols–methanol
Authors: Conway B. E. , Lakhanpal M. L.
Published: April 2003

The thermodynamic properties of the polyoxypropylene glycol fractions in methanol, experimentally determined as described in Part I, have been examined in terms of various statistical mechanical theories. The Flory‐Huggins interaction parameter χ has been calculated and enthalpic and entropic components of χ deduced from the experimental data. Deviations from the Flory‐Huggins theory are discussed. The thermodynamic excess functions for free energy and entropy of mixing are calculated, and it is concluded that strong orientation effects are operative in the polymer–solvent interaction, presumably through hydrogen bonding with the solvent. The hydroxylic endgroups on the short chain fractions play an important role in determining the thermodynamic behavior of the solutions. The role of orientation effects is examined by calculating the partial molar heat content and the partial molar entropy of the solvent and applying the theory of Münster for polymer solutions in which solvent orientation effects are operative. A semiempirical treatment, less arbitrary than that used by Münster, gives satisfactory results for polymer fractions of M. W. 150 and 1120.