bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of the anionic polymerization of methyl methacrylate. IV. Calculated molecular weight distributions resulting from a reversible termination by a bimolecular exchange reaction
Authors: Krause Sonja , Defonso Lester , Glusker Donald L.
Published: April 2003

The previous papers in this series contain the experimental results which demonstrated the complexity of the homogeneous, nonterminated, anionic polymerization of methyl methacrylate. In order to explain the observed broad molecular weight distributions, it was necessary to postulate reversible “pseudo‐termination” reactions, by which a large fraction of the total anions present in the system became inactive toward further polymerization, yet had a finite probability of recovery of polymerization activity by some process, such as ligand exchange, ring opening of a cyclic complex, etc. In this paper, we have examined the quantitative consequences of a mechanism in which this pseudotermination reaction occurs by a bimolecular exchange of activity between one active and one inactive chain. It has been possible to calculate Mw/Mn, the ratio of weight‐average to number‐average molecular weights, as a function of the fractional conversion α, the initial monomer to initiator ratio, M0/I0, the fraction of total initiator as active chains, C1/I0, and the ratio of rate of exchange of activity to rate of propagation, kt/kp. The major results of these calculations are: (1) any value of Mw/Mn between 1 and infinity is possible at α = 1; (2) Mw/Mn at α = 1 decreases as kt/kp increases; (3) Mw/Mn at α = 1 increases as M0/I0 increases when kt/kp and C1/I0 are small—under some conditions Mw/Mn at α = 1 increases and then decreases slightly as M0/I0 increases; (4) Mw/Mn goes through a maximum during polymerization if kt ≠ 0; (5) Mw/Mn at any α decreases as C1/I0 increases, for constant M0/I0 and kt/kp. Concentrations of individual chains of any given length as a function of time may be readily calculated for the two special cases kt/kp → 0 or ∞.
A study on a three‐component polymer formation
Authors: Ravve A. , Khamis J. T. , Mallavarapu L. X.
Published: April 2003

Solution terpolymerization studies, with addition of a mixture of monomers and initiator at a constant rate to the solvent, are reported. The monomers represented are styrene, 2‐ethylhexyl acrylate, and glycidyl acrylate, with polymerization initiated either by di‐tert‐butyl peroxide or dicumyl peroxide. Data are presented regarding polymer composition with respect to the three monomers, rates of conversion to polymer, and effect of changes in monomer and initiator composition. Also included are results of polymer fractionation studies utilizing molecular weight determination of the fractions by high‐speed membrane osmometry. The steady‐state equation, which is commonly used in the kinetic treatment of solution or bulk polymerizations carried to low conversions, was applied to this continuous feed system even up to high conversions. Furthermore, with the proper choice of initiator, narrower molecular weight distributions were obtained.
Entropy and heat of fusion of polymers
Authors: Kirshenbaum I.
Published: April 2003

Methods are presented for estimating the entropy and heat of fusion of polyolefins, polyamides, polyesters, etc. Although the formulas are approximate, good agreement is obtained with experimental values, where available. For example, the calculated entropies for polypropylene, polyoxymethylene, nylon 66, polyester 210, and poly(ethylene terephthalate) are 5.4, 3.4, 11.2, 8.3, and 5.9 e.u./mole of repeating unit, respectively, as compared to the experimental values of 5.4, 3.5(3.9), 11, 7, and 5.8(5.4), respectively. Application of the formulas to the polyamides support the calorimetric and DTA estimates of the heats of fusion which are significantly greater (by 25–75%) than those determined by the diluent method. Thus, the calculations also indicate that the heats of fusion of the polyamides are higher than those of similar polyesters.
Sugar polythioacetals
Authors: Horvath Elizabeth G. , Gardlund Sharon , Sen Subodh K. , Berry James W. , Deutschman Archie J.
Published: April 2003

Sugar polythioacetals have been prepared by polymerization of sugars with dithiols in dioxane solution with hydrogen fluoride catalyst. Polymerization was also carried out by using liquid hydrogen fluoride as solvent and catalyst. The polymers are colorless powders with inherent viscosities in the range of 0.03–0.24 and melting points of 81–160°C. The polythioacetals of the shorter‐chain dithiols are soluble in polar solvents; those of the longer‐chain dithiols are partially soluble.
Thermochemiluminescence of polycarbonate and polypropylene
Authors: Barker R. E. , Daane J. H. , Rentzepis P. M.
Published: April 2003

Experimental techniques for observing total and spectral thermochemiluminescence (TCL) are discussed in general along with some data for the systems polycarbonate–O2, polycarbonate–CO, and polypropylene–O2. Since TCL is the process whereby heated materials undergo thermally activated reactions and emit light in excess of the amount prescribed by the blackbody radiation law, its study may be expected to yield information about the structure and degradation of the materials. It has been observed that TCL spectra are both time‐ and temperature‐dependent. A simple mathematical model for analyzing TCL data under conditions of a linear heating rate is discussed. The result also should be of use in thermogravimetric analysis.
Ethylene–propylene copolymers. I. Monomer reactivity ratios
Authors: Bushick R. D.
Published: April 2003

The copolymerization of ethylene and propylene with diisobutylaluminum chloride and various vanadium‐containing compounds gave a series of reactivity ratio values for ethylene which decreased in the order: VO(O‐n‐Bu)3 > VOCl(OEt)2 > VOCl2OEt > VO(OEt)3 ≃ VOCl3. All of the catalyst systems were extremely sensitive to changes in the ethylene feed concentration. The reactivity ratio product suggested a random arrangement of monomer units with each catalyst system except VOCl3.
Synthesis of vinylphosphonium compounds
Authors: Rabinowitz Robert , Henry Arthur C. , Marcus Ruth
Published: April 2003

Tributylvinylphosphonium bromide has been prepared by sodium carbonate dehydrobromination of the 2‐bromoethyl salt resultant from the reaction of tributylphosphine and dibromoethane. Tributylvinylphosphonium chloride was prepared from the bromide by ion exchange. Triethylvinylphosphonium bromide, tricyclohexylvinylphosphonium bromide, and dimethylphenylvinylphosphonium bromide were prepared by sodium carbonate treatment of the acetate resulting from acetic anhydride acetylation of the salt formed from the reaction of ethylenebromohydrin and the corresponding phosphine. An attempt to prepare a vinylphosphonium salt directly by heating vinyl bromide and tributylphosphine at 160°C. in an autoclave gave no isolable product; however, infrared evidence indicated the possible presence of the expected vinylphosphonium salt.
Structural study of phenol–formaldehyde polymers with proton magnetic resonance
Authors: Hirst Robert C. , Grant David M. , Hoff Raymond E. , Burke William J.
Published: April 2003

Proton magnetic resonance spectra were obtained for a number of representative phenol–formaldehyde dimers and trimers of known structure and for related compounds having methyl or chloro substituents on the aromatic ring. The data thus obtained, particularly for the methylene protons, were used in the interpretation of the structure of well characterized, linear phenol–formaldehyde polymers and the corresponding halogenated polymers prepared by the condensation of o‐ and p‐chlorophenol with formaldehyde. In all cases there was a shift to lower field as the methylene linkage was varied from para‐para to ortho‐para to ortho‐ortho, although in certain instances the ortho‐para and ortho‐ortho peaks moved very close together. The spectra obtained indicated that the condensation of o‐chlorophenol with formaldehyde proceeds in an essentially random manner, since the ratio of ortho‐ortho to ortho‐para to para‐para methylene linkages was found to be 1:2:1, within the limits of experimental error. The preliminary results obtained in this work clearly demonstrate the potential utility of PMR as a valuable tool in the characterization of the highly complex products obtained from phenol–formaldehyde systems.
Copolymer composition and microstructure
Authors: Ito Koichi , Yamashita Yuya
Published: April 2003

A simple theory and treatment to characterize copolymer composition and microstructure was developed by applying the statistical stationary process given by Coleman and Fox to the three models in binary copolymerization in which the last one, two, and three monomer units in the growing polymer chain affect the probability of monomer addition. A simple method to distinguish the three models from each other is also presented. The theory was applied to a cationically obtained β‐propiolactone–3,3‐bischloromethyloxetane copolymer reported by Tada et al., to indicate how the penultimate units affect the copolymer composition and microstructure. The significance of the monomer reactivity ratios from the standpoint of copolymer microstructure is discussed briefly.
Study of the effects of additives in homogeneous anionic polymerization of α‐methylstyrene by n‐butyllithium (to prepare polymers having narrow molecular weight distribution)
Authors: Fujimoto Teruo , Ozaki Noriyoshi , Nagasawa Mitsuru
Published: April 2003

Polymerization of α‐methylstyrene with n‐butyllithium was carried out in the presence of some additives such as LiBr, LiOH, LiOBu, and LiN(Et)2 in THF. The change in the color of the α‐methylstyryl anion with amount of the additives, the activity of n‐BuLi, the average molecular weights, and the molecular weight distributions of polymers obtained were observed to clarify the interaction of n‐BuLi (or of α‐methylstyryl anion) with these additives. It was concluded that LiBr and LiOH deactivate the initiator in the mole ratio of 1:1 and only the remaining part of n‐BuLi participates in polymerization, while LiOBu and LiN(Et)2 do not. The order of the additives in the capacity to form deactivating centers (possibly by complex formation) follows the order of nucleophilicity and is opposite to the order of activity for initiating the polymerization. The molecular weight distribution of the polymer obtained with pure n‐BuLi in the absence of additives was extremely sharp.
Photodegradation of poly(α‐methylstyrene) in solution
Authors: Fox R. B. , Price T. R.
Published: April 2003

Apparent quantum yields for the random scission of poly(α‐methylstyrene) in solution by 2537 A. radiation were shown to be solvent‐dependent, indicating that processes other than the direct photolysis of the polymer are taking place. Quantum yields on the order of 10−3 scissions per quantum absorbed by the polymer were found in benzene, dioxane, cyclohexane, and methylene chloride and about 0.2 in chloroform and carbon tetrachloride; the quantum yields were unaffected by oxygen. In carbon tetrachloride, the quantum yields decreased slightly with increasing polymer concentration. Ethanol and cyclohexane were inhibitors for the photolysis in carbon tetrachloride, while the latter solvent acted as a sensitizer in cyclohexane. By comparison with model compounds irradiated in carbon tetrachloride, it was shown that an early step in the photolysis of poly(α‐methylstyrene) in this solvent involves reaction with a main‐chain methylene group and eventual substitution with a trichloromethyl group.
Redox kinetics of the peroxydisulfate–iron–sulfoxylate system
Authors: Andersen H. M. , Proctor S. I.
Published: April 2003

Inhibition kinetics were used to study the peroxydisulfate–iron–sulfoxylate redox initiation system. Onset of polymerization was detected by a thermometric technique permitting accurate measurement of short inhibition periods. Rate constants were derived from the inhibition periods by using an analog simulation. A good fit of calculated to observed results was obtained, based on a simple model, for experiments in ammonia buffer (pH ca 10). In bicarbonate buffer (pH ca 8.5), however, the same simple model was inadequate; additional involvement of iron is indicated. Evidence was found that the reduction of ferric versenate by sulfoxylate yields a free radical, tentatively (HCHO)SO2·. Absolute rates of radical generation were calculated.
Multicomponent copolymer calculations. I. Basic equations
Authors: Seiner Jerome A.
Published: April 2003

A scheme is presented for simulating n‐component vinyl polymerization on a digital computer. Price‐Alfrey Q and e values are used to enhance usefulness of the equations into areas where reactivity ratios are not available.
Synthesis of polyhydrazones and polypyrazoles by a polycyclization reaction
Authors: Korshak V. V. , Krongauz E. S. , Berlin A. M.
Published: April 2003

By the interaction of linear or branched bis(β‐diketones) and dihydrazides of dicarboxylic acids or dihydrazines unknown high molecular compounds with pyrazole rings in the chain have been prepared. Polypyrazoles of the second type (with a free NH‐group in the pyrazole ring) were prepared by the interaction of bisdiazoalkanes and diacetylenes. Some features of the polycyclization reaction as well as the structure and properties of polymers obtained are discussed.
Alkaline hydrolysis of polyacrylamide
Authors: Nagase Kunihiko , Sakaguchi Kahei
Published: April 2003

Polyacrylamide has been reported to show an abnormal behavior on alkaline hydrolysis, that is, the reaction rate is quite high at the initial stage and decreases rapidly with increasing conversion. This phenomenon has been attributed to the polymer structure. We have found that the low molecular weight diamides show essentially the same behavior and concluded that this abnormality is due to the polyfunctionality and is not necessarily specific to polymers.
Studies on melt spinning. I. Fundamental equations on the dynamics of melt spinning
Authors: Kase Susumu , Matsuo Tatsuki
Published: April 2003

The dynamics of melt spinning was analyzed by deriving a set of simultaneous partial differential equations.

Equation of heat balance:

Equation of force balance:

Equation of material balance:

In the above equations, the distance x from the spinneret and time τ are the independent variables; temperature t, local velocity v, and cross‐sectional area A are the dependent variables. It is assumed that tensile viscosity β is a function of temperature t alone, and the spinning tension F is a pure time function. Steady‐state (∂/∂τ = 0) solutions of the above equations showed a fairly good agreement with the experimentally measured values of temperature t(x) and thickness A(x).
Potentiometric study of the conformational transition in poly(acrylic acid)
Authors: Mathieson A. R. , McLaren J. V.
Published: April 2003

Detailed potentiometric titration curves have been obtained for poly(acrylic acid) (Mn = 2.6 × 106) in solution at four different ionic strengths at 25°C. When plotted as pH + log [(1 − α)/α] versus α (where α is the degree of dissociation), they reveal the presence of two different molecular conformations, denoted PAA(a) and PAA(b), with a transition between them. The proportion of the material present in the two conformations has been calculated for different degrees of dissociation and is found to be independent of ionic strength. PAA(a) is intact up to α = 0.22 and is completely converted into PAA(b) by α = 0.75. The free energy of transition from PAA(a) to PAA(b) when both forms are uncharged decreases numerically from −275 to −157 cal./mole monomer residues as the ionic strength increases from 0.02 to 0.20. The increase of the pH of solutions of the PAA(a) from over those of the PAA(b) form at a given value of α, is largely independent of α. This makes it possible to calculate the free energy of transition from PAA(a) to PAA(b) when both forms are charged to the same extent. This free energy is proportional to α and decreases numerically from −944α to −561α (cal.) as ionic strength increases from 0.02 to 0.20. The charge‐independent part of the free energy of transition is a constant fraction of the total, at a given value of α, independent of the ionic strength. The PAA(a) form is the more compact, less contractile, and more ordered structure. The possibility is suggested that this conformation may be partly helical in nature.
Cationic polymerization α,β‐disubstituted olefins. Part I. Cationic copolymerization of β‐methylstyrenes
Authors: Mizote A. , Tanaka T. , Higashimura T. , Okamura S.
Published: April 2003

Steric and electronic effects of the β‐methyl group on monomer reactivity have been studied by copolymerization of styrenes and β‐methylstyrenes. Steric hindrance of the β‐methyl group in the transition state of homopolymerization is so great that the rate of the propagation reaction is considered to be depressed by as much as 1/10−1/20 of the corresponding styrene derivatives. In contrast to this, steric hindrance of the β‐methyl group in cross propagation reactions with styrene is found to be very small. The monomer reactivity itself of β‐methylstyrenes is a little lower than that of corresponding styrenes. This lowered reactivity of β‐methylstyrenes is considered to be due to the electronic effect of the β‐methyl group.
Effect of crosslinking density on the viscoelastic properties of unsaturated polyesters
Authors: Shibayama K. , Suzuki Y.
Published: April 2003

Viscoelastic properties of unsaturated polyesters were investigated in the glass‐rubber transition region in relation to the temperature dependence of specific volume. Polyesters which are homologous with respect to crosslinking density were prepared by using mixtures of succinic and fumaric acid as the dibasic acid component. The temperature dependence of the specific volume was determined by refractive index measurement, the specific refractivity being assumed to be independent of temperature. The temperature dispersion of dynamic viscoelasticity was measured at a constant frequency. Results are summarized as follows. Specific volume and glass temperature are linearly related to the logarithm of crosslinking density. The thermal expansion coefficient and steepness of viscoelastic dispersion decrease with increasing crosslinking density. Fractional free volume and expansion coefficient of free volume, both of which were calculated by WLF equation, are in good agreement with the temperature dependence of specific volume. The results indicate that the effect of crosslinking is largely attributable to the change in amount and distribution of free volume in polymer networks.
Polymerization of adsorbed monolayers. II. Thermal degradation of the inserted polymer
Authors: Blumstein Alexandre
Published: April 2003

Monomolecular layers of methyl methacrylate inserted between the lamellae of montmorillonite clay were polymerized. Finely divided complexes of poly(methyl methacrylate)–montmorillonite were suspended in boiling hydrocarbons and subjected to thermal degradation at 215°C. and above, under air and nitrogen, with constant vigorous stirring. Aliquots were regularly withdrawn, centrifuged, and extracted with appropriate solvents. The weight losses upon calcination at 1000°C. were determined, and from them the rates of reversal to monomer were followed. Complexes containing inserted and external polymer were studied. The inserted polymer was found to resist thermal degradation under conditions at which complete degradation of the external polymer was found. This effect seems to be due to steric factors hindering the thermal motion of the segments of the polymer sandwiched between the lamellae of the crystallites. The insertion polymer isolated from the polymer–clay complex, had a greater thermal stability than poly(methyl methacrylate) made in a conventional free radical system without the presence of clay.
Copolymerization of acrylonitrile and sodium p‐styrenesulfonate in dimethyl sulfoxide solution
Authors: Izumi Z. , Kiuchi H. , Watanabe M. , Uchiyama H.
Published: April 2003

The copolymerization of acrylonitrile (AN) with sodium p‐styrenesulfonate (SSS) in dimethyl sulfoxide solution has been investigated. Monomer reactivity ratios at 45°C., for AN and SSS are found to be r1 = 0.15 ± 0.02, r2 = 0.55 ± 0.03. From these data Price Q and e values for SSS of 0.44 and −0.38, respectively, are calculated. The values are found to be different from those in aqueous solutions, which may be attributed to the different electron distributions in all solvents. Initial rates of copolymerization at 45°C. with azobisisobutyronitrile as initiator were determined over the entire range of composition from pure AN to pure SSS. It was found that there is a slight rise in copolymerization rates in the range of 90–95 mole‐% SSS in the monomer feed; this is attributed to the coexistence of liquids of different optical density. Homopolymerization of AN and SSS in dimethyl sulfoxide was also investigated and δ = (k/kp) for AN and SSS found to be 6.55 (mole‐sec./1.)½ and 2.46 (mole‐sec./1.)½, respectively. From these values the cross‐termination constant φ is calculated to be 6.5.
Polymer–solvent interactions of bisphenol a polycarbonate in different solvents
Authors: Sitaramaiah Gullapalli
Published: April 2003

Bisphenol A polycarbonate (Lexan, General Electric) was fractionated from methylene chloride by progressive precipitation with methanol and the fractions were characterized by osmometry, light scattering, and viscometry. Intrinsic viscosities of eight fractions in the molecular weight range 10,000–70,000 were obtained in five solvents at different temperatures to study the molecular expansion of polycarbonate. Light‐scattering molecular weights, measured for the three high viscosity fractions, agreed within ±5% with the Mv values. The Mv/Mn ratio of the fractions was between 1.1 and 1.3, as compared to 2.7 for the unfractionated polymer. This indicates a relatively narrow distribution of the fractions. The exponent, a, in the Mark‐Houwink equation showed no appreciable change with temperature. Values of d[η]/dT were generally negative. The unperturbed dimensions of polycarbonate, evaluated by the relation [η] = KM½‐α2.43, suggest a stiff molecule. Values of K and d log α3/dT indicate increased chain flexibility at higher temperatures. Experimental data demonstrate that the Kurata‐Stockmayer‐Roig expression, based on the equivalent ellipsoidal model of a linear polymer molecule, is well suited to interpret the molecular expansion of polycarbonate. The Flory relation, α5 − α3 versus M½, is found to be of limited applicability.
Polymerization of acrylonitrile by electron transfer initiation
Authors: Tsukamoto Akira
Published: April 2003

The homogeneous polymerization of acrylonitrile by electron transfer initiators is investigated. In a rigorously purified system at low temperatures it is demonstrated that “living” polyacrylonitrile is formed, and that its molecular weight can be predetermined. The number‐average molecular weight of “living” polyacrylonitrile is approximately given by 2M/I, where M represents grams of monomer and I is the number of moles of the initiator. For polyacrylonitrile prepared by homogeneous anionic polymerization with an electron‐transfer initiator, it is found that the viscosity average molecular weight calculated by using the conventional values of K and α in the Mark‐Houwink equation is considerably smaller than the osmotic number‐average molecular weight. This clearly indicates a structural difference between the free‐radical and anionic polyacrylonitrile; the anionic polyacrylonitrile appears to have a highly branched structure formed by a chain transfer process to the polymer.
Copolymerization studies. VI. Spontaneous copolymerization of bicyclo[2.2.1]hept‐2‐ene and sulfur dioxide. Evidence for propagation by biradical coupling
Authors: Zutty N. L. , Wilson C. W. , Potter G. H. , Priest D. C. , Whitworth C. J.
Published: April 2003

The alternating copolymerization of bicyclo[2.2.1]hept‐2‐ene and sulfur dioxide has been found to be quite unusual for a free‐radical polymerization: (1) the initiation of copolymerization is spontaneous, even at −40°C.; (2) solution copolymerization is extremely fast, yielding very high molecular weight polymer within a few seconds; (3) conversions are high (up to 93% within a minute); (4) molecular weight during copolymerization increases at essentially constant conversion; (5) the reaction is incapable of being chemically inhibited indefinitely, short of exhausting one of the constituent monomers; (6) at elevated temperatures, the monomers and copolymer appear to be in equilibrium; (7) large concentrations of free radicals have been detected by electron paramagnetic resonance to be associated with the bulk copolymerization; and (8) the copolymerization appears to result in “living” free‐radical polymers. A copolymerization mechanism is proposed to explain these observations. Bicycloheptene and sulfur dioxide initially form a 1 : 1 molecular charge transfer complex which rearranges to a biradical; subsequent coupling of biradicals with each other (and possibly also with the molecular complexes themselves) leads to rapid propagation to high molecular weight, alternating copolymer. Speculations that similar mechanisms may be important in other copolymerization reactions are also made.
Ziegler polymerization of olefins without added metal alkyls
Authors: Matlack A. S. , Breslow D. S.
Published: April 2003

Ethylene has been polymerized under mild conditions by (1) transition metals plus alkyl halides, (2) transition metal hydrides, (3) certain transition metals alone, and (4) certain divalent transition metal halides and oxides. Propylene has been polymerized to mixtures of amorphous and crystalline polymer in low conversions by (1) transition metals plus alkyl halides and (2) certain divalent transition metal halides. A vibratory ball mill was used as the polymerization vessel to provide a continuous supply of fresh catalyst surface during the polymerizations. The transient existence of transition metal alkyls is postulated to account for the observed catalysis. This work provides one of the most direct proofs that polymerization occurs on the transition metal, rather than on aluminum, zinc, or other metals usually associated with it in typical Ziegler catalysts.
Variation of crystallinity with temperature for homopolymers and random copolymers
Authors: Krigbaum William R. , Uematsu Ichitara
Published: April 2003

An earlier treatment assumed that crystallization places portions of the polymer molecule between tie‐points under strain, which limits the equilibrium crystallinity at any temperature. If these strained chains can be treated in the Gaussian approximation, (1 – ω)−2 should be a linear function of T−1, where ω is the degree of crystallinity. This prediction is unchanged by inclusion of the crystal surface energy. The degree of crystallinity is primarily governed by the deformation entropy at high supercoolings, while near the apparent melting point the crystal surface energy dominates, hence the Hoffman and Weeks procedure for evaluating thermodynamic melting point remains valid. Random introduction of comonomer lowers the apparent melting point and increases the tie‐point density. The latter limits both the degree of crystallinity and the initial Young's modulus of a random copolymer at high supercoolings. Values obtained for N (the number of statistical links between tie‐points) by fitting crystallinity data near the melting points for isothermally crystallized isotactic polypropylene and linear and branched polyethylene by using the Gaussian approximation, are identical to those previously obtained at high supercoolings by using inverse Langevin statistics. In fact, if the effects of crystal surface energy and the presence of a comonomer are included and the amorphous chains are treated by inverse Langevin statistics, one obtains a satisfactory representation of the variation of crystallinity with temperature over the entire range studied. Finally, the predicted linear variation of ω at high supercoolings with N−½ is verified for polyethylene.
Effect of thiourea on the radical polymerization of vinyl monomers. Part I. Polymerization of acrylonitrile with the hydrogen peroxide–thiourea catalyst system
Authors: Sugimura Takaaki , Yasumoto Noboru , Minoura Yuji
Published: April 2003

The polymerization of acrylonitrile (AN) was studied in aqueous solution with hydrogen peroxide (H2O2) as catalyst and thiourea (TU) as cocatalyst at 30°C. Since the polymerization was carried out at a relatively low temperature, AN was not polymerized by hydrogen peroxide alone. Upon addition of TU to the reaction system, polymerization occurred immediately, and the rate of polymerization increased with increasing TU concentration. In order to obtain the overall polymerization equation, the dependence of polymerization rate on H2O2 and AN concentration was studied kinetically. It was found that the overall polymerization rate Rp was represented by the equation: Rp = K[TU]frac12;[H2O2]frac12;[AN], where K is the rate constant. The acceleration in the presence of TU might be attributed to a redox reaction between H2O2 and TU which would produce free radicals rapidly. The effect of substituents was investigated by use of various N‐substituted derivatives of TU. The polymerization rate increased linearly with the σ* constants of the substituents as electron‐withdrawing substituents were added. The polymerization mechanism is discussed on the basis of the results.
Effect of reaction medium on copolymerization of acrylonitrile and sodium allyl sulfonate
Authors: Izumi Zenzi , Kiuchi Hiroshi , Watanabe Masamoto
Published: April 2003

The copolymerization of acrylonitrile (AN) with sodium allyl sulfonate (SAS) in dimethyl sulfoxide (DMSO) at pH 7, aqueous DMSO solution (6% H2O), DMSO at pH 1.5, and aqueous solution at pH 7 has been investigated. Monomer reactivity ratios at 45°C. for AN and SAS are found to be r1 = 1.00 ± 0.01, r2 = 0.38 ± 0.02 in DMSO at pH 7; r1 = 1.25 ± 0.01, r2 = 0.28 ± 0.02 in aqueous DMSO; r1 = 1.85 ± 0.01, r2 = 0.43 ± 0.01 in DMSO at pH 1.5. From these values Price Q and e values, respectively, calculated for SAS were 0.19 and 0.22 in DMSO at pH 7, 0.14 and 0.18 in aqueous DMSO, and 0.18 and 0.70 in DMSO at pH 1.5. The large differences in reactivity of SAS may be attributed to the different electron distributions in SAS in each solvent which are caused by the poor solvating power of dimethyl sulfoxide and by the addition of protons. In copolymerization in aqueous solution, the physical condition depends upon the content of SAS in the monomer feed, and SAS is copolymerized to only a small extent in the range of heterogeneous systems, whereas SAS is copolymerized rather well in the range of homogeneous systems. Homopolymerization of SAS shows a first‐order dependence on initiator concentration and a three‐halves‐order dependence on monomer concentration; this is attributed to degradative chain transfer of SAS. Rates of copolymerization of AN and SAS decrease with increasing SAS content.
Coupling of xylylene dihalides with divalent chromium. Aspects of copolymerization and mechanism
Authors: Lunk H. E. , Youngman E. A.
Published: April 2003

Copolymers of p‐ and m‐xylylene have been prepared by coupling of the corresponding dihalides with chromous chloride. A stepwise mechanism is proposed for the formation of polyxylylenes, and evidence is given for the occurrence of free radicals in the decomposition of the intermediate organochromium complex.
Crystallization kinetics of polypropylene fractions
Authors: Hoshino S. , Meinecke E. , Powers J. , Stein R. S. , Newman S.
Published: April 2003

The overall crystallization rate of polypropylene fractions was studied dilatometrically, and the crystallization behavior was considered in relation to the stereoregularity of the samples. The study includes a photomicroscopic analysis of the nucleation, formation, and growth of spherulites, as well as an evaluation by means of rapid x‐ray scanning techniques of the increase of crystallinity within the spherulites. A theory was applied to the discussion of crystallization behavior in which two stages of growth were introduced: (a) growth at the spherulite interface, and (b) secondary crystallization within the spherulite. These were described in terms of Avrami‐type equations with differing parameters.
Modified avrami equation for the bulk crystallization kinetics of spherulitic polymers
Authors: Hillier I. H.
Published: April 2003

An explanation of the anomalous fractional values of the Avrami exponent found for the crystallization of a number of polymers is presented. The interpretation is based on a model which postulates the constant radial growth of spherulites, followed by an increase in crystallinity within them by a first order process. The model is supported by direct microscopic observations of other workers. Crystallization isotherms for polymethylene, poly(ethylene oxide), and poly(decamethylene terephthalate) are fitted to this model. Apart from the removal of the fractional values of the Avrami exponent, which have no physical meaning, this model gives a considerably better fit than the Avrami equation to most isotherms analyzed. The temperature dependence of the rate constants found for the two rate processes of this model is also discussed. An interpretation of the results of seeded experiments is presented in terms of this model.
Heteroaromatic polymers. The polybithiazoles
Authors: Longone Daniel T. , Un Howard H.
Published: April 2003

The polycondensation of dithioöxamide with bifunctional aromatic bromomethyl ketones affords a series of poly‐4,4′‐diaryl‐2,2′‐bithiazoles. These polymers exhibit outstanding thermal stability. They are characteristically insoluble, infusible, highly crystalline, and of high molecular weight. Controlled structural variations within the polymer recurring unit allow for modifications of gross polymer properties. Structural characterization and thermal stability measurements are discussed.
Polymers containing the 3,3,3′,3′‐tetramethyl‐1,1′‐spirobiindane residue
Authors: Stueben K. C.
Published: April 2003

A variety of condensation polymers were prepared from the 6,6′‐dihydroxy‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobiindanes including polyesters, polyurethanes, and a polyhydroxyether. The polycarbonate displayed good oxidative resistance at 200°C. but was found to lack toughness despite the presence of a low temperature transition at −100°C. A tendency toward brittleness was also evident in the other polymers and copolymers prepared. The contribution of the spiroindane structure to polymer properties is discussed. All of the polymers studied were amorphous and displayed high glass transition temperatures.
Polymer–filler interaction. Thermodynamic calculations and a proposed model
Authors: Kwei T. K.
Published: April 2003

From a study of the sorption of water vapor by epoxy polymers filled with titanium dioxide, the differences in enthalpy and entropy of the filled and the unfilled polymers are calculated. The enthalpy and the entropy of the filled polymer are smaller than those of the unfilled polymer by about 2 cal./g. and 6 × 10−3 e.u., respectively. These differences may be explained by the existence of a higher degree of local ordering of the polymer segments. A model is proposed to describe the interaction between the polymer and the filler as a function of the distance from the interface. It appears that polymer segments at a distance less than 1500 A. from the surface of the filler particle are within the sphere of influence of the filler. The effects of filler incorporation of the thermal expansion coefficient, heat capacity, and partial molar heat of solution of the polymer are discussed in terms of the model.
Oxonium ion‐initiated polymerization of tetrahydrofuran
Authors: Vofsi David , Tobolsky Arthur V.
Published: April 2003

The kinetics of polymerization of tetrahydrofuran was studied, with the use of triethyloxonium tetrafluoroborate as initiator and dichloroethane as solvent. Conversion versus time and degree of polymerization versus time were measured at 0°C. at various monomer and initiator concentrations. The data were systematized by means of a kinetic equation, and the absolute rate constants for initiation and propagation were determined.
Range of practical validity of the debye and the rayleigh equations for determining molecular weights from light scattering and methods allowing a limited extension of this range
Authors: Heller Wilfried
Published: April 2003

Using the equivalence of the Rayleigh and the Debye equations on light scattering as a basis, the per cent error in molecular weight committed on using the latter is evaluated by comparing results with those derived from the exact Mie scattering functions. The variable is, by necessity, the quantity M V/λ3 as long as the radiation diagram is symmetrical, where M is the molecular weight, V the partial specific volume of the solute, and λ the wave length in the medium. The errors committed are consequential only if the dissymmetry is finite. A possible method is outlined for correcting M values obtained from the Debye equation outside of its range of practical validity. It may be applied as long as the dissymmetry does not exceed about 30%. The possibility of determining from light scattering the approximate degree of swelling of latex particles and the size of clusters of spheres is discussed briefly.
A unified approach to failure and its application to highly filled polymers
Authors: Majerus J. N.
Published: April 2003

Two interrelated general approaches to the study of structural failure of highly filled polymeric materials, e.g., a solid propellant, are described. These consist of the macroscopic (thermodynamics and continuum mechanics) and microscopic (molecular model) methods of analysis in conjunction with solid propellant experimental data. The thermodynamic investigation indicates that propellant material under loading goes through stages of stable and unstable behavior which depend upon the rate at which work is absorbed and dissipated by the material. The instability point seems to correlate with results from subscale motors. The thermodynamic investigation is then extended by a functional analysis of failure treated from a viewpoint of continuum mechanics. Since fracture, per se, is a physical observable, it is represented by a “state vector” in n‐dimensional space. The number of dimensions of this space depends upon the basic variables involved in fracture. Since the correct failure criteria must be tensorally consistent with the tensor rank of fracture, distinct sets of functions can be applied to experimental data. The data are compared to the classical scalar functions of failure. They were obtained from uniaxial and biaxial creep and relaxation tests to failure, uniaxial and biaxial tension tests conducted under constant rates of loading and of strain, with and without superimposed hydrostatic pressure, and pure shear tests to failure. The correlation between the different types of induced failure is demonstrated through the microscopic approach by use of molecular models and the application of statistical mechanics.
Radiation‐induced polymerization of 1,2‐cyclohexene oxide
Authors: Cordischi D. , Lenzi M. , Mele A.
Published: April 2003

Radiation‐induced polymerization of 1,2‐cyclohexene oxide was investigated in the liquid and in the solid state. Addition of water drastically reduces the rate of polymerization and the molecular weight of the obtained polymer. The results have been interpreted according to an ionic mechanism.
Preparation and polymerization of propenyldiphenylphosphine oxide isomers
Authors: Welch F. J. , Paxton H. J.
Published: April 2003

Isopropenyldiphenylphosphine oxide (I) and both cis‐ and trans‐n‐propenyldiphenylphosphine oxides (II) have been prepared and their structures assigned primarily on the basis of infrared and NMR analyses. Like vinyldiphenylphosphine oxide, these monomers are polymerized sluggishly by free radical catalysts although copolymers with may common vinyl monomers can be prepared. Grignard reagents polymerize (I) very rapidly to low molecular weight products, but the polymerization of II by these catalysts is slower and requires larger amounts of catalyst. Evidence is presented which indicates that in the polymerization of vinyldiphenylphosphine oxide by Grignard reagents molecular weight may be limited by a chain transfer to monomer process.
Reactions of high molecular weight polyacrolein
Authors: Bergman Elliot , Tsatsos W. T. , Fischer R. F.
Published: April 2003

High molecular weight polyacrolein reacts readily with a variety of aldehyde reagents to form soluble derivatives. The reactions proceed at a measureable rate at room temperature when suitably catalyzed by acid or base. Gentle warming is occasionally required to attain useful reaction rates. The reactions of polyacrolein are conveniently divided into those involving (a) the aldehyde function alone or (b) the active hydrogen alpha to the carbonyl. The first class includes reactions with HCN, NaHSO3 (SO2), Na2S2O4, primary and secondary amines, alcohols, thiols, and aqueous based. The second type reaction includes additions to the α‐carbanion and oxidations involving chain scission. Depending on the reagent employed and conditions, reaction of polyacrolein gives open‐chain derivatives or the 2,6‐disubstituted tetrahydropyran structure which is present to a large extent in hydrated polyacrolein.

Base‐catalyzed disproportionation of polyacrolein yields a polymethylol polycarboxylic acid via internal Cannizzaro reaction. In the presence of formaldehyde, α‐methylol groups are introduced during the disproportionation.
cis‐trans isomerization in polyisoprenes. Part VII. Double bond movement during the isomerization of natural rubber and related olefins
Authors: Cunneen J. I. , Higgins G. M. C. , Wilkes R. A.
Published: April 2003

When trans‐3‐methylpent‐2‐ene or trans‐3‐methylhex‐3‐ene is treated with butadiene sulfone, thiolbenzoic acid, and dibenzoyl disulfide under anaerobic conditions, the olefin undergoes only cis—trans isomerization. However, similar reactions in the presence of oxygen or peroxides also cause changes in the position of the double bond. The latter structural modification is probably caused by acidic compounds formed by oxidation of the isomerization reagents. With natural rubber the nonrubber substances prevent movement of the double bond, and cis–trans isomerization is the sole change, even when the reaction with sulfur dioxide is carried out under aerobic conditions.
Benzaldehyde polymerization and copolymerization studies
Authors: Raff R. , Cook J. L. , Ettling B. V.
Published: April 2003

In attempts to homopolymerize benzaldehyde with various ionic and coordination catalysts, or by γ‐radiation, only the ionic catalyst BF3 etherate formed a polymeric product. This product was identified as polybenzyl with a degree of polymerization (DP) of 133. Mixtures of benzaldehyde and styrene did not copolymerize under γ‐irradiation, but yielded only polystyrene. With a BF3 etherate catalyst, however, mixtures of styrene and benzaldehyde were found to have copolymerized through the carbonyl group of the latter, and a 50 : 50 styrene–benzaldehyde monomer mixture yielded an 80:20 styrene–benzaldehyde copolymer with a DP of 139.
Divinyl copolymerization initiated by high intensity, low energy electrons
Authors: Burlant W. , Hinsch J.
Published: April 2003

Solutions of unsaturated esters in styrene were copolymerized by 0.04 M.e.v. electrons at dose rates of 0.44–85.8 Mrad/min. Disappearance of each monomer and gel fractions were measured as a function of dose rate. Rates noted under these conditions of high linear energy transfer exhibited linear dependence on intensity, followed by a region independent of intensity. The data suggest that polymerization occurs in discrete volume elements, and that chain growth is initiated by hot radicals. For 65% ester solutions, the polymerization rate of the bulk sample, dαt/dt, is given by dαt/dt = {(kp*2/kt,)[M20]}V, where kp* is an activated propagation rate constant tenfold greater than that for more conventional polymerizations, kt is the termination rate constant, [M20] is the starting ester concentration, and V, proportional to the radiation intensity, is the volume fraction of the sample occupied by the reacting elements. The volume of the element in which polymerization is occurring, estimated from experimental data and using reasonable values for the life of a growing radical, is 3 × 109 A.3, a value consistent with what is known of electron impact processes in liquids.
Phase separation, viscosity, and thermodynamic parameters for poly‐2‐methyl‐5‐vinylpyridine–diluent systems
Authors: Gechele G. B. , Crescentini L.
Published: April 2003

Liquid–liquid phase separation has been investigated for several poly‐2‐methyl‐5‐vinylpyridine fractions in eleven solvents. The plots of precipitation temperatures against polymer volume fractions are shown for a few systems. The agreement between two curves calculated according to Flory and the experimental ones is only qualitative, and the calculated critical concentrations are much smaller than the experimental ones. Plots of reciprocal critical precipitation temperature against reciprocal square root molecular weight of the polymer are straight lines. From the intercepts and slopes the values of the thermodynamic paramerers θ and ψ were calculated. Intrinsic viscosities were determined for a fraction of 990,000 molecular weight in five solvents at various temperatures. Theta measurements yielded for Flory's constant K the value 8.4 × 10−4, which can be assumed to be constant with the temperature and the solvent. Moreover the parameter θ and ψ were calculated according to Flory and Fox, Kurata, Stockmayer, and Roig, and Kurata and Stockmayer. The viscometric ψ are different from each other and all much smaller than the ones from phase separation. An attempt is made to compare the above theories by utilizing intrinsic viscosity results on fractions of various molecular weights in n‐propyl acetate and methyl isobutyl ketone. The results show nearly the same behavior for all the three theories.
Thioureas and isothiuronium salts. Polymeric derivatives
Authors: Overberger C. G. , Friedman Herbert A.
Published: April 2003

A series of derivatives of N‐(p‐vinylphenyl)thiourea were found to be capable of free radical polymerization. N‐(p‐Vinylphenyl)‐N'‐methylthiourea was copolymerized with p‐aminostyrene, p‐N,N‐dimethylaminostyrene, and N‐vinyl‐phthalimide. S,N‐Dimethyl‐N‐(p‐vinylphenyl) isothiuronium iodide was also polymerized in a similar fashion. p‐Vinylphenyl isothiocyanate was found to undergo polymerization with difficulty. The latter polymer was reacted with dimethylamine to yield the polymeric thiourea.
Gel permeation chromatograms: Approximate relation of line shape to polymer polydispersity
Authors: Berger H. L. , Shultz A. R.
Published: April 2003

Characteristics of gel permeation chromatograms are investigated for three molecular distribution functions assuming a linear relation between elution volume and the logarithm of solute molecular weight. The average molecular weight, Mgpc, determined by the peak position of a chromatogram lies between the Mw and Mn for a polydisperse polymer.