bluuebunny/crossref_metadata_2025 huggingface dataset:
Heats of mixing of polymers with ester and ether solvents
Authors: Patterson D.
Published: April 2003

Heats of mixing at infinite dilution have been obtained for polydimethylsiloxane in four series of ester solvents: the methyl and ethyl esters of the aliphatic acids, and the acetic and propionic esters derived from the normal alcohols. Heats have also been obtained in certain ethers including the dialkyl ethers. The solvent molecules are considered to be chains of two types of segments: CH2CH2 and COO, or CH2O. The heat of mixing is ascribed to two contributions: I, a difference in force fields between segments of polymer and solvent molecules, and II, a difference in the Prigogine structural factors of the molecules. Contribution II has been assumed to be approximately the same as with n‐alkane solvents of corresponding chain lengths. By subtracting heats found with n‐alkane solvents from those with esters or ethers II is eliminated and the resulting difference in I may be treated using a lattice model and assuming random mixing. This approach is successful for the ester solvents but somewhat less so for the ethers, where some departure from randomness due to steric factors may be present.
Electrochemical transformations of polymeric acid solutions. I. Crossed Koble synthesis
Authors: Smets G. , Van der Borght X. , Van Haeren G.
Published: April 2003

Poly(methacrylic acid) was electrolyzed at 20°C. in 0.2 M dry methanol solution in a glass apparatus provided with two polished platinum disk electrodes; the current density was kept constant (300, 800, or 1000 ma.). Before electrolysis the acid was partially neutralized in order to increase the electrical conductivity. The electrolysis was characterized by evolution of carbon dioxide at the anode, while the acid content of the polymer decreased. When the degree of decarboxylation was about 30%, intramolecular lactonization occurred by interaction of unsaturated groups with neighboring acid groups. The changes of chemical composition of the polymer in function of the time were followed by determination of free carboxylic acid groups, of γ‐lactones, and unsaturated groups (bromine addition). The amount of methyl ester formed by methanolysis of the lactones was calculated from methoxyl determinations. At the end of electrolysis only 5–6% free carboxylic groups were present, 35–40% lactones, 30% ester groups; the residue was mainly a hydrocarbon fraction (partially unsaturated). The electrolysis was also carried out in the presence of low molecular weight carboxylic acids, acetic, ϵ‐acetaminocarproic, and cyanoacetic acids, the ratio of the concentration of these acids to that of polymeric acid being varied over a wide range. With acetic acid the chemical composition of the polymer was only slightly affected through grafting of side methyl groups, as was shown by the use of C14 acetic acid. With ϵ‐acetaminocaproic and cyanoacetic acids the crossed Kolbe synthesis reactions are much more important, 20–24% side alkyl acetamino groups and 15% cyanomethylene groups being grafted to the main chain by this method. Chain degradation during these experiments can be practically avoided.
Copolymerization of nonconjugated diolefins: General composition relationships
Authors: Gibbs W. E. , McHenry R. J.
Published: April 2003

The copolymerization of nonconjugated diolefins with vinyl monomers involves departures from conventional vinyl copolymerization kinetics and the standard forms of the binary or ternary copolymerization composition equations are inadequate. These departures include intramolecular cyclization reactions and generally the formation of some pendent double‐bonds. A general treatment of the copolymerization of symmetrical nonconjugated diolefins with vinyl monomers gives closed form relationships which take such reactions and their consequences into account. The general relationships may be approximated by a new series of composition equations which take into account the formation of both cyclized and noncyclized units in the chain and are simple enough for experimental use. The latter expressions are:

where: αc = kc/k11, α4 = k14/k11, δ1 = k41/k44, and β4 = k24/k21, and [M1], [M3], and [M4] refer to the concentrations of diolefin double bonds, pendent double bonds, and comonomer, respectively.
α,ω‐glycols from isobutylene and some derived block copolymers
Authors: Jones E. B. , Marvel C. S.
Published: April 2003

Butyl rubber containing 2 mole‐% of isoprene was ozonized and reduced producing polyisobutylene glycol. Hydroxyl equivalent determinations on the glycol and elemental analyses of the chain extended polymers indicate the glycol to be difunctional. Possible structures of the glycol and extended polymer are suggested.
Kinetics of the polymerization of divinylbenzene isomers
Authors: Wiley Richard H. , Devenuto Giovanni
Published: April 2003

The overall rates of polymerization of m‐ and p‐divinylbenzene, a 2:1 mixture of the meta and para isomers, and commercial divinylbenzene have been followed viscometrically. Data at 60 and 80°C. show that the meta isomer polymerizes most rapidly. Ratios of rates show differences in activation energies. An effect on the overall rates is tentatively attributed to the increased resonance stabilization of the p‐vinylphenyl‐derived radical which further decreases the already low reactivity of the styrene‐derived radical. The possibility that steric factors contribute significantly to the rate difference is considered to be unlikely.
Some remarks on amorphous and atactic α‐olefin polymers and random ethylene–propylene copolymers
Authors: Natta G. , Valvassori A. , Ciampelli F. , Mazzanti G.
Published: April 2003

The necessity is pointed out to distinguish between an “amorphous” α‐olefin polymer and an “atactic” α‐olefin polymer. It is convenient to limit the term “atactic” only to those amorphous linear regularly head‐to‐tail polymers which possess the same chemical regularity as the corresponding tactic polymers, from which they differ only for the lack of steric regularity. A clear interpretation is given of the presence of bands at 1155 and 915 cm.−1 in the IR spectra of isotactic and atactic polypropylenes. The presence of these bands is due to the monomeric unit, with a regular head‐to‐tail arrangement. The absence of these bands in the propylene polymers obtained with the aid of cationic‐type catalysts depends on the presence of a very small content of monomeric units of this type. Finally the conclusion is drawn that the presence of the two above‐mentioned bands in the IR spectrum of the ethylene–propylene copolymers does not indicate the presence of long propylene sequences of the isotactic type, and therefore the existence of a block copolymer, but only the presence of the monomeric unit mentioned above.
X‐ray study of some isotactic substituted poly‐carboalkoxybutadienes
Authors: Natta G. , Corradini P. , Ganis P.
Published: April 2003

The chain conformation and configuration of some polysorbates and poly‐β‐styryl‐acrylates is discussed in this paper. From x‐ray fiber spectra of these polymers we obtained the identity period of 4.80 ± 0.05 A. The conformation of the main chain is the same as that of 1,4 trans polybutadiene and isotactic 1–4 trans polypentadiene. From considerations of the mode of packing of the chains and of the encumbrance of the side groups in respect to the main chain it was possible to assign an erythro configuration in regard to the relative placement of lateral groups. The examined polymers are tritactic and have a trans‐erythro‐isotactic configuration.
Polyamides of 1,4‐cyclohexanebis(methylamine)
Authors: Bell Alan , Smith James G. , Kibler Charles J.
Published: April 2003

Polyamides of both cis‐ and trans‐1,4‐cyclohexanebis(methylamine) with aliphatic dicarboxylic acids and copolyamides of trans‐1,4‐cyclohexanebis(methylamine) with p‐xylene‐α,α′‐diamine were prepared in order to discover the effect of cycloalkane rings on melting point. Analogous polyamides of p‐xylene‐α,α′‐diamine were prepared for comparison. The polyamides of trans‐1,4‐cyclohexanebis(methylamine) had higher melting points than the analogous polyamides of p‐xylene‐α,α′‐diamine. This result is believed to be due to the slightly contracted conformation which trans‐1,4‐cyclohexanebis(methylamine) can adopt in the polymer chain. The polyamides of cis‐1,4‐cyclohexanebis(methylamine) melted lower than those of the trans isomer. The lower symmetry of the cis‐diamine accounts for this result. The melting points of the copolyamides of trans‐1,4‐cyclohexanebis(methylamine) and p‐xylene‐α,α′‐diamine were higher than expected. It is suggested that these compositions are examples of partially isomorphous copolyamides.
Influence of the nature of the initiator on the bulk polymerization of methyl methacrylate
Authors: Rafikov S. R. , Gladishev G. P. , Khasanova N. F. , Churbakova N. V.
Published: April 2003

The kinetics of polymerization of MMA activated by ultraviolet irradiation at various temperatures and the polymerization of monomer with dicyclohexylperoxycarbonate have been studied. The activation energy of the polymerization with percarbonate is 14.9 kcal./mole, and that of polymerization with photooxidized monomer is 11.2 kcal./mole. The temperature at which ultraviolet‐oxidation of MMA (0–40°C.) is carried out has no significant influence on the kinetics of polymerization of activated monomer. The gel effect in the case of the dicyclohexylperoxycarbonate‐initiated polymerization of MMA is somewhat greater than that of monomer activated by photooxidation.
Synthesis of trichain and tetrachain radial polybutadienes
Authors: Zelinski R. P. , Wofford C. F.
Published: April 2003

Tri‐ and tetrachain radial polybutadienes have been synthesized by coupling very dilute solutions of linear polybutadienyllithium with stoichiometric amounts of methyltrichlorosilane or silicon tetrachloride. These polymers have three or four long chains (100–2000 carbon atoms) attached to a single atom.
Stereospecific polymerization of 2‐substituted 1,3‐butadienes. II. Stereospecific polymers of 2‐n‐propyl‐1,3‐butadiene
Authors: Marconi W. , Mazzei A. , Cucinella S. , Cesari M. , Pauluzzi E.
Published: April 2003

The stereospecific polymerization of 2‐n‐propyl‐1,3‐butadiene with aluminum alkyls or aluminum hydride and different transition metal salts was investigated. The behavior of this monomer with respect to the various catalysts employed is similar to that of isoprene. With the AlEt3–TiCl4 and AlHCl2·(C2H5)2O–TiCl4 systems, rubbery polymers are obtained whose infrared spectra are consistent with the 1,4‐cis structure. With the AlEt3–Ti(i‐C3H7O)4 catalyst, a low molecular weight polymer with a prevailing 3,4 structure is obtained. The AlEt3–VCl3 system gives a crystalline product melting at 42°C. The identity period has been determined, and two possible chain conformations are proposed.
Kinetics of polymerization of butadiene, isoprene, and styrene with alkyllithiums. Part III. Rate of propagation
Authors: Hsieh Henry L.
Published: April 2003

Initial propagation rates Rp for butadiene, isoprene, and styrene were obtained by using sec‐BuLi as the initiator. With this alkyllithium, initiation was so very rapid that propagation alone was easily studied. In the case of diene monomers at [RLi] > 10−2M and for styrene, Rp = kp [RLi]1/2[M]. Here no unreacted BuLi is present to associate with polymer‐Li. However, polymer‐Li association can occur to temporarily inactivate the propagating anion. A mechanism was proposed and the kinetic equations were derived. When [RLi] was 10−4 to 10−2M, Rp = kp[RLi]1/3[M] for both dienes, but not for styrene. Some propagation rate constants were calculated. The order of rate of propagation for three monomers was styrene > isoprene > butadiene.
Microstructures of polydienes prepared from alkyllithium
Authors: Hsieh Henry L.
Published: April 2003

The stereochemistry of polymerization of isoprene and butadiene by means of alkyllithium initiators was examined. The stereochemistry of polybutadiene and polyisoprene responded to the same variables in anionic polymerization. Microstructure of both polymers is sensitive to initiator level, solvent type, and polymerization temperature, but is independent of monomer concentration, conversion and initiator structure. The heat activation energy leading to 1,2 addition is greater than that leading to trans‐1,4 addition (1200 cal./mole). The exact pictorial sequence leading to stereospecific polymerization of dienes by means of alkyllithium is still not clear. However, it seems to involve the orientation of the incoming monomer units by association and passage through a transition complex in which all bonds are largely covalent in character and within which polymerization occurs.
Polymerization of butadiene by n‐butyllithium‐titanium tetrachloride (tetraiodide) catalysts
Authors: Lehr Marvin H. , Moyer Patricia H.
Published: April 2003

The structure of polybutadiene obtained with a n‐BuLi–TiX4 (X = Cl, I) catalyst depends on the Li/Ti ratio. At Li/Ti < 2.5 the result is similar to that with (i‐Bu)3Al–TiX4, predominantly, cis‐1,4‐polybutadiene. On the other hand, in the range Li/Ti = 3–4, the chloride catalyst produces largely 1,2‐polybutadiene, and at Li/Ti = 3 it is unaffected by ether in contrast to other ratios investigated. At Li/Ti ≥ 5 in both halide systems, the structure is essentially a mixture of isomers characteristic of the n‐BuLi catalyst alone.
Polyacrylonitrile prepared in ethylene carbonate solution. III. Molecular parameters
Authors: Peebles L. H.
Published: April 2003

The intrinsic viscosity–molecular weight equation for polyacrylonitrile polymerized in ethylene carbonate by an azo catalyst is [η] = 6.98 × 10−4 M̄w0.645 ± 0.036 dl./g. at 25°C. in DMF. The flexibility of the chain is found to be between that of poly(vinyl acetate) and a polycarbonate. The intrinsic viscosity decreases as the temperature is increased. This is shown to be due to two processes which occur simultaneously: A decrease in the polymer radius and an increase in the polymer–solvent interaction. The decrease in the radius overrides the increased solvent attraction. Comparison of the data with those of Fujisaki and Kobayashi suggests that polymers prepared by the aqueous redox and the homogeneous azo polymerization processes are different.
On the ultrastructure of cellulose microfibrils
Authors: Ohad I. , Mejzler D.
Published: April 2003

Statistical formulae based on generally accepted models for cellulose microfibril structure were developed to calculate the mean length of microfibril segments which do not contain molecular chain‐ends, i.e., “continuous segments.” The calculated length of such “continuous segments” for microfibrils of 2–3 mμ cross section, containing molecules of a degree of polymerization from 2 × 103 to 6 × 103, is in the range of 300–1500 A. The relationship between “continuous segments” and crystalline and amorphous regions of cellulose microfibrils is discussed.
Anionic polymerization of butadiene and styrene
Authors: Johnson A. F. , Worsfold D. J.
Published: April 2003

A kinetic study has been made of the polymerization of butadiene and styrene in an aliphatic hydrocarbon solvent with the use of butyllithium as an initiator. It is shown that the anomalous behavior in the initiation reaction exhibited by isoprene under these conditions is also found for these two monomers. These monomers give a sigmoidal rate curve in the initiation reaction in cyclohexane solution, and the reaction appears to be auto‐catalytic. The propagation reactions were studied also, and the results compared with the rather discordant sets of data published by other authors.
Crystallization and dissolution temperatures of polyacrylonitrile
Authors: Chiang R. , Rhodes J. H. , Holland V. F.
Published: April 2003

The dissolution temperature of the crystalline platelets of polyacrylonitrile in propylene carbonate bears a linear relationship with the crystallization temperature Tc. The step heights ζ of the crystalline platelets measured by electron microscopy increase with increase in crystallization temperature, in accordance with the current theory of high polymer crystallization in dilute solution. The step heights were found to be 100, 130, and 150 A. for Tc of 95, 116, and 125°C., respectively. By extrapolating the experimental values of Ts to the value at ζ = ∞, a characteristic constant (Tm)∞ is obtained. The (Tm)∞ was 175°C. for the sample studied in propylene carbonate. The interfacial free energy, σe, calculated from the melting point and the step height is of the order of 1950 cal./mole of emerging chain repeat unit, or 45 ergs/cm.2 as compared to 1900 cal./mole or 70 ergs/cm.2 for polyethylene. It appears that the surface free energies of various organic polymers are remarkably similar. Although the degree of crystalline perfection of polyacrylonitrile is inferior to that of organic crystals with three‐dimensional order, polyacrylonitrile displays a crystallization behavior similar to other semicrystalline polymers; this conclusion is supported by the linear relationship between Ts and Tc, the variation of the step height with the crystallization temperature, and the sigmoid relationship of the fractional change in specific volume as a function of time during crystallization.
Studies in cyclocopolymerization. Relative rates of addition in the free radical‐initiated copolymerization of 1,4‐dienes and substituted olefins
Authors: Barton John M. , Butler George B. , Chapin Earl C.
Published: April 2003

A general copolymer composition equation is developed for the cyclocopolymerization of 1,4‐dienes (M1) and monoolefins (M2). The general equation relates copolymer composition to monomer feed composition in terms of five reactivity ratio parameters. When cyclization is very rapid relative to other chain propagation steps the general equation simplifies to the form: n = (1 + r1x)(1 + rcx)/[rcx + (r2/x) + 2], where n = [m1]/[m2] in the copolymer, x = [M1][M2] in the monomer feed, and r1, r2, and rc are reactivity ratios for the chain propagation steps of diene, monoolefin, and cyclized radicals, respectively. The theory is applied to the free radical initiated copolymerization of (A) divinyl ether/maleic anhydride, (B) 1,4‐pentadiene/maleic anhydride, (C) divinyl ether/N‐phenylmaleimide, (D), divinyl ether/acrylonitrile; and (E) 1,4‐pentadiene/acrylonitrile. Systems A, B, and C form alternating copolymers of composition n = 0.5. For system D, r1 = 0.024, r2 = 0.938, rc = 0.017. For system E, r1 ⋍ rc ⋍ O, r2 = 1.13.
Copolymerization of 4‐cyclopentene‐1,3‐dione with styrene
Authors: Winston Anthony , Hamb F. Lynn
Published: April 2003

The copolymerization of 4‐cyclopentene‐1,3‐dione (D) with styrene (S) is reported. The copolymers were prepared by heating sealed tubes containing the monomer feeds and azobisisobutyronitrile. The copolymers exhibited infrared bands for the phenyl and β‐diketone groups, indicating that copolymerization had occurred. The copolymers were completely insoluble in all solvents. Some swelling was observed in tetrahydrofuran, nitrobenzene, and aqueous sodium hydroxide. From the compositions of the copolymers, as determined from the carbon and hydrogen analyses, it was found that the copolymers were about 40 mole‐% styrene over an appreciable range of feed compositions (0.1–0.6 mole fraction styrene). The results at styrene feeds <0.5 were in general agreement with the equation: d[D]/d[S] = 1 1/2 + (kDD/2kDCK[S]). This equation was derived on the basis of monomer complex (C) participating in the propagation and a penultimate effect preventing the occurrence of a sequence of three dione units.
Differential thermal analysis of the cocrystal peak in linear–high pressure polyethylene blends
Authors: Clampitt Bert H.
Published: April 2003

A DTA study of over 60 linear–high pressure polyethylene blends is reported. From this study a preliminary phase diagram for this type of system is derived; however, the main emphasis is on the nature of the cocrystal peak. The results appear to indicate that there are two classes of cocrystals in linear–high pressure polyethylene blends with the linear component being responsible for the division of the blends into two groups. The property of the linear component which is responsible for this division is related to the crystallite size of the pure linear crystal. While the division of the blends into two groups is primarily dependent on the linear component, the magnitude of the cocrystal peak height is dependent on the high pressure polyethylene component. Low melt index and low branching of the high pressure polyethylene favor large cocrystal formation. Indeed, resins containing 30 methyls per 1000 carbons do not possess a cocrystal peak.
Sound velocity in polyethylene at ultrasonic frequencies
Authors: Levene A. , Pullen W. J. , Roberts J.
Published: April 2003

An ultrasonic interferometer was used to measure the sound velocity at 1.45 Mcycle/sec. and 20°C. in small disk samples of polyethylene. A plot of sound velocity versus density does not conclusively show that the relationship is linear or cubic. The velocities were converted to dynamic Young's moduli by using Poisson's ratios given by Schuyer. Comparison of these results with the lower frequency moduli of Davidse, Waterman, and Westerdijk indicates that the test conditions may well be close to those pertaining when the viscoelastic effects have been more or less eliminated.
Rate of densification of gel during coagulation of viscose
Authors: Gupta Maharaj K. , Marker Leon , Wellisch Eric , Sweeting Orville J.
Published: April 2003

We have developed a simple method which permits measurement of the rate of densification of the gel forming during the coagulation of viscose and in effect experimentally separates the coagulation process from the regeneration process. The method is based on changes in density of a drop of viscose as it passes through a column of a salt solution. In devising the experimental program, three assumptions have been made: (1) Stokes' law is assumed to be valid for the movement of a drop of viscose through a column of a salt solution; (2) the volumes of sodium cellulose xanthate and water are assumed additive in viscose, permitting the calculation of the density of anhydrous xanthate; (3) the mechanics of loss of water initially from a surface are assumed to be the same whether the area is planar or spherical, i.e., a drop of viscose initially dehydrates in the same manner as does a thin film. Using this experimental technique, we have studied the coagulation of viscose as a function of salt index, ripening temperature, type of salt, and concentration of salt.
Stereospecific polymerization of 1,3‐butadiene. II. Kinetic studies
Authors: Mazzei A. , Araldi M. , Marconi W. , De Maldé M.
Published: April 2003

The kinetics of the polymerization of butadiene with catalysts prepared from some aluminum hydride derivatives, AlI3, and TiCl4 was investigated. It was found that the reaction rate is first‐order with respect to monomer and catalyst concentration when the catalyst is prepared in the presence of monomer. In such a case the polymerization takes place in a homogeneous medium. When the catalyst is prepared in the absence of monomer, the reaction takes place in an heterogeneous medium and the rate is still first order with respect to monomer concentration, while the dependence on the catalyst concentration is no longer linear. The activation energy of the entire process is about 8500 cal./mole. In addition, a comparison is made of the polymerization rate of catalysts obtained from AlI3, TiCl4, and various aluminum hydride derivatives.
Heat and entropy of fusion of isotactic polypropylene
Authors: Krigbaum W. R. , Uematsu Ichitaro
Published: April 2003

Heats and entropies of fusion of polymers are customarily evaluated through melting point depression measurements with the assumption that the observed and thermodynamic melting points are nearly identical. However, it has recently become evident that the crystal surface free energy is not negligible, so that apparent melting points measured dilatometrically or calorimetrically are low by perhaps 5–15°C. the status of the accumulated body of thermodynamic data is rendered still more uncertain by the possibility that the surface free energy may vary in a systematic manner with diluent concentration. To investigate this question, dilatometric data were obtained by two procedures for tetralin solutions of isotactic polypropylene. The first set of measurements was performed upon samples which had been slowly cooled from the melt, while in the second procedure the apparent melting point was measured as a function of the isothermal crystallization temperature. Extrapolation of the latter data gave tM° = 186 ± 2°C., a value of 12°C. higher than the apparent melting temperature observed according to the first procedure; however, the heats of fusion obtained by the two methods agreed to within the experimental error. A possible explanation for this behavior may be offered by the observations that both the parameter β of Hoffman and Weeks, and the ratio of the temperature of maximum crystallization rate to the melting temperature, are independent of diluent concentration over the range investigated. This suggests that the addition of diluent does not affect the distribution of fold lengths. If this behavior proves to be general, dilatometric heats of fusion will be reinstated as valid thermodynamic data for polymers.
Investigation of comonomer distribution in ethylene copolymers with thermal methods
Authors: Bombaugh Karl J. , Clampitt Bert H.
Published: April 2003

This paper is an extension of an earlier work in which thermal pyrolysis gas chromatography and differential thermal analysis were combined to elucidate comonomer distribution in ethylene–acrylate copolymers. In this work consideration is given to the thermal degradation products of ethylene–acrylate and ethylene–vinyl acetate copolymers. The influence of cracking temperature is considered in terms of the utility of the data. The DTA measurements are primarily concerned with the crystallization of the ethylene chains between the branch points. Indeed, a linear relationship between DTA crystallinity and branching is indicated.
Preparation and hyperfiltration properties of a polyacrylate–cellophane membrane
Authors: Baldwin W. H. , Holcomb D. L. , Johnson J. S.
Published: April 2003

Preparation of a carboxylic ion‐exchange membrane by grafting poly(acrylic acid) onto cellophane is described. This membrane filters appreciable fractions of dissolved salt from solutions 1M and less in NaCl; flow rates through the membrane at 2500 psi are 0.5 cm./hr. and higher. Comparison is made of salt rejection properties and flow rates with a film of cellulose acetate in which rejection does not depend on fixed ionizable groups. Rejections of salts having ions of different charges are presented. Experimental apparatus for hyperfiltration is described.
Mechanisms of thermal degradation of phenolic condensation polymers. II. Thermal stability and degradation schemes of epoxy resins
Authors: Lee Lieng‐Huang
Published: April 2003

The thermal degradation of uncured and cured epoxy resins was studied. By the use of the thermogravimetric analysis, the thermal stability of the cured epoxy resins, D.E.N. 438 and D.E.R. 331 resins, was compared with those of polycarbonate and polyphenylene sulfide. The resins, including novolac resin and D.E.R. 669 resins, were pyrolyzed, and their volatiles were determined with a mass spectrometer. The experimental results showed that the phenolic compounds were the major volatile products. Thus, the data do not support the degradation scheme proposed by Neiman and co‐workers. Several degradation schemes for epoxides are proposed based on the principles of the cleavage of simple ethers and the products obtained from the pyrolysis study.
Diffusion‐controlled termination in free radical polymerizations
Authors: Burkhart R. D.
Published: April 2003

The theory of Kuhn and Kuhn for the diffusion of polymer chain ends has been applied to the termination mechanism for free radical polymerizations, proposed by Benson and North. By using the dimensions for a Gaussian chain, an expression for this diffusion‐controlled termination rate constant in terms of solvent viscosity, polymer chain flexibility, and chain length has been derived. The theory predicts that the termination rate constant is inversely proportional to solvent viscosity for flexible polymer chains and independent of solvent viscosity for very stiff polymer chains. Several previously reported effects of solvent viscosity on the termination rate constant may be explained with the present theory. The effect of polymer chain length on the termination rate constant depends upon the range of chain lengths considered and upon the relative chain stiffness. The necessity of taking into account the frequency distribution of radicals which exists during polymerization is discussed. Calculated values of the termination rate constant have been carried out with the use of values for the various parameters which are believed to be typical of vinyl polymers in solution. These calculated values are in general agreement with those which are usually obtained experimentally.
Elastic, strength, and viscous properties of polymer (polyethylene and polystyrene) melts
Authors: Vinogradov G. V. , Belkin I. M.
Published: April 2003

A description is given of a rotational elastoviscometer with a very rigid dynamometer designed for the investigation of the rheological properties of polymer melts and concentrated polymer solutions by the constant deformation rate method. Alkathene‐2 and polystyrene were studied over a wide range of temperatures. The deformation dependences of the shear stress obtained for these polymers became non‐monotonic with rising deformation rates. This was characteristic of the reversible destruction of the polymer structure which increased with growing rates of shear. The maximum on the shear stress vs. deformation curve enabled the ultimate shear strength to be determined as a specific point on this curve. The ultimate shear strengths were reached at a deformations of several hundred per cent, while steady flow conditions were attained at deformations of several thousand per cent. With rising deformation rates, the time for attaining the ultimate strength decreased, as did, to some extent, the time of attainment of steady flow conditions. The deformation corresponding to the ultimate strength increased slightly, and the deformation corresponding to the attainment of steady flow conditions increased greatly with growing deformation rates. The activation energies of steady flow and of the passage through the ultimate strength were close in value. The dependence of the modulus of highly elastic deformation in a polymer of intact structure on the deformation rate is expressed by a function of saturation. The saturation corresponds to the deformation rates at which viscous flow cannot develop without breakdown of the melt structure (without passage through the ultimate strength).
Ziegler polymerization of olefins. V. Site removal and site activation by electron donors
Authors: Boor J.
Published: April 2003

Electron donors having different structures have been incorporated into the Ziegler catalyst, ZnEt2 + γ‐Alx Tiy Clz‐160, in order to understand the site removal and the site activation processes. Donors which were studied in the present work include: azulenes, unsaturated compounds, aromatics, substituted pyridines and quinolines, cyclopentadienyl compounds of V, Cr, Ni, and Co, (C6H6)2Cr, and PF3. Their effect on the polymerization of propylene was determined. It was found that the site removal and the site activation processes could be brought about by many different donors. Variations were noted among the donor types. This finding shows that a variety of isolated sites with different abilities to coordinate and orient the α‐olefin are found on the crystal surface of the titanium chloride cocatalyst.
Polyquinoxalines. II.
Authors: Stille J. K. , Williamson J. R. , Arnold F. E.
Published: April 2003

Five new high molecular weight polyquinoxalines have been prepared by the reactions of combinations of two tetramines, 3,3′‐diaminobenzidine (II) and 3,3′,4,4′‐tetraminodiphenyl ether (IV), with the three bisglyoxals, 1,4‐phenylenediglyoxal (I), 1,3‐phenylenediglyoxal (VI), and 4,4′‐oxydiphenylenediglyoxal (IX). Solution and melt polymerization techniques afford intermediate molecular weight polymers which can be converted to high molecular weight samples (ηinh > 1.0) by heating at 375°C. under reduced pressure. All the polyquinoxalines have excellent thermal stability both in nitrogen and in air. Of these polymers, poly[2,2′‐(4,4′‐oxydiphenylene)‐6,6′‐oxydiquinoxaline] (XI) has the highest solubility in hexamethylphosphoramide (HMP), and films can be cast from intermediate molecular weight (ηinh = 0.3–0.7) polymer solutions in HMP. Tough, insoluble films can be obtained by heating the cast films in nitrogen or under reduced pressure to 350–400°C.
Copolymerization of methyl methacrylate with unsaturated esters of granular starch
Authors: Brockway C. E.
Published: April 2003

Methyl methacrylate readily copolymerizes with methacrylate ester groups present at a degree of substitution of about 0.1 in granular starch. This is shown by (1) over 50% grafting efficiency by initiation with azoisobutyronitrile; (2) higher grafting efficiency with than without the methacrylate groups when initiation is by peroxide; (3) crosslinked structure of the copolymers obtained; (4) crosslinks which persist in the PMMA recovered after acid hydrolysis to remove starch. By the same set of criteria, maleate half‐ester groups in granular starch copolymerize with methyl methacrylate hardly at all.
Proton magnetic resonance study on the structures of phenol–formaldehyde resins
Authors: Woodbrey James C. , Higginbottom Harold P. , Culbertson Harry M.
Published: April 2003

Because of their commercial importance, the reaction sequences and structures of resins produced when phenol reacts with formaldehyde have been studied by numerous different chemical and physical methods. Many details concerning these reactions and complex chemical structures are still not entirely understood. Most of the experimental methods used have yielded only qualitative information. Many of these methods have been applicable only to the lower molecular weight portions of soluble prepolymers. The present work describes proton magnetic resonance (PMR) methods which yield detailed and quantitative number‐average structures for any soluble phenol‐formaldehyde resin. It is shown that benzyl‐type hemiformals make substantial contributions to the structures of many resoles and that these functionalities exhibit relatively high stability under certain conditions of initial cure. The structures of several resins are discussed in terms of certain aspects of reactions which occurred during the resin syntheses. These reactions include hydroxymethylations and condensations yielding diphenylmethane‐type and dibenzyl ether‐type bridges. To define the mechanisms and rates of the various reactions at different temperatures and under different catalytic conditions, a much more detailed study is required. Potentially, the PMR methods described can provide most of the necessary quantitative data.
Dye‐sensitized photopolymerization. I. Polymerization of acrylamide in aqueous solution sensitized by methylene blue–triethanolamine system
Authors: Chen Catherine S. Hsia
Published: April 2003

The polymerization of aqueous acrylamide induced by visible light in the presence of methylene blue–triethanolamine as the sensitizing system has been investigated. The polymerization was found to follow a nonsteady‐state kinetic scheme. The rate was proportional to the first power of the absorbed light intensity and approximately proportional to the initial monomer concentration. The rate passed through a maximum as a function of the initial dye concentration. The molecular weights of the polymers were in the range of one million. The molecular weights were independent of the absorbed light intensity, essentially directly proportional to the initial monomer concentration, and decreased logarithmically with the initial dye concentration. Both spectroscopy and polymerization behavior suggest that the monomeric form of the dye is a photosensitizer while the associated form is a chain terminator. The kinetic chains were terminated unimolecularly, and the molecular weights were governed by a chain transfer process.
Dilute solution properties of nylon 66 dissolved in 2,2,3,3‐tetrafluoropropanol
Authors: Saundres P. R.
Published: April 2003

Light‐scattering and viscosity measurements have been made on dilute solutions of nylon 66 dissolved in 2,2,3,3‐tetrafluoropropanol. The polyelectrolyte behavior of polyamides in carefully distilled solvent is due to traces of water in the solvent. If care is taken to exclude water, 2,2,3,3‐tetrafluoropropanol is a nonionic solvent for nylon 66. The polyelectrolyte effects of nylon 66 in the wet solvent can be repressed by the addition of sodium trifluoroacetate. The action of the sodium trifluoroacetate is to immobilize the water molecules in solution rather than to act as an electrostatic screen. Molecular weights estimated from the light‐scattering data and the relation between intrinsic viscosity and second virial coefficient are identical with the results based on measurements in the solvent system formic acid–water–sodium formate.
Crystalline state of cellulose in fresh and dried mature cotton fiber from unopened bolls as studied by x‐ray diffraction
Authors: Heyn A. N. J.
Published: April 2003

The crystallinity of cellulose in the undried cotton fiber, fresh from the unopened but mature boll, was studied by x‐ray diffractometer methods and compared with the crystallinity of portions of fibers from the same samples either dried directly or from which the water has been removed in various “indirect” ways calculated to better preserve the original structure including: (a) Solvent exchange, (b) freeze‐drying, (c) drying above the critical temperature of liquids and (d) drying after the cellulose of the wet fiber has been crosslinked. The difference in crystallinity observed between directly and indirectly dried fibers indicates that a crystallization process must take place during the direct drying of the water‐wet fiber. This crystallization process is promoted by the presence of water and inhibited or prevented when the fiber is dried indirectly. An increase of the degree of crystallinity due to wetting can be explained by assuming that the crystallization, which had been suppressed in the indirectly dried fiber takes place subsequently upon drying of the rewetted fiber. That the indirect methods preserve entirely or partially, such amorphous structure as is originally present is confirmed by the lower density and higher dyestuff accessibility of such fibers.
Heterogeneous polymer systems. I. Polymeric oil‐in‐oil emulsions
Authors: Molau Gunther E.
Published: April 2003

A novel class of emulsions has been introduced. Emulsions of this class comprise two immiscible polymer solutions and a graft copolymer as an emulsifying agent. The name polymeric oil‐in‐oil emulsions (POO emulsions) has been suggested for the new emulsions. The concept has been verified with several systems of polymer solutions. The polymers used here are poly(ethyl acrylate), poly(methyl methacrylate), polystyrene, polyvinyltoluene, poly‐p‐tert‐butylstyrene, and a styrene/acrylonitrile copolymer.
Branching in poly(butadiene‐co‐styrene). IV. Retardation of radiation‐induced branching
Authors: Blachford J. , Robertson R. F.
Published: April 2003

The composition and yield of the evolved gas and the resulting changes in infrared and ultraviolet spectra have been examined for the irradiation of poly(butadiene‐co‐styrene). Apart from crosslinking, the major changes which occurred during the reaction were the evolution of hydrogen and the destruction of vinyl groups. For every 100 e.v. of radiation energy absorbed 0.45 molecules of hydrogen were evolved, G(H2) = 0.45, and 6.1 vinyl groups were destroyed, G(‐vinyl) = 6.1. These results have been compared with the yield of crosslinks, Gx = 1.60. Addition of N‐phenyl‐β‐naphthyl‐amine to the polymer reduced the gas yield to a greater extent than predicted by the “mixture law” (which states that the yield of a product from component X is directly proportional to the electron fraction of X). Over the additive concentration range of 2–11%, the gas yield was constant. This behavior is identical to that found previously for the crosslink yield. An explanation of these results has been given which involves the occurrence of processes which exhibit a negative deviation from the mixture law together with processes which exhibit a positive deviation. The destruction of the additive during the irradiation of a sample containing initially 0.52% additive has been determined. The results indicate that the additive protects the polymer mainly by charge transfer or excitation energy transfer.
Viscosity behavior of branched and linear potassium carboxymethyl dextrans
Authors: Pasika W. M. , Cragg L. H.
Published: April 2003

Samples of branched and linear dextran of near identical intrinsic viscosities have been carboxymethylated to varying degrees and converted to the potassium salts. The reduced viscosity–concentration curves of the branched and linear carboxymethyl dextran polyelectrolytes of identical degree of substitution in aqueous potassium chloride solutions (0.001N and 0.0005N) were compared. Significant differences were observed to exist. At low degrees of substitution (0.06–0.20 carboxymethyl group per anhydroglucose unit) the branched macroion possessed larger reduced viscosities than did its linear counterpart. At a higher degree of substitution (ca. 1.0 carboxymethyl group per anhydroglucose unit) the reduced viscosity curves of the branched and linear macroions crossed. These differences were shown to be independent of shear rate, molecular weight and molecular weight distribution. It is concluded that branching is responsible for the differences in the reduced viscosity–concentration behavior of the branched and linear potassium carboxymethyl dextran samples because of the higher charge density in the branched macroion.
Investigation of thiazole polymers for heat‐resistant fibers and films
Authors: Sheehan W. C. , Cole T. B. , Picklesimer L. G.
Published: April 2003

Seventeen thiazole polymers were prepared by the polycondensation of bis‐α‐bromoketones with dithioamides, and the polymers were investigated for preparing heat‐resistant fibers and films. Tough fibers and films were made from four of the polymers; however, these polymers had low melting points (164–250°C.). All of the other polymers studied except these did not melt below 500°C., and they had excellent thermal stabilities, but they did not have good fiber‐ and film‐forming properties because of their low molecular weights. All of the polymers prepared had some crystallinity. Two of the polymers were soluble in organic solvents; the other were soluble only in strong acids. Model compounds of four of the polymers were prepared, and the properties and structures of the compounds were compared with those of the polymers.
Study of swelling in two new ion exchange membranes
Authors: Hodgdon Russell B. , Boyack James R.
Published: April 2003

The synthesis of two new ion‐exchange membranes is presented. These are a partially sulfonated polystyrenesulfonic acid resin and an interpolymer system composed of sulfonated polystyrene–divinylbenzene polymerized within a poly(vinylidene fluoride) matrix. Each of these systems allows control of ion exchange capacity and physical properties over a wide range. The second is especially useful, in that ion‐exchange capacity and swelling characteristics may be controlled independently. It also has the distinct advantage of giving a clear, flexible film even with high crosslinking. On the basis of certain simplifying assumptions an equation is derived which permits approximate calculation from equilibrium water uptake data of an elastic constant which measures the resistance of the membrane to swelling forces. Equilibrium water content data for the two membrane systems are treated with this equation and analyzed in terms of internal structure.
Ferrocene‐containing polymers. V. Polycondensation of N,N‐dimethylaminomethylferrocene
Authors: Neuse Eberhard W. , Quo Edward
Published: April 2003

The self‐condensation of the ferrocenyl Mannich base, N,N‐dimethylaminomethylferrocene, in the presence of a ZnCl2HCl catalyst system in the melt phase leads to soluble polymers containing ferrocenylene units interlinked by methylene groups. The crude condensation products exhibit number‐average molecular weights in the range 4000–8000. Elemental and infrared spectroscopic analyses as well as viscometric data show the structure to be essentially identical with that of the polymer derived from hydroxymethylferrocene described in an earlier communication. The optimum molar ratio of the reactants (Mannich base, ZnCl2, and HCl) is 2:1:2. Dimethylammonium tetrachlorozincate has been isolated as by‐product, and an intermediary complex composed of Mannich base, ZnCl2, and HCl in the same 2:1:2 ratio has been intercepted during the polycondensation. Some mechanistic inferences are discussed.
Poly‐α‐cyanostyrene
Authors: Hughes L. J. , Perry Eli
Published: April 2003

The monomer α‐cyanostyrene polymerized at a very slow rate under the influence of free‐radical initiators. Rapid polymerization to high molecular weight material was achieved by using anionic initiators (tri‐n‐butylphosphine and tetrakisdimethylaminotitanium). The polymer made at −78°C. was colorless, fusible, soluble, and had a number‐average molecular weight of over 5,000. The polymer prepared at 0°C. was brown, insoluble, and infusible. None of the polymer showed order in the x‐ray diagram. The rate of dimerization of α‐cyanostyrene under a wide variety of conditions was measured. Two new derivatives of the intermediate, 3‐(N,N‐dimethylamino)‐2‐phenylpropionitrile were prepared: the methiodide, m.p. 242–245°C. (decomp.), and the picrate, m.p. 116.5–117.5°C.
Preparation and aromatization of poly‐1,3‐cyclohexadiene and subsequent crosslinking. III
Authors: Cassidy P. E. , Marvel C. S. , Ray Suvas
Published: April 2003

The polymerization of 1,3‐cyclohexadiene with n‐butyllithium has given white polymers with inherent viscosities up to 0.23 and conversions to 98%. Bromination and pyrolysis of these polymers lead to polyphenyls which can be successfully sulfonated. then fused in molten alkali to give phenols, and finally crosslinked with formaldehyde. The final products display good heat stability, in that there is no weight loss on heating to 400°C. and only 30% loss at 900°C.
Reactivity of condensed‐ring hydrocarbons as polymerization retarders
Authors: Ihrig Judson L. , Sood Satya Pal
Published: April 2003

Seventeen condensed‐ring hydrocarbons have been investigated as retarders or inhibitors of styrene and methyl methacrylate polymerization. Rates were measured dilatometrically. Nine of the compounds tested retarded or inhibited the polymerization of styrene, but methyl methacrylate appears not to be affected by this class of substances. Styrene data obtained are examined in the light of Fukui's “frontier electron” formalism for correlating structure and reactivity. It is concluded that the principal locus of radical attack is at the meso carbon atoms, Fukui's (Ss) region, and that a substantial value of the (Ss) density index is required for retardation, although when the molecule also possesses an appreciable (Sp) index, a synergistic action is noted. The point is made that since condensed‐ring hydrocarbons do not have “functional groups” in the sense that quinones and other retarders do, the effect of monomer reactivity is likely to be of added importance in determining retarder efficiency. The lack of retardation effects in polymerizing methyl methacrylate is interpreted from this standpoint. A reverse chaintransfer reaction is tentatively proposed to account for the observed behavior.