bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization by oxidative coupling. IV. Polymerization of 4‐bromo‐ and 4‐chloro‐2,6‐dimethylphenol and preparation and decomposition of the silver and copper salts of certain other phenols
Authors: Blanchard H. S. , Finkbeiner H. L. , Russell G. A.
Published: April 2003

In the present paper it has been shown that the 4‐halo‐2,6‐dimethylphenols can be polymerized to high molecular weight poly‐2,6‐dimethylphenylene ethers by the action of cupric ions, providing pyridine is also present. This reaction requires a stoichiometric amount of cupric ions and probably proceeds through complexed phenoxy radicals. Although the polymerization cannot be initiated by catalytic quantities of cupric ions, the same cupric salts which are active in the stoichiometric reaction will initiate the polymerization of the 4‐halo‐2,6‐dimethylphenols in basic solution. Here too, the products are high molecular weight polyarylethers and this reaction probably involves the displacement of halide ions by phenoxy radicals. The presumed di‐2,4,6‐trihalophenolate–bispyridine–copper(II) complexes were prepared and characterized. These complexes were decomposed under a variety of conditions, yielding polyhalophenylene ethers, which are highly branched as evidenced by their low intrinsic viscosities. Moreover, they are also terminated, probably through dioxin formation, since they show little or no residual hydroxyl in the infrared. Similarly, the polyhalophenylene ethers prepared by decomposition of the silver salts are also branched and terminated. In this connection, however, silver 4‐chloro‐ and silver 4‐bromo‐2,6‐dimethylphenolates were prepared and decomposed to a poly‐2,6‐dimethylphenylene ether of molecular weight 1800–2200 possessing one halogen and one hydroxyl per polymer chain. The infrared spectrum of this polymer, with the exception of the hydroxyl region, agrees in detail with the infrared spectrum of high molecular weight poly‐2,6‐dimethylphenylene ether prepared by oxidation of 2,6‐dimethylphenol and thus provides a proof for the gross structure of the polymer. Finally, it was found that the blue to blue‐green solutions produced from the decomposition of certain of the copper complexes and the silver salts, respectively, are diamagnetic. This finding mitigates against the participation of phenoxy radicals as the active species in these polymerizations.
Complex metaphosphate polymers
Authors: Mehrotra R. C. , Gupta V. S.
Published: April 2003

The complexation reaction of the polymeric metaphosphate ions has been studied with copper, calcium, barium, zinc, lead, and iron ions by physicochemical measurements indicating the formation of complex derivatives of the type (NaxM1−x/aPO3)n where a is the valency of the metal ion complexed. It has been possible to synthesize a large number of derivatives for the first time by the reactions of the following type:

equation image

The progress of the reaction has been studied on a Stanton Thermogravimetric balance and the properties (composition, viscosity, molecular weight, and conductivity) of the transparent glassy complex metaphosphates have been studied in detail throwing fresh light on Graham's salt itself as well as these new derivatives.
Polymerization by oxidative coupling. II. Oxidation of 2,6‐disubstituted phenols
Authors: Hay Allan S.
Published: April 2003

Many 2,6‐disubstituted phenols are readily oxidized with oxygen, a tertiary amine and a copper (I) salt being used as catalyst. The products are diphenoquinones (I) or 1,4‐polyphenylene ethers (II):
magnified image
The effect of variation of the substituents on the phenol and the infrared spectra of the polymers is discussed. Amine complexes of copper salts are the only effective catalysts found for the polymer‐forming reaction. The effect on the catalyst of varying the copper salt and the ligand is discussed.
Polymerization by oxidative coupling. III. Mechanistic type in the copper–amine catalyzed polymerization of 2,6‐dimethylphenol
Authors: Endres G. F. , Kwiatek Jack
Published: April 2003

Since the oxidative polymerization of 2,6‐disubstituted phenols through copper–amine catalysis represents a novel polymerization reaction, particular interest attaches to the question of mechanistic type, i.e., stepwise or chain reaction. In the oxidation of 2,6‐dimethylphenol in the presence of copper(I) chloride in pyridine solvent, the dependence of the degree of polymerization on the extent of reaction corresponds to a stepwise reaction of the type where polymer growth occurs through reaction of polymer molecules with each other, as well as with the monomer. The reaction is thus formally analogous to a bifunctional polycondensation. The isolation of low intermediate polymers from the reaction mixture and the facile polymerization of these intermediates or the synthetic dimer or trimer in the absence of monomer supports this view. Comparison of the infrared spectra of the intermediates with the model compounds supports the poly(1,4‐phenylene ether) structure, and the absorbance in the hydroxyl region indicates one hydroxyl group per molecule. Partially oxidized reaction mixtures also yielded small amounts of the compound 4,4′‐dihydroxy‐3,5,3′,5′‐tetramethyldiphenyl, the precursor of the tetramethyldiphenoquinone formed as by‐product on complete oxidation. A study of the rates of oxygen absorption in the polymerization of the monomer, dimer, trimer, and intermediate polymer showed little dependence on the degree of polymerization from the dimer upward.
Condensation polymers from 3,9‐bis(7‐carbomethoxyheptyl)‐2,4,8,10‐tetraoxaspiro[5.5]undecane. II. Poly(amide‐acetals)
Authors: Pryde E. H. , Moore D. J. , Teeter H. M. , Cowan J. C.
Published: April 2003

3,9‐Bis(7‐carbomethoxyheptyl)‐2,4,8,10‐tetraoxaspiro[5.5]undecane (the pentaerythritol acetal of methyl azelaaldehydate) was found to undergo condensation polymerization with diamines to give linear polymers, either alone or in conjunction with dimethyl azelate. These novel, linear poly(amide‐acetals) were susceptible to crosslinking by p‐toluenesulfonic acid and by various metal oxides and salts, such as zinc oxide, zinc acetate, litharge, and magnesium oxide. The crosslinked polymers were insoluble, infusible, transparent solids which were strongly adherent to glass.
Chain propagation constants in the cationic polymerization of styrene
Authors: Pepper D. C. , Reilly P. J.
Published: April 2003

Perchloric acid initiates reproducible polymerization of styrene (unaffected by traces of water) in ethylene dichloride and mixtures with carbon tetrachloride over the temperature range 25–30°C. The rate of polymerization is accurately first order in monomer concentration, with a rate constant (k) proportional to the initial concentration of perchloric acid. The constant k/[HClO4]0 is identified with the rate constant for the propagation reaction (kp), since in these polymerizations there is no true termination step, and the initiation rate is believed to be so fast as not to be rate‐determining. Values of the rate constants, activation energies, and frequency factors are presented. Ep and log kp show linear relationships with the reciprocal of the dielectric constant (ε) of the solution in ethylene dichloride–carbon tetrachloride mixtures over the range ε = 5–10. In solution in ethyl chloride, and in ethylene dichloride mixtures with nitrobenzene and nitroethane, the rates are anomalously low.
Light‐scattering studies of crosslinking unsaturated polyesters with methyl acrylate
Authors: Gallacher Lawrence , Bettelheim Frederick A.
Published: April 2003

The Debye‐Bueche theory of light scattering of inhomogeneous solids was applied to a three‐dimensional crosslinking process. A series of unsaturated polyesters of an average degree of polymerization of 7.4 were prepared in which the double bond spacings were varied. These polyesters were crosslinked with methyl acrylate in 1 : 2, 1 : 3, and 1 : 4 polyester double bond: monomer ratios. The crosslinking process was followed up with measurements of the light‐scattering envelope beyond the gel point. Parameters corresponding to the extent of inhomogeneities and the mean square deviation of the local refractive index from the average were evaluated. The data were interpreted by proposing a gelation mechanism which can be separated into three phases by optical means.
Thermal x‐ray diffraction study of highly acetylated cotton cellulose
Authors: Conrad Carl M. , Creely Joseph J.
Published: April 2003

Cotton cellulose in the form of scoured yarn was acetylated at 15°C. in a mixture of isopropyl acetate and acetic anhydride in the presence of perchloric acid catalyst to various degrees from 1.1 to 2.9 acetyl groups per anhydroglucose unit. For comparative purposes some of the yarn was acetylated at 20°C. by a more conventional method with a 3:1 mixture of acetic acid and acetic anhydride, also with perchloric acid as catalyst. The products were studied by x‐ray diffraction, both at room temperature and, with the aid of a specially controlled diffractometer furnace, at elevated temperatures. Diffractograms of the products show that as acetylation proceeds, the crystal structure of native cellulose disappears progressively until at a substitution of 2.93 acetyls per anhydroglucose unit it is nearly all gone. Examination with the diffractometer furnace shows in an impressive way the acetyl content and temperature at which cellulose acetate first begins to crystallize, the progressive increase in crystallizable acetate as acetylation proceeds, the temperature range over which the crystal structure is stable, the temperature at which it melts, and finally the temperature at which the acetate eventually carbonizes.
The anionic polymerization of acrylonitrile
Authors: Cundall R. B. , Eley D. D. , Worrall J.
Published: April 2003

The polymerization of acrylonitrile initiated by diethyl sodiomalonate in dimethylformamide has been investigated. The degree of polymerization was found to be independent of the monomer conversion but was dependent on the extent of polymerization. The polymers produced were examined for functional groups by infrared spectroscopy. An anionic mechanism involving hydride ion transfer to monomer has been suggested. The kinetics of the reaction can be followed because of the slow initiation step and are found to be governed by the rate expression −d[M]/dt = k[M]2[C]. The decrease in DP with increasing conversion is due to degradation of the polyacrylonitrile by basic ions. The ratios of the rate constants for both the monomer and polymer transfer reactions to the rate constant for propagation have been determined. The coloration of the polymers appears independent of the degradation reaction.
Kinetics of the oxidation of cotton with hypochlorite in the pH range 5–10
Authors: Epstein Joseph A. , Lewin Menachem
Published: April 2003

The rate of consumption of oxygen by cotton and cottom cellulose from solutions of hypochlorite in the pH range 5–10 has been studied. Kinetic plots were obtained either by periodically titrating aliquots or by automatically recording the amount of alkali required to keep the pH constant. In the case of pure cotton cellulose the plots are linear, whereas in the case of cotton the plots consist of two parts, an initial, rapid oxidation of the impurities followed by a slower, linear oxidation of the cellulose. The dependence of the rate of oxidation on the pH may be expressed by:

which also accounts for the dependence of the rate on the initial concentration of oxidant. A mechanism is suggested in terms of the free‐radical OH and Cl2OOH.
Functional groups and degradation of cotton oxidized by hypochlorite
Authors: Lewin Menachem , Epstein Joseph A.
Published: April 2003

Functional groups and degradation of cotton oxidized by hypochlorite at several pH values in the range 5–10 were studied. The carboxyl group content of the oxidized cottons increases, while the aldehyde and ketone group contents decrease with increase in pH. Approximately 40% of the oxidant consumed is accounted for by the functional groups at all pH values. The ratio of carboxyl, aldehyde, and ketone groups formed per scission is 1–1.5:3:3.5 at the acidic pH range and 5:0.8:0.0 at pH 10. Oxygen consumption per scission is 26 atoms, out of which 10.4 atoms are accounted for by the functional groups. The rest of the oxygen is explained by oxidation of the soluble products of the short chain material in the fiber phase and by the functional groups of the short chains with D.P. up to 37. The degradation was found to be random at the whole pH range studied, as proved by the ratio of the number‐average and weight‐average molecular weights and by the linearity of the plot of log [η] vs. log (Oc + Oc0) where Oc is the oxygen consumed and Oco a constant. It is suggested that the degradation and oxidation reactions occur simultaneously and, at a given pH, with similar rates, so that all carbon atoms of an anhydroglucose unit in all chains of the amorphous phase will have a similar probability of being attacked.
Investigation of the mechanism of radiolysis of polymers containing quaternary atoms of carbon
Authors: Pravednikov A. N. , Teleshov E. N. , Shen‐Kan In , Medvedev S. S.
Published: April 2003

The initial act of interaction of radiation in a polymer, irrespective of its chemical structure, is abstraction of an electron with formation of a positive ion. Neutralization of this ion by the electron leads to the formation of an excited molecule which subsequently breaks up with formation of free radicals. The pattern of changes occurring in the structure of the polymer will evidently depend upon the stabilization mechanism of these radicals. The fact that up to now the process of crosslinking during the radiolysis of polymers containing quaternary carbon atoms (polyisobutylene, poly‐α‐methylstyrene) has not been observed as well as the available data concerning the pattern of temperature dependence of the destruction rate, make it possible to draw the conclusion that, in these polymers, due to steric hindrances, the radicals formed as a result of the abstraction of side groups or hydrogen atoms react with each other with the breaking of the backbone chain of the polymer molecule. A study of the radiolysis of copolymers of styrene with α‐methylstyrene in a swollen state showed that, in this case, because of the absence of steric hindrances, the interaction between the polymer radicals and radicals formed from the solvent results in the insertion of the solvent molecules into the polymer chains (demonstrated by a tracer technique); in this case the rate of degradation is decreased. Data obtained during the study of the radiolysis of the mixture of low molecular radioactive polyisobutylene with the conventional high molecular polyisobutylene show that interaction of radicals formed during the radiolysis of this polymer represents a kind of a disproportionation reaction accompanied by a transferal of the low molecular groups from one polymer radical to another.
Observations on the thermolytic decomposition of poly(tert‐butyl acrylate)
Authors: Schaefgen J. R. , Sarasohn I. M.
Published: April 2003

The thermolytic decomposition of crystalline and amorphous poly(tert‐butyl acrylate) was investigated. At elevated temperatures thin films of polymer were found to evolve isobutylene quantitatively. The weight loss curve has been analyzed, and a mechanism has been suggested involving a slow random decomposition of tert‐butyl ester groups followed by a faster decomposition of ester groups due to neighboring carboxyl groups. The rate and activation energy for isobutylene evolution in both sections of the weightloss curve are not very different for tactic and atactic polymer modifications.
Infrared study of the reaction of polyisoprene and polybutadiene with sulfur by use of deuterated polymers
Authors: Shipman J. J. , Golub M. A.
Published: April 2003

An infrared study of the sulfur vulcanization process was carried out with very high cis polymers of isoprene‐d8, isoprene‐3‐d1 and butadiene‐2,3‐d2 as well as the corresponding perprotio polymers. The use of deuterated polymers permitted more definitive interpretations of the spectral changes associated with vulcanization than those previously reported or were possible with the undeuterated polyisoprene or polybutadiene. It was concluded that the 10.4 μ band which develops in the spectrum of cis‐polyisoprene on extended reaction with sulfur at 140°C., and which has been the subject of some controversy, arises largely from a combination of saturated ring structures, such as cyclic sulfides, and conjugated double bonds, and to a minor extent from shifted double bonds. In addition to the processes leading to these various structures, crosslinking also occurs, but it apparently produces no important changes in the spectra of the polyisoprene vulcanizate other than that associated with a decrease in the original unsaturation. Polybutadiene, in contrast to polyisoprene, undergoes extensive cis—trans isomerization when extensively vulcanized with sulfur. Apparently, ring formation and concurrent production of conjugated double bonds also occur, but there is only a very slight amount of double‐bond shifting in polybutadiene.
Molecular weight of silk fibroin
Authors: Hyde A. J. , Wippler C.
Published: April 2003

The molecular weight of silk fibroin in several different solvent systems has been measured by light‐scattering techniques. The values obtained lie between 250,000 and 450,000, with a tendency to lie fairly close to 300,000. The difference between this value of the molecular weight and the values obtained by other workers is discussed.
Hydrodynamic studies on sodium carboxymethyl cellulose in aqueous solutions
Authors: Sitaramaiah G. , Goring D. A. I.
Published: April 2003

Sodium carboxymethyl cellulose was fractionated and the fractions characterized by light scattering, viscometry, and sedimentation and diffusion in 0.1M NaCl. Viscosity and sedimentation measurements were extended to lower ionic strengths by the isoionic dilution technique. Light‐scattering molecular weights were from 3 to 9 times higher than the values computed by the hydrodynamic equations of Svedberg or Mandelkern and Flory. It appeared that the light‐scattering method yielded anomalously high Mw values because of a small proportion of colloidal material persisting in solution in spite of the rigorous ultraclarification procedure adopted. Interpretation of the results was therefore based on the sedimentation‐diffusion molecular weights which ranged from 45,000 to 350,000. The exponents determined from the logarithmic dependence of [η] on MsD were 0.95 and 1.40, respectively, in 0.1M and 0.001M NaCl. This indicated an extended, non‐Gaussian configuration at low ionic strength due to expansion of the polyelectrolyte molecule. The corresponding exponents for the molecular weight dependence of s0 were 0.35 and 0.11 at 0.1M and 0.001M NaCl respectively. Tests of the Kirkwood‐Riseman and Debye‐Bueche theories were made by substituting the parameters [η], MsD and the frictional constant, F0 in cubic equations derived from the approximate relationships recently proposed by Marrinan and Hermans. In this way, the monomer frictional constant, ζ could be calculated from data for each fraction. From both theories values of ζ were considerably lower than an approximate figure of 4 × 10−9 g./sec. deduced from the diffusion coefficient of sucrose at 25°C. However, at low molecular weights in 0.1M NaCl and at all molecular weights in 0.001M NaCl, ζ approached most closely the expected value indicating that the theories hold best for a highly extended configuration.
Polymerization catalyzed by lithium and lithium alkyl
Authors: Spirin Yu. L. , Arest‐Yakubovich A. A. , Polyakov D. K. , Gantmakher A. R. , Medvedev S. S.
Published: April 2003

In previous kinetic investigations it was found that polymerization initiated by alkyllithium in hydrocarbon media is not a typical anionic process. The peculiarities of this type of polymerization have been explained by the participation of both carbanion and lithium components of an active center in the chain propagation. In connection with suggestions previously made, the effect of the solvents (toluene, triethylamine, ethyl ether, dioxane, and tetrahydrofuran) on the homo‐ and copolymerization of styrene, butadiene, and isoprene in the presence of ethyllithium was studied. It was found that in hydrocarbon media these monomers form mutually associated “living” polymers. Regarding the nature of monomers the degree of association increases as follows: styrene < isoprene < butadiene. The reactivity of these monomers increases in the same sequence. The solvation of the growing lithium chains or its association complexes with monomers gives rise to the possibility of chain propagation in hydrocarbon media by a two‐step mechanism. In electron‐donating solvents the total activation energy of polymerization decreases, and reaches a minimum in THF. The relative reactivity of the investigated monomers in chain propagation increases in the sequence: isoprene > butadiene > styrene.
Mechanism of alternating inter‐intramolecular propagation. I. Methacrylic anhydride
Authors: Gibbs William E. , Murray Joseph T.
Published: April 2003

The solution polymerization of methacrylic anhydride, a monomer which undergoes predominantly inter‐intramolecular propagation, shows kinetics similar to vinyl polymerization. The overall rate of polymerization is proportional to the square root of the initiator concentration and to the 3/2 power of the monomer concentration. The apparent, overall energy of activation was found to be 23.0 kcal./mole when azobisisobutyronitrile was used as the initiator. The value of Ep − Et/2 obtained is 8.0 kcal./mole. This compares with the value of Ep − Et/2 found for methacrylic acid in the same solvent (DMF) of 9.8 kcal./mole. Both values are in the range of values for other vinyl monomers. The polymer obtained from reactions carried out at monomer concentrations of 17% and lower were completely soluble, showed low amounts of residual unsaturation, and did not appear to be branching to a measureable extent. At higher monomer concentrations, gel was formed, and the polymers showed higher residual unsaturation levels. Poly(methacrylic anhydride) hydrolyzed to the polyacid did not show any enhancement in crystallinity over the polyacid prepared directly from methacrylic acid. Both show only low orders of crystalline content.
Study of polydispersity of cotton cellulose according to molecular weight
Authors: Usmanov Kh. U. , Sushkevitch T. I.
Published: April 2003

A study has been made of the molecular heterogeneity of cotton fiber cellulose from fibers of different age. Analysis was carried out by the precipitation fractionation (10 to 12 fractions) and turbidity titration methods. The molecular weight distribution curves show that the cotton fiber in its early development period (grown 5 days) contains mainly low molecular weight cellulose and a small quantity of high molecular weight cellulose. Therefore, the sample is to some extent polydisperse. With continued fiber development (grown 10 to 20 days), the quantity of high molecular weight cellulose increases and the polydispersity increases also. Finally, in the late development period, the polydispersity of the sample decreases, and the fibers grown 50 days and more contain mainly homogeneous cellulose of high molecular weight. The distribution curve of the youngest fiber has only one maximum. As the fiber development proceeds, the number of maxima increases to three and reduces to one maximum again as growth is carried to maturity.
On the cutting mechanism of high polymers
Authors: Kobayashi Akira , Saito Katsumasa
Published: April 2003

The characteristics of the cutting phenomena in linear high polymers, such as polytetrafluoroethylene, polystyrene, and poly(methyl methacrylate) are described in order to make clear the cutting mechanism which is available to produce high quality and accurate parts. Thus, the types of chips, the deformation of the work material, and the critical rake angle defined by the authors are described. Several discussions on the thermal, the time (or cutting speed), and the frictional dependencies are also described. The chips are divided into two main categories the continuous (curl, flow, and shear type) and discontinuous (crack and tear type). These are influenced by the kinds and temperature of the work materials, the rake angle of a tool, and the depth of the cut and cutting speed. It was clarified by the discussions that the viscoelastic behavior of the work material was important during cutting of high polymers. Therefore, the Voight and Maxwell Model were introduced to explain the time dependencies. We could say that the types of cutting mechanism of high polymers are classified as, slip on the shear plane, crack at the tip of a tool, tear at the cutting edge accompanied by heavy strain, and some combinations of these. Cutting with the critical rake angle (that is a rake angle which makes the thrust force during cutting equal to zero), the work material was neither deformed upwards nor downwards, thus the highest accuracy was obtained. Furthermore, the work material must be equal to the frictional angle of the rake surface of the tool, and was decided upon by the frictional behavior of the chip on the rake surface.
Viscoelastic properties of branched whole polymers. II. Regularities in the solution viscosity, melt viscosity, and molecular weight
Authors: Peticolas Warner L.
Published: April 2003

For linear polymers there is generally an experimental relation between the melt viscosity η, intrinsic viscosity [η], and viscosity‐average molecular weight M̄v, which forms a one‐dimensional curve in the three‐dimensional space, η, [η], M̄v. Thus, from a knowledge of one of these quantities it is possible to obtain the other two. For randomly branched polymers, evidence is given in this paper to show that there exists a twodimensional surface in this same space so that any one of these three variables may be obtained from a determination of the other two. In such cases the viscosity‐average weight may be obtained from a measurement of both [η] and η. Such a relationship is shown to exist from the data of Charlesby on branched silicones as well as our own data on polyolefins.
Statistical thermodynamics of swollen polymer networks
Authors: Hermans J. J.
Published: April 2003

To obtain an expression for the entropy S of a polymer network at volume V, the assumption is made that a volume V0 can be defined a which the distribution of end‐to‐end distances is the same as in a solution of freely dispersed chains and is Gaussian, and that the distribution of end‐to‐end distances at the volume V is likewise Gaussian. Although these assumptions are the same as those made by Flory, the formula obtained differs from Flory's. The results is

where n is the number of solvent molecules, ϕ the volume fraction of polymer, G the number of chains (i. e., chain portions between crosslinks), and Ω the factor by which the structural pattern of the network reduces the number of accessible configurations. The customary assumption is made that Ω is volume independent. The consequences of the result obtained for S are discussed. Flory's method was to calculated the “entropy of crosslinking” by considering the probability that in a polymer solution certain segments are found in each other's vicinity. The error in the calculation lies in the assumption that the probability for two arbitrary segments to be in each other's vicinity is independent of whether other pairs of segments are or not. If this error is avoided, Flory's result becomes identical with the one derived in the present article. Arguments are given to show that the distribution of end‐to‐end distances assumed by Guth and James is erroneous. A consideration of the equilibrium between the network and a polymer solution proves that their formula must be rejected also on experimental grounds.
The chemistry of xylylenes. XIII. The problem of crystallinity and crosslinking in poly(p‐xylylene)
Authors: Errede L. A. , Gregorian R. S.
Published: April 2003

The problem of crystallinity and crosslinking in poly(p‐xylylene) was re‐investigated with the use of polymer that was prepared by polymerization of p‐xylylene in solution. It was found that amorphous polymer is converted irreversibly to α‐crystalline polymer at 50–140°C. The α‐form in turn is converted irreversibly to the β‐form at 220–260°C. The rate of change and the ultimate proportion of change is dependent upon the temperature. The polymer appears to soften and reharden at 220–250°C. and subsequently to melt at 410–420°C. This is followed by rapid thermal degradation. It was shown that the properties associated with a three‐dimensional network are imparted to poly(p‐xylylene) by reactions that occur when the mixture of insoluble polymer and residual monomer (<0.01M) is warmed from −78°C. to room temperature. This result appears to be independent of reactions that commonly afford covalent crosslinks. On the other hand, there is a close correlation with the experimental conditions that afford low molecular weight cyclic poly(p‐xylylene). It is spectulated that some cycllization might occur in such a way that two or more chains of poly(p‐xylylene) from an interlaced structure which might be responsible for the properties of poly(p‐xylyene) heretofore attributed to covalent crosslinks.
The microscopic structure of rigid polyurethane foam
Authors: Giuffria Ruth
Published: April 2003

In a microscopic study of rigid polyurethane foam, the fundamental cell is described as an irregular polyhedron whose edges form the structural “ribs” of the foam. Blowing conditions and location in the block or panel influence the shape of the cell. Cells are elongated in the direction of movement of the foam mass.
Crosslinking polyepichlorohydrins with dimercaptans
Authors: West David W. , Marvel C. S.
Published: April 2003

Some polyepichlorohydrins and some copolymers of epichlorohydrin and butylene oxide have been crosslinked with dimercaptans to yield rubbery materials. Further work is needed to evaluate these products.
Elasticity of crosslinked amorphous polymers in swelling equilibrium with diluents
Authors: Hoeve C. A. J. , Flory P. J.
Published: April 2003

Thermoelastic measurements conducted at constant pressure on systems of fixed composition must be corrected to constant volume in order to achieve the desired resolution of the stress into its energy and entropy components. In the case of simple elongation deduction of the energy component f9 =(∂E/∂L)T,V = [∂(f/T)/∂(1/T)]L,Vof the tension f from measurements at constant pressure requires the equation of state p(T, V, L), or equivalent information. If the system is a polymer network swollen with a diluent or a diluent mixture, and equilibrium is maintained with a surrounding diluent phase, additional complications may arise from changes in composition with deformation and/or temperature. If, however, the diluent mixture is so chosen as to render the equilibrium volume of swelling independent of temperature, then, as we have pointed out previously, fe may be equated to the coefficient = [∂(f/T)/∂(1/T)]L,p,eq, which may be determined directly from measurements on the system maintained in equilibrium with excess diluent. The basis for this simplification is set forth in detail. The conversion of measurements conducted at constant pressure to constant volume is obviated by this procedure, and a simple means is provided for evaluating the internal energy changes accompanying distortion of a polymer network and the concurrent orientation of the chains of which it is composed. Allegations that the indicated procedure is invalidated by disregard of changes of composition of the network phase with temperature and deformation are unfounded. Inconsistencies in recent publications on the analysis of thermoelastic data for networks in swelling equilibrium are pointed out.
Kinetics of anionic copolymerization of monomers of similar polarities
Authors: O'Driscoll K. F. , Kuntz Irving
Published: April 2003

The reasons underlying the experimental fact that r1r2 = 1 for some ionic copolymerizations are reexamined. It is shown that it is not necessary to consider all propagating ions of equal reactivity in order to explain this fact. It is then shown that anomalous results from anionic copolymerizations may be readily interpreted in terms of classical copolymerization kinetics.
Polymerization of vinyl acetate in aqueous media. Part I. The kinetic behavior in the absence of added stabilizing agents
Authors: Napper D. H. , Parts A. G.
Published: April 2003

Vinyl acetate has been polymerized in buffered aqueous solution at 40°C., with potassium peroxydisulfate as initiator, a dilatometric method being used to follow the reaction. Without the addition of emulsifying agents, a stable suspension of polymer particles is formed resembling a latex obtained in emulsion polymerization. It has been found that the number of latex particles after increasing in the initial stages remains constant for the major part of the reaction. The kinetics of the polymerization conform to the third case of the Smith and Ewart scheme, if it is assumed that the concentration of the monomer in the latex particles remains constant. The calculated propagation constant compares favorably with that for bulk polymerization, while the termination constant compares with that found for highly viscous systems.
Polymerization of vinyl acetate in aqueous media. Part II. The kinetic behavior in the presence of low concentrations of added soaps
Authors: Napper D. H. , Alexander A. E.
Published: April 2003

The effect of adding low concentrations of the three different types of soaps on the heterogeneous polymerization of vinyl acetate in aqueous solution, with K2S2O8 as initiator, has been studied. Neutral soaps produced no appreciable effect on the polymerization rate, whereas anionic soap increased the rate, the magnitude of the increase being affected by the length of the paraffin chain in the anion. Cationic soaps decreased the rate of polymerization in the early stages of the reaction, but in this case the length of the paraffin chain in the cation had no influence. The results have been interpreted in terms of the adsorption of the soap onto the surface of the small polymer particles, and the resultant reduction or promotion of the coalescence of these small particles.
Studies on the enzymatic synthesis of dextran. Part II
Authors: Braswell Emory , Goodman Albert , Stern Kurt G.
Published: April 2003

Increasing the reaction time or the temperature, or decreasing the enzyme or sucrose concentration, produced dextrans with higher molecular weights (light scattering) and lower intrinsic viscosities. This was consistent with the results of periodate titrations, which indicated that under these conditions the degree of branching of the samples was increased. The increase in branching which occurs when the reaction time is increased or the sucrose concentration is decreased may be due to the resulting increase in the ratio of acceptor sites for branching (chain glucose units) to the number of sucrose molecules. In addition, as the molecule grows larger with increasing reaction time, an increase in steric factors would reduce the availability of the reducing end of the chain. After allowance has been made for the change in the steric factor, it seems that the effect of enzyme concentration on branching is negligible, but that a decrease in the temperature decreases the degree of branching. The effect of temperature on the velocity of synthesis corresponds to an Arrhenius activation energy of 10.6 kcal./mole.
Some results of cesium‐initiated diene polymerization and copolymerization
Authors: Rembaum A. , Ells F. R. , Morrow R. C. , Tobolsky A. V.
Published: April 2003

A study of the homogeneous polymerization of isoprene and butadiene by means of alkali aromatic complexes confirmed the influence of polarity of the medium on the microstructure of the homopolymer. Cesium napthalene in tetrahydrofuran yielded a high concentration of the 1,2‐adduct (29%) and 3,4‐adduct (43%) in polyisoprene, but a comparatively low concentration of 1,2‐structures (74.5%) in polybutadiene. Practically pure 1,2‐polybutadiene was synthesized by means of Li naphthalene. A gradual decrease in the concentration of 1,2‐polybutadiene structures was noted as the electropositivity of the alkali counterion increased. The influence of solvent, temperature, and molecular weight on the structure of polybutadiene was examined. Copolymerization of the isoprene–styrene monomer pair yielded block polymers. The determination of the torsional modulus–temperature spectrum afforded a simple method for distinguishing block from rando compolymers.
Stress relaxation in nylon and terylene: Influence of strain, temperature, and humidity
Authors: Meredith R. , Hsu Bay‐Sung
Published: April 2003

Stress relaxation data are presented for nylon 66 and Terylene yarns held at constant extensions from ½% to 15% for dry, 65% R.H. and wet conditions all at 25°C. and in the dry condition at 25, 50, and 75°C. A single composite relaxation curve fitted the data for Terylene at all strains at 25°C. A theory of stress relaxation gives a good fit for the experimental results of dry nylon at all temperatures between 25°C. and 75°C. In moist nylon, there are two relaxation processes superimposed on each other, one due to thermal agitation and the other due to absorption of extra moisture as the fiber is stretched. It is shown that the relaxation caused by the extra moisture absorbed is consistent with the change in moisture regain with strain at constant humidity calculated thermodynamically.
Dynamic bending properties of fibers: Effect of temperature on nylon 66, terylene, orlon, and viscose rayon
Authors: Meredith R. , Hsu Bay‐Sung
Published: April 2003

The dynamic bending modulus and loss modulus have been measured over a range of temperature from −70 to 170°C. for single textile filaments of nylon 66, Terylene, Orlon, and viscose rayon in the dry state, using a vacuum electrostatic method which is described. Maximum loss modulus occurred at −40°C. and 115°C. for nylon, at −60°C. and 140°C. for Terylene, at 70°C. and 110°C. for Orlon, and at −20°C. and 90°C. for viscose rayon. Application of rate process theory to these transition regions gave activation energies in support of the interpretation that the low‐temperature transition is associated with segmental motion and the high‐temperature transition involves breaking of secondary bonds, e.g., hydrogen bonds in nylon 66. In an appendix, the theory of lateral vibration of viscoelastic bars is treated in some detail, in particular as it applies to calculate successfully the large correction for air damping of fine filaments.
Polyallöcimene. II
Authors: Marvel C. S. , Kiener P. E.
Published: April 2003

Alloöcimene has been polymerized by a variety of catalysts, including triisobutylaluminium/titanium tetrachloride, triisobutylaluminum/vanadium trichloride, boron fluoride etherate, and titanium tetrachloride. These initiators give polymers at different temperatures and of differing molecular weights but all seem to produce the same recurring structural units in the polymers in approximately the same proportions. It seems that only a slight amount if any cyclopolymerization occurs and it is probable that all of the catalysts are acting as cationic‐type initiators.
Monomers and polymers containing the trifluoromethyl group
Authors: Overberger C. G. , Davidson E. B.
Published: April 2003

3,3,3‐Trifluoropropene, 4,4,4‐trifluorobutene‐1, 5,5,5‐trifluoropentene‐1, 3‐trifluoromethylbutene‐1, and 4‐trifluoromethylpentene‐1 were prepared and subjected to polymerization conditions with a variety of heterogeneous catalysts. The latter four monomers were polymerized to crystalline, high melting solids by means of vanadium trichloride–triisobuty aluminum catalyst. Infrared analysis indicates that there was no isomerization of the polymer chain.
Crystal structure and morphology of polyacrylonitrile in dilute solution
Authors: Holland V. F. , Mitchell S. B. , Hunter W. L. , Lindenmeyer P. H.
Published: April 2003

It has been possible to crystallize polyacrylonitrile from dilute solutions of propylene carbonate in the form of thin platelets. These platelets are ellipsoidal in shape and approximately 100 A. thick. Electron diffraction shows that the platelets are essential single crystals and the polymer axis is nearly perpendicular to the plane of the platelet. Five separate reflections were measured and indexed. The spacings calculated for these reflections agree with previously reported x‐ray values obtained from drawn fiber. However, the present electron diffraction data require a different indexing of the reflections resulting in revised unit cell dimensions.
Network polymers. I. Theoretical remarks
Authors: Alfrey T. , Lloyd W. G.
Published: April 2003

This paper consists of some general theoretical comments on the structure and swelling behavior of network polymers. The importance of network topology is emphasized. A hypothetical network consisting of “ghost” chains, which could pass freely through one another, would tend to shrink to submicroscopic size. This supercontraction would be prevented by either a volume exclusion effect or a restriction against cutting through (i.e., against alteration of network topology). In real networks, both of these restrictions are present. The swelling behavior of network polymers which were swollen at the time of network formation is discussed in terms of a crude molecular model.
Dielectric properties of water of adsorption on protein crystals
Authors: Takashima Shiro
Published: April 2003

The dielectric properties of dry and wet protein crystals were studied in a wide frequency range. The dry protein crystals did not have appreciable dielectric constant until the water content was about 15–20%. However, further increase of water of hydration (and/or adsorption) suddenly increased the dielectric constant of the crystals, and it reached a very large value which cannot be explained merely by the orientation of water of hydration (and/or adsorption). However the increase of dielectric constant leveled off rapidly, and further addition of water did not have significant effect. Thus the dielectric constant–water content plot followed a curve which was similar to the Langmuir adsorption isotherm. This fact strongly indicates that the dielectric constant of hydrated crystals arises, for the most part, from the polarizability of the first hydration layer of the protein molecules, which supposedly have an icelike structure.
Analysis of copolymers by pyrolysis and mass spectrometry
Authors: Wanless G. G.
Published: April 2003

The depolymerization behavior of the copolymers of 1‐pentene and 4‐methyl‐1‐pentene has been studied. Regularities found in the spectra are employed to develop an analytical method for assaying such copolymers. The results obtained are confirmed by NMR assays. Variations in cracking severity did not influence the analytical results much. It is concluded that the results are dominated by the bond strengths of the polymer chains, since rapid escape of the fragments from the reaction zone is possible. A direct and simplified analytical method resulted, employing direct depolymerization within the sample system of the mass spectrometer.
Halogenation of polyethylene single crystals
Authors: Keller A. , Matreyek W. , Winslow F. H.
Published: April 2003

The halogenation of melt‐crystallized and solution‐crystallized linear polyethylene indicated that halogen atoms have no effect on the fold length on recrystallization. At temperatures of 60°C. or higher, reaction of the crystal lattice with chlorine proceeded to completion. Extremely thin layers of both solution and melt crystallized polyethylene exhibited no difference in reactivity with chlorine, but the reactivity of molded polyethylene films to chlorine was apparently limited by chemically combined chlorine occupying the free volume in the surface layer of the polymer. There was a coexistence of highly halogenated and essentially unreacted phases during chlorination of individual crystal layers. Finally, this phase separation involved dimensions of about 100 A. and may well be related to some inherent structural feature of single crystals.
Electroinitiated polymerization of methyl methacrylate in a homogeneous medium
Authors: Funt B. L. , Yu K. C.
Published: April 2003

Methyl methacrylate was polymerized in a homogeneous organic medium composed of a solvent of high dielectric constant an ionizable salt and the monomer. Application of a direct current provided a controlled initiation of the polymerization process by the discharged ionic species. The influence of the type of solvent electrode material and salt on the yield and molecular weight of polymer was assessed in preliminary experiments. Polymers of high molecular weight were obtained in contrast to low degrees of polymerization reported in earlier work. The yield of polymer was linearly dependent on the time, and kinetic analysis showed that the rate of reaction was proportional to the current density. The molecular weight showed an inverse dependence on current density. A rate scheme is proposed which provides a kinetic interpretation of the experimental results on the basis of a free radical mechanism initiated by the electrolytic discharge of acetate ions. The electrical control of the physical properties of the resultant polymer by programming of the current‐time dependence is discussed.
Relationship of catalyst composition to catalytic activity for the polymerization of α‐olefins
Authors: Coover H. W. , McConnell Richard L. , Joyner F. B.
Published: April 2003

Heterogeneous olefin polymerization catalysts generally consist of a transition metal compound from groups IVB or VB in combination with an organometallic compound from groups I, II, and III of the periodic table of the elements, but in some instances may contain a third component possessing at least one strongly complexing ligand atom. The composition of a coordination catalyst of this type determines both the rate of polymerization of the α‐olefin and the stereoregularity of the polymer produced. In order to predict activity and stereospecificity of catalysts for the polymerization of α‐olefins, data from the polymerization of propylene using catalysts of the following types were correlated: (1) titanium(III) chloride catalysts in which the organometallic component was varied, (2) coordination catalysts containinig a ligand third component in which the ligand was varied, and (3) coordination catalysts in which the transition metal component was varied.

The electronegativity of an orgariometallic compound is known to be important in determining its reactivity with ethers, hydrogen, and other reagents. Both the ionic size and the electronegativity of the central atom appear to be important in determining the utility of both the organometallic and the transition metal compounds as components for coordination catalysts. In general, organometallic and transition metal compounds having small central atoms with similar electronegativities favor the formation of stereospecific catalysts.

The present correlation has made it possible to predict the activity and stereospecificity of coordination catalysts for olefin polymerization.
Flow reversal effects in a simple laminated membrance diffusion system
Authors: Petropoulos J. H.
Published: April 2003

The dependence of the magnitude of the permeation flux on the sense of flow is studied in the case of a simple membrane laminate AB. The permeability of phase A is assumed to change from a low value at low permeant activity to a higher one at high permeant activity, whereas the permeability of phase B is constant. The results of the analysis of this simple system provide considerable insight into the factors influencing flow reversal effects in binary laminated membranes in general. The conditions under which marked effects of this kind are possible have been established.