bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrophobic interaction in poly(2‐hydroxyethyl methacrylate) homogeneous hydrogel
Authors: Refojo Miguel F.
Published: April 2003

Homogeneous poly(2‐hydroxyethyl methacrylate) (PHEMA) hydrogel exhibits a narrow range of swelling at equilibrium in water (% H2O, 41.09 ± 0.15 standard error of the mean of 24 samples), regardless of the dilution of the monomer solution and relatively low level of crosslinking. It is postulated that PHEMA hydrogel has, in addition to its covalently linked network structure, a secondary structure stabilized by hydrophobic bonding. The addition of microsolutes to the hydrogel seems to confirm this hypothesis. The hydrogel swells beyond its swelling equilibrium in water in presence of urea and its methyl derivatives. Swelling is also induced by organic solvents like alcohol and acetone, and by anions like iodide, acetate, trichloroacetate, and thiocyanate. Chlorides and sulfates produce a less swollen hydrogel than pure water, while bromides and cetylpyridinium chloride, in the concentrations tested, induce only a slight deswelling of the gel. When PHEMA gel prepared in organic solvent–water solutions is placed in water, the gel passes through an opaque state before becoming transparent again. This phenomenon is interpreted as being caused by the inability of water to solvate the hydrophilic ends of the unorganized polymer segments. Homogeneity returns to the gel after a rearrangement of the chains, directed by the interaction of the hydrophobic portions of the polymer segments, exposing to the solvent–water most of the hydrophilic sites in the network.
A redox‐initiated xylan–poly(sodium acrylate) graft copolymer
Authors: Church John A.
Published: April 2003

An aspen 4‐O‐methylglucuronoxylan was grafted with poly(sodium acrylate) (PSA) in 3.4N NaOH at 25–30°C. with the use of a persulfate–thiosulfate redox initiator system. The formation of a true graft copolymer was indicated by fractional precipitation and light‐scattering studies, physical mixtures of the two pure polymers being used as references. A grafted fraction was isolated, containing no ungrafted xylan but possibly some PSA homopolymer, which contained 96.5% PSA and 3.5% xylan, or an average of 3.2 PSA chains of M̄n approximately 90,500 per xylan chain of M̄n approximately 10,500.
Reactive fiber. V. Preparation and polymerization of p‐styrenesulfonyl (β‐chloroethyl)amide
Authors: Iwakura Yoshio , Uno Keikichi , Nakabayashi Nobuo , Chiang Wen‐Yen
Published: April 2003

p‐Styrenesulfonyl(β‐chloroethyl)amide (III) was prepared and copolymerized with styrene (M1). The monomer reactivity ratios were determined (r1 = 0.25 = 0.1, r2 = 1.25 ± 0.25), and Q and e values were calculated (1.69 and 0.28, respectively). The polymer reacts with nucleophilic reagents such as amines and phenols in the presence of pyridine to the extent of 15–98%. Fibers from copolymers of acrylonitrile and III react with Congo Red in the presence of pyridine.
Dilute solution studies on a polycarbonate in good and poor solvents
Authors: Berry G. C. , Nomura H. , Mayhan K. G.
Published: April 2003

Light‐scattering, viscometric and osmometric studies have been carried out on dilute solutions of polycarbonate fractions both in a good solvent and in theta solvents. The data span the molecular weight interval 5 < 10−3M < 760. It has been concluded that: (1) the overall behavior in dilute solution is consistent with a flexible chain conformation; (2) the ratio of the unperturbed mean‐square radius to the molecular weight, or to the number of chain elements, is larger than commonly observed for vinyl polymers; (3) the ratio of the unperturbed radius to the radius calculated for a chain with free rotation about valence bonds has the unusually small value 1.3; and (4) the hydrodynamic behavior of the chain may reflect partical draining affects.
Microstrain investigation of polyethylene
Authors: Rabinowitz Stephen , Brown Norman
Published: April 2003

The small‐strain mechanical behavior of crystalline polyethylene has been studied by using a microstrain technique with strain resolution on the order of 10−6. The strain rate was varied from 10−6 to 10−4 sec.−1, and a temperature range of 17–28°C. was investigated. A strong dependence on strain rate and temperature has been observed for the following parameters which characterize the mechanical response of polyethylene in the microstrain region: the initial modulus of the stress–strain curve, the deviation in strain from ideal linear elastic behavior at a given stress amplitude, and the energy dissipated in a deformation cycle. The Young's moduli that were observed by means of tensile tests in the microstrain region were only about 20% lower than the values reported in other investigations at kilocycle and megacycle frequencies. The experimental method made it possible to isolate a deformation process which was attributed to a crystallographic shear mechanism corresponding to a yield point of 27 psi. This shear mechanism is discussed in terms of the various shear processes, such as slip, twinning, and the orthorhombic–monoclinic phase change.
Effect of morphology and degree of crystallinity on the infrared absorption spectra of linear polyethylene
Authors: Okada T. , Mandelkern L.
Published: April 2003

The infrared absorption spectra of selected crystalline and noncrystalline bands were studied in bulk‐crystallized specimens of linear polyethylene which encompassed the extremely wide density range of 0.92–0.99 g./cm.3. The analysis of the data obtained at room temperature yield degrees of crystallinity by infrared methods which are in very good accord with the values deduced from the density measurements. Studies of the infrared spectra as a function of temperature give fusion curves which are in agreement with those obtained by thermodynamic methods. However, in order to obtain these latter results cognizance must be taken of the large negative temperature coefficient of the specific extinction coefficients of the crystalline bands from room temperature to the melting point. The necessary data to account for this phenomena were obtained from studies of the spectra of the n‐paraffin, C94H190, where molecular crystals are formed. Analysis of the two gauche bands, at 1352 and 1303 cm.−1, which are assigned to the noncrystalline regions demonstrate that for bulk‐crystallized samples of lowest densities the intensity ratio at room temperature is identical to that expected from the pure melt at this temperature. The conclusion is thus reached that the noncrystalline regions in these cases and the pure melt are structurally very similar. For samples of higher density, where the crystallite size is comparable to the extended chain length, the intensity ratio of the two gauche bands is altered. This change could reflect a change in the sequential distribution of gauche bonds. This intensity ratio for crystals formed from dilute solution is very similar to that for the high‐density bulk‐crystallized material and indicates a similarity in structure of the noncrystalline regions in the two cases.
Adsorption of iodine from aqueous solutions by samples of tire yarn from regenerated cellulose
Authors: Doppert H. L.
Published: April 2003

The adsorption of iodine by rayon tire yarn samples from aqueous solutions in which the concentration of iodide and triiodide ions is suppressed was studied. Fowler and Guggenheim's model of adsorption on regular localized monolayers appeared to be applicable to the adsorption phenomena considered. It is concluded that adsorption takes place on patches of sites in the cellulose–water gel.
Relaxation spectra of polymer melts from relaxation and steady‐state flow data
Authors: Ajroldi Giuseppe , Garbuglio Carmine , Pezzin Giovanni
Published: April 2003

Accurate measurements of stress relaxation after steady‐state flow have been carried out, in the Newtonian flow region, for a polystyrene and a poly(methyl methacrylate) melt, with a cone‐and‐plate rotational rheometer. From the stress relaxation σ(t) versus t curves the relaxation spectra H were calculated by means of the first approximation equation: \documentclass{article}\pagestyle{empty}\begin{document}$ H = - ({1 \mathord{\left/ {\vphantom {1 {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}} \right. \kern-\nulldelimiterspace} {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}\ln t $\end{document}. The shear stress–shear rate curves, σ versus \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document} were also measured, in large ranges of shear rates, for the same melts, and from these data the relaxation spectra H were obtained by means of equations given by Faucher and Ferry. The Faucher equation, \documentclass{article}\pagestyle{empty}\begin{document}$ H = - \dot \gamma ^2 d{\sigma \mathord{\left/ {\vphantom {\sigma d}} \right. \kern-\nulldelimiterspace} d}\dot \gamma ^2 $\end{document}, has been found to give results which compare satisfactorily with those obtained from the first approximation equation. It has been found that the Ferry equation has to be modified for comparable agreement.
Study of crystallization kinetics of trans‐1,4‐polyisoprene
Authors: Fischer E. , Henderson J. F.
Published: April 2003

The concentrations and the growth rates of high‐ and low‐melting type spherulites of trans‐1,4‐polyisoprene were measured in the temperature range 39–49°C. It was shown that above about 40°C., the crystallization rate of trans‐1,4‐polyisoprene is determined primarily by the radial growth rate of high‐melting form (HMF) spherulites, whereas the predominance of the low‐melting form (LMF) crystals below 40°C. can be attributed to the high rate of formation of LMF primary nuclei at lower crystallization temperatures. Temperature‐independent rate parameters were calculated from optical and dilatometric measurements and were found to be in good agreement. Both the change in nucleation habit and spherulite growth rate with temperature can be explained on the basis of a lower end surface free energy of LMF crystals of trans‐1,4‐polyisoprene compared to that of the HMF crystals.
Configurational statistics of polyamide chains
Authors: Flory P. J. , Williams A. D.
Published: April 2003

The statistical mechanical treatment of polymeric chains in terms of the largest eigenvalue of the product of statistical weight matrices for the rotational interactions of skeletal bonds of the repeat unit becomes excessively complicated if the repeat unit spans more than three or four skeletal bonds. Moreover, such treatment is necessarily limited to chains in which the number of repeat units is indefinitely large. Newer methods are readily applicable to chains of any degree of polymerization comprising repeat units of any realizable length. If interdependence of neighboring bond rotations is confined to bond pairs within a given unit, rotations about a pair of bonds belonging to neighboring units being mutually independent, further simplifications may be introduced without sacrifice of rigor. Polyamides, in which rotation about bonds on opposite sides of the amide group are independent, are polymers of this type. Adherence of the amide group to the planar trans conformation favors a more extended configuration of the chain, but this effect is dominated by the smaller steric repulsions affecting rotations about bonds which are first, second, and third neighbors of the amide group. It is for this reason that the characteristic ratio 〈r2〉0〉/nl2 for poly(hexamethylene adipamide), ca. 6.0 according to experimental results of Saunders, is less than the value, 8.0, for polymethylene at 25°C. The characteristic ratios and molecular dipole moments are computed as functions of the degree of polymerization. The poly(εaminocaproamide) chain also is treated.
Transmission electron microscopy of polypropylene lamellae delineated by staining
Authors: Hock Charles W.
Published: April 2003

Aqueous solutions of phosphotungstic acid were used to stain melt‐crystallized polypropylene which had been oxidized to the leveled‐off stage by boiling in 70% HNO3. Electron microscopy of thin sections of the polymer revealed unstained crystalline lamellae bordered by stained interlamellar layers. The lamella height, which is equivalent to the fold period of the molecules, increased as the crystallization temperature increased. In polypropylene which had crystallized in ice water, and at 125, 145, or 161°C., the heights of the visually delineated lamellae were 80, 105, 158, and 210 A., respectively. Those heights were, in turn, approximately the same as the length of the perpendicularly aligned molecules in the lamellae, which survived the acid etch. The stained interlamellar layers, regardless of the crystallization temperature, were about half the height of the lamellae.
Disorientation of crystallites in highly stretched polyethylene
Authors: Miyasaka Keizo , Makishima Kunio
Published: April 2003

Crystallite orientation in polyethylene has been investigated in the high range of stretching. Crystallite disorientation can be observed in samples subjected to various stretching procedures: hot drawing and elongation of oriented fibers at room temperature at constant rate and at constant load. Crystallite disorientation does not take place during elongation but is induced upon removal of the applied stress. The higher the rate of removal of stress the greater is the disorientation. Two mechanisms are postulated for the disorientation: one relating to the irregular residual strain developed in fibrils by high stretching, and the other concerning rotational movement of crystallites caused by amorphous chains terminated on the interfaces. The fibrillation brought about by high stretching is thought to play an important role in the crystallite disorientation.
Isothermal calorimeter for studies of polymer solution processes
Authors: Schreiber H. P. , Waldman M. H.
Published: April 2003

A simple differential, isothermal calorimeter has been built to study the thermodynamics of interactions associated with a variety of polymer solution processes. The calorimeter is readily operated at temperatures ranging from ambient to about 200°C., temperature adjustments are rapid, and the apparatus is rugged enough to permit application to commercial process studies. Though less sensitive than microcalorimeters, it represents an attractive combination of satisfactory accuracy, speed, and flexibility of operation. The operation of the calorimeter is demonstrated by measurements of the heat of solution of sodium chloride in water and the heats of solution of various polyolefins in Tetralin and α‐chloronaphthalene. The latter tend to confirm the presence of polymer aggregates in chloronaphthalene solutions below the thermodynamic melting temperature of the polymer.
Application of significant structures theory to amorphous polyethylene
Authors: Stewart Charles W. , Frankenberg C. A. Von
Published: April 2003

The thermodynamic properties of amorphous polyethylene are calculated from a model based on the method of significant structures. The motion of a molecule as a whole is described by the motion of segments, each segment moving independently of all others. It is assumed that on melting, holes appear in the solid lattice and the segments can move into these vacancies, obtaining some gaslike degrees of freedom. The complete frequency distribution for polyethylene is used for the solidlike degrees of freedom, while a corrected classical partition function is used for the gaslike degrees of freedom. The calculated thermodynamic properties are in reasonable agreement with experimentally determined values, assuming each gaslike segment to consist of 20 CH2 groups.
Aromatic poly(amic acids): Fundamental structural studies
Authors: Wallach M. L.
Published: April 2003

Aromatic poly(amic acids) derived from pyromellitic dianhydride and 4,4′,‐diaminodiphenyl ether were characterized by dilute solution techniques. Number‐average molecular weights M̄n of 13 samples ranged from 13,000 to 55,000 (DP 31–131). Weight‐average molecular weights M̄w of 21 samples ranged from 9,900 to 266,000. The ratio M̄w/M̄n was between 2.2 and 4.8. Heterogeneous polymerization yielded higher molecular weight polymer than homogeneous polymerization. The molecular weight could be varied systematically by control of stoichiometric imbalance. Use of very pure monomers and solvent gave polymers of relatively high number‐average molecular weight (∼50, 000) and the most probable molecular weight distribution M̄w/M̄n = 2. Impure monomers and/or solvent resulted in lower number‐average molecular weight (M̄n ≅ 20,000–30,000) and wider distributions (M̄w/M̄n = 3–5). The Mark‐Houwink relation obtained was [η] = 1.85 × 10−4M̄w0.80 The exponent is characteristic of moderately extended solvated coils. The unperturbed chain dimensions (r02/M)1/2 were 0.848 A., and the steric factor σ was 1.24 which is close to the limiting value of unity for an equivalent chain with free internal rotations. The sedimentation constant–molecular weight relation was S0 = 2.70 × 10−2M̄w0.39. This exponent is consistent with the Mark‐Houwink exponent.
Solubility and diffusion of water in acetal polymers
Authors: Hardy G. F.
Published: April 2003

The rate of water sorption at 25°C. has been determined for a number of polyacetal films differing in structure, density, and orientation induced by extrusion. The equilibrium water uptake was found to be a linear function of density only; no other effect of structure or orientation was detectable. The extrapolated density for zero sorption was 1.51 g./cc., not far from the theoretical crystalline density. The diffusivity of water in unoriented films rose with decreasing density; for linear copolymer, the trend was parallel to that of the area under the dynamic mechanical loss peak associated with long‐range chain motions in the disordered regions (β‐transition). Less pronounced effects of molecular weight and long chain branching on diffusivity were also noted. Films crystallized while an extruded melt was still oriented showed considerable increases in water diffusivity, but no significant changes in the apparent activation energies of permeation (about 6.6 kcal./mole) or diffusion (about 11.5 kcal./mole). On annealing these films, the diffusivity remained almost constant while the sorption coefficient and retraction on remelting decreased.
Configurational enthalpy of polystyrene
Authors: Joshi R. M. , Zwolinski B. J. , O'Reilly J. M. , Karasz F. E.
Published: April 2003

Recent precision measurements of the heats of combustion of atactic and isotactic polystyrene permit an unequivocal calculation of the enthalpy difference in the bulk amorphous forms of the two isomers of this polymer. Contributions to this quantity arise mainly from the differences in nonbonded interactions in the two configurations but may also contain terms relating to higher energy conformations and to intermolecular interactions. The thermochemical and NMR data of specific polymers and of simple molecules are discussed in a comparison with model compound calculations. The thermochemical method has potentially important applications in studying molecular interactions in stereoregular polymers.
Energy contents of amorphous polystyrene with different thermal histories
Authors: Bianchi Umberto , Cuniberti Carla , Pedemonte Enrico , Rossi Corrado
Published: April 2003

The Tian‐Calvet microcalorimeter has been used to measure the heat of solution of atactic polystyrene in toluene at 30°C. By using a special technique for polymer sample preparation, it has been possible to measure directly the difference in conformational energy of the polystyrene chain at different temperatures, from 30 to 100°C. and to calculate its contribution to the specific heat.
Dynamic mechanical properties of aromatic, aliphatic, and partially fluorinated epoxy resins
Authors: Dammont F. R. , Kwei T. K.
Published: April 2003

The α, β, and γ transitions at temperatures between −200 and +100°C. of crosslinked aromatic and aliphatic epoxy polymers were determined from damping and shear modulus data, and compared with their fluorine containing analogs. Loci of segmental relaxation are suggested at various temperatures, and similarities between aliphatic and fluorocarbon segments, and polyethylene and polytetrafluoroethylene are discussed. Two systems of structurally similar monomers 2,2,3,3,4,4‐hexafluoropentane diglycidyl ether‐1,5 and 1,4‐butane diglycidyl ether, and 2,2‐bis(4‐glycidyl phenyl ether)hexafluoropropane and 2,2‐bis(4‐glycidyl phenyl ether) propane were polymerized with the aid of two diamine curing agents, namely, ethylenediamine and m‐xylylenediamine. Polymers of the aromatic diepoxides showed transitions with peaks at −56°C. and above +70°C. Three main peaks were registered for the aliphatic and fluorocarbon diepoxides: at −125 and at −100°C., at −56°C., and at 0°C. It is suggested that the Tg is affected by an interdependence of relaxation of all components of the polymer main chain.
Molecular dimensions of polydipropylsiloxamer
Authors: Lee C.‐L. , Emerson F. A.
Published: April 2003

The molecular dimensions of polydipropylsiloxamer were studied by intrinsic viscosity measurements in toluene and in 2‐pentanone. The relationships between the molecualr weight and the intrinsic viscosity were found to be: [η]25°C., toluene = 4.35 × 10−4 M0.58; [η]θ(10°C.), toluene = 1.09 × 10−3 M0.5; [η]θ(76°C.), 2‐pentanone = 8.71 × 10−4 M0.5. This held reasonably well for molecular weights from 25,000 to 3000,000. The root‐mean‐square end‐to‐end length ratio, (r02/M)1/2 as calculated from the constant K, exceeds the free rotation value by approximately 100%. The disparity is greater than that found with polydimethylsiloxamer, indicating a lower degree of flexibility for the polydipropylsiloxamer. This is largely due to the short range steric interaction between near neighboring units of the chain. Gel permeation chromatography was also employed to demonstrate the lower degree of flexibility for polydipropylsiloxamer as compared with polydimethylsiloxamer.
Corresponding state relations for the Newtonian viscosity of polymer solutions. II. Further systems and concentrated solutions
Authors: Simha Robert , Utracki Lechoslaw
Published: April 2003

In earlier work we have indicated a superposition principle for moderately concentrated mixtures (c ≲ 2/[η]) in good and poor solvents. By an examination of data on a number of vinyl polymers and cellulose derivatives in good as well as poor solvents, the validity of this principle is extended to concentrated solutions (c ≲ 50%). The characteristic concentration factor γ is proportional to M over the whole concentration range, with 0.47 ≤ a1 ≤ 1.10 being larger for good than for poor solvents, the result obtained earlier. Significant deviations from this relationship are noted in good solvents for those low molecular weights at which deviations from the usual intrinsic viscosity relationship occur. This may be related to the expansion factor of the polymer coil. On the basis of these results, the concentration and molecular weight dependence of the viscosity in the concentrated solution can be related to each other in terms of the parameter a1 and thus to thermodynamic characteristics. In this manner a bridge between the relatively dilute and concentrated regions is established. Currently used semiempirical expressions are analyzed in terms of these results. For the polystyrene–cyclohexane systems and θ − 9 ≦ T ≦ θ + 3, γ can be identified with the critical concentration for phase separation. Provided an “entanglement” concentration ce exists, in the neighbourhood of which the concentration dependence of the viscosity changes reapidly, γ can alternatively be shown to be proportional to ce, or ce ∝ M. The temperature reduction scheme suggested earlier remains to be investigated.
Dependence of viscosity of concentrated polymer solutions upon molecular weight and concentration
Authors: Onogi Shigeharu , Masuda Toshiro , Miyanaga Nobuyuki , Kimura Yasuo
Published: April 2003

Molecular weight M and concentration c dependencies of the zero‐shear viscosity (η) were measured over wide ranges of M and c for concentrated solutions of linear and branched poly(vinyl acetate) as well as of polystyrene under θ conditions. The log η versus log M and log η versus log c curves for a given system can be superposed by the horizontal shift along the abscissa, giving smooth master curves. From the shift factors the ratio of two exponents β and α, which appear in the following equation, can be evaluated: η = K′(cρ)αMβ, where ρ is the density of the solution and K′ is a constant at constant temperature. The evaluated values of β/α for the systems under θ conditions are equal to or very close to 0.50 as was anticipated from the previous work. The above superposition method was also applied to available viscosity data, and it was found that β/α had a good correlation with a in [η] = KMa. This indicates that the individual molecules in concentrated solutions maintain the same individuality as in dilute solutions, and might be a positive support to the packed sphere model proposed previously by the authors. The effect of solvent on the molecular weight and the concentration dependencies of viscosity was also discussed.
Determination of osmotic coefficients in polyelectrolyte solutions by potentionmetric measurements during phase separation
Authors: Shatkay A. , Michaeli I.
Published: April 2003

A method of evaluating osmotic coefficients of polyelectrolyte solutions is suggested for systems in which a two‐phase equilibrium is maintained between the polymer solution and a polymer precipitate so that the “polymer” terms Cpdμp in the Gibbs‐Duhem relationship may be neglected. The method is applied to a polybase system, and the osmotic coefficients calculated from the experimental data are discussed in terms of the theory of Alexandrowicz. The results are found to be in line with the above theory but the characteristic parameter ϕp, the fraction of free counterions, is about twice as large as values previously observed in polyacids.
Microstructure of bulk polymers as revealed in ultrathin sections
Authors: Andrews E. H. , Bennett M. W. , Markham A.
Published: April 2003

An improved method is described for obtaining ultrathin sections of soft polymers for examination in the electron microscope. The method involves cooling the specimens in the temperature range 0 to −160°C. during sectioning. The method has proved particularly useful for the study of microstructure in bulk polymers, especially semi‐crystalline materials such as polyethylene. The visibility of some features can be improved by electron staining. Preliminary results obtained on polyethylene and polypropylene are illustrated and discussed.
Mechanical structures in polymer melts. II. Roles of entanglements in viscosity and elastic turbulence
Authors: Busse W. F.
Published: April 2003

Current theories of polymer flow processes often sacrifice realistic molecular models for simplicity of their mathematical equations. An analysis of what might happen to molecules of more realistic sizes and shapes under shear flow, shows the importance of the rapid Brownian motion of chain segments, the elastic deformations of polymer random coils, and the dissipation of this elastic random coil energy by the relatively slow slippage of the chains past each other at a few entanglements where steric hindrance causes long relaxation times. This makes the energy loss depend on the time at each local deformation, and not on the overall shear rate. At high shear rates this model leads to “cluster flow” and low loss cyclic deformations, rather than the high loss processes of steady‐state shear. This model gives reasonable qualitative explanations for many anomalous flow properties, and it has predicted new effects that have since been observed.
Vinyl polymerization. 179. Effects of substituents on chain transfer reaction of substituted cumenes toward poly(methyl methacrylate) radical
Authors: Yamamoto Tadahiro , Otsu Takayuki
Published: April 2003

In order to study the effects of substituents on the chain transfer reaction to cumenes, the polymerization of methyl methacrylate in a series of nuclear‐substituted cumenes with α,α′‐azobisisobutyronitrile as initiator was carried out at 60°C. and the chain transfer constants C were determined. The C values obtained for all substituted cumenes were greater than that (C0) for unsubstituted cumene, regardless of the electronattracting or ‐repelling nature of the substituents. Hence the plot of log (C/C0) against the Hammett σ constants gave no linear relationship. When the plots were made by the modified Hammett equation including resonance effect of the substituents: log (C/C) = ρσ + γER, however, a straight line with ρ = 0.03 and γ = 0.9 was obtained. From these results, it may be concluded that the effect of the substitutents on the chain transfer reactivities of cumenes toward attack of a poly(methyl methacrylate) radical is attributable mainly to the resonance contribution in the transition state. These results are also compared with those for polystyryl radical reported previously and discussed.
Polymerization of cyclic iminoethers. III. Effect of ring substituents
Authors: Levy A. , Litt M.
Published: April 2003

2‐Substituted oxazolines with substituents in the 4 or 5 positions essentially cannot be polymerized. This is probably due to steric hindrance.
Polymerization of cyclic iminoethers. IV. Oxazoline polymerization in solvents containing different functional groups
Authors: Levy A. , Litt M.
Published: April 2003

The polymerization of 2‐n‐pentyloxazoline in solvents containing various functional groups showed that many solvents demonstrated no interaction or moderate interaction, whereas others interfered extensively, in some cases preventing polymerization entirely.
Dynamic mechanical properties of plasticized poly(vinyl chloride). Linear free energy relationship in the poly(vinyl chloride)–ester system
Authors: Hammond R. J. , Work J. L.
Published: April 2003

A considerable number of quantitative attempts have been made to predict the properties of solutions containing polar polymers and polar solvents. Thermodynamic approaches have generally failed to accurately describe these systems. This can be be ascribed to the difficulty in determining structural characteristics arising from the variety of secondary interactions present in these highly complex solutions. A linear free energy relationship has been used here to explore changes encountered in solutions of monofunctional esters in poly(vinyl chloride) undergoing mechanical deformation. This treatment appears valid only for the rubbery region of the viscoelastic spectrum of this polymer. The data indicate that the observed changes are a function of corresponding changes in polymer intramolecular interactions.
Cyclopolymerization of diallylcyanamide
Authors: Uno K. , Tsuruoka K. , Iwakura Y.
Published: April 2003

A soluble polymer of cyclic structure has been obtained by radical polymerization of diallyleyanamide. A kinetic analysis of the polymerization indicated that the overall rate of the system is first‐order with respect to concentration of initiator and either first‐ or second‐order with respect to monomer concentration, depending on the solvent used. The molecular weight of the polymer is independent of the concentration of the initiator and the monomer. The intramolecular abstraction of hydrogen is proposed as a termination reaction.
Cyclo‐ and cyclized diene polymers. XVI. Nature of the active species and a proposed mechanism of cyclopolymerization of isoprene with catalysts containing ethylaluminum halides
Authors: Gaylord N. G. , Kössler I. , Matyska B. , Mach K.
Published: April 2003

The polymerization of isoprene with C2H5AlCl2 to yield solid cyclopolyisoprene is markedly accelerated by the addition of TiCl4. The polymer yield passes through a maximum on increasing the catalyst reaction time with or without monomer present. The active species are probably cations formed by dissociation of the reaction product of C2H5AlCl2 and TiCl4. The polymerization of isoprene with (C2H5)2AlX–TiCl4 (X = F, Br, Cl) has maximum activity at an Al/Ti mole ratio of 0.75 corresponding to conversion of R2AlX to RAIX2 which then reacts with remaining TiCl4. A proposed mechanism of cyclopolymerization of conjugated dienes involves monomer activation, i.e., conversion to cation radical by one‐electron transfer to catalyst cation which is itself neutralized, addition of cation end of monomer cation radical to terminal or internal unsaturation of fused cyclohexane polymer chain, one‐electron transfer from “neutral” catalyst to cation on polymer chain which is then transformed to a diradical which undergoes coupling to form a cyclohexene ring. The mechanism of the “living” polymerization involves addition of catalyst‐activated monomer to a “dead” polymer with a terminal cyclohexene ring and regeneration of the active catalyst.
Cationic polymerization of 4‐methyl‐1,3‐dioxene‐4 and copolymerization with tetrahydrofuran
Authors: Kawai Wasaburo
Published: April 2003

A new monomer, 4‐methyl‐1,3‐dioxene‐4 was synthesized from allyl chloride and paraformaldehyde. The monomer was polymerized at room temperature or −78°C. by boron trifluoride etherate catalyst, and the structure of the obtained polymer was determined by infrared, nuclear magnetic resonance spectra, and chemical analysis. It was ascertained that the polymerization process proceeded through a ring‐opening mechanism at the dioxane ring. In the presence of tetrahydrofuran, the polymerization of 4‐methyl‐1–1,3‐dioxene‐4 led to copolymer. The mechanism of the copolymerization is described in detail.
Polyelectrolytes prepared from perfluoroalkylaryl macromolecules
Authors: Hodgdon Russell B.
Published: April 2003

The synthesis of a new generation of high‐capacity oxidation‐resistant ion‐exchange resins and membranes is described which are sulfonic acid polyelectrolytes prepared from high molecular weight poly‐α,β,β‐trifluorostyrene. The difficult sulfonation of poly‐α,β,β‐trifluorostyrene is discussed in terms of the finding that this sulfonation must be effected upon an aromatic ring possessing a meta‐directing substituent group. The oxidative stability of these new types of perfluoroalkyl aromatic sulfonic acid polyelectrolytes is both demonstrated and described with comparisons to their polystyrenesulfonic acid homologs. The difference in their oxidation–depolymerization stabilities is described in terms of benzylic carbon substituents.
Studies of chlorinated polyisobutenes. Part I. Investigations of structure by proton magnetic resonance and of thermal stability by thermal volatilization analysis
Authors: McGuchan R. , McNeill I. C.
Published: April 2003

Polyisobutene was chlorinated in carbon tetrachloride solution at 60°C. with radiochlorine, and the degree of chlorination was determined radiochemically. The extent of chlorination was varied by using a wide range of chlorine/polyisobutene ratios in the reaction mixture. The products were examined by PMR spectroscopy, which showed that both methyl and methylene groups were chlorinated but that the methylene hydrogens were more readily substituted and some disubstitution of the methylene groups occurred. The effect of chlorination on the thermal stability compared to the original polymer was studied by the new technique of thermal volatilization analysis. All the chlorinated derivatives were found to degrade at lower temperatures than polyisobutene. The stability dropped progressively as the chlorine content was increased to one chlorine atom per isobutene unit and then showed less change with further increase in chlorine content.
Polymerization and copolymerization of methacrylic esters derived from glycidyl methacrylate
Authors: Uno K. , Makita M. , Ooi S. , Iwakura Y.
Published: April 2003

Copolymerization of methacrylic esters derived from glycidyl methacrylate and nucleophiles with styrene was carried out. The monomer reactivity ratios of these methacrylic esters were varied with the alkoxy groups of the esters and the solvent used.
Polymerization and copolymerization studies on vinyl fluoride
Authors: Sianesi Dario , Caporiccio Gerardo
Published: April 2003

The polymerization of vinyl fluoride has been studied in the temperature range of 0–50°C. with the aid of different types of initiators. Ziegler‐Natta systems based on vanadyl acetylacetonate and AIR(OR)Cl compounds showed good activity. Enhanced reaction rates and higher polymerization degrees were achieved with boron alkyls (and, to a lesser degree, Cd, Zn, and Be alkyls) activated by oxygen. With either types of initiator, the main features and the kinetic parameters of the polymerization were determined. In all cases, the polymerization is considered to be of the free‐radical type, though some properties (crystallinity, melting temperature) of the polymer are shown to be markedly improved over the previously described high‐pressure polymer. This is chiefly ascribed to an improved degree of chemical regularity of the chains. The copolymerization of vinyl fluoride in the presence of the cited initiators was studied with a number of monomers. The values of the copolymerization parameters allow us to obtain Q (0.010 ± 0.005) and e (−0.8±0.2) values and to discuss the reactivity of vinyl fluoride in radical chain propagation.
PVC–rubber blends. VI. The structure
Authors: Zítek P. , Zelinger J.
Published: April 2003

The dependence of the dynamic shear modulus of blends of polyvinyl chloride and rubber on the temperature and concentration of the rubber was investigated. For a calculation of a theoretical value of the modulus a formula recently derived by Uemura and Takayanagi was adopted. This formula is based on the assumption of a two‐phase system, in which one phase is a continual matrix and the other is discrete spherical particles, and of perfect adhesion between the phases. Most of the theories that clarify the part played by rubber in rubber‐modified vitreous materials are based on these assumptions. In most cases we have found a good conformity between the theoretical and experimental values of the modulus. In a certain system with an outstanding impact strength, however, a severe discrepancy has been found. This implies that the present structural explanation of the high impact strengths of two‐phase systems is not quite generally applicable.
Electron spin resonance study of polyglycols
Authors: Thryion F. C. , Baijal M. D.
Published: April 2003

Polyethylene glycols and polypropylene glycols were irradiated with gamma‐rays from a 60Co source at 77°K. Electron spin resonance spectra of the free radicals produced were recorded. It was found that the rupture in the polymer chain takes place at *CC and CO bonds. The radicals identified were OCH2 in polyethylene glycols and mainly
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in polypropylene glycols. Thermal decay of these radicals followed a second‐order law, and the decay constant calculated was k = 2.32 × 105 cm.3 mole−1 sec.−1 A complete discussion of the results is presented.
Effect of the initiator solvation on the change in polymerization rates of dioxolane and tetrahydrofuran
Authors: Kučera M. , Majerová K.
Published: April 2003

The cocatalytical effects of water and ethanol on the cationic polymerization of dioxolane and tetrahydrofuran were studied. The ion pair or were used for initiating the polymerization. The dependence of the polymerization rate on the concentration of cocatalyst was examined with various temperatures, concentrations of monomer, solvents (heptane, tetrachloroethane, tetrachloroethane‐heptane mixtures, and 1,4‐dioxane), and concentrations of initiator. The abscissa of the maximum of the reaction rate in the dependence mentioned above was the criterion for evaluation of the effect of the reaction variables. The changes observed are small; nevertheless, they prove the share of all components of the polymerizing system in establishing solvation equilibria, which determine the number and the reactivity of active centers and, in fact, the reaction rate.
Linear molecules based on dimethylgermanium and dimethylsilicon groups bridged with oxygen atoms and terminated with chlorine atoms
Authors: Moedritzer Kurt , Van Wazer John R.
Published: April 2003

This article deals with the equilibrated system (CH3)2SiCl2–(CH3)2GeCl2–[(CH3)2SiO]–[(CH3)2GeO], which consists of a range of various chain, and some ring, molecules resulting from scrambling of the bridging oxygen with the monofunctional chlorine atoms between the dimethylgermanium and dimethylsilicon moieties. The proton nuclear magnetic resonance of the methyl groups (which do not exchange appreciably under the conditions employed) bonded to the germanium and silicon atoms shows that there is a strong preference of the chlorine atoms for being on the dimethylgermanium and the bridging group for being on the dimethlysilicon moiety at equilibrium. This means that thermodynamic factors alone cause the germanium atoms to be found as “unreacted” dimethyldichlorogermane with siloxane polymers or to be preferentially arranged at the ends of the chain molecules in the case of the mixed germoxane–siloxanes. The NMR fine structure is interpreted in these terms, and it is shown that the experimental data may be fitted by appropriate calculations based on only four equilibrium constants, which define the arrangement of neighboring atoms about any given atom in a molecule and the size distribution of the linear molecules.
Emulsion polymerization. I. Recalculation and extension of the Smith‐Ewart theory
Authors: Gardon J. L.
Published: April 2003

The most important assumptions underlying the Smith‐Ewart theory are that the locus of chain propagation is the monomer‐swollen latex particle, polymeric chains are initiated by radicals entering from the water phase into the particles, chain termination is an instantaneous reaction between two radicals within one particle, and particles are nucleated by radicals absorbed into monomer‐swollen soap micelles. Right or wrong, these and other assumptions used by Smith and Ewart are retained in this paper. The newly derived and experimentally verifiable equations contain only such parameters which can be determined by experiments not involving emulsion polymerization. The proportionality constant between the particle number and the appropriate powers of soap and initiator concentrations is defined in terms of these independent parameters. Absolute rate equations are presented for the intervals before and after the completion of particle nucleation. To calculate these rates it is not necessary to have prior knowledge of the experimental particle number. The conversion at which particle nucleation is complete is calculated. The molecular weight is defined in terms of independent parameters. Predictions are made for the particle size distribution. It is shown that the validity of the theory is confined to specifiable intervals of conversion, to a certain range of monomer/water ratio, and to soap concentrations whose upper and lower limits are given.
Crystalline titanium dichloride—an active catalyst in ethylene polymerization. I. Catalyst activation
Authors: Werber F. X. , Benning C. J. , Wszolek W. R. , Ashby G. E.
Published: April 2003

Crystalline titanium dichloride, in the absence of organometallic cocatalyst, is a very poor catalyst for the polymerization of ethylene. It is transformed into a very active catalyst through mechanical activation (ball‐milling). This catalyst is active in the absence not only of organometallic cocatalysts, but also metals and compounds (such as aluminium and AlCl3) capable of forming organometallic compoundsin situ(i.e., with ethylene, before polymerization starts). Ball‐milling causes not only the expected increase in surface area but also disproportionation of Ti++to Ti+++and metallic titanium, as well as a crystal phase change to a structure not previously identified with those of TiCl2or TiCl3. Catalyst activity (polymerization rate) is shown to be proportional to surface area and a direct function of Ti++content of the catalyst; an empirical equation relates catalyst activity to surface area and to Ti++lost through disproportionation. Titanium trichloride was found to be inactive in the absence of organometallic cocatalyst, even after ball‐milling. The difference in structure of the catalytically active species in the conventional Ziegler (organometallic cocatalyst) and in the titanium dichloride catalyst are discussed. The mechanism of polymerization is compared with that of the supported (CrO3on SiO2/Al2O3and MoO3on Al2O3) catalyst systems.
Photoinduced microstructural changes in 1,4‐polyisoprene
Authors: Golub Morton A. , Stephens C. L.
Published: April 2003

An infrared and NMR study was made of the microstructural changes produced in thin films of purified cis‐ and trans‐1,4‐polyisoprene when irradiated with ultraviolet light in vacuo at room temperature. The major photochemical processes observed were cis–trans isomerization and loss of 1,4 double bonds, the latter process being accompanied by the formation of vinylidene and vinyl double bonds as well as some endlinking. Very surprisingly, the loss of original double bonds contributed also to a novel photocyclization which gave rise to cyclopropyl groups in the polyisoprene chain. The isomerization and the formation of cycloprophyl groups are presumed to proceed through triplet and biradical states of the 1,4 double bonds, while the vinylidene and vinyl double bonds must result from chain repture at the carbon–carbon bond joining successive isoprene units. Hydrogen abstraction and double‐bond migration are of neglible importance in the overall photochemistry of polyisoprene.
Synthesis of polyamideamines from 5‐oxazolones
Authors: Iwakura Yoshio , Toda Fujio , Torii Yoshinori , Murata Katsuaki
Published: April 2003

Polyamideamines with a sequence of two amide and one amine linkage in a main chain were synthesized from the polyaddition of 2‐isopropylidene‐4‐alkyl‐3‐oxazolin‐5‐ones and primary diamines. The polyaddition reaction proceeded through 1,4‐conjugate addition of an amine group to 3‐oxazolin‐5‐one and subsequent ring opening of the intermediate addition product with another amine. Although aliphatic diamines gave oily polymers, xylylenediamines afforded amorphous solid polymers. The reduced viscosities and polymer melt temperature of the polymers were 0.05–0.12 and 90–130°C., respectively.
Preparation of highly branched graft copolymers by the ceric ion method
Authors: Iwakura Yoshio , Imai Yohji , Yagi Kohji
Published: April 2003

Grafting of methyl methacrylate onto poly(6‐methacryloyl‐D‐galactose) was very rapid, and the increase in weight reached about 1500% after 2–3 min. The maximum number of branches of the graft copolymers obtained was about 50. In the closest position two adjacent grafted branches were separated from each other by about 45–50 units of 6‐methacryloyl‐D‐galactose on the average. Susceptibility of the various polymers containing sugar residues to grafting was compared, and the importance of the hemiacetal group in the grafting was revealed. Solubility of the backbone polymer in water was also important for rapid grafting by the ceric ion method.