bluuebunny/crossref_metadata_2025 huggingface dataset:
On the mechanism of polymerization retardation by hydroquinone
Authors: Caldwell Robert G. , Ihrig Judson L.
Published: April 2003

The retardation of methyl methacrylate polymerization by hydroquinone, 1,4‐napthalenediol, and benzoquinone was studied by an accurate dilatometric method. The degree of retardation was found to be very small for the phenols in the absence of air and very sensitive to the presence of impurities. Kinetic analysis of the experimental results indicates that the intermediate radicals formed in the reaction between the chain radicals and the phenols disappear from solution principally by reinitiating polymerization. Comparison with results obtained for retardation by benzoquinone indicates that semiquinone radicals are probably not formed in the initial reaction of the phenols with the chain radicals. It is suggested that the intermediate radicals produced in phenolic retardation are addition complexes between the phenols and the chain radicals which may involve hydrogen bridging. The breakdown of these complexes then causes reinitiation of polymerization.
Reactivity ratios of vinyl 2‐chloroethyl ether in cationic copolymerization with vinyl alkyl ethers and para‐substituted α‐methylstyrenes
Authors: Dunphy J. F. , Marvel C. S.
Published: April 2003

Reactivity ratios have been determined for vinyl 2‐chloroethyl ether (M2) and vinyl isobutyl ether, vinyl octadecyl ether, α‐methylstyrene, p‐methyl‐α‐methylstyrene and p‐methoxy‐α‐methylstyrene in a stannic chloride‐initiated polymerization system.
Evidence for retention of the crystalline‐amorphous ratio of cellulose during heterogeneous acid hydrolysis
Authors: McKeown J. J. , Lyness W. I.
Published: April 2003

The literature reports that hydrolysis of cellulose under heterogeneous conditions proceeds by an initially rapid attack on the amorphous regions and then a much slower hydrolysis of the ordered regions or “crystallites.” During such hydrolysis, the degree of polymerization (D.P.) of cellulose initially decreases quite sharply and then levels off and declines at a much slower rate. This leveling off of the D.P. has been interpreted as being due to the slow hydrolysis of the “crystallites.” Some results obtained in our laboratories suggested that heterogeneous hydrolysis does not generate “crystallites” as has been assumed. Hence, a study of the crystallinity of the hydrolysis products was undertaken. The x‐ray crystallinity of cellulose was evaluated by comparing the integrated intensities of the main diffraction peaks before and after hydrolysis. The effects of variations in sample preparation and orientation of cellulose samples as well as fluctuations in the operation of the diffractometer were assessed and were found to introduce no artifacts. The x‐ray crystallinity of slash pine sulfate pulp did not increase upon hydrolysis as would be expected if hydrolysis had liberated “crystallites.” Cotton linters and slash pine sulfite pump exhibited only small increases in crystallinity upon hydrolysis. A decrease in x‐ray crystallinity was observed for gum sulfate pulp which cannot be explained at this time. Thus it appears that hydrolysis does not convert cellulose to a wholly crystalline or ordered state. It might be well to review past work in which complete crystallinity of cellulose “crystallites” has been assumed.
Aqueous solutions of salts of poly(vinylsulfonic acid)
Authors: Eisenberg Henryk , Casassa Edward F.
Published: April 2003

Specific ion effects in solutions of salts of poly(vinyl sulfonic acid) in aqueous univalent supporting electrolyte are described in regard to observations of phase separation, dialysis equilibrium, light scattering, viscosity, and sedimentation. The most complete data have been obtained on two systems, ammonium poly(vinyl sulfonate) in 0.5M NH4Cl and potassium poly(vinyl sulfonate) in 0.5M KCl. Although the distribution of small ions across a semipermeable membrane is not markedly different in the two cases, other thermodynamic properties, the occurrence of phase separation in the KCl solution and its absence with NH4Cl, together with a larger second virial coefficient in the latter case, indicate that NH4Cl is a much better solvent for the corresponding polymer than is KCl. The hydrodynamic measurements concur in showing that the polymer chain configuration is more expanded in the NH4Cl solution. The interrelations among thermodynamic and hydrodynamic properties developed and generally substantiated for solutions of unionized polymers are found to be valid, at least qualitatively, for both these systems. This study also illustrates how the thermodynamic formalism for a two‐component system is applicable to three components, two diffusible and one non‐diffusible, provided solutions are equilibrated by dialysis against the solvent mixture.
Reaction of ferric chloride with benzene
Authors: Kovacic Peter , Wu Chisung
Published: April 2003

Black, insoluble organic material was obtained, together with chlorobenzene in low yield, from the reaction of benzene with ferric chloride. Small amounts of Brönsted acids, such as water, hydrogen sulfide, acetic acid, and nitroethane, markedly promoted the formation of black solid. The principal product, whose properties were investigated, is believed to be formed by a cationic polymerization of benzene, leading to chlorinated polynuclear hydrocarbons. In contrast, under similar conditions aluminum chloride yielded a high‐boiling oil, but no black solid.
Osmotic pressure and dimensions in moderately concentrated polymer solutions
Authors: Fixman Marshall
Published: April 2003

Concluding calculations are reported for a recent theory of the concentration dependence of polymer dimensions. In a prior theory of the osmotic pressure, the polymer size appeared as a parameter. It is here shown that a better agreement of the osmotic pressure theory with experiment is obtained if the polymer size is allowed to depend on concentration in such a way as to minimize the free energy of solution, than if the polymer size is taken independent of concentration. A brief résumé and critique of the model is given.
On the characterization of stereoregular polymers. II. Polypropylene
Authors: Newman S.
Published: April 2003

In this study, a survey has been made of the applicability to the crystallization of partially tactic polypropylene of Flory's theoretical relations concerning crystallization in copolymers. To this end, the crystallinity and modulus of several fractions of polypropylene of varying tacticity were measured and compared with theoretical calculations.
A theory of the thermodynamic behavior of nonelectrolyte solutions. V. The scattering of light by polymer solutions
Authors: Maron Samuel H. , Nakajima Nobuyuki
Published: April 2003

Maron's theory of the thermodynamics of non‐electrolyte solutions has been used to examine the light scattering behavior of both dilute and concentrated solutions of polystyrene in several solvents. It is shown that for each polymer‐solvent system at a given temperature the behavior can be characterized, as in the case of osmotic pressure, by a single interaction parameter μ which varies linearly with volume fraction v2, i.e. μ=μ°+σ°v2, where μ° and σ° are constants. Introduction of this equation into Maron's theory leads to functional plots in dilute solutions which are linear even when the conventional plots of HC/τ versus C plots are not. These plots yield the molecular weight from the intercepts and (μ° − σ°) from the slopes. However, to obtain the individual values of μ° and σ° data are required for concentrations higher than those normally used for molecular weight determinations. It is further shown that once μ° and σ° are evaluated, they may be used to calculate satisfactorily the turbidities up to a concentration of v2 = 0.62. Under the same circumstances the Flory‐Huggins interaction parameter χ does not reproduce the observed data as well even when χ is taken to be a linear function of v2.
“Steric” stabilization of colloidal solutions by adsorption of flexible macromolecules
Authors: Heller Wilfried , Pugh Thomas L.
Published: April 2003

It had previously been found in this laboratory that flexible polymer molecules adsorbed at colloidal particles most likely extend with many segments into the interior of the surrounding medium. This led one to expect a possible “steric protection” of colloidal particles by adsorption of flexible polymers of sufficiently high molecular weight since the merely slight interpenetration of polymer chains protruding from two colliding particles should keep them at distances too large to give a van der Waals interaction energy sufficient for coherence. This new type of stabilization was now proved using gold hydrosols as test systems and polyethylene glycols as adsorptives. The stabilization was found to increase with polymer concentration and, particularly, with the molecular weight of the polymer. In analogy with the previous finding, that the adsorption equilibrium is being approached very slowly if the molecular weight of the polymer exceeds several thousand, it was found that the degree of stabilization achieved by addition of polymer to the gold sols increases with the time elapsed before the subsequent addition of coagulating electrolyte. This increase is particularly strong during the first hour following addition of the polymer. The potential significance of the results for stabilization of organosols is discussed.
Coagulation and stabilization of colloidal solutions with polyelectrolytes
Authors: Pugh Thomas L. , Heller Wilfried
Published: April 2003

Polyelectrolytes are found to be powerful coagulating agents for colloidal solutions at concentrations as low as 10—8 moles/l., and excellent stabilizing agents at somewhat higher concentrations (in excess of 10—6 moles/l.). This applies if the polyions have a charge opposite to that of the colloidal particles. If polyions and colloidal particles have like charges, the stability of the colloidal solutions is only slightly altered, primarily in the direction of sensitization. The investigations were carried out with FeOOH sols (positively charged particles), gold sols (negatively charged particles), sodium polystyrene sulfonate and polyvinylbenzyltrimethylammonium chloride. The stability was tested by means of a modified gold number (Au sols) or by considering the rate of coagulum formation (FeOOH sols). The stabilizing effect is interpreted as being both electrostatic and steric.
Ultrasonic degradation of polystyrene. Part III. The molecular weight distributions of degraded fractions
Authors: Gooberman G.
Published: April 2003

A method is given for calculating the molecular weight distributions of ultrasonically degraded polystyrene. This method is based on the assumption that the bond which is most likely to break is situated in a plane passing through the center of the polymer molecule and which is normal to the propagation direction of the shock wave from a collapsed cavity. The theoretical distribution has been calculated for a polystyrene fraction of average molecular weight of 4.8 × 105 dissolved in benzene after 2 hr. irradiation. The undegraded fraction is assumed to possess a rectangular differential number distribution. The theoretical distribution is peakier than that found experimentally by turbidimetric titration. The difference may be due to the lack of resolving power shown by turbidimetric titration.
Dynamic mechanical properties of polymerized epoxy resins
Authors: Kline Donald E.
Published: April 2003

The dynamic mechanical properties of polymerized epoxy resins have been studied over the 80—600°K. temperature region using an appratus which drives rodlike specimens in a transverse mode. Experimental results for the mechanical loss indicate several dispersion peaks throughout the temperature range. The dynamic modulus is found to be monotonically decreasing everywhere except near the 480—550°K. range. Effects of cure time, filler, and low dose irradiations are included in the investigation.
Chromatographic fractionation of polyethylene
Authors: Guillet J. E. , Combs R. L. , Slonaker D. F. , Coover H. W.
Published: April 2003

A new method has been developed for the fractionation of polyethylene, providing more reliable data on molecular weight distribution in a fraction of the time required by previous methods. The fractionation is carried out on a column of glass beads, using a combination of solvent and temperature gradients by a method similar to that used by Baker and Williams for polystyrene. The lowest temperature in the column is above the melting point of the polyethylene, so that fractionation takes place by partition of the polymer molecules between two liquid phases in transient equilibrium. Because of the combined solvent and temperature gradients, the polymer is transferred from the stationary to the moving phase many times in its passage down the column; consequently, the fractions are considerably narrower than those obtained from a single‐step fractionation. A simple apparatus which will fractionate up to 5 g. of polyethylene in a 24‐hr. period is described. The effect of such experimental variables as column load, solvent flow rate, and the type of solvent gradient was determined. Experimental data obtained on several commercial polyethylenes are given.
A vorticity effect in anisotropic fluids
Authors: Ericksen J. L.
Published: April 2003

We analyze equations describing the motion of a preferred direction in an anisotropic fluid undergoing plane, steady homogeneous flow. These equations are essentially the same as those deduced by Jeffery for the motion of a rigid ellipsoid of revolution suspended in a Newtonian fluid. When the ratio of vorticity to rate of strain is sufficiently small, we find that the flow produces a high degree of orientation. This can be destroyed or at least diminished by making the ratio sufficiently large. We suggest conditions under which this hydrodynamic orientation effect might give rise to elasticity phenomena in polymer solutions.
The synthesis of polythiolcarbamates
Authors: Dyer Elizabeth , Osborne D. Wendell
Published: April 2003

A series of polythiolcarbamates, [—CONH—X—NHCOS—Y—S]m, have been prepared in which X was either aliphatic or aromatic and Y was a wide variety of aliphatic groups. Synthesis of the polymers by two different methods, the tertiary aminecatalyzed solution polymerization of diisocyanates with dimercaptans and the interfacial polycondensation of bischlorothiolformates and diamines, proved that the polymers had the desired thiolcarbamate structure. Greater yields of lower molecular weight polymers were obtained by the diisocyanate method. Polythiolcarbamates were found to be highly insoluble white powders which tend to decompose in light, in hot solvents, and in aqueous base. They melt somewhat higher than their oxygen analogues, but are less thermally stable.
Structural transformations in poly‐L‐hydroxyproline and poly‐o‐acetyl‐L‐hydroxyproline
Authors: Sasisekharan V.
Published: April 2003

The structural modifications in poly‐L‐hydroxyproline and poly‐O‐acetyl‐L‐hydroxyproline as revealed by x‐ray diffraction and optical activity studies are discussed. Like the proline polymer these also exhibit polymorphism. The possible structures of the various forms in relation to the various forms of poly‐L‐proline are also mentioned.
Interpolymerization of acrylonitrile and vinylidene chloride in tert‐butyl alcohol
Authors: Hill E. H. , Caldwell J. R.
Published: April 2003

True interpolymers of acrylonitrile and vinylidene chloride were prepared with the use of tert‐butyl alcohol or a mixture of tert‐butyl alcohol and water as the polymerization solvent. Analysis of the polymers showed that the ratio of the two monomers in the copolymers was very close to the initial monomer ratio. The polymers were tested for homogeneity by their solubility in acetone or acetonitrile.
Size distribution and gelation in condensation polymers with one unsymmetric reactant
Authors: Giacomo Armand Di
Published: April 2003

Equations are derived which give the molecular weight distribution and the gelation characteristics of a condensation polymer which involves four kinetically different (but otherwise equivalent) polymerization steps in its preparation. Their use is illustrated by application to the system, toluene‐2,4‐diisocyanate and a polymeric primary glycol. Comparison is made with the published expressions for the case of “equal reactivity of all functional groups.”
Dilute solution study of poly(n‐lauryl methacrylate) in an ideal solvent
Authors: Lee H. T. , Levi D. W.
Published: April 2003

Due to abnormally small root‐mean‐square end‐to‐end distances for poly(n‐lauryl methacrylate) fractions in an ideal solvent reported previously, investigation of this polymer in another ideal solvent was carried out. Phase separation studies indicated that in n‐amyl alcohol the θ‐temperature is 29.5°C., and viscosity and light‐scattering measurements were made in this temperature. Dimensions in this solvent were found to be in the expected range. K values in the two ideal solvents are compared.
Viscosity‐temperature relationships for dilute solutions of cellulose derivatives. III. Solutions of an incompletely substituted cellulose nitrate
Authors: Moore W. R. , Edge G. D.
Published: April 2003

Viscosities of dilute solutions of six fractions of a 12.2% N cellulose nitrate, covering a molecular weight range of 68,000 to 224,000, in representative solvents have been determined at temperatures between 18 and 60°C. Values of Q in the expression η =AeQ/RT vary with concentration c and molecular weight M in a manner similar to that previously observed with solutions of ethyl cellulose, but the variation of A with c and M appears to be rather more complex in most cases. Intrinsic viscosities can be related to Q, A, the absolute temperature T, and M. With good solvents negative temperature coefficients of [η] are similar in magnitude to those obtained with cellulose trinitrate, but with poorer solvents the temperature coefficients are smaller. Negative temperature coefficients appear to be primarily due to decreases in the value of (ro2/M) where ro2 is the mean square unperturbed end‐to‐end distance of the chains. The contribution of the swelling factor α appears to be greater with acetone as solvent, and in all cases values of α3 are greater than those obtained with the trinitrate, suggesting that the chains are less stiff. Values of the exponent a in the expression [η] = KMa decrease with increasing temperature suggesting decreasing chain extension, except in the case of nitrobenzene in which association is probable. The values of a also suggest that the chains are less extended than those of the trinitrate.
Quaternization kinetics of poly‐4‐vinylpyridine
Authors: Fuoss Raymond M. , Watanabe Masamoto , Coleman Bernard D.
Published: April 2003

The quaternization of poly‐4‐vinylpyridine by n‐butyl bromide in tetramethylene sulfone and in propylene carbonate at 25, 50, and 75°C. begins as a simple second‐order reaction with a rate constant approximately equal to that for 4‐picoline. As the quaternization proceeds, the rate decreases due to the charge which is being built up on the polymer, and the quaternization of the last half of the pyridine side groups occurs at about one‐tenth the initial rate. The kinetics can be summarized by the equation:

where x is concentration of bromide ion at time t, A is initial concentration of butyl bromide, B is initial concentration of polymer in monomoles per liter, k0 is the initial rate constant for quaternizing isolated pyridine groups, k2 is the rate constant for quaternizing pyridine groups both of whose neighbors are already quarternized, and α is a parameter which depends on temperature, initial concentrations, and on the intrinsic rate constants. A simple graphical method is described which permits evaluation of k0, k2, and α from the data. At 25° in tetramethylene sulfone, k0 = 5.0 × 10−4 l./mole min., k2 = 5 × 10−5, and α/A = 2 × 10−4.
Molecular distributions in polycondensations involving unlike reactants. VII. Treatment of reactants involving nonindependent groups
Authors: Case L. C.
Published: April 2003

The molecular distributions involving the use of reactants with nonindependent groups are considered in this paper. The distributions are shown to depend on the relative amounts of reactant in the unreacted state, the once‐reacted state, and the twice‐reacted state. The kinetic considerations determining these relative amounts are reviewed for several different types of reactants, including cyclic acid anhydrides and certain diisocyanates. The general linear distribution for a condensation polymerization of two reactants is derived. The calculations for nonindependent groups in other types of distributions are briefly indicated. The molecular distributions arising in polyurethane condensations, particularly those of chain extension, are slightly specialized forms of the general distribution. The methods of this paper are the only available tools to deal with these distributions. It is shown that a diacid or glycol can be treated as a reactant having nonindependent groups. The kinetic calculations for such a unit are seen to be the same as for a cyclic acid anhydride. Somewhat improved distributions for polymers of such units are thus made available.
Polymerization in the solid and near‐solid states
Authors: Bamford C. H. , Jenkins A. D. , Ward J. C.
Published: April 2003

Some recent observations on the behavior of radicals in solid and near‐solid media are reviewed. Polymerization in a matrix of swollen polymer molecules is first discussed, and this is followed by a consideration of the photochemical polymerization of crystalline methacrylic acid as studied by electron spin resonance, optical microscopy, and kinetics methods. The behavior of radicals produced on crystal faces was also investigated, and it is suggested that their behavior may be explained by assuming that their energies of interaction with the surface cover a wide range and that, on raising the temperature, propagation and termination reactions occur. Two types of polymer were produced by bulk polymerization of the crystals, one clear and glassy, the other fibrous or granular; both were amorphous and not oriented, and it was concluded that the crystal lattice exerted no influence on the configuration of the polymer produced from it. The reaction seems to proceed by a phase boundary process rather than by propagation through the lattice.
Macromolecules with groups of high reactivity
Authors: Kern W. , Schulz R. C. , Braun D.
Published: April 2003

Reactions on the reactive groups of macromolecular substances (e.g., cellulose) have long been known, even since before the structures of macromolecules were understood. H. Staudinger carried out numerous reactions with macromolecules, maintaining the degree of polymerization constant, in order to substantiate the macromolecular structure of the substances investigated (polymeric‐analogous reactions). During the last fifteen years reactions with macromolecules have been investigated because it was desirable to compare the chemical diversity of low molecular weight compounds with the corresponding chemical diversity of macromolecular compounds. These endeavors bring forth materials which supplement the numerous macromolecular substances which are produced and used as materials for plastics, and therefore these materials should have as low reactivity and high stability as possible. Objectives are given for the preparation of macromolecules with a large variety of groups. From these objectives it is evident that, as in low molecular weight chemistry, macromolecular substances which possess functional groups of high reactivity are suitable as starting materials. Some of these which have been known for a long time but have been investigated only in recent years are polyaldehydes (polyacroleins and polymethylacroleins), polyacyl halides such as polyacryl chlorides and polyvinylsulfonyl chlorides and fluorides, and, most recently, polymeric organometallic compounds such as poly‐p‐lithiumstyrene. The reactions with these macromolecules are described and the properties of the resulting new polymeric substances are given.
Synthèse des copolymeres greffés à partir des polymères ayant subi l'action des radiations ionisantes. III. Etude comparée du greffage sur le polyéthylène et sur le polypropylène
Authors: Chapiro Adolphe
Published: April 2003

On a comparé les cinétiques du greffage de l'acrylonitrile sur un polyéthylène basse pression et sur un polypropylène, tous deux prépaés à l'aide du même catalyseur. Les deux polymères étaient préirradiés avec des rayons gamma en présence d'air et chauffés ensuite sous vide dans le monomère à différentes températures. La cinétique du greffage sur le polyéthylène présente les mêmes caractères que ceux qui avaient été décrits dans les deux premières parties de cette étude relatives au greffage sur le polyéthyléne haute pression. Avec le polypropylène par contre, la cinétique est trè différente. La forme des courbes de conversion varie avec la dose de préirradiation. Pour les doses élevées, la réaction de greffage est d'abord très rapide mais s'arrête rapidement pour un taux de greffage limite. Ce taux limite est d'autant plus petit que la dose de préirradiation est plus élevée. Les relations entre la vitesse de greffage d'une part et la dose et l'intensité de la préirradiation d'autre part sont différentes pour le polyéthylène et le polypropylène. II en est de m6me de l'influence de la température de greffage sur la réaction. Par ailleurs la quantité d'homopolymkre (polyacrylonitrile) formee au cours de la réaction est beaucoup plus importante dans le cas du greffage sur le polypropylène. On montre que ces résultats peuvent être interprétés en admettant que la peroxydation radiochimique conduit principalement à des hydroperoxydes POOH dans le polypropylène et à des biperoxydes POOP dans le polyéthylène. Dans le cas du polypropyène, la réaction est en outre contrôlée par la vitesse de diffusion du monomère dans le film de polymére. D'autre part la différence entre les températures de fusion des cristallites du polyéthyène et du polypropylène respectivement permet de comprendre l'effet de la température de greffage sur la cinétique observée dans ces deux systèmes.
Quelques aspects de la cinétique de formation des copolymerères greffés
Authors: Sebban‐Danon J.
Published: April 2003

Dans la plupart des méthodes permettant la synthèse des copolymères greffés (ou ǎ blocs) ǎ partir d'une solution d'un polymère An déjà formé dans un monomère B, on produit simultanément le copolymère greffé AnBm et l'homopolymère Bm, dans un milieu contenant l'homopolyměre An. Lorsque les deux homopolyměres An et Bm sont incompatibles—ce qui est la règle pour la plupart des polymères—la réaction de greffage est perturbée. En effet, une séparation en deux phases se produit alors. Dans le présent travail, on a étudié les modifications cinétiques, introduites par cette séparation en deux phases, au cours du greffage radiochimique du styrolène sur le polyisobutylène. On discute les résultats obtenus par d'autres auteurs avec d'autres couples polymère‐monomère qui conduisent également à une séparation en deux phases.
Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. I. Experimental procedure and results
Authors: Chaudhuri D. K. Ray , Hermans J. J.
Published: April 2003

Cellulose acetate films, cellophane, and cellulose model fibers are mercaptoethylated by an addition reaction with ethylene sulfide. A monomer is polymerized in the presence of the cellulose derivative obtained, so that chain transfer to SH groups can take place. Evidence for grafting is presented. The effect of reaction time, catalyst concentration, and monomer concentration is given in the form of tables and graphs. The initial rate of grafting is shown to be proportional to the square root of the catalyst concentration, and, roughly, to the concentration of the monomer. Rates of grafting of the order of 10–15 wt.‐%/hr. are easily obtained.
Quelques observations sur la polymérisation radiochimique de l'acrylonitrile
Authors: Bernas A. , Bodard M.
Published: April 2003

On sait que certains des caractères de la polymérisation en masse de l'acrylonitrile disparaissent quand la réaction est conduite en phase homogène et que l'occlusion des radicaux macromoléculaires n'intervient pas. Nous avons voulu examiner si ces mêmes caractères pouvaient s'atténuer ou disparaître par une élévation de température, vitesse d'initiation constante. Nous avons observé: (1) que l'exposant α de la relation V1 = KV'1 diminue régulièremcnt quand la tempèrature augmente et (2) que l'énergie d'activation globale décroit notablement an‐dessus de 60°C. Ces résultats s'interprètent bien en supposant qu'au dessus de cette température I'occlusion devient beaucoup plus faible; cependant elle n'est pas encorc négligeable à 100°C ainsi qu'en atteste le post‐effet observé.
The mechanism of free radical polymerization in the solid state
Authors: Adler G. , Ballantine D. , Baysal B.
Published: April 2003

The solid state polymerization of acrylamide and related monomers has been studied using the tools of electron spin resonance and optical microscopy. The data indicate that the reaction involves free radicals which do not terminate in the usual fashion. The reaction apparently involves a nucleation mechanism in which crystalline defects and the buildup and release of internal stresses affect the rate of reaction.
Recent developments in polymerization by an alternating intra‐intermolecular mechanism
Authors: Butler George B.
Published: April 2003

Recent developments in polymerization by an alternating intra‐intermolecular mechanism are summarized and discussed briefly. The methods used to prove the structure of typical polymers, which in turn established the mechanism of polymerization, are reviewed. A study of larger ring formation by Marvel and Garrison is also summarized. Ring of sizes from 7 to 21 members were formed from α‐diolefins in yields of from 4 to 25%. A study of certain unsymmetrical dienes has shown that cyclization occurs in yields up to 60%, but that gelation eventually occurs because of the difference in relative reactivities of the two olefinic double bonds. Copolymerization of certain 1,4‐dienes with certain olefins to produce linear copolymers containing six‐membered rings is discussed. In an effort to explain the strong driving force to close a six‐membered ring during polymerization of 1,6‐diolefins, a pronounced interaction between the double bonds, which can be represented by several resonance forms of the molecule, is proposed.
Photochemical modifications of high polymers by visible light
Authors: Oster Gisela K. , Oster Gerald
Published: April 2003

Methods have been developed in our laboratory to induce oxidation—reduction reactions with visible light using dyes as sensitizers. Applying this general technique to high polymers one can photochemically crosslink or decrosslink a polymer by changing the oxidation state of certain groups. Thus, gelatin containing dichromate ion, a dye, and a compound which serves as an electron donor for the light‐excited dye only becomes crosslinked by visible light. This is due to the photoreduction of chromate ion to chromic ion, the latter crosslinking the polymer. Similarly polyacrylamide which is crosslinked by complexation with mercuric ion and which is sensitized will decrosslink rapidly with visible light due to photoreduction of mercuric ion to mercurous ion. Mercaptans are photooxidized in the presence of sensitizing dyes. Hence polymers containing thiol groups can be crosslinked by dye‐sensitized photooxidation. This process can be reversed by far ultraviolet light.
The effect of high pressure on the individual steps of free radical polymerization
Authors: Walling Cheves
Published: April 2003

A study of the effect of pressure on the emulsion polymerization of styrene gives a value of ΔV‡ for chain propagation of −11.5 cc./mole, close to the value for the peroxideinitiated bulk reaction. Chain initiation and termination are both somewhat pressureretarded, the latter presumably because the reaction becomes diffusion‐controlled. Pressure has little effect upon the chain‐transfer constant of styrene–CCl4 or upon transfer with monomer in allyl acetate polymerization. However, the overall rate of allyl acetate polymerization is greatly accelerated, indicating that transfer is no longer degradative. Pressure retards the unimolecular decomposition of both di‐tert‐butyl peroxide and benzoyl peroxides, and some complications in these reactions are discussed as well as the principles governing the effect of pressure on radical reactions in general.
Synthesis and polymerization of epiperchloratohydrin
Authors: Radell Jack , Connolly Joseph W.
Published: April 2003

Epiperchloratohydrin (I) was synthesized and polymerized. Although covalent perchlorates are known to be hydrolytically unstable, I dissolved in benzene could be rapidly washed with water without causing major hydrolysis. A simple method for dehydrating silver perchlorate by an azeotropic distillation was used. Compound I before and after polymerization was explosive and required special care.
Stereospecific polymerization of some polar vinyl monomers
Authors: Butler K. , Thomas P. R. , Tyler G. J.
Published: April 2003

Anionic polymerization of N,N‐disubstituted acrylamides in hydrocarbon media is stereospecific and yields a new series of crystalline tactic polymers containing polar groups. These tactic polymers melt above 300°C. and have different solubilities from the atactic isomers. There are also differences in the rates of hydrolysis and infrared spectra. The presence of ethers in the polymerization lowers both the tacticity of the product and its molecular weight. A heterogeneous surface is not necessary for stereospecificity, and, in cases where monomer and initiator are soluble in hydrocarbons, the reaction is homogeneous throughout.
Principles of lignin growth
Authors: Freudenberg Karl
Published: April 2003

Spruce wood lignin has molecular weight of the order of magnitude of 10,000–100,000. Furthermore, it is bonded, to a large extent, if not completely, with the polysaccharides of the wood. It is formed by enzymatic dehydrogenation of coniferyl alcohol I. The mesomeric forms II–IV of the radical produced stabilize themselves by combining together to form dimers, the largest proportion of which—owing to the preponderant occurrence of the form III—are quinone methides. The latter stabilize themselves intramolecularly, steric arrangements permitting, forming ethers like V and VI. In the case of the quinone methide VIII alone, an intramolecular stabilization is impossible; this methide is stabilized by addition of water or of a hydroxyl group of the carbohydrates. In the latter case, an etherlike carbohydrate compound is formed which contains a phenolic group and which can hence be incorporated into lignin on further dehydrogenation. Substance VIII can also add on coniferyl alcohol, substance V, or other phenols, and hence it condenses units without further loss of hydrogen (XII and XIII). All of the processes described thus far proceed automatically after the formation of the radicals. The new building units thus formed (V, VI, and other similar units) can also be welded together by renewed dehydrogenation or by the formation of more quinone methides which give rise to addition reactions. By means of this combination of dehydrogenative condensation with addition of phenols and alcohols to quinone methides formed intermediarily, lignin grows to a polymolecule, grafting itself in the process onto the polysaccharides. The path of formation of the molecule also explains the extraordinarily great differences between the oligomeric building units, although in the case of conifer lignin they all proceed from the one substance, coniferyl alcohol. The branching of lignin is explained by the addition reaction. The sequence of the units is fully random, since no matrix provides for a definite order.
Influence des rayonnements ionisants sur les systèmes polymérisables
Authors: Magat M.
Published: April 2003

Aprés un bref rappel des résultats essentiels concernant la polymérisation des monomères vinyliques induite par les rayonnements ionisant.s et procédant par un mécanisme radicalaire, on examine les trois domaines de recherches plus récents, à savoir: la production de polymères greffés, la polymérisation ionique et la polymérisation à l'état solide. C'est dans ce domaine que les progrès sont les plus spectaculaires et les problèmes à résoudre les plus complexes. Si au début, la possibilité de polymérisation à l'état solide paraissait restreinte à quelques monomères particuliers, il s'est révélé plus récemment que presque tous les monomères courants pouvaient être polymérisés à l'état solide, même à de basses températures. On examine successivement les preuves que la polymérisation a effectivement lieu à l'état solide, l'influence de l'état solide tant sur la vitesse globale que sur les vitesses partielles de propagation et de terminaison, ainai que les difficultés que soulève la détermination du mécanisme (ionique ou radicalaire) de ces polymérisations. Pour conclure, on examine le cas de polymérisations “explosives” des monomères solides et l'on montre qu'elles peuvent être interprêtées à l'aide de la théorie de Semenoff des explosions thermiques.
Polymerization and the low‐frequency electromagnetic field
Authors: Piccardi Giorgio , Cini Renato
Published: April 2003

In the present work, the effect of a low‐frequency electromagnetic field, 10kHz (in hertzian units), on the polymerization of acrylonitrile in aqueus solution is studied with a differential method. The experiments are performed on three standard acrylonitrile series of samples respectively placed: (1) in electromagnetic field; (2) in a screened space; (3) in unscreened space. The results, obtained by comparing the masses of the solid polymer in standard conditions, show: (1) an appreciable effect on the polymerization of acrylonitrile in an electromagnetic field of 10 kHz; (2) an effect due to the screen's acting on the natural electromagnetic field; (3) a significant correlation between the data obtained in the present work and the data of the chemical test P collected at the same time.
Some kinetic effects in the polymerization of 1,3,5‐trioxane
Authors: Kern W. , Jaacks V.
Published: April 2003

The cationic polymerization of 1,3,5‐trioxane in methylene dichloride with boron trifluoride, producing polyoxymethylene, was investigated. An ionogenic cocatalyst is not required in this polymerization. During the induction period, initially formed, short polyoxymethylene chains depolymerize to formaldehyde until a constant equilibrium concentration of formaldehyde is reached. This concentration is equal to the ceiling concentration of formaldehyde in cationic polymerization under the conditions chosen for the experiments. The nonstationary state and the strong acceleration of the polymerization of trioxane are due mainly to the lack of an effective kinetic termination reaction. Thus the concentration of growing polyoxymethylene cations increases with time.
Contribution purement chimique à la connaissance de la forme des macromolécules en solution
Authors: Loucheux Marie‐H. , Banderet A.
Published: April 2003

L'étude cinétique de l'aminolyse de la fonction anhydride nous a permis de préciser l'influence de la chaîne macromoléculaire sur la réactivité d'un groupe fonctionnel. La stoechiométrie de cette réaction a été établie sur des micromoléculcs. La vitesse de la réaction est suivie par spectroscopie ultra‐violette; il s'agit d'une réaction bimoléculaire catalysée par l'acide formé. Dans le cas où la fonction anhydride est seule sur une chaîne marcromoléculaire, elle réagit avec la même vitesse que l'anhydride butyrique. Mais pour les polyanhydrides que nous avons utilisés (obtenus par copolymérisation de l'anhydride maléique et dn méthacrylate de méthyle), la vitesse de réaction, comparée à celle de l'anhydride succinique, est très faible. Nous tentons d'expliquer cette différence par la faible solubilité des groupes anhydrides dans le benzène: la chaîne de PMM formerait écran autour des groupes anhydrosucciniques, qui, moins solublcs, se rassemblent au milieu de la pelote macromoléculaire.
New methods of modifying the properties of cellulose
Authors: Rogovin Z. A.
Published: April 2003

The chief scientific trends worked out in the laboratory of the author concerning the problems of modifying cellulose have been considered. Special attention is given the following: (1) synthesis of new cellulose ethers and esters, (2) the introduction of new functional groups into the cellulose macromolecules, and (3) the synthesis of graft copolymers of cellulose.
The influence of monomer concentration and diluents on the polymerization of isobutene
Authors: Kennedy J. P. , Thomas R. M.
Published: April 2003

The relation existing between monomer concentration and degree of polymerization of polyisobutenes obtained in various diluents with AlCl3 catalyst has been investigated at −78°C. Methyl chloride, ethyl chloride, methylene chloride, vinyl chloride, and n‐pentane were used as diluents. It was demonstrated that the DP increases with decreasing monomer concentration irrespective of the investigated polymerization medium. A hypothesis which could explain the experimental facts is presented. The influence of dielectric constant on the molecular weight of polyisobutene has been studied in methyl chloride—carbon disulfide mixtures. The seeming contradiction existing between experimental findings and expectation based on older theories has been resolved by the introduction of “effective D.C.” theory. The “lifetime” of carbonium ions and the “temperature build‐up” in the fast low‐temperature polymerization has been estimated.
The chemistry of xylylenes. X. Some polymers and telomers of spiro‐di‐o‐xylylene
Authors: Errede L. A.
Published: April 2003

Spiro‐di‐o‐xylylene polymerizes via a free‐radical mechanism to give high molecular weight poly(o‐xylylene). It reacts with olefinic molecules, such as styrene, acrylonitrile, methyl methacrylate, vinylidine fluoride, and butadiene to give copolymers containing di‐o‐xylylene units in its backbone. Solutions of spiro‐di‐o‐xylylene can be titrated with iodine, and di‐o‐xylylene‐di‐iodide is produced stoichiometrically. Telomers of di‐o‐xylylene are obtained when the spiro compound is allowed to react in the presence of chain transfer agents such as HSR and CBr4.
Polyethers. XII. Poly‐(2,6‐disubstituted‐1,4‐phenylene oxides)
Authors: Kurian C. J. , Price Charles C.
Published: April 2003

A number of poly(p‐phenylene oxide) polymers have been prepared from 4‐bromophenols with various combinations of methyl, propyl, allyl, and phenyl groups in the 2,6‐positions. Potassium ferricyanide, lead dioxide, and 2,4,6‐tri‐tert‐butylphenoxy radical have been used as initiators. The reactions proceed to higher molecular weights under nitrogen. These polymers are soluble resins of low molecular weight, softening somewhat above 100°. Those with allyl groups become insoluble and infusible on exposure to air for several days.
Critical conditions for the formation of infinite networks
Authors: Khan Allan
Published: April 2003

The general expression for determining the critical point in the condensation of mixtures of A‐monomers of varying functionality with mixtures of B‐monomers of varying functionality has been obtained utilizing the assumptions made by Flory in his early work on the formation of infinite networks. It is shown that at the critical point, pApB = 1/[(f′ – 1)(g′ – 1)] where pA and pB are the respective probabilities that an A or B group has reacted, and f′ and g′, respectively, give the average functionality of A and B.
The mechanism of the anionic polymerization of methyl methacrylate. II. The use of molecular weight distributions to establish a mechanism
Authors: Glusker Donald L. , Lysloff Irene , Stiles Elise
Published: April 2003

Calculations of the molecular weight distribution to be expected from a nonterminated polymerization in which the rate of initiation is rapid with respect to that of propagation predict that the weight‐ to number‐average molecular weight ratio should approach 1.0. The ratios actually obtained are considerably larger than the predicted value; the resolution of this apparent contradiction is the central problem of this paper. Fractionation of isotactic poly(methyl methacrylate) was accomplished by a combination of two techniques: liquid‐liquid counter‐current extraction and elution chromatography. The fractionation indicated that: (1) The molecular weight distribution of these polymers is bimodal. (2) More than 90 mole‐% of the polymer chains has a molecular weight less than 2000. (3) These low molecular weight chains add tritium upon reaction with tritiated acetic acid and do not therefore result from irreversible termination reactions. (4) The molecular weight distribution of the high molecular weight material separated by elution chromatography is sufficiently broad to approximate a log‐normal distribution. (The log‐normal distribution is commonly used to characterize linear polyethylenes, which have very broad molecular weight distributions.) Kinetics were measured in a 90% toluene‐10% diethyl ether by volume mixture at −60°C. These experiments showed that: (1) The rate of polymerization appears to be first order in monomer and remains constant to very high conversion of monomer to polymer. (2) Plots of –In M/M0 versus time (where M and M0 represent monomer concentration at time t and 0. respectively) can be extrapolated to a finite conversion intercept at zero time. (3) This conversion corresponds to that required to form a species containing one fluorenyl group and three monomer units. (4) Plots of number‐average molecular weight versus time converge to the same intercept at zero time, regardless of the ratio of initial concentration of monomer to that of initiator, and that intercept is the molecular weight of the species just mentioned, FlM3. The mechanism which has been derived from these data has the following essential postulates: (1) Chains of different steric configurations may propagate at different rates even in a homogeneous medium. (2) A high percentage of the total number of chains started undergoes a “pseudotermination” whose probability is a function of the configurations of the last three monomer units in the chain. (3) When a chain attains a minimum length of 8–10 monomer units, the probability that further additions will take place in isotactic sequence is greatly increased. (4) The source of this increased probability is thought to lie in the inherent asymmetry of preferred helical conformations which may exist for chains of this minimum length in solution at −60°C.
Color and radical formation in irradiated polyvinyl chloride
Authors: Atchison G. J.
Published: April 2003

When polyvinyl chloride is irradiated with high energy radiation a visible color change varying through green‐yellow to deep red‐black is produced, depending upon the dose and temperature. Spectrophotometric and electron spin resonance techniques were used to investigate the formation of colored material by 2‐m.e.v. electron irradiation of unplasticized polyvinyl chloride moldings. The observed chemistry of the colored material is in agreement with the postulations of earlier workers that colored polyene structures are formed. Three radiation‐produced free radicals decaying at room temperature with half‐lives of 4.5, 63, and 1630 hr. were observed. The color in the 550 mμ region was found to be inversely proportional to the concentration of the long‐lived radical. The presence of absorption maxima in the 350–500 mμ region was observed in irradiated moldings and in tetrahydrofuran solutions of irradiated moldings.