bluuebunny/crossref_metadata_2025 huggingface dataset:
Osmometry with membranes permeable to solute
Authors: Staverman A. J. , Pals D. T. F. , Kruissink Ch. A.
Published: April 2003

Simultaneous measurements of osmotic pressure and permeation of solute have been made for a nonfractionated polystyrene with a number of membranes of widely different permeability. It is shown that, even after many days, no real equilibrium is reached in an osmometer with a membrane permeable to part of the polymer. The theory of equilibria in such osmometers is developed and shows that, in first approximation, the distribution of permeating solute over the two osmometer cells is not affected by the presence of nonpermeating solute. In second approximation, this distribution is affected indeed, but in this approximation the osmotic pressure is not affected by this unequal distribution. Some short‐time experiments also show that when the number of permeated molecules is negligible (t → 0) the contribution of a molecular species to the osmotic pressure is less than the value given by equilibrium thermodynamics if the membrane is not completely impermeable to that molecular species. This phenomenon is in accordance with the theory of permeability of membranes based upon nonequilibrium thermodynamics.
Velocity of dissolution of polystyrene
Authors: Ueberreiter K. , Asmussen F.
Published: April 2003

Six polystyrene fractions of molecular weights ranging from 1,300 to 250,000 were dissolved in amyl acetate a t various temperatures. The velocity of dissolution was measured by the increase in the refractive index. An assumption was made to describe the experimental results, namely, that the adhesive layer on the surface of solid polystyrene in solvent consists of macromolecular coils the diameter of which can be calculated by Flory's formula. Comparison of the value of the exponent A (from MA) obtained from viscosity measurements with the value calculated from the velocity of dissolution shows excellent agreement. The temperature dependence of the velocity of dissolution is dependent also on the diffusion process of the solvent molecules into the polymer. The expression for this diffusion derived by considering it, as usual, as a rate process, can be introduced into the equation for the velocity of dissolution. The resulting equation accurately describes the experimental results. The velocity of dissolution is different above and below the glass temperature of the polymer. It is possible to use the velocity of dissolution for a determination of molecular weight if the constant of the apparatus has been found by means of a standard sample of known molecular weight. This method helps in the difficult range of molecular weights from 5,000–40,000, where it is very sensitive, whereas other methods are not.
Diffusion de la lumière par des solutions de molécules en chaînes soumises à un champ électrique
Authors: Wippler C.
Published: April 2003

Dans le but de déterminer la portée pratique de l'étude de la lumière diffusée par des particules soumises à un champ d'orientation, nous avons établi les équations permettant de relier la variation de l'intensité diffusée aux caractéristiques moléculaires en fonction du champ d'orientation. Nous donnons tout d'abord les premiers termes du développement en série de ces équations dans le cas où la forme des particules et la nature du champ d'orientation sont quelconques. Puis, nous donnons l'expression complète de la fonction de répartition de l'intensité lumineuse dans le cas où le champ d'orientation est un champ électrique et où les molécules sont assimilables à des pelotes de Gauss. Les résultats de cette analyse théorique suggèrent une méthode expérimentale simple qui permet de caractériser la rigidité des molécules. Après une brève description de l'appareillage utilisé, nous citons, comme exemple d'applications, les expériences faites sur un échantillon de poly‐DL‐phénylalanine. En solution dans le benzène ces molécules se comportent comme des chaǐnes de Gauss flexibles. A partir des résultats expérimentaux il est possible de calculer, entre autres grandeurs physiques, la valeur du moment électrique porté par ses chaǐnons. Du point de vue pratique, le choix d'un champ électrique limite les applications aux molécules en chaǐnes porteuses d'un moment électrique. Cette restriction tomberait si l'on remplaçait le champ électrique par un champ hydrodynamique.
Group association equilibria in isolated polymer coils
Authors: Morawetz Herbert
Published: April 2003

When two or more groups attached to a single chain molecule participate in the formation of an association complex, the equilibrium for complex formation in dilute polymer solution depends on the local concentrations in the swollen polymer coil rather than on the stoichiometric concentration in the bulk of the solution. The theory of intramolecular group association is developed using two models. In the first, the interacting groups are evenly spaced along the polymer chain and the probabilities of their association are governed by Kuhn's statistics of chain configuration. In the second model, every segment of the chain has the same probability of carrying an interacting group and the Kuhn statistics are applied only to large rings, the probability of small ring formation being governed by steric factors. The predictions of the theory are in agreement with the extent of carboxyl association in dilute solutions of seven styrene‐methacrylic acid copolymers, measured by infrared spectroscopy. The chelation of cations in dilute polyelectrolyte solution also involves the participation of groups attached to a single macromolecule, but the interpretation of experimental data requires that the electrostatic free energy of complex formation be taken into account. Spectroscopic evidence shows that in copper(II) binding to poly(methacrylic acid) or poly(N, ε‐methacrylyllysine) higher complexes are formed than in solutions of simple carboxylic acids or α‐amino acids, respectively. Dialysis equilibrium studies indicate that, in the concentration range 4.7 × 10−3 to 15.6 × 10−3 N poly(acrylic acid), the polymer coils act independently of each other in chelating small amounts of copper(II), while the copper (II) affinity of poly(methacrylic acid) molecules drops off with rising polyacid concentration.
Solution behavior of chemically synthesized polyglucoses
Authors: Mora P. T.
Published: April 2003

The solution behavior of polyglucoses prepared by the acid catalyzed polycondensation of Pacsu and Mora is discussed. According to this method glucose enters the polycondensation through the hemiacetal hydroxyl joining any of the other hydroxyls of a second glucose unit. Branching occurs up to the functionality of glucose but infinite network is not formed since the branching probability can only approach but never reach unity. The resulting polyglucose is a highly branched spherical molecule, readily soluble in water. Each polyglucose molecule contains one unreacted glucosidic hydroxyl in accordance with the suggested polycondensation scheme, as the agreement between osmotic and reducing end group number‐average molecular weights indicate. The intrinsic viscosity is very low ([η] = 0.08 at Mw 100,000) and increases only slightly with the weight‐average molecular weight, suggesting that the molecule is highly branched: a double logarithmic plot of [η] against Mw has a downward curvature and does not follow the straight line with a slope of 0.50, valid for linear molecules. Periodate oxidation data indicate that fractionation occurs not only by molecular weight but also by the extent of branching, and the lower molecular weight products appear to have relatively less branching.
A simple theory of thermodynamic properties of polyelectrolyte solutions
Authors: Oosawa Fumio
Published: April 2003

The osmotic coefficient and the activity coefficient of polyelectrolyte solutions were calculated by applying the relation of the chemical equilibrium between counterions retained in the apparent volume of polyelectrolyte molecules and those free from molecules. The relation of these coefficients to the concentration of polyelectrolytes depends on the shape of molecules and thus the qualitative difference observed in the behavior of the coefficients of different polyelectrolytes can be explained. The effect of valencies of ions was studied. In a mixture of counterions, all ions of the larger valency are bound by polyelectrolyte molecules when the density of ionized groups on molecules is larger than a certain value determined by the mixing ratio of counterions. The swelling force of polyelectrolyte gels was obtained by a similar method. A new formula is presented in which the osmotic force of counterions retained by chains plays an important role. the anisotropy of the swelling force of gels with oriented chains is attributable to the anisotropy of this osmotic force.
Potentiometric titration of polyacrylic and polymethacrylic acids with alkali metal and quaternary ammonium bases
Authors: Gregor Harry P. , Frederick Michael
Published: April 2003

Lithium ions, and, to a lesser extent, the sodium ions are bound by polyacrylic acid, as evidenced by pH titrations of polyacrylic acid in dilute (0.01 M) solutions of the alkali metal bases and solutions of their corresponding salts. The formation constant for the binding of lithium to polyacrylic acid was found to be 1.9. When dilute solutions of polyacrylic and polymethacrylic acids were titrated with quaternary ammonium bases, the polyacids became progressively weaker with increasing size of the counterion. These phenomena suggest that the counterions are largely held in close proximity to the polyanion chain, with distances of approach comparable to the sum of the ionic radii. Titrations of these acids with a mixture of a large and small cation also served to point up the increased chain potential in the presence of large cations. All of these effects are absent with the analogous low molecular weight acids.
Viscometric and conductometric titrations of polymethacrylic acid with alkali metal and quaternary ammonium bases
Authors: Gregor Harry P. , Gold Daniel H. , Frederick Michael
Published: April 2003

The reduced specific viscosity of polymethacrylic acid increased with counterion size at the same degree of neutralization for the cations: sodium < tetramethylammonium < tetraethylammonium < tetrapropylammonium < tetrabutylammonium. The increase on going from sodium to tetrapropylammonium at 50–70% neutralization was 20–25% for 0.003–0.01 M polymer, about 4% in 0.001 M solutions. These data indicate that a significant fraction of even large counterions are close to the chain. Conductometric titrations showed that the equivalent conductance of the polyanion was about 40 for most of the salts studied and at low values of α. The binding of counterions based upon the assumption that this value was constant over α led to values which were in reasonable agreement with those determined by Wall using transport experiments.
Theory of the effect of counterion size upon titration behavior of polycarboxylic acids
Authors: Kagawa Ikumi , Gregor Harry P.
Published: April 2003

The effect of the ionic radius of counterions has been introduced into the dissociation theory of polyelectrolytes, using the familiar rod‐like model. Increments in the average dissociation constant pKa and slope n for polyacrylic acid with increasing size of the gegenion have been calculated and compared with data using potassium and some tetraalkylammonium hydroxides. Good agreement is encountered. The effects of changes in concentration of the polyacid and of the presence of neutral salt are also considered.
Sur la notion de l'activité dans les solutions colloïdales
Authors: Dobry‐Duclaux A.
Published: April 2003

Sur diverses solutions colloïdales de polyélectrolytes globulaires ou filiformes j'ai mesuré, à diverses concentrations, la conductivité électrique, la vitesse de migration des particules et de leur ions compensateurs (counterions), ainsi que l'activité électrométrique de ces derniers. La vitesse de migration et le coefficient d'activité des ions compensateurs augmentent par dilution pour atteindre les valeurs des ions dans les solutions salines ordinaires. J'assimile la particule colloïdale réelle à une particule fictive équivalente qui est libre dans son mouvement et entourée par des ions compensateurs également libres. J'admets que l'influence des interactions électrostatiques est la měme sur la mobilité et sur l'activité; ainsi le nombre d'ions compensateurs “libres” est donné par l'activité. Cette hypothèse donne des résultat conformes à l'expérience. Elle permet de calculer la conductivité d'une solution colloïdale et de prévoir le sens et la grandeur de la vitesse de migration des ions compensateurs à partir des données d'activité. Elle donne pour le nombre de charges de la particule colloïdale des chiffres concordants quel que soit le mode de calcul: à partir de la vitesse de migration, de la conductivité ou de l'activité, contrairement à la méthode usuelle qui conduit à des chiffres discordants. Les résultats expérimentaux concernant la vitesse de migration ont été comparés avec les valeurs calculées d'après la théorie d'Overbeek, basée sur le freinage électrophorétique. Aux concentrations très faibles, l'accord entre les valeurs calculées et observées est bon. Aux concentrations plus fortes, les vitesses théoriques sont trop faibles.
Some statistical problems concerning linear macromolecules
Authors: Hill Terrell L.
Published: April 2003

The matrix method which has been employed in the theory of ferromagnetism is potentially very useful in treating statistical problems concerning linear macromolecules with repeating units. The method is reviewed briefly and applied to seven illustrative problems (two of which are not worked out completely). Six of these involve ion binding or titration curves of polyelectrolytes and one has to do with the question of imperfections (missing hydrogen bonds) in the α‐helix.
A dielectric study of sodium alginate in aqueous solution
Authors: Allgén L.‐G. , Roswall Siw
Published: April 2003

Specimens of sodium alginate have been investigated dielectrically in aqueous solution at low concentrations. The effect on the dielectric increment and dispersion of concentration of polyions and counterions, isoionic dilution, degree of polymerization and degree of neutralization of polyions, and the dielectric constant of the solvent has been studied mainly. Qualitative interpretation of the data in accordance with the present polyelectrolyte theory as Maxwell‐Wagner or Debye‐Falkenhagen effects has been attempted.
Surface chemistry of synthetic electrolytic polypeptides
Authors: Isemura Toshizo , Hamaguchi Kozo , Ikeda Shoichi
Published: April 2003

The copolypeptide of L‐lysine, L‐leucine, and L‐glutamic acid, and that of DL‐lysine, DL‐phenylalanine, and DL‐glutamic acid were studied by surface pressure and surface viscosity measurement. The relationships between ionization and monolayer properties were thoroughly studied. The monolayer of poly‐L‐glutamic acid was also investigated. These polyelectrolytic monolayers were affected by pH of the substrate and the concentration of salt in it. The monolayer behavior could be interpreted in terms of effective free charges and the number of salt linkages. The two‐dimensional Donnan equilibrium was applied to the polyelectrolyte monolayer. The derived relation is formally identical to that derived by Davies from an entirely different point of view.
Potentiometric titration of polyelectrolyte gels
Authors: Michaeli I. , Katchalsky A.
Published: April 2003

The dependence of the degree of ionization of highly swollen, crosslinked polyelectrolyte gels (immersed in salt solution) on the pH of the external equilibrium solution was investigated. A potentiometric equation was derived theoretically, comprising an ideal term, a Donnan term, and a term due to polyelectrolyte electrostatic interactions. Measurements were carried out with polymethacrylate gels in solution of LiCl, NaCl, or KCl. No difference in behavior was found with the different cations, and the observed dependence of the titration curves on ionic strength, degree of crosslinking, and degree of swelling was satisfactorily accounted for by the theory.
Sur le comportement physico‐chimique des solutions d'acide désoxyribonucléique du phage D4 de salmonella enteritidis
Authors: Barbu E. , Basset J. , Joly M. , Wahl R.
Published: April 2003

L'acide desoxyribonucléique est extrait du phage D4 par différentes techniques: compression, chaffage, alcalinisation, etc. Les solutions aqueuses correspondantes sont étudiées, en fonction de divers facteurs physiques (concentration, pression, température, pH, force ionique...) par viscosité, par biréfringence d'écoulement et par absorption UV. L'activité biologique des phages au cours des différents traitements est également déterminée. Toutes les solutions étudiées sont fortement polydispersées. Pour chacune d'elles on a déterminé la longueur des particules d'ADN les plus fréquentes, leur anisotropie optique et leur taux de polydispersion. Les résultats obtenus sont comparés à ceux relatifs à l'ADN du thymus de veau. La question de la compatibilité des dimensions des particules du phage et de celles beaucoup plus grandes des particules de l'ADN libéré est discutée et une interprétation est proposée en vue de lever les contradictions apparentes.
Études physico‐chimiques sur deux catégories d'acides désoxyribonucléiques
Authors: Pouyet J. , Weill G.
Published: April 2003

L'examen des viscosités intrinsèques d'échantillons de DNA en fonction de la masse permet de mettre en évidence deux catégories d'acides thymonucléiques. On a étudié systématiquement le coefficient d'extinction molaire à 2 590 å et montré qu'il existe également und différence sur εp entre les deux catégories. Il n'y a pas de différence de comportement vis‐à‐vis de la dégradation ou de la dénaturation thermique, ni de variation systématique dans les données analytiques. On donne deux mécanismes possibles permettant d'interprěter les deux catégories.
Des études physico‐chimiques les plus récentes sur l'amidon
Authors: Samec M.
Published: April 2003

Les amidons de plantes différentes et de leurs fractions donnent après leur dissolution et leur dessication des images très diverses dans le microscope électronique. Elles se différencient aussi dans leur spectre infrarouge et surtout dans le domaine d'absorption qui correspond aux groupes d'atomes qui contiennent de l'oxygène. Dans ce domaine d'absorption, les processus de vieillissement deviennent perceptibles eux aussi. Les spectres infrarouges des films d'amidons désséchés laissent conclure à des liaisons d'hydrogène très importantes. Des phénomènes de vieillissement peuvent s'observer également à l'aide du spectre ultra‐violet, surtout dans un milieu alcalin.
Cupriethylenediamine and cuprammonium hydroxide as solvents in molecular fractionation of cellulose
Authors: Sihtola Hannes , Kaila Ermo , Laamanen Lauri
Published: April 2003

The possibilities of using cupriethylenediamine (or cuprammonium hydroxide) solution as solvent in molecular fractionation of cellulose was investigated. From the results the following conclusions could be drawn. (1) A real fractionation based on different dissolving power of cuene or cuoxam solutions of different copper concentration seems not to be possible. The results of such fractionations presented in the literature seem rather to be due to a fractionation on the basis of the accessibility. A clear relationship seems to exist between molar concentration of the excess copper in solution and, respectively, per cent dissolved substance and [η] value of the undissolved substance. (2) Precipitation of cellulose from a cuene solution by means of an acid does not bring about a fractionation according to chain length. (3) Fractionation takes place according to chain length when the precipitation of cellulose from a cuene solution is carried out by means of organic liquids, among which propanol has proved to be the most suitable one. In this case the precipitation is caused by decrease of the degree of solvation of the cellulose‐cuene complex. (4) Fractionation can be brought about by raising the temperature of a propanolcontaining cuene solution of cellulose. (5) Considering the depolymerization of cellulose in cuene and cuoxam solutions these solvents cannot be regarded as suitable for determination of the chain length distribution of cellulose.
Le mécanisme du gonflement de la cellulose régenerée
Authors: Nowakowski Aleksander
Published: April 2003

(1) En se referrant à la littérature et ses propres expériences l'auteur arrive à la conclusion que, si l'on veut améliorer les qualités physicochimiques des fibres de cellulose par des résines polycondensées, il faut s'en tenir à trois principes; notamment: il faut empêcher la formation d'un polycondensé sur la surface des fibres, incorporer les matières plastiques aux pores et à l'interieur des fibres et adapter à chaque cas particulier la qualité de la résine au type des fibres données. (2) Pour approfondir l'étude des lois fondamentales de nature physico‐chimique qui régissent le domaine de la cellulose, le degré de gonflement des hydro‐, aero‐ et organogels isotropiques de la cellulose régenerée a été mesuré ainsi que la dialyse des macromolecules à travers des membranes. (3) Les degrès de gonflement (v) des fils isotropiques de la cellulose régénerée ont été determinés dans l'eau et dans 7 solvants organiques (anhydriques et dilués a l'eau à de differentes concentrations). A la suite de ces résultats les conclusions suivantes peuvent êntre tirées: (a) Le dioxane, la pyridine et le formamide constituent des moyens ideaux pour extruder l'eau liée dans les hydrogels (v = 6,6 à 7,6). Ils se prêtent donc parfaitement à l'impregnation des soies artificielles et à des expériences sur la dialyse. Ce qui est pourtant frappant, c'est la faible aptitude de gonflement de la cellulose sèche dans les solvants mentionnés. (b) L'acide formique occupe une place intermédaire, ayant un degré de gonflement v = 5,8, event. 5,4 pour la filature humide ainsi que pour la matière sèche. (c) Certains solvants (acétone, tétrahydrofurane) donnent des degrés moyens de gonflement (v = 5,3, event. 5,0), si l'extrusion de l'eau du hydrogel par des solvants organiques dont la concentration s'élève graduellement.
Reversible heat coagulation of some water‐soluble amino acid copolymers
Authors: Noguchi Junzo , Hayakawa Tadao , Ebata Mituo
Published: April 2003

Poly‐ε‐aminocaproyl‐DL‐alanine, [HN(CH2)5COHNCH(CH3)CO]n, was prepared by the polymerization of N‐carbothiophenyl‐ε‐aminocaproyl‐DL‐alanine. The copolymer synthesized precipitates from an aqueous saturated solution on heating (40 to 60°). The precipitate formed goes back into solution on cooling. Repeated precipitation and dissolution by change of temperature show that the heat coagulation is reversible. The coagulation phenomenon discussed is pH‐dependent, but practically independent of ionic strength or the presence of denaturing agents such as urea. The ability of the following polymers to coagulate from an aqueous solution on heating was investigated: H[HN(CH2)mCOHNCH(CH3)CO]nOH (I), m = 1,2,3,4,5; and H[HN(CH2)mCO]nOH (II), m = 1.2,3,4,5. None of the polymers investigated, except poly‐ε‐aminocaproyl‐DL‐alanine (I, m = 5) showed reversible heat coagulation. The polymers of group I dissolve in water more readily than those of group II. The aqueous solutions of I, m = 1; I, m = 3; and II, m = 1, give a distinct positive biuret reaction. In a series of copolymers of α‐amino acids with ε‐aminocaproic acid it was observed that reversible heat coagulation in water occurs in copolymers containing L‐proline or α‐aminoisobutyric acid, but not in copolymers containing glycine, L‐leucine, or L‐phenylalanine. Reversible heat coagulation was also observed in the case of poly‐L‐proline.
Effect of long‐chain branching on some solution properties of polyethylene
Authors: Trementozzi Q. A.
Published: April 2003

Two polyethylene samples polymerized by the standard high‐pressure technique employing oxygen as the initiator were resolved into a total of 19 fractions. Also, a Zieglertype polyethylene was separated into 12 fractions. A comparison of the intrinsic viscosities and the number‐average molecular weights of the polyethylene fractions prepared at high pressure over a broad molecular weight range shows that the spatial requirements of the polymer molecules increase anomalously with molecular weight. It is shown that this behavior is not due to increasing frequency of over‐all chain branching. Rather, it is due to the increasing degree of long‐chain branching with molecular weight. A comparison of the intrinsic viscosities of unbranched with branched polyethylene at a number‐average molecular weight of 200,000 indicates there are approximately 4 tetrafunctional branch points per molecule. It is demonstrated that polyethylene solutions can be passed through ultrafine filters without loss of soluble polymer under the proper conditions. Angular light scattering intensity measurements of clarified polyethylene solutions in Tetralin show that unbranched polyethylene has a normal M̄w/M̄n ratio, whereas branched polyethylenes have M̄w/M̄n ratios from 7 to more than 100. For the more highly branched polyethylenes it is shown that the dissymmetry method seriously undercorrects the weight‐average molecular weight because of nonconformity to a randomly coiled molecule. The M̄w values of fractions of high‐pressure polyethylene show increasing polydispersity with increasing molecular weight, which is attributed to the influence of long‐chain branching. The magnitude of the polydispersity of these fractions and the parent polymers (high‐pressure) suggests that the degree of long‐chain branching is much greater than previously assumed.
Polymers and group interaction. IV. Hofmann reaction on polyvinylamides
Authors: Mullier M. , Smets G.
Published: April 2003

The Hofmann degradation reaction has been applied to polyvinylamides in order to obtain aminocarboxylic polyampholytes. When the reaction is effected in aqueous solution, interactions occur between isocyanate and neighboring chloroimide ions, with the formation of butyrolactam ring units incorporated in the polymeric chain. The structural composition of the polymers has been determined on the basis of the following analytical results: total and volatile nitrogen, total and ionic chlorine, and conductometric and potentiometric titrations. In the case of polymethacrylamide the end product consists of about 57% lactam rings, 28% free amine chlorohydrate, and 8% methacrylic acid units, while about 5 to 6% amide groups remain unreacted. In the case of polyacrylamide the degree of conversion is usually lower; this difference in behavior has been interpreted as being due to the high substitution in the methacrylic derivative. When the reaction is effected in water‐methanol (50/50) solution, any ring formation is absent; contrariwise, the isocyanate functions are transformed into carbamate units. In alcoholic medium it is possible to obtain polymers containing about 50% carbamic functions, as well as small amounts of free amines (3%); the residual percentages are acid or unreacted amide groups. On alkaline hydrolysis of these carbamic functions, free amine functions are produced; however, the rate of hydrolysis is very low if compared to that of usual amides. This effect has been attributed to the nitrogen substitution in the carbamate units
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and to the electrostatic repulsion effect of the carboxylate functions toward the hydroxyl ion. For verification, the alkaline hydrolysis rate constants of N‐isopropyl methylcarbamate have been compared with those of methylcarbamate; they were found to be about ten times slower. Moreover, the corresponding activation energy of alkaline hydrolysis was 18.7 kcal./mole instead of 14.1 in the case of the unsubstituted methylcarbamate. The products obtained by Hofmann degradation on polymethacrylamide have been compared to those obtained by Lossen rearrangement reaction on polymethacroyl chloride; the structural units were found to be identical in both cases.
Poly‐2‐ and poly‐4‐vinylpiperidine
Authors: Katchalsky A. , Rosenheck K. , Altmann B.
Published: April 2003

Poly‐2‐vinylpiperidine and poly‐4‐vinylpiperidine were prepared from poly‐2‐vinylpyridine and poly‐4‐vinylpyridine, respectively, by catalytic hydrogenation at a hydrogen pressure of 3500 p.s.i. and a temperature of 220–250°C., using a palladium catalyst. The hydrochlorides, acetyl derivatives, and phenyl thioureates of the new polymers could also be obtained. The molecular weights of the polymers were estimated by light scattering and viscosity in chloroform and methanol solution and were found to lie in the range of 10,000 to 35,000. The electrochemical properties were investigated by potentiometric titration and electrophoresis. From the character of the titration curves it was concluded that no appreciable nearest neighbor interaction exists in polyvinylpiperidine. By an analysis of the combined potentiometric‐electrophoretic data an intrinsic acid dissociation constant pK0 = 10.08 ± 0.07 was calculated. The discrepancy between this value and the value of the dissociation constants of monomeric piperidines, pK ≈ 11, has been further investigated by thermochemical measurements.
Viscometric properties of salicyloxymethyldimethyl end‐blocked dimethylpolysiloxanes
Authors: Merker Robert L. , Scott Mary Jane
Published: April 2003

Viscometric data obtained over a temperature range of 0–150°C. for a series of salicyloxymethyldimethyl end‐blocked dimethylpolysiloxane fluids have shown that the molecular weight at which a minimum viscosity is exhibited is temperature‐dependent. Thus, with decreasing temperature, minimum viscosities were manifested at higher molecular weights. With increasing molecular weight, i.e., increasing siloxane character, the energy of activation of viscous flor (Evisc) not only decreases, but also is less temperature dependent. An empirical expression relating Evisc and temperature for such fluids is presented.
Acrylonitrile polymerization in aqueous suspension
Authors: Thomas W. M. , Gleason E. H. , Mino G.
Published: April 2003

Polymerization of acrylonitrile in dilute aqueous solution initiated by the chloratesulfite redox was studied kinetically and with the aid of the electron microscope. Polymerization rate depended on the [ClO] [H2SO3] product, the monomer content and the sodium lauryl sulfate concentration. The rate was depressed by agitation and by salts; it was accelerated by Fe++ and by Cu++ and was only moderately dependent on temperature. Particles of polymer separated from the start as spheroids less than 200 A. across and grew rather uniformly to 2000 to 3000 A. After a short time no new particles formed unless more initiator was added. Rate of polymerization per particle was reasonably constant. Salts and agitation led to aggregation of particles and polymerization rate was reduced. Sodium lauryl sulfate and Methocel had the opposite effect. The system bears a general resemblance to typical emulsion polymerization, and thus treatments based on homogeneous kinetics appear to be inadequate.
The system cellulose—methanol
Authors: Lauer K. , Ayer J. E. , A. Seoud Abdel Latif
Published: April 2003

The determination of nonsolvent methanol by a drying technique on cotton and mercerized cotton fibers and a comparison with corresponding values of nonsolvent water showed that methanol forms solvates only with half the number of hydroxyl groups available for hydrate formation in the amorphous part of the fibers. It showed, furthermore, that methanol does not form solvates with hydroxyl groups in semicrystalline regions of mercerized fibers. The method also permits determination of nonsolvent methanol with fibers which reach equilibrium from the wet side. A schematic approach to fiber structure gives good agreement between the quantities of nonsolvent water and methanol and molar integral heats of wetting, respectively. Both characteristics permit an estimation of fiber composition of natural cellulose fibers.
New polymerization catalysts for methyl methacrylate
Authors: Lal Joginder , Green Richard , Ellis Sylvia
Published: April 2003

New free radical catalysts for the polymerization of methyl methacrylate and other acrylic monomers have been reported. They comprise mixtures or salts of N,N‐dialkyl aryl amines and o‐benzoic sulfimide (saccharin). A p‐substituent on N,N‐dimethylaniline or N,N‐diethylaniline had a significant influence upon polymerization. Electron‐donating groups such as methyl or methoxy increased the total yield of the polymer, while electron‐withdrawing groups, namely, chlorine, bromine, or aldehyde, reduced the yield of the polymer. When electron‐withdrawing groups, namely, nitro, nitroso, or phenylazo, were present in the para position of dimethylaniline, no polymer was obtained. Presence of a methyl group in the meta position in dimethylaniline enhanced the yield of the polymer. However, when a methyl group was present in the ortho position, the yield of the polymer was significantly reduced, probably due to a steric factor. Binary mixtures containing equimolar proportions of saccharin and the amine were better initiators for methyl methacrylate polymerization than the corresponding salts of saccharin and amine. A number of organic acids in admixture with dimethylaniline also polymerized methyl methacrylate. The stronger the acid, the greater was the yield of the polymer. However, the yields were considerably lower than in case of dimethaniline‐saccharin mixture as catalyst.
Anomalous behavior of vinylidene cyanide in copolymerization
Authors: Ham George E.
Published: April 2003

Copolymerization data involving a wide variety of monomers containing methylenic double bonds led to the conclusion that only acrylonitrile exhibited repulsive effects between adding monomer and copolymer containing higher proportions of the same monomer. Employing a modified procedure based on the Barb equation r1 and r1′ values were determined for the following systems: methyl α‐chloroacrylate‐vinylidene cyanide, methyl methacrylate‐vinylidene cyanide, acrylic acid‐vinylidene cyanide, 2,5‐dichlorostyrene‐vinylidene cyanide, vinylidene chloride‐vinylidene cyanide, and 2‐chlorobutadiene‐vinylidene cyanide. These results confirm the predicted diversions from normal copolymerization behavior of vinylidene cyanide as well.
A comparison of different membranes for osmotic determination of the molecular weight of nitrocellulose
Authors: Alvång Folke , Samuelson Olof
Published: April 2003

Osmotic determinations of the degree of polymerization of cellulose nitrate have been performed using different types of cellulosic membranes. For unfractionated samples the results were dependent upon the type of membrane, whereas for fractionated samples good agreement was obtained for different membranes. The leakage of nitrocellulose through the membrane has been determined. In separate experiments the solution used for measurements in osmometers with coarse membranes were transferred to osmometers with tighter membranes. A considerable increase in osmotic pressure was observed in the latter case; this shows that the lower osmotic pressure obtained in osmometers with nonselective membranes cannot be ascribed solely to a lowering in the molar concentration because of leakage. The results are in agreement with the theory postulated by Staverman. Plots of osmotic pressure against time as well as direct determinations of the leakage give insufficient information about the error obtained when using nonselective membranes.
Preparation of graft copolymers by the reaction of primary amine‐terminated polystyrene with copolymers containing β‐isocyanatoethyl methacrylate
Authors: Graham Roger K.
Published: April 2003

A variety of polymers containing pendant isocyanate groups was prepared by the copolymerization of small amounts of β‐isocyanatoethyl methacrylate. Polystyrenes prepared by sodium amide initiation in liquid ammonia at −33°C. were characterized and shown to contain one terminal primary amine group per polymer chain. Approximately equivalent amounts (by functional group) were reacted in a dry inert solvent, generally at room temperature for one to two days. Graft copolymers were formed in high efficiency; this was conclusively shown for graft copolymers of poly(methyl methacrylate)‐polystyrene by disappearance of titratable amine groups, extraction of the graft copolymer with diethyl ether, ultraviolet analysis of the product, and agreement between calculated and actual number‐average molecular weight. The preparative method allows control of the length of the backbone and number of attached polystyrene side chains; the complete structure of the graft copolymer is known, including the number and length of side chains.
The rate of particle growth in persulfate initiated emulsion polymerization
Authors: Roe Charles P. , Brass P. D.
Published: April 2003

The initial growth rate of a particle in a polymerizing emulsion is constant with respect to time and also with respect to the aqueous concentration of the initiator. However, as a particle becomes larger, a size is reached where positive deviations from this constant rate are observed. It is shown that the kinetic analysis of Ewart and Smith qualitatively implies this type of behavior. In order to obtain quantitative agreement between theory and experiment, It is necessary to assume that free radicals entering a particle are generated at the particle‐water interface. When this restriction is imposed on the kinetic analysis, the latter gives a highly satisfactory account of the experimental results throughout the region in which the approximation employed in the analysis is valid. The results of the analysis indicate specifically a nontrivial dependence of the kinetics of emulsion polymerization on particle size and initiator concentration.
A study of the creep of nitrocellulose
Authors: van Holde Kensal
Published: April 2003

The creep of a highly nitrated cellulose under constant tensile load has been investigated. Over a wide time range, the strain–time curves were found to obey an equation frequently used to describe the creep of metals. This analysis separates the creep into two components, a rapid elastic deformation and a deformation increasing with the 1/3 power of the time. The first of these components was found to be directly proportional to the applied stress, while the second increased very rapidly with increasing stress, again in accord with observations on metallic creep. The recovery following short creep experiments was found to be complete and accurately predictable from the creep curves and a modified form of the Boltzmann superposition principle. This was not true of the recovery following a very long creep experiment. The superposition principle was also used to calculate a “stress–strain” curve from creep data. This curve was found to be qualitatively similar to curves which have been reported for nitrocellulose.
Viscometric evidence of critical concentration in dilute polymer solution
Authors: Cragg L. H. , Bigelow C. C.
Published: April 2003

Two viscometric methods have been developed for detecting the “critical concentration” (the concentration at which individual polymer molecules interfere with each other) of a dilute solution of a high polymer, B. In the first of these, the intrinsic viscosity, [η], of another polymer, A, is measured in a series of mixed solvents, each consisting of a solution of Polymer B in the solvent S, and each differing from the others only in the concentration of B (CB). For a number of polymer‐polymer‐solvent systems, data are presented which show that [η] is essentially independent of CB, except over a small range where its value changes fairly abruptly. This change marks the critical concentration. The second method is much faster but probably less reliable than the first. Nevertheless, the two gave values in good agreement. A method of calculating the critical concentration, based on the Flory‐Fox theory of intrinsic viscosity, is described. Critical concentrations calculated for the several systems investigated agreed well with those obtained experimentally. The critical concentration was shown to be inversely proportional to the intrinsic viscosity of the Polymer B in experiments in which [η]B was varied by changing the molecular weight of the polymer and by changing the solvent. The effects observed are explained as resulting from interactions of the two polymer species in the solutions.
Some aspects of the direct and cyclohexanone‐sensitized photopolymerization of vinyl chloride
Authors: Valentine L.
Published: April 2003

It is shown that the direct photopolymerization of pure vinyl chloride in bulk shows a “gel effect,” i.e., a long period of accelerating rate at the beginning of the reaction. Cyclohexanone acts as both a solvent for the polymer and a photosensitizer for the polymerization. The mechanism of initiation by cyclohexanone is discussed; it is by no means certain that diradicals are formed.
Mastication. V. Separation and structural investigation of natural rubber‐polymethyl methacrylate interpolymers formed by mastication
Authors: Angier D. J. , Watson W. F.
Published: April 2003

Polymerization of methyl methacrylate admixed with natural rubber occurs on rupture of rubber molecules to free radicals by applied shearing forces. The polymeric products after different conditions and extents of reaction have been separated into uncombined rubber, two interpolymer fractions, and uncombined polymethyl methacrylate by fractional precipitation and extraction methods. The structure of the interpolymers has been investigated by measurement of composition and osmotic molecular weight, ozonolysis to degrade the rubber segments and isolation of the polymethyl methacrylate fragments, autoxidation of the rubber segments, and viscosity measurements on the uncombined rubber. The interpolymer is a linear block polymer containing one polymethyl methacrylate segment and of the order of one or two rubber segments per molecule. The Trommsdorff gel effect has a profound influence on the rate of formation, composition, and structure of the interpolymer.
Molecular weight heterogeneity in starch amylopectins
Authors: Stacy Carl J. , Foster Joseph F.
Published: April 2003

The number‐average molecular weight of a corn amylopectin sample is concluded to be approximately 300,000 on basis of both osmotic pressure and reducing group determination. The weight‐average molecular weight of this preparation was previously shown to be approximately 80 × 106. The ratio of Mw/Mn is in accord with that expected on the basis of an essentially random synthesis of the branched polymer. Further evidence for an extreme heterogeneity in amylopectins in provided by light scattering studies on subfractions prepared by fractional centrifugation. Conclusive evidence for this broad heterogeneity is obtained by ultracentrifugal analysis. The distribution of sedimentation coefficients is shown to be extreme, significant percentages of the polymer having sedimentation constants ranging from almost zero to above 400 Svedberg units. Some observations on the sedimentation behavior of other amylopectins, their β amylase limit dextrins, and corn amylose are given.
Colligative properties of polyelectrolyte solutions. IV. Activity coefficient of sodium ion
Authors: Nagasawa Mitsuru , Kagawa Ikumi
Published: April 2003

By the concurrent use of the ion exchange membrane electrode in addition to the sodium amalgam electrode, the ionic activity of sodium ion in salt‐free polyelectrolyte solutions was determined over a considerably wide range of sample concentration. As polyelectrolyte samples, several kinds of sodium polyvinyl alcohol sulfates differing in their degrees of esterification and degrees of polymerization (sodium polystyrene sulfonate, sodium cellulose sulfate, and carboxymethylcellulose) were used. The peculiar dependency of the activity coefficient of sodium ion upon the sample concentration first noted by Kern was confirmed with all samples in this study; that is, γNa+ decreases with dilution of the sample solution. Further, it was confirmed that the degree of esterification, viz., the charge density on a linear polymer, is a most important factor while the activity coefficient is entirely independent of the degree of polymerization. The influence of structure of the polymer skeleton upon the activity coefficient was found to be comparatively small. Some of the above results were discussed on the basis of the authors' theory published in a previous paper.
Transitions in plasticized and unplasticized cellulose acetates
Authors: Russell J. , Van Kerpel R. G.
Published: April 2003

The temperature‐dependence of specific volume, rigidity modulus, and mechanical losses of plasticized and unplasticized cellulose acetates in the temperature range −100 to +200°C. has been studied. Two cellulose acetates, a triacetate and a cellulose (2.2) acetate were used, these being plasticized with varying amounts of either benzyl acetate, m‐cresol, o‐ethylphenol, γ‐butyrolactone, monomethylaniline, benzylphenol, or Santophen 7 (a phthallyl glycolate). The specific volume measurements, made using an extremely sensitive dilatometer, indicated three apparent second‐order transitions and one first‐order (melting) transition in cellulose triacetate and three or possibly four apparent second‐order transitions but no first‐order transition in the cellulose (2.2) acetate. Both the first‐order and second‐order transitions were depressed by the addition of plasticizer, the depression being most marked with the phenolic‐type plasticizers. Because of polymer decomposition at temperatures above 200°C., it was not possible to study the melting of mixtures containing less than 30% plasticizer and subsequently no reliable values for the melting temperature, the entropy, and the heat of crystallization could be determined. Rigidity modulus measurements, obtained using a torsional pendulum technique and the mechanical loss (damping) measurements, confirmed the existences of these second‐order transitions in both acetates and indicated that only the highest temperature transition, 175°C. in the triacetate and 195°C. in the secondary acetate, had the characteristics of a normal glass to rubber transition.
Filler reinforcement of silicone rubber
Authors: Bueche A. M.
Published: April 2003

Modulus and swelling measurements were made on silicone rubber samples compounded with five different fillers. The data were at variance with the predictions of the theory of modulus reinforcement by Weiss, Rehner, Smallwood, and Guth. The results, when analyzed using a modification of the kinetic theory of elasticity proposed by the author, indicate that the increase in modulus and decrease in swelling are due primarily to polymer‐filler attachments. The areas per attachment were found to be of the order of a few square angstroms and to vary with the filler. With some fillers the same area values were obtained from modulus and swelling measurements. With others, the swelling liquid apparently displaces polymer from the filler surfaces.