Showing papers in "Journal of Polymer Science Part C: Polymer Symposia in 1967"

On the Structure and Properties of Polyamides. XXVII. The Mechanism of Water Sorption in Polyamides

Abstract: The sorption and the desorption isotherms of water are described for several crystalline polyamides (nylons 2, 3, 6, 7, 8, 11), amorphous polyamides (poly-C-methylcaprolactam, terpolymer of caprolactam, aminoheptanoic acid and aminoundecanoic acid) and model amides (N-ethyl acetamide, Y-ethyl butyramide, N-butyl capronamide) at 27°C., with amides also at 40 and 55°C. On the basis of our own as well as reported data (on sorption isotherms, heat balance of sorption, sorption heats, infrared absorption, nuclear magnetic resonance, mechanical properties of polyamide-water systems), we propose the following mechanism for the sorption of water in polyamides (capillary condensation is not considered): In nylon 6, three molecules of water are sorbed on two neighboring amide groups in an accessible region. The first molecule forms a double H-bonds between the CO groups (firmly bound water) and the other two molecules form H-bonds between the CO and the NH groups (loosely bound water). It turns out that even in nylons 2 to 6, water is probably sorbed by this mechanism whereas in nylons 8 to 12 only one molecule of water is sorbed on two amide groups, probably as a firmly bound water. Nylon 7 stands somewhere between the two groups.

Yielding of glassy polymers: Volume effects

Abstract: A yield criterion is constructed for glassy polymers from results of constant strain-rate tests in different stress fields. A significant effect of hydrostatic pressure (or volume change) on the yield stress of polystyrene was found. Direct dilatometric measurements were made on polystyrene, poly(methyl methacrylate), polycarbonate, and poly(vinyl formal) samples subjected to uniaxial compression. Both a volume contraction proportional to stress (Poisson's ratio effect) and a volume expansion, which depends on the extent and the history of plastic yielding, were observed. These results are discussed qualitatively in terms of structural models for the glassy state of amorphous polymers. Un critere de rendement est construit pour les polymeres vitreux au depart des resultats des tests de vitesse a tension constante pour differents champs de tension. Un effect significatif de la pression hydrostatique (ou variation de volume) sur la tension de rendement de polystyrene a ete trouve. Des mesures dilatometriques directes ont ete effectuees sur le polystyrene, le polymethacrylate de methyle, le polycarbonate et des echantillons polyvinyliques, soumis a une compression uniaxiale. On a observe a la fois une contraction de volume proportionnelle a la tension (effet du rapport de Poisson) et une dilatation de volume qui dependait du degre d'avancement et de l'histoire du rendement plastique. Ces resultats sont discutes qualitativement sur la base de modeles structuraux pour l'etat vitreux de polymeres amorphes. Ein Fliesskriterium fur Polymere im Glaszustand wird aus Ergebnissen von Versuchen bei konstanter Verformungsgeschwindigkeit in verschiedenen Spannungsfeldern abgeleitet. Es besteht ein signifikanter Einfluss des hydrostatischen Druckes (oder der Volumsanderung) auf die Fliessgrenze von Polystyrol. Direkte dilatometrische Messungen wurden an Polystyrol-, Polymethylmethacrylat-, Polycarbonat- und Polyvinylformalproben unter uniaxialer Kompression ausgefuhrt. Es wurden eine der Spannung proportionale Volumskontraktion (Effekt des Poisson-Verhaltnisses) und eine vom Ausmass und der Vorgeschichte des plastischen Fliessens abhangige Volumsexpansion beobachtet. Die Ergebnisse werden qualitativ an Structurmodellen fur den Glaszustand von amorphen Polymeren diskutiert.

Dynamic mechanical properties and impact strength

Abstract: Impact strength and damping as functions of temperature have been compared for eight polymers with typical differences in damping behavior, viz., four methacrylate polymers, a polyphenylene oxide, a polycarbonate, a polyoxymethylene, and a rigid polyethylene. If a damping maximum is caused by a movement within the main polymer chain, it is generally connected with an appreciable increase in impact strength. The temperature of the mechanical damping maximum and that of the transition in the impact strength may, however, differ considerably. If the damping maximum is caused by movements of sidechains only, it has at most a slight influence on the impact strength. Also a polymer with very low damping can have high impact strength and can even show a brittle-tough transition. This occurs in the case of polyphenylene oxide.

The models of the denaturation of globular proteins. I. Theory of globula–coil transitions in macromolecules

Abstract: The theory of long-range interactions in macromolecules is proposed for the region where the attraction forces predominate (that is below τ-point). In an approximate analytical variant of the theory the free energy of segment–segment interactions is calculated without taking into account their bonding in the single chain, that is, by means of strict and approximate equation for the free energy of interaction of real gas molecules. The theory predicts that under some conditions the macromolecule undergoes below the τ-point, during the change of temperature or solvent composition, the first-order phase transition from the statistically coiled state to the compact (globular) state. The transition predicted by the theory is similar to the condensation of the real gas cloud to the liquid drop. This result is confirmed by the more strict Monte Carlo calculation which takes into account the bonding of the segments in a single chain. This calculation not only confirms the existence of a drastic compression of the macromolecule, when the attractive forces between its segments increase, but show also that, in the transition region, the macromolecules divide into poorly coiled chains (statistical coils) and highly coiled chains (globula), which directly prove the phase character of the transition. In common macromolecules the “intramolecular condensation” predicted by the theory must occur near to the point of intermolecular condensation so it is difficult to observe it experimentally. However, in macromolecules containing both lyophobic and lyophilic groups the intramolecular condensation may well occur due to the mutual attraction of lyophobic groups and lyophilic groups covering the surfaces of obtained globulas may prevent them from aggregation. In these macromolecules one can observe the intermolecular globula–coil phase transitions by changing the temperature or the solvent composition. It is most likely that the denaturation (and renaturation) of the globular proteins are the examples of such transitions.

The models of the denaturation of globular proteins. II. Hydrophobic interactions and conformational transition in polymethacrylic acid

Abstract: To model the compact structures of globular proteins and the processes of their breakdown, the local compact structures have been investigated in the nonionized (or weakly ionized) molecules of polymethacrylic acid (PMA) in aqueous solutions. The potentiometric titration curves differ markedly from the analogous curves for polyacrylic acid (PAA) and show the existence of the cooperative breakdown of the local compact structures in a definite region of the ionization degree. The presence of the local compact structures in the PMA molecules is also manifested in sharp differences between the luminescent characteristics of the dyes (auramine and acridine orange) in aqueous solutions with PMA and the same characteristics in aqueous solutions with PAA. In a certain range (which coincides with the interval of the breakdown of local compact structures) these differences disappear. This permits us to interpret them as the result of the dye molecules binding on the structurized parts of PMA. The assumption has been made that the local compact structures in the PMA molecules in aqueous solutions are stabilized by the hydrophobic interactions of methyl groups. This assumption explains the abnormal temperature dependencies of the properties of the aqueous solutions of PMA and the absence of the local compact structures in the PMA molecules in methanol as well as in the PAA molecules in any solvents. To check this assumption we have investigated the breakdown of the local compact structures in the PMA molecules when aliphatic alcohols are added to the aqueous PMA solution. It was shown that the transition of dye molecules from the bound state to the free one (which is the evidence of the breakdown of the local compact structures) takes place in the narrow range of alcohol concentrations decreasing in the series methanol–ethanol-propanol–butanol. It means that alcohol destroys compact structures the better, the more hydrophobic groups it possesses. The investigations of intrinsic viscosity of PMA in the water–methanol mixtures have shown that the addition of alcohol leads not only to the breakdown of the local compact structures, but also the unfolding of the macromolecule as a whole. The analogy between the local compact structures in PMA molecules and the compact structures of globular proteins has been discussed.

Phase separation during the formation of three-dimensional polymers

Abstract: Phase separation during the formation of three-dimensional polymers in the presence of inert diluents, by crosslinking of linear polymers, or by polymerization of multifunctional monomers, was treated under the assumption of thermodynamic equilibrium by using the Flory theory of swelling equilibria and rubber elasticity. The separation begins when the maximum swelling of the network in the diluent or diluent-monomer mixture drops to the degree of dilution of the network; the two quantities remain equal even after separation of phases. The network formed in this way is a composite one. Relations have been derived for the dependence of composition and volume of the network phase upon initial conditions and degree of crosslinking or extent of polymerization. The results of calculations for binary and ternary model systems are discussed with respect to syneresis or formation of porous structures, as two possible modes of phase separation.

The pore structure of macroreticular ion exchange resins

Abstract: A series of new cation and anion exchange resins differing entirely from conventional homogeneous (microreticular) gels and having a rigid macroporous structure similar to those of conventional adsorbents are characterized. These ion exchangers have been designated as macroreticular ion exchange resins. A detailed analysis is made of the pore structure of the resins including pore size distribution, surface area, and electron micrographs. From these data a model of the physical structure is presented. The relationship between the physical structure and utility of these ion exchange resins is developed for various areas of application, including catalysis, adsorption from nonpolar solvents, and the adsorption of large molecules such as peptides and proteins. The effect of hydration upon the pore structure of several of the macroreticular ion exchange resins is critically evaluated also. During the course of hydration, the gel portion hydrates first and this is followed by the filling of the macroreticular pores. From these data one is able to ascertain the pore structure not only in the anhydrous state but also in aqueous media.

Role of free volume changes in polymer solution thermodynamics

Abstract: The thermodynamic effect of free volume changes in mixing is treated with the use of the corresponding states theory of Prigogine and collaborators. The interaction parameters χ1, κ1, ψ1 and their concentration dependences are derived. Each parameter contains two terms. The first is due to differences in cohesive energy and sizes between segments of polymer and solvent: the second or “structural” contribution is due principally to the difference in chain lengths between polymer and solvent. The structural effect gives a large value of χ1 ∼ 0.4 for a polymer with a chemically identical short oligomer as solvent. A minimum but nonzero value of χ1 occurs for a solvent with higher cohesive energy than between polymer segments. At high temperatures a lower critical solution temperature must occur due to the increase of the solvent configurational heat capacity to infinity as the solvent vapor-liquid critical point is approached, the heat and entropy of dilution becoming negative. At ordinary temperatures χ and κ increase with polymer concentration. The solubility parameter approach is compared; particular polymer liquid models used by Prigogine and by Flory are briefly discussed. χ1 as calculated for natural rubber and a variety of solvents and fair agreement is obtained with published values.

Conductivité Electronique et Propriétés Chimiques de Polyanilines Oligomères

Abstract: Les produits obtenus a partir d'une methode simple de preparation des emeraldines out ete etudies en ce qui concerne leurs proprietes d'acidite, d'oxydo-reduction et de formation de complexes: (1) l'analyse des courbes de neutralisation de suspensions aqueuses d'emeraldines par des bases fortes a permis d'etablir que ces composes avaient deux comportements acides differents respectivement fort et faible; (2) l'analyse des caracteristiques quantitatives de ces courbes permet de conclure a la formation de complexes avec les anions sulfate, chlorure et formiate; (3) l'action de divers couples oxydants et reducteurs sur les emeraldines en suspension aqueuse ou en solution colloidale acetique a ete etudiee. Des parametres definissant les bilans des reactions d'oxydor-eduction caracteristiques des materiaux etudies ont ete determines. Cette etude des proprietes chimiques des produits d'oxydation de l'aniline a permis de preciser les conditions d'obtention de differents derives appartenant a la famille des polyanilines. L'etude de la conductivite d'une classe de complexes des emeraldines (sulfates) montre qu'elle est electronique et reproductible. Elle est fonction des parametres definissant l'etat d'hydratation et l'etat acide–base des differents derives. Elle est tres elevee pour un materiau organique, et varie de 10 a 10−4 ohm−1 cm−1 selon la valeur de ces parametres. Products obtained by a simple method of preparing emeraldines have been studied with respect to their acidity, redox, and complex formation properties: (1) analysis of neutralization curves with strong bases relating to aqueous suspensions of emeraldines show these compounds to behave as two different acids, a strong and a weak one; (2) analysis of quantitative characteristics of these curves indicates complex formation with sulfate, chloride, and formiate anions; (3) the interaction between different redox couples and emeraldines in aqueous suspension and in colloid solution has been investigated. The conversion parameters characteristic for the oxydo-reduction reactions of the materials studied have been determined. This study of chemical properties of aniline oxidation products establishes conditions of preparation for different derivatives pertaining to the polyaniline family. Conductivity results obtained on an emeraldine complex class (sulfates) indicate a reproducible electronic conductivity. The conductivity varies with the hydration and acid–base parameters of different derivatives; its value is very high for an organic material and ranges from 10 to 10−4 ohm−1 cm.−1 depending on the values of the parameters indicated. Die mit einer einfachen Darstellungsmethode fur Emeraldine erhaltenen Produkte wurden bezuglich ihrer Saure-, Redox- und Komplexbildungseigenschaften untersucht: (1) die Analyse der Neutralisationskurven von wassrigen Emeraldinsuspensionen mit starken Basen zeigt, dass diese Verbindungen ein Saureverhalten entsprechend zwei verschiedenen Sauren, einer starken und einer schwachen aufweisen; (2) die Analyse der quantitativen Charakteristika dieser Kurven erlaubt auf eine Komplexbildung mit Sulfat-, Chlorid- und Formiatanionen zu schliessen, (3) die Einwirkung verschiedener Redoxpaare auf die Emeraldine in wassriger Suspension oder in kolloider Losung in Essigsaure wurde untersucht. Die fur die Oxydo-Reduktionsreaktionen der untersuchten Stoffe charakteristischen Umsatzparameter wurden bestimmt. Die Untersuchung der chemischen Eigenschaften der Oxydationsprodukte von Anilin ermoglichte eine Festlegung der Bildungsbedingungen der verschiedenen, zur Familie der Polyaniline gehorenden Derivate. Die Untersuchung der Leitfahigkeit einer Klasse von Emeraldinkomplexen (sulfate) zeigt, dass es sich um eine reproduzierbare elektronische Leitfahigkeit handelt. Sie ist eine Funktion der fur den Hydratationszustand und den Saure–Basenzustand der verschiedenen Derivate massgebenden Parameter. Sie liegt fur eine organische Verbindung sehr hoch und zwar je nach den Werten dieser Parameter bei 10 bis 10−4 Ω−1cm−1.

Anisotropy and structure in uniaxially stretched amorphous high polymers

Abstract: When an amorphous polymer is stretched uniaxially, the chain molecules are oriented along the stretching direction. Orientation causes an anisotropy of the macroscopic physical properties with rotational symmetry about the stretching direction. The phenomenological treatment of the properties exhibited by a uniaxially oriented polymer follows mathematical methods known from crystal physics. Earlier data on anisotropy of linear thermal expansion, thermal conductivity, and linear compressibility for PVC are quantitatively explained with the aid of a known distribution function. The complete set of the five elastic compliances of hot-stretched PVC are experimentally determined as function of stretch up to 180%. The correspondent compliances for the perfectly oriented material are calculated yielding, e.g., 5 × 1010 dynes/cm.2 for the Young's modulus along the chains. Finally, the lengths of the statistical segments in natural rubber and polychloroprene are evaluated from thermal conductivity measurements on these substances in the strained state. As is expected the polyisoprene chains prove to be considerably more flexible than those of polychloroprene. Lorsqu'un polymere amorphe est etire uniaxialement, les molecules en chaines sont orientees le long de la direction d'etirement. L'orientation cause une anisotropie des proprietes physiques macroscopiques avec la symetrie rotationelle autour de la direction d'etirement. Le traitement phenomenologique des proprietes manifestees par un polymere oriente uniaxialement, suit des methodes mathematiques connues pour la physique des cristaux. Des resultats anterieurs concernant l'anisotropie de l'extension thermique lineaire, la conductivite thermique et la compressibilite lineaire du PVC sont expliques de facon quantitative a l'aide d'une fonction de distribution connue. L'ensemble des cinq proprietes elastiques du PVC etire a chaud sont determines experimentalement en fonction de l'etirement a 180%. Les proprietes correspondantes pour un materiau parfaitement oriente sont calculees et fournissent par exemple 5 × 1010 dynes/cm2 pour le module de Young le long des chaines. Finalement les longueurs des segments statistiques sur le caoutchouc naturel et le polychloroprene ont ete evaluees au depart des mesures de conductivite thermique sur ces substances a l'etat de tension. Comme attendu, les chaines de polyisoprene sont considerablement plus flexibles que celles de polychloroprene. Durch eine einachsige Verstreckung werden in amorphen Polymeren die Kettenmolekeln in Streckrichtung orientiert. Als Folge dieser Orientierung tritt eine Anisotropie der makroskopischen physikalischen Eigenschaften auf, welche sich als rotationssymmetrisch um die Streckrichtung erweist. Die phanomenologische Behandlung der Eigenschaften eines einachsig orientierten Polymeren lasst sich mit den aus der Kristallphysik bekannten mathematischen Methoden durchfuhren. Fruhere Messungen zur Anisotropie der linearen thermischen Ausdehnung, der Warmeleitfahigkeit und der linearen Kompressibilitat von PVC werden mit Hilfe einer bekannten Verteilungsfunktion quantitativ beschrieben. Der vollstandige Satz der 5 elastischen Konstanten von warm verstrecktem PVC werden bis zu einem Verstreckungsgrad von 180% ermittelt. Die entsprechenden Konstanten fur das vollig orientierte Material werden berechnet; dabei ergibt sich z.B. fur den E-Modul parallel zu den Ketten 5 × 1010 dyn/cm.2. Schliesslich werden die Segmentlangen fur Naturkautschuk und Polychloropren aus Messungen der Warmeleitfahigkeit an den gedehnten Substanzen errechnet. Wie erwartet, erweisen sich die Ketten des Polyisoprens als viel beweglicher als diejenigen des Polychloroprens.

Stereospecific polymerization of butadiene by catalysts prepared from π‐allyl nickel halides

Abstract: Butadiene has been polymerized by π-allyl-Ni-halides (I) to low molecular weight stereoregular polymers, with either benzene, n-pentane, tetrahydrofuran, cyclohexanol, or ethyl alcohol used as solvents. Solid polymers and oily products were simultaneously obtained as polymerization products. In benzene as solvent, π-allyl-Ni-I and π-allyl-Ni-Br gave predominantly trans-1,4 polymers, while π-allyl-Ni-Cl gave polymers largely composed of cis-1,4 units. In the other solvents predominantly trans-1,4 polymers were obtained, irrespective of the nickel derivative used. By reacting π-allyl-Ni-Br, in benzene solution, with either AlBr3, Al2(O-i-C3H7)3Br3, BF3 or TiCl2 (O-i-C3H7)2, complexes were obtained (II) which polymerize butadiene to predominantly cis-1,4 polymers. Evidence is reported that these complexes are of ionic type and contain the cation The different stereospecificity observed in the polymerizations by I and II is interpreted on the basis of the different mode of coordination of butadiene to Ni of the complexes I and II, respectively.

The theory of branching processes and kinetically controlled ring—chain competition processes

Abstract: The statistical theory of branching processes provides unified and powerful methods for calculating statistical parameters, especially for branched polymer systems. A review of some recent calculations provides examples such as the sol fraction, molecular weight and configurational size averages, and the concentration and mean length of active network chains in f functional random or nonrandom polycondensations. The theory furnishes a useful approximation to the calculation of thermodynamically or kinetically controlled ring–chain competition processes in branched systems.

Influence de la Stereorégularite des Chaînes sur les Transitions du Polyméthacrylate de Méthyle

Abstract: Dilatometric studies on five PMM samples of different tacticities show generally three transition ranges between −35 and 150°C. The main glass transition temperature depends on the relative proportion of the iso- or syndiotactic segments. The secondary transition, located around 60°C., seems to be related to the presence of heterotactic segments. The third transition range, common to all the five samples, located around 0°C., may be attributed tentatively to the freezing in of the ester side groups.

Inclusion compounds of linear polymers and polymerization of monomers included in perhydrotriphenylene

Abstract: The trans-anti-trans-anti-trans isomer of perhydrotriphenylene C18H30 forms crystalline inclusion compounds with linear macromolecules, such as polyethylene, 1,4-polybutadiene, and poly(oxyethylene glycol). The main results concerning the constitution, determined by x-ray diffraction and by differential thermal analysis, as well as the stability of these compounds, are reported here. Moreover, studies were made on the polymerization of various monomers included in PHTP by γ-rays radiation. In several cases, an inclusion compound of the polymer in PHTP is obtained from such a reaction. A high degree of stereoregularity has been observed for some of the polymers obtained (e.g., polydiolefins); the first reported example of an isotactic polymer obtained by γ-rays polymerization is due to the above method; it is the isotactic trans-poly-1,4-pentadiene. L'isomere trans-anti-trans-anti-trans du perhydrotriphenylene C18H30) forme des derives d'inclusion cristallins avec des macromolecules lineaires telles que le Polyethylene, polybutadiene-1,4 et le polyoxyethyleneglycol. Les principaux resultats concernant la constitution determinee par la diffraction aux rayons-X er par analyse thermique differentielle, aussi bien que la stabilite de ces composes sont rapportes dans le present travail. En outre, des etudes ont ete faites sur la polymerisation des differents monomeres inclus dans PHTP par radiation γ. dans de nombreux cas, un compose d'inclusion du polymere dans le PHTP est obtenu au depart d'une telle reaction. Un haut degre de stereoregulaire a ete observe pour certains des polymeres obtenus (par exemple, les polydiolefines); le premier exemple rapporte d'un polymere isotactique obtenu par polymerisation aux rayons-γ est du a la methode ci-dessus: le polypentadiene isotactique trans-1,4. Das trans-anti-trans-anti-trans-Isomere des Perhydrotriphenylens C18H30 bildet mit linearen Makromolekulen, wie Polyathylen, 1,4-Polybutadien und Polyoxyathylenglykol kristalline Einschlussverbindungen. Uber die Hauptergebnisse bezuglich der durch Rontgenbeugung und Differentialthermoanalyse bestimmten Konstitution und der Stabilitat dieser Verbindungen wird hier berichtet. Ausserdam wurden Versuche uber die Polymerisation verschiedener, in PHTP eingeschlossener Monomerer durch γ-Strahlung ausgefuhrt; in mehreren Fallen wird durch diese Reaktion eine Einschlussverbindung des Polymeren in PHTP erhalten. Bei einigen der erhaltenen Polymeren (z.B. Polydiolefine) wurde ein hoher Grad an Stereoregularitat beobachtet; das erste Beispiel eines durch γ-Strahlen-Polymerisation erhaltenen isotaktischen Polymeren, isotaktisches trans-Poly-1,4-pentadien, verdankt man dieser Methode.

The polymerization of 1,3-dioxolane. I. Structure of the polymer and thermodynamics of its formation

Abstract: We have polymerized 1,3-dioxolane in our adiabatic reaction calorimeter under vacuum in methylene dichloride with anhydrous perchloric acid as catalyst. We confirm previous findings that the polymer consists of a regularly alternating sequence of “formaldehyde” and “ethylene oxide” units. The polymer prepared in the presence of water has terminal OH groups, but that prepared under strictly anhydrous conditions has no detectable end groups, and we conclude that it is cyclic; we suggest a reaction mechanism involving ring expansion. The polymerization is an equilibrium involving polymer and monomer only, without side reactions. For a one molar solution the ceiling temperature is +1°C., ΔSss° = −18.6 ± 1.2 cal. deg.−1 mole−1: ΔHss° = −5.2 ± 0.2 kcal./mole, direct calorimetric measurements for polymerization and depolymerization, and calculation from d log K/dT giving identical results.

Large deformation tensile properties of elastomers. I. Temperature dependence of c1 and c2 in the mooney-rivlin equation

Abstract: Tensile stress-strain data were determined at various extension rates and temperatures on unfilled butyl and silicone vulcanizates and on six hydrofluorocarbon (Viton A-HV) vulcanizates that contain between 0.90 and 12.2 × 10−5 mole of effective network chains per unit volume of gel rubber. From 1-min. isochronal data, values of C1 and C2 in the Mooney-Rivlin equation were derived. For the butyl and silicone vulcanizates from, respectively, −20 to 150°C. and −45 to 200°C., C1 increases with temperature at a rate which is in reasonable agreement with published data from forcetemperature measurements. Because C2 is sensibly temperature independent over these extended temperature ranges, it is concluded that C2 is a finite quantity under equilibrium conditions. Time-dependent behavior was observed on the Viton A-HV vulcanizates between −5 and 230°C. For each vulcanizate between about 25 and 230°C., C1273/T is temperature independent, but it increases with decreasing temperature below about 25°C. Except at the lowest temperatures, C2273/T decreases with increasing temperature, the rate of decrease becoming progressively less with an increase in crosslink density. Above 25°C. the ratio C2/C1, which ranges from about 90 to 0.6, decreases with an increase in either temperature or crosslink density. The time-dependent behavior of C2273/T appears to arise primarily from molecular processes whose relaxation times are considerably longer than the terminal relaxation time of individual chains.

Reactivities of alkyl methacrylates in their radical polymerization

Abstract: The effect of the alkyl group on radical polymerizations of alkyl methacrylates (RMA) has been investigated. From the results on copolymerizations of RMA(M2) with styrene or B-chloroethyl methacrylate (M1), the relative reactivities (lr1) of RMA toward attack of polymer radicals were plotted by the Taft's equation: log (1/r1) = ρ* σ*+δE8. The plot could correlate with polar substituent constants (σ*), but not steric substituent constants (E8) of the alkyl substituents in RMA. These results might strongly indicate that the radical reactivities of RMA depended on the polar character of the alkyl groups, but not on their steric character. This conclusion is compared with other experimental results and discussed.

ESR studies on transient free radicals during redox polymerization of some monomers

Abstract: By application of a flow system, ESR spectra of transient free radicals are obtained during liquid-phase polymerization initiated by ·CH3. The coupling constants of the radicals are discussed with respect to previous findings with , , and ·CH2OH initiation. Some differences in the reactions of acrylic acid with HO· and ·CH3 are also reported. In total, the results strongly support the usual assumptions on reaction schemes of radical polymerization. En utilisant un systeme d'ecoulement on a pu obtenir des spectres ESR de radicaux libres de courtes durees de vie du dours de la polymerisation en phase liquide initiee par des radicaux methyles de certains monomeres. Les constantes de couplage des radicaux sont discutees en rapport avec les donnees precedentes concernant l'initiation par HO, NH2 et CH2OH. Certaines differences dans les reactions de l'acide acrylique avec OH et CH3 sont egalement rapportees. Au total les resultats confirment fortement les hypotheses habitulles concernant les schemas de reaction des polymerisations radicalaires. Durch Anwendung eines Durchflusssystems werden ESR-Spektren kurzlebiger freier Radikale wahrend der durch ·CH3 initiierten Polymerisation einiger Monomeren in Losung beobachtet. Die ESR-Daten der Radikale werden diskutiert und mit den Ergebnissen fruherer Arbeiten verglichen. Es wird weiterhin uber einige Unterschiede der Reaktionen von und ·CH3 mit Acrylsaure berichtet. Insgesamt liefern die Ergebnisse einen Beweis fur die Reaktionsmechanismen der radikalischen Polymerisation.

The calculation of average functions of local conformations for a non-interacting copolymer system with neighbor interactions

Abstract: In the present paper a new treatment is given for the calculation of average conformations over a non-interacting copolymer system, where two kinds of monomer units are present. It is based on the calculation of the arithmetical average partition function over a properly restricted class of distributions of A and B units. This method permits in principle any required degree of approximation and also may be extended to copolymer systems with three or more types of monomer units. Moreover, it has the advantage that any average of conformational functions may be calculated in a way which is formally analogous to the matrix method given by Lifson in the case of homopolymers. Dans cet article on presente un nouveau traitement du calcul des conformations moyennes dans un systeme copolymerique sans interactions ou les deux types d'unites monomeriques sont presents. Elle est basee sur le calcul de la moyenne arithmetique de la fonction de partition sur une classe bien definie de distribution d'unites A et B. Cette methode permet en principe n'importe quel degre d'approximation et peut egalement etre etendu a des systemes copolymeriques avec trois et plusieurs unites monomeriques. En outre, elle a l'avantage que n'importe quelle moyenne de fonction conformationnelle peut etre calculee de facon formellemene analogue a la methode des matrices donnee par Lifson dans le cas des homopolymeres. In der vorliegenden Mitteilung wird eine neue Behandlung zur Berechnung der mittleren Konformation eines Copolymersystems mit zwei Arten von Monomerbausteinen ohne Wechselwirkung gegeben. Sie beruht auf der Berechnung der arithmetisch mittleren Verteilungsfunktion fur eine geeignet begrenzte Klasse von Verteilungen der A- und B-Einheiten. Diese Methode erlaubt im Prinzip jeden erforderlichen Naherungsgrad und kann auch auf Copolymersysteme mit drei oder mehr Typen von Monomerbausteinen ausgedehnt werden. Ausserdem hat sie den Vorteil, dass jedes Mittel der Konformationsfunktionen in einer zu der von Lifson fur den Fall von Homopolymeren angegebenen analogen Weise berechnet werden kann.

Modification de Polymères Insaturés par Époxydation

Abstract: Conditions of epoxidation of unsaturated polymers were studied. Perphthalic monoacid appeared to be one of the most efficient epoxidation agents, particularly when the double bond is enriched with electrons. Some properties of the new polymers thus obtained were revealed and functional crosslinkings were achieved.

Effect of artificial nucleating agents on polymers structure and properties

Abstract: The possibility of forming and stabilizing a supermolecular structure and properties of polymers by adding small amounts of dispersive solids to them is shown. Some problems concerning the mechanism of actions of artificial nucleating agents are discussed.

Polymerization of ethylene glycol monomethacrylate in the presence of solvents

Abstract: Hydrophilic gels have been prepared by polymerization of glycol methacrylate monoesters in the range of very low diester concentrations The monomer mixture has been diluted with various solvents and the range has been investigated, in which swelling is independent of the dilution of the monomer mixture on polymerization The quality of the gel is independent of the concentration and character of the solvent used in polymerization in a very broad range

Mechanismus der Dreidimensionalen Polymerisation von Glykolmethacrylaten

Abstract: The three-dimensional, homogeneous, and heterogeneous polymerizations in systems monoglycol or diglycol monomethacrylate–dimethacrylates of glycols in various solvents were studied dilatometrically. The network density and the content of pendant vinyl groups were determined at various conversions. The influence of physical crosslinks formed by hydrophobic crosslinking agents was estimated by the comparison with copolymers of diglycol monomethacrylate–methyl methacrylate. By correlation of kinetics of polymerization with the three-dimensional network formation, it was possible to characterize the polymerizing systems within the whole range of conversion.

Dynamic birefringence of poly(methyl methacrylate)

Abstract: The dynamic modulus, strain-optical coefficient, and stress-optical coefficient have been measured for conventional poly(methyl methacrylate) (PMMA) in the frequency range 16–10−2.5 cps and at temperatures between −130 and +140°C. Both the α (glass–rubber) relaxation and the β relaxation have been detected in plots of each of these observables, or the appropriate phase angles, against temperature or frequency. The extremely broad mechanical β relaxation suggests a wide distribution of relaxation frequencies. The high-frequency modes lead to a relaxation of the strain-optical coefficient while the stress-optical coefficient remains essentially constant. Conversely, the low-frequency modes result in a relaxation of the stress-optical coefficient at constant strain-optical coefficient. The results are discussed in relation to the polarizability anisotropy of the PMMA repeat unit, and comparisons are made with dielectric data and with earlier dynamic birefringence data obtained for poly(methyl acrylate) (PMA).

Optically active vinyl polymers. XIV. Stereoselective and stereoelective polymerization of racemic α‐olefins

Abstract: Polymers of racemic 4-methyl-1-hexene, 3-methyl-1-pentene, and 3,7-dimethyl-1-octene have been separated in fractions having optical activity of opposite sign by adsorption chromatography on highly crystalline poly-(S)-3-methyl-1-pentene. It is shown that the observed prevalence of S or R monomeric units in the optically active polymers thus obtained cannot be explained on the basis of a model of a purely statistical copolymer of the two monomeric antipodes. This conclusion is confirmed by the fact that at-acticpoly-(R)(S)-4-methyl-1-hexene, obtained by hydrogenation of poly-(R)(S)-4-methyl-1-hexyne prepared with a substantially soluble catalyst, has not been separated in fractions having optical activity of opposite sign in the adopted experimental conditions. The reported results prove that the stereospecific polymerization of the above-cited racemic α-olefins by heterogeneous catalysts is stereoselective, giving rise to macromolecules formed prevailingly by one single monomeric antipode. On the basis of the experimental results obtained in the stereoselective and stereoelective polymerization of racemic α-olefins, the structure of the catalytic centers of the heterogeneous catalysts for the stereospecific polymerization of α-olefins is discussed.

On the phenomenological description of the nonlinear deformation behavior of rubberlike high polymers

Abstract: The theoretical relationships for the description of the nonlinear deformation behavior of solids can be controlled rather easily by measurements on rubberlike polymers, because of the very small time dependence of their mechanical properties, and because of their large strain range. The data of recent investigations of the biaxial stress–strain behavior of a natural rubber are used for the evaluation of the gradients of the strain energy function given by Rivlin. It is demonstrated that even for a material for which the assumption of incompressibility is practically valid, the actual mechanical behavior is described much too complicated especially in the region of smaller deformations. Les relations theoriques pour la description du comportement de deformation lineaire de solides peuvent etre controlees plutot facilement par des mesures sur des polymeres caoutchouteux par suite de la tres petite dependance du temps de leurs proprietes mecaniques et parce qu'ils ont un vaste domaine de tension. Les resultats de recherches recentes du comportement tension–elongation biaxial de caoutchouc naturel ont ete utilises pour l'evaluation des gradients de la fonction d'energie de tension donnee par Rivlin. On a montre que meme pour un materiel pour lequel l'hypothese de l'incompressibilite est pratiquement valable, le comportement mecanique reel est beaucoup plus complique particulierement dans la region des faibles deformations. Die theoretischen Beziehungen zur Beschreibung des nichtlinearen Deformationsverhaltens fester Stoffe konnen verhaltnismassig einfach durch Messungen an gummielastischen Polymeren gepruft werden, da sich diese Stoffe bei sehr geringer Zeitabhangigkeit ihrer mechanischen Eigenschaften durch einen grossen Deformationsbereich auszeichnen. Die Ergebnisse neuerer Untersuchungen des zweiachsigen Spannungs-Dehnungsverhaltens von Naturkautschuk werden zur Berechnung der Differentialquotienten der elastischen Energiedichtefunktion nach Rivlin herangezogen. Es wird gezeigt, dass sogar bei einem Material, bei dem die Annahme der Inkompressibilitat im wesentlichen zutrifft, das tatsachliche mechanische Verhalten besonders im Bereich kleiner Deformationen viel zu kompliziert wiedergegeben wird.

Polymerization of propylene to syndiotactic polymer. II. Behavior of the catalytic system VCl4–Al(C2H5)2Cl

Abstract: Some data on the kinetic behavior of the catalytic system VCl4–Al(C2H5)2Cl, which is stereospecific (at low temperatures) for the polymerization of propylene to syndiotactic polymer, are reported here. The effect was studied of the reaction time and of the concentration of VCl4, of Al(C2H5)2Cl, and of the monomer on the polymerization rate, on the molecular weight, and on the index of syndiotacticity of the polymers obtained. The data reported are discussed on the basis of the hypotheses previously put forth about the nature of the catalytic complexes and the polymerization mechanism. Certain resultats sur le comportement cinetique du systeme catalytique VCl4–Al-(C2H5)2Cl (stereospecifique aux basses temperatures) dans la polymerisation du polypropylene en polymere syndiotactique sont rapportes. L'effet de la duree de reaction a ete etudie de meme que celui de la concentration en VCl4, en Al(C2H5)2Cl et de la concentration en monomere sur la vitesse de polymerisation, sur le poids moleculaire et sur le taux de syndiotacticite des polymeres obtenus. Les resultats rapportes sont discutes sur la base d'hypotheses precedemment presentees concernant la nature des complexes catalytiques et le mecanisme de polymerisation. Einige Ergebnisse fur das kinetische Verhalten des bei tiefen Temperaturen fur die Polymerisation von Propylen zu einem syndiotaktischen Polymeren stereospezifischen Katalysatorsystems VCl4–Al(C2H5)2Cl werden mitgeteilt. Der Einfluss der Reaktionsdauer und der Konzentration von VCl4, Al(C2H5)2Cl und Monomerem auf Polymerisationsgeschwindigkeit, Molekulargewicht und Syndiotaktizitatsindex des erhaltenen Polymeren wurde untersucht. Die Ergebnisse werden auf Grundlage der fruher uber die Natur des katalytischen Komplexes und des Polymerisationsmechanismus entwickelten Hypothesen diskutiert.

Crystallization kinetics of polycarbonates. I

Abstract: Research on the kinetics of crystallization of polycarbonates based on bisphenol A at 190°C. has been carried out on six polydisperse samples. It was found that the process of crystallization, after a long period of induction, follows a course which can be described by the classical equation of Avrami. The final amounts of crystallization are small, ranging from 18 to 28%. Crystallization kinetics of polycarbonates depends on molecular weight and on the previous treatment of the polymer.