bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on alcohol‐modified transition metal polymerization catalysts. II. Interaction of TiCl4 with cellulose and model compounds
Authors: Hidkr S. , Marchessault R. H.
Published: June 2010

Experiments have been performed to obtain evidence concerning the chemical and physical reactions which may be expected to occur when TiCl4 is sorbed onto cellulose from nonswelling solvents. For model compounds such as 1,2‐butanediol, cis‐ and trans‐1,2‐cyclohexanediol, one ionic bond per TiCl4 was the general rule. The presence of multiple electron donating groups in the diols leads to chelation and/or polymer formation, so that insoluble reaction products were obtained. Analysis of the reaction products permitted the assignment of characteristic formulae, which accounted for variations in composition and physical properties of the reactants as a function of diol: TiCl4 ratio. The foregoing studies have provided a base for interpreting, respectively, the homogeneous and heterogeneous reactions between ethyl cellulose (DS = 2.5) and cellulose fibers with TiCl4. It appears that all the oxygens of cellulosics (not just the hydroxyls) can take part in the completing, which otherwise is similar to the diol reaction. Drying history has an important effect on the titanium content of the cellulose after reaction with TiCl4.
Degradation of wood pulp during acetylation
Authors: Neal J. L.
Published: June 2010

A comparison of the DP distributions of wood pulps and the cellulose acetates prepared from them shows that the DP distributions of the acetates are essentially exponential and virtually independent of the DP distribution of the original pulp. The DP of a number of acetates prepared under identical conditions from different pulps were unrelated to the DP to the starting pulps. Although the pulp DP is thus not a factor which determines the acetate DP, there are other intrinsic properties of the pulp which do affect the final DP of the cellulose acetate. The nature of these properties is not understood, but it can be shown that they are altered by changes in wood pulp processing. The ratio of hemicellulose in pulp to hemicellulose in the acetate made from it varies from one pulp to another. The acetate solution properties of the cellulose are more closely related to the composition of the acetate flake than to the composition of the original pulp. The viscosity of the concentrated acetate dope can be accounted for almost entirely in terms of flake DP and flake mannan content. Pulp manufacturers and acetate producers should strive toward conditions which increase the rate of degradation of the he mi celluloses and decrease the rate of cellulose degradation during acetylation.
Mechanism of multiple dielectric loss peaks in dilute solution
Authors: Stockmayer W. H.
Published: June 2010

It has long been recognized that the detailed selection rules describing the dielectric loss spectrum of a macromolecule in solution depend on the manner in which the individual polar groups are attached to the structure. As many as three distinct loss peaks may appear, due to contributions respectively from (1) long‐range dipoles whose magnitude and direction are proportional to the overall dimensions of the molecule; (2) dipoles rigidly attached to the chain but without long‐range correlation; and (3) dipoles on flexible side chains. In addition, there is the Kirkwood‐Shumaker mechanism of “proton polarizahility.” Theoretical and experimental examples of the above generalities are discussed.
Specific heat studies of transition and relaxation behavior in polymers
Authors: O'Reilly J. M. , Karasz F. E.
Published: June 2010

Specific heat studies of polymers are reviewed within the framework of Buyer's classification: (a) melting transition (Tm); (b) glass transition (Tg); (c) subglass relaxation (T < Tg); and (d) intermediate relaxation (Tg < T < Tm). The melting transition is readily apparent in specific heat measurements because of the heat of fusion resulting from the transition. Thermodynamic parameters obtained from calorimetric measurements confirm that melting is a first‐order transition and, in general, the phenomena are well understood. The change in Cp at Tg probably provides the least ambiguous assignment of Tg by precision calorimetric measurements. Specific heat studies focus sharply on the thermodynamic aspects of glass formation but still show the relaxational properties. Although complicated, the specific heat behavior of semi crystal line polymers is less complex than other techniques. There are no abrupt changes in Cp from near 0°K. to Tt similar to the mechanical or dielectric relaxations observed below Tg. Although the molecular processes responsible for the low temperature relaxations contribute to Cp, the processes are not sufficiently cooperative to occur over a narrow temperature range. Some examples of molecular processes such as methyl or other group rotation and con‐formational isomerism, which contribute to Cp, are discussed. The intermediate relaxations (Tg < T < Tm) which occur in semi crystalline polymers are complex, and many mechanisms, such as premelting, crystal‐crystal transitions, defects and crystal‐amorphous interactions have been proposed. The few specific heat results available are not conclusive and considerable work is needed in this area.
A survey of multiple transitions by dynamic mechanical methods
Authors: Turley S. G. , Keskkula Henno
Published: June 2010

In the last several years, studies of the dynamic behavior of polymers have shown that many, if not all, polymers exhibit more than one transition region when the investigation covers a sufficiently wide temperature or frequency range. The purpose of this paper is to discuss, for a few selected polymers, those multiple transitions which have been found by using dynamic mechanical methods, with particular emphasis on those exhibited by certain olefinic polymers and copolymers. In addition to work published in the literature, this paper also covers some unpublished results based on measurements made in our laboratory. Although attempts have been made to relate secondary transitions with such types of motion as the rotation and/or oscillation of short side chains, subgroups, and short segments of the main polymer chain, there are few polymers for which secondary transitions have been definitely assigned to a particular motion of a specific group. For the most part, the results to be discussed in this paper are based on measurements made with a torsion pendulum, vibrating reed, or transverse vibration apparatus.
Molecular motion in high molecular weight siloxane polymers
Authors: Haberland Gerald G. , Carmichael Jack B.
Published: June 2010

Molecular motions in a series of siloxane polymers and copolymers were studied over the temperature range of 77–296°K. using broadline NMR techniques. From data of second moment versus temperature it is concluded that phenyl groups on silicon are rigid at 77°K. and exhibit only limited motion at 296°K. In contrast, methyl groups exhibit free C3 rotation at 77°K. regardless of the other groups attached to silicon. It is concluded that segmental motion is sterically controlled in siloxane polymers with only phenyl, methyl, and hydrogen groups attached to silicon. It is apparent from the similarity of the broadline NMR data of poly(vinylmethyl)siloxamer, poly(3,3,3‐trinuoropropylmethyl)siloxamer, and poly(dimethyl)siloxamer that other factors, not well understood, also play a significant role in molecular motion.
The viscoelastic relaxation mechanism of inorganic polymers. IV. Simultaneous multiple mechanisms
Authors: Eisenberg A. , Saito S. , Teter L. A.
Published: June 2010

The viscoelastic properties of two polymers have been studied in which both molecular (diffusional) motions and bond interchange were present in the glass transition region. The materials were a lanthanum‐doped (La3+) sodium polyphosphate and an arsenic‐doped sulfur polymer. It is shown that (just as in the case of the acrylate polymers studied by Ferry) the two mechanisms have two different compliance curves associated with them which move with temperature at different rates along the time axis. One of these is due to bond interchange and the other to the diffusional motion of the chains. On the basis of activation energy arguments the compliance curves are matched with the mechanisms, and the relative contributions to the total viscosity due to each mechanism are given as a function of temperature.
Unperturbed chain dimensions of polyethylene in theta solvents
Authors: Nakajima Akio , Hamada Fumiyuki , Hayashi Seiichi
Published: June 2010

The theta temperatures for linear polyethylene in diphenyl, diphenyl methane, and diphenyl ether were determined by the precipitation temperature measurements. The unperturbed mean‐square end‐to‐end distance (R02) and its temperature variationdIn (R02)/dT were estimated from direct intrinsic viscosity measurements in these three theta solvents: <R02/nl2(wherenis the Dumber of bonds, andlis the bond length) in diphenyl, diphenyl methane, and diphenyl ether was 7.10 at 127.5°C, 6.99 at 142.2°C, and 6.80 at 163.9°C., respectively. These numerical values gavedIn <R02/dT = −1.21 × 10−3deg.−1. The results obtained here were in good agreement with those reported by Flory1,2and Chiang,3and in support of the theoretical calculation by Hoeve4and Nagai5.
A semi‐empirical method for estimating unperturbed dimensions of chain polymers from the intrinsic viscosity‐molecular weight relationship
Authors: Inagaki Hiroshi , Suzuki Hidematsu , Kurata Michio
Published: June 2010

A semi‐empirical method for estimating unperturbed chain dimensions from relationships between intrinsic viscosity M and molecular weight M is proposed. This method is based on combining the Ptitsyn equation of the excluded volume effect with a semi‐empirical relation between two expansion factors αη and α for the hydrodynamic radius and the end‐to‐end distance, respectively, i.e., αη3 = α5/2, which has been suggested by Yamakawa and Kurata. This combination gives ([η]/M1/2)4/5 = 0.786K4/5 + 0.950‐K4/5*2/3M1/3 for large α, presumably for a larger than 1.4, Experimental tests are made with viscosity data obtained for polystyrene fractions in trans‐decalin, benzene, and butanone and also with those obtained for poly(methyl methacrylate) in various solvents. Light‐scattering data by Berry are discussed in the light of present results. The parameter B describing long‐range interactions is found to be nonlinearly related to the reciprocal of temperature 1/T, that is, the quantity B0 as defined by B/[(1 ‐ (η)/T)] is a decreasing function of T. On (he basis of experimental result, disagreement between two B values deduced from intra‐ and inter‐chain interactions is pointed out.
Streaming Birefringence. VI. Polar Diagrams
Authors: Munk P.
Published: June 2010

The polar plots of streaming birefringence data are sensitive to the types of particles. The effect of deformability of particles is very strong; in contrast, polydispersity affects the plots only little. The method is rewarding, too, if several different types of particles are present in the system. We have devised a nomograph for rapid construction of the polar plots and for the correction of data for streaming birefringence of solvent and of the possibly present microgels.
Aqueous Polymerization Initiated by Hydrazine Hydrate. Part I
Authors: Das Rajat K. , Palit Santi R.
Published: June 2010

It has been shown that hydrazine hydrate initiates aqueous polymerization of methyl methacrylate in the presence of oxygen in alkaline pH. During the induction period oxygen is fixed as monomer peroxide, which at the end of induction period sets up a redox system with an unreacted hydrazine generating N2H3 radical. N2H3 radical is partly captured by monomer and partly oxidized by peroxide, depending upon the relative ratio of peroxide and monomer. This partitioning of the initiating N2H3 radical brings about interesting kinetic features to the study of which a detailed investigation has been devoted in this paper.
Thermal Flow Method for Kinetic Investigation of Fast Reactions
Authors: Bekhli E. Yu , Nesterov O. V. , Entelis S. G.
Published: June 2010

Reactions of mono‐ and bifunctional acid chlorides with amines have been studied with the help of a flow thermal method both in homogeneous (heptane) and heterogeneous (heptane‐water) media. The multistage character of the reactions may be explained by two coexisting reaction paths with different intermediate products.
Hydrodynamical and Optical Properties of Styrene—Methyl Methacrylate and Styrene—Butyl Methacrylate Graft Copolymers
Authors: Tsvetkov V. N. , Andreeva G. A. , Baranovskaya I. A. , Eskin V. E. , Klenin S. I. , Magarik S. Ya.
Published: June 2010

The hydrodynamical (viscosity, diffusion, sedimentation) and optical (light scattering and flow birefringence) properties of solutions of polymers obtained by the grafting of styrene chains on poly(methyl methacrylate) and poly(butyl methacrylate) chains have been investigated. The graft copolymers have a positive optical anisotropy, despite the negative optical anisotropy of the main component (polystyrene). This is explained by the specific features of the graft structure. It is shown that the rigidity of such macromolecules considerably exceeds that of linear chains.
Relaxation Behavior of Poly(methacrylic Acid) Esters Swollen by Low Molecular Weight Substances at Temperatures Below the Glass Transition Point
Authors: Janáček J. , Kolařik J.
Published: June 2010

Changes in temperature of the secondary β loss maximum of poly(ethylene glycol monomethacrylate) and poly(n‐propyl methacrylate) swollen by means of various low molecular weight substances over a wide concentration range were measured. Correlations were found among the temperature Tβ, concentration of the low molecular weight substances, and their molecular weights. Differences were established in the mechanism of function of monofunctional and difunctional low molecular weight substances. It has been found that the temperature Tβ of the swollen poly(ethylene glycol monomethacry–late) depends upon the molecular weight of a complex consisting of a molecule of the low molecular weight substance and one or two kinetic units partaking in the γ process of the dry polymer according to the mechanism of interaction suggested. The rise of the β process and changes in its temperature position were explained on the basis of change occurring in intermolecular interactions polymer–polymer and polymer–low molecular weight substance. Evidence was presented for a correlation between the γ process of dry and the β process of swollen polymers.
Infrared Study on the Distribution of Propylene Units in Ethylene—Propylene Copolymers
Authors: Ciampelli F. , Valvassori A.
Published: June 2010

An accurate comparison of the infrared spectra of ethylene‐propylene copolymers, the infrared spectrum of alternate ethylene‐propylene copolymer obtained by complete hydrogenation of natural rubber, and the infrared spectra of various branched hydrocarbons made it possible to find a method for determining the distribution of the propylene sequences in ethylene‐propylene copolymers. This method is based on the measurement of the ratio of absorbancies at 10.3 and 10.675μ, which are proportional to the number of propylene units in sequences of two or more units and to isolated propylene units, respectively. A distribution index φ is also defined as a ratio between the number of isolated propylene units and the number of units present in sequences of two or more propylene units. This index is compared with that obtained from the calculation for an ideal copolymerization. The comparison suggests that some catalysts give rise to copolymers for which the plot of φ versus propylene units content is very similar to the plot predicted for an ideal copolymerization. Some other catalysts yield copolymers for which the plot of φ is somehow different. However, these copolymers contain considerable amounts of (CH2)2 groups (which are not foreseen in the calculations performed for the ideal copolymerization) that might be responsible for the anomalous behavior of the φ values.
Der Bewitterungsabbau von Polypropylen
Authors: Veselý R.
Published: June 2010

The natural and accelerated weathering of many unstrained samples of isotactic poly‐propylene has been investigated. Changes in some basic properties of the samples during outdoor exposure as well as during treatment in a weatherometer have been compared. As a result of the study two fundamental processes of aging were established: photoinitiated oxidative chain degradation and secondary crystallization accompanied by a volume shrinkage. Mechanisms of these processes are distinct, mainly in the first stages of aging.
Polymerization of Propylene Catalyzed by TiCl3 with Large Specific Surface
Authors: Ambrož J. , Osecký P. , MejzlíK J. , Hamřík O.
Published: June 2010

The kinetics of polymerization of propylene with the use of highly dispersed TiCl3 and triethylaluminum as catalysts have been studied. The overall rate of polymerization decreases with time as a consequence of the deactivation of active centers with time. The interaction of TiCl3 with triethylaluminum yields Al(C2H5)2Cl; the solid phase is depleted in Cl− and contains fragments of the organometallic compound. This reaction, which is in essence the reduction of TiCl3, takes place also in the course of polymerization and brings about the decomposition of active centers. Rate constants in the equation characterizing the course of the overall rate of polymerization with the number of active centers changing with time have been calculated.
Thermodynamic properties of extended chain polymethylene single crystals
Authors: Arakawa Tamio , Wunderlich Bernhard
Published: June 2010

Density, morphology, and melting data on linear polyethylene and high molecular weight polymethylene crystallized from the melt under elevated pressure are presented. For approximately constant supercooling a sharp density increase is noted above 2300 atm. crystallization pressure. Above 4000 atm. densities above 0.99 are achieved. The high molecular weight polymethylene has larger lamellar thickness than polyethylene, but does not reach full chain extension. The melting of polymethylene is extremely sharp with no evidence of premelting up to at least 136°C. Equilibrium maximum melting points of 138.7 and 141.4°C. have been measured for polyethylene of 105 weight‐average molecular weight and polymethylene of 107 molecular weight.
Structure and properties of rubber networks. Part II
Authors: Meissner B. , Klier I. , Kuchařìk S.
Published: June 2010

By the method described in Part I, experimental data have been obtained on cis‐polybutadiene and natural rubber which further elucidate the dependence of the concentration of elastically effective network chains on the network parameters. The results have been interpreted in terms of the equation proposed in Part I. The dependence of the elastic constant C2, defined by the Mooney‐Rivlin equation, upon the network parameters, type of polymer, and presence of diluent has been investigated. The constant C2 has been related to the network parameters by means of a simple equation on the assumption that the magnitude of the C2 effect is proportional to the fraction of elastically effective network.
Chemical transformations of polymers. IV. Chemical reactions of glycol methacrylate gels
Authors: Ševčík S. , Štamberg J. , Schmidt P.
Published: June 2010

One step as well as multisteps of polymeranalogous reactions of hydrophilic gels based on poly(glycol methacrylate) were studied. The reaction medium for these transformations was chosen with respect to the result of linear swelling capacity measurements to reach a satisfactory rate. Attention was devoted to the determination of the region where the gels are chemically stable as well as to the preparation of the new, practically useful, gel system.
Structural investigations of crosslinked cellulose derivatives
Authors: Nikonovich G. V. , Leontyeva S. A. , Usmanov Kh. U.
Published: June 2010

Electron microscopy methods are used for investigation of the structure of cellulose fibers modified by some bifunctional reagents (dimethylolurea, formaldehyde, acrolein, epichlorohydrin, and propylene oxide). For sample preparation, mechanical and ultrasonic dispersion, ultrathin sectioning, and treatment by some reagents were used. Some data were obtained indicating extensive changes of the fiber supermolecular structure as a result of crosslinking between the structural elements. These changes are expressed in redistribution of the effective dimensions of structural elements toward their increasing (increase in layer thickness and diameters of fibrillar bundles) and even in the alteration of mutual arrangement of structural elements under very high degrees of substitution, as compared with the untreated fibers. Modification may proceed not only in the most accessible regions of the fiber, between the microfibrils as well as between the secondary wall layers, but also inside the microfibrils themselves, and in some cases affects the most dense fiber regions—crystallites. All these changes of the supermolecular structure after modification leads to essential alterations in the mechanical properties of the fibers.
Dissymmetric der lichtstreuung in polyvinylchlorid‐lösungen
Authors: Hloušek Miroslav , Lánková Jiřina
Published: June 2010

The dependence of the dissymmetry of light scattering on the molecular weight and on the degree of conversion of poly(vinyl chloride) in cyclohexanone solutions was studied. The dissymmetry of unfractionated samples increases with increasing molecular weight Mw. Fractions have a lower dissymmetry than unfractionated polymer of the same Mw. During the polymerization, the dissymmetry of the polymer increases with the conversion, especially at conversions of 90% and above, i.e., in circumstances when other properties of poly(vinyl chloride) (i.e., solubility, filterbility of solutions, thermal stability) also deteriorate, and when increasing branching or crosslinking of macromolecules is believed to occur. The dissymmetry is found to be caused by the presence of microgel particles in the solution. Analysis of the angular dependence of the scattered light has shown that with increasing conversion the concentration of microgel particles increases while their dimensions remain practically unchanged. The molecular weight Mw (determined by light scattering) increases slowly throughout the polymerization, while the intrinsic viscosity [M] decreases slightly at high conversions. This is believed to be caused by the presence of branched macromolecules in the solution. Both the microgel particles and the branched macromolecules can adversely affect the thermal stability of the polymer.
Effect of solvent on the optical behavior of macromolecules in a laminar flow
Authors: Frisman E. V. , Dadivanian A. K.
Published: June 2010

The segmental anisotropy of a series of macromolecules in different solvents was measured by means of streaming birefringence and viscosity. It is shown that the measured segmental anisotropy (α1 — α2) substantially depends on properties of the solvent applied. Analysis of experimental data leads to an assumption that in the vicinity of polymer chains an ordered disposition of solvent molecules (short‐range order) occurs, contributing a value (α1 — α2)s to the measured anisotropy. The magnitude of this contribution depends on the optical anisotropy of solvent molecules and their orientation relative to the macromolecule. Thus the actual segmental optical anisotropy (α1 — α2)K can be evaluated in an isotropic solvent only. Comparison of (α1 — α2)K with the value of (α1 — α2) obtained for the macromolecule in an anisotropic solvent gives (α1 — α2)s. It follows from the estimation that in spite of a strong solvent effect on the measured segmental anisotropy, the actual mutual orientation of solvent‐solute molecules is rather low. It is also shown that the short‐range order is particularly pronounced in systems where polymer‐solvent interactions are favored in comparison to polymer‐polymer and solvent‐solvent interactions.
Fractionnement du polyterephthalate d'ethylene par une methode en continu
Authors: Pailhes F. , Alliot‐Lugaz M. , Duveau N. , Kyritsos Et J.
Published: June 2010

A method for the continuous fractionation of poly(ethylene terephthalate) is described. It is based on the distribution of the polymer between two liquid phases in a ternary system solvent‐nonsolvent‐polymer. Continuous fractionation is achieved in a cell where both phases coexist. A solvent‐nonsolvent mixture, with a time increasing solvent concentration, enters the lower layer, whereas the upper phase overflows continuously drop‐wise into the collector tubes. The polymer is thus progressively extracted in the order of increasing molecular weights, while the volume of the lower phase diminishes to zero. The choice of experimental conditions is indicated by establishing the ternary phase diagram solvent‐nonsolvent‐polymer in the demixing region. Among different solvent‐nonsolvent systems tested, the most convenient is the phenol‐n‐heptane mixture at 56°C. The molecular weight distribution of different samples obtained by this method is very close to Flory's theoretical distribution. Morever, a mathematical derivation is given which leads to a plot from which the discrepancy from this law may be estimated.
Polyimides
Authors: Sroog C. E.
Published: June 2010

The preparation and properties of aliphatic and aromatic polyimides are reviewed. The discussion includes a comparison of methods of synthesis of the aliphatic vs. aromatic polymers and a detailed consideration of chemical structure vs. properties. The discussion of properties includes, in addition to properties of films and similar articles, various aspects of polymer properties such as crystallinity and solution viscosity relationships.
Some peculiarities of the polymerization of propiolic acid and its salts
Authors: Davidov B. E. , Krentsel B. A. , Kchutareva G. V.
Published: June 2010

This paper treats some theoretical premises determining peculiarities of acetylene polymerization and properties of polyene systems containing carboxy groups. Some kinetic mechanisms of the radiation polymerization of propiolic acid in the liquid phase were experimentally studied. It is shown that solid‐state polymerization of propiolic acid leads to the formation of the polymer with a higher molecular mass and greater effective conjugate length. The solid‐state polymerization of propiolic acid salts illustrates the dependence of the inclination to polymerization of ion metal radius. Some properties of polypropiolic acid and its salts were investigated, in particular, their inclination to photochemical reactions. A certain influence of the polyconjugate system and of the type of polyene chain configuration on the polypropiolic acid property as polyelectrolyte was discovered.
On the cross‐fractionalion of copolymers
Authors: Litmanovich A. D. , Shtern V. Ya.
Published: June 2010

A method of theoretical analysis of copolymers fraction is described. Using the method the cross‐fractionation of copolymers is considered. It is found for copolymers of a typical molecular and composition distribution that: the differential molecular distribution curves for almost all the fractions are symmetrical in shape; most of the fractions have sufficiently broad composition distribution, the composition heterogeneity of some light fractions being especially high; the molecular distribution curves of the original copolymer constructed from the cross‐fractionation data deviate, although insignificantly, from the true curves; the composition distribution curve of the original copolymer constructed from the cross‐fractionation data deviates essentially from the true curve, but does not distort the character of composition heterogeneity of the original sample in such degree, as in the case of successive precipitation procedure. The efficiency of the procedure of the cross‐fractionation of copolymers is discussed.
Precipitation of acidic polysaccharides by salts in ethanol–water mixtures
Authors: Smidsrød Olav , Haug Arne
Published: June 2010

The results of the present investigation show that precipitation with ethanol and inorganic salts may be a useful tool for the separation of the components of a polysac‐charide mixture. The solubility of neutal polysaccharides in ethanol–water mixtures is independent of the presence of salt except for high salt concentrations. The presence of anionic groups in the polysaccharide makes the solubility of the compound sensitive to the presence of ions, and the effect of the different cations depends on the type of anionic group on the polymer. Determination of cation activity by a cationic electrode revealed no correlation between the formation of ion pairs and the precipitating effect of the different cations. Viscosity determinations of dextran sulfate solutions showed that the viscosity at the salt concentration leading to precipitation was independent of the type of salt used. This result indicates that the different ion pairs formed on the polymer chain have a different effect on the interaction between the solvent molecules and the chain segments. Experiments with alginate showed that the divalent cations caused precipitation at higher viscosities than the monovalent ions, indicating that the divalent ions in this case have a different effect, probably by forming intermolecular bonds.
Formation of radicals in polymers
Authors: Sharpaty V. A. , Pravednikov A. N.
Published: June 2010

The results of the investigations of radiolysisof polyamides, polyacrylamide and its nitrogen derivatives, polymers of the triazine series and their low molecular analogs are reported. It was detected that the main radical formed during the radiolysis of polyamides is the radical with the formula –CONHĊHCH2—. Arcording to ESR and mass spectrometric investigations, some conclusions on mechanism of transformat ion of radicals are given. In the case of radiolysis of polyacrylamide and its nitrogen derivatives radicals arise as a result of breaking of CH bond of main polymer chain next to the amide group. The paramagnetic particles registered in irradiated polymers of triazine series are assumed to result from the transformation of the triazine cycle.
Critical opalescence of polymer solutions
Authors: Eskin V. E. , Nesterov A. E.
Published: June 2010

The critical opalescence of poly(butyl methacrylate) (PBMA) in isopropanol, poly(di‐methyl siloxane) (PDMS) in tetralin, poly(β‐vinyl naphthalene) (PVN) in three solvents, and poly (β‐naphthyl methacrylate) (PNMA) in four solvents has been studied. The general character of the phenomenon is in accord with the Debye theory. The critical concentrations V2c of the solutions are from 1.5 to 4 times greater than the theoretical values calculated according to the Flory‐Huggins theory. The relative dimensions (R̄c2/R̄o2)1/2 of the polymer coils near the critical temperature Tc decrease when the ratio of V2c to its theoretical value increases. The dependence of the square of the interaction distance for intermolecular forces l2 on the molecular weight M for PBMA and PNMA is nonlinear. For PVN in phenylethyl alcohol does not depend on M. A tendency is noted toward larger values of (1/R2)(dR2/dT) and of the range ΔT0 in which the dimensions (Rc2)1/2 remain constant for systems with small (R̄c2/R̄o2)1/2) values. The cohesive nergies of the polymers δ22V2 calculated from the critical opalescence data are as a rule in satisfactory agreement with the values obtained by other methods. The range l of the intermolecular forces and (R̄c2)1/2 are variable and depend on the difference between the cohesive energy densities of the polymer and the mixture δ22 –δ12 A correlation is noted between δ11 + δ22 – 2δ12 calculated from the critical opalescence data and the heat of dilution Rϕψ1.
Preparation of high molecular weight compounds on the basis of cyclic imides and diimides of dicarboxylic acids
Authors: Sheremeteva T. V. , Larina G. N. , Zhenevskaya M. G. , Gusinskaya V. A.
Published: June 2010

Investigation has been conducted in two directions: incorporation of the imide cycles into the macromolecule owing to the reactivity of double bonds, and preparation of polyamides involving the aminolysis of the imide cycles. Citraconimides are shown to polymerize by radical mechanism forming linear macromolecules consisting of the imide cycles. At the initial period the polymerization rate is proportional to the square root of the initiator concentration. The absolute values of the polymerization rates are low. Conversions attains 3% for 75 min. at 70°C. with 0.102 × 10−3 mole/liter of the initiator. The intrinsic viscosities are 0.07–0.1% Low polymerization rates and low molecular weights are due to the structure of this cyclic derivative of 1,2,2‐substituted ethylene with the methyl group at the double bond. An attempt to polymerize N‐methylcitraconimide by UV irradiation resulted in the formation of a mixture of crystalline oligomers; a tetramer was isolated and characterized. Migration copolymerization of diamines with diimides of unsaturated and saturated acids was also investigated. It was shown that the reaction depends on pH of the medium. In neutral medium in the absence of water diamines are added to the double bonds of maleindiimides forming poly‐alkylene‐polyimides of asparagic acid. In aqueous alcohol at pH 9–9.5 aminolysis of succinimides occurs and mixed polysueeinamides are formed with regular structure and molecular weight up to 20,000.
Poly[vinyl(oxyacetoxy)phosphinic acids]
Authors: Kafikov S. R. , Chelnokova G. N. , Artyemova Yu. V.
Published: June 2010

Oxidative chlorophosphination of poly(vinyl acetate) (PVA) results in poly[vinyl (acetoxy)phosphoryl chloride] formation and is not accompanied by significant destruction of the main chain. The maximum phosphorus contents in the product obtained have been as high as 12%, which corresponds to one phosphoryl chloride unit per two PVA units. Oxidative chlorophosphination is accompanied with side reaction of acetyl groupsphosphoryl oxychloride interaction. Depending on hydrolysis conditions of poly[vinyl‐(acetoxy)phosphoryl chloride], the mixture of poly [vinyl(oxyacetoxy)phosphinic acids] is formed with different ratio of acetyl and hydroxy groups, down to complete disappearance of acetyl groups. The derivatives of poly(vinylphosphinic acids) have been obtained which are soluble in DMFA, aqueous alkalis and (if phosphorus contents is high) in water. These compounds are very labile, easily undergo crosslinking, and when reacting with alkalis or metal acetates yield salts. The films obtained from acids and their salts are of amorphous structure and have certain complex of mechanical properties.
The nature of friction of polymers in high elastic and glasslike states
Authors: Bartenev G. M. , Elkin A. I.
Published: June 2010

The temperature dependence of the friction of polymers against hard surface is characterized by two maxima: main and low temperatures. The main maximum observed in the glass transition range, contrary to the widespread opinion, is not associated with the maximum of the mechanical losses observed in polymers. The temperature dependence of the friction force consists of three ranges. In the high elasticity range, with decreasing temperature, the friction force is observed to increase according to the molecular kinetic theory of the friction of rubberlike polymers. The nature of the friction for all polymers in this range is associated with the mechanical losses in the surface monomolecular layer of the polymer. The bulk‐mechanical losses in the polymer are not essential. The deviation from the theoretical dependence and the decrease of the friction force below a certain temperature in the transition range are associated mainly with the decrease in the actual contact area of suriaces of the friction pair at the glass transition of the polymer. In the glasslike state, for polymers the friction is essentially dependent on the bulk‐mechanical losses in the polymer at elastic and forced elasticity strain of the roughnesses in the polymer layer being in contact with a solid. Therefore, the low temperature maximum is associated with the maximum of the mechanical losses observed in the same range of temperature at dynamic tests. For polymers with no maximum of the mechanical losses at low temperatures, the maximum of the friction can be attributed to the increase in the adhesion forces and the drop in the actual contact area at temperatures at which the forced elasticity mechanism of compression of the polymer roughnesses is not realized.
Block polymers of controlled chain length
Authors: Yamazaki N. , Shirakawa H. , Kambara S.
Published: June 2010

To obtain block polymers of controlled chain length, the condensation reactions of poly‐α‐methylstyrene dianion polymerized with sodium naphthalene in tetrahydrofuran with α,ω‐dihalogenopolymethylene were investigated. The polymers obtained correspond to the formula + (α‐methylstyrene)m‐(methylene)n+x (m = 2, 4, and 10 and n = 4, 10, 20, and 34). Molecular weight of the polymers was 103‐104. Intensity of bands in the fingerprint region in infrared spectra of the polymers was found to change with increasing m. Melting point due to polymethylene microcrystallites was dilatometrically observed in the block polymers containing over 20 methylene groups.
The effect of extreme supercooling on the number of spherulitic centers in isotactic polystyrene
Authors: Boon J.
Published: June 2010

The bulk crystallization of isotactic polystyrene has been investigated by means of hot‐stage microscopy and dilatometry between 120 and 200°C. The linear growth rate of spherulites is independent of the thermal history. However, heating from the glassy state yields a ca. 102 times faster overall crystallization than cooling from the melt. So the number of spherulites in the former case is ca. 106 times as great as the number in the latter. This increase in density of spherulitic centers does not originate from nucleation during the thermal pretreatment, but from subcritical ordering near Tg. The density can be regulated between 1012 and 107/cc. by choosing pretreatment temperatures in the range from 75 to 110°C. and is independent of the later crystallization temperature (140–180°C.). It has been possible to determine the rate of nucleation out of the sub‐critical ordering over a wide temperature range. It shows a maximum at ca. 160°C., while the maximum of growth is at 175°C. The nucleation constants Kn and Kg were analyzed to obtain σ2σe = 174 ergs3/cm.6 and σσe, = 167 ergs2/cm.4, respectively. A work of chain folding q of 4.4 kcal./mole of folds was calculated.
Influence de l'Initiateur de Polymérisation et de la Masse Moléculaire du Produit Formé, sur l'Absorption des Ultrasons par les Solutions de Polyméthacrylate de Méthyle
Authors: Tondre C. , Cerf K.
Published: June 2010

The variation of the characteristic frequency N* (i.e., the frequency at which the rapid decrease of the ultrasonic absorption occurs) has been studied as a function of molecular weight Mw for different poly(methyl methacrylate) samples dissolved in benzene. Two categories of these products show up according to the initiator of polymerization. For the first one N* increases with Mw; for the second one N* does not depend on Mw. It appears that the variations of N*, either as a function of the initiator for the same molecular weight, or as a function of the molecular weight for a series of fractions, are not determined only by the global degree of NMR tacticity. The molecular weight does not seem to have a direct influence on the value of N*.
Über die Synthese und das Verhalten von Polyoxypropylenglykol‐Diglycidäthern
Authors: Jahn H. , Raubach H. , Goetzky P.
Published: June 2010

Polyoxypropylene glycols with average molecular weights of 270, 425, 565, and 920 are converted by two different methods to the corresponding diglycidyl ethers. Polyoxypropylene glycol diglycidylethers (A) synthesized via chlorohydrin contain ClCH2 groups as a result of competition between the secondary hydroxyl groups of the poly‐oxypropylene glycol and those of the already formed chlorohydrin ethers in the presence of the epichlorohydrin. The formation of these ClCH2 groups consumes epichlorohydrin, thus causing a corresponding deficit of glycidyl groups. Treating the sodium alkoxides of the polyoxypropylene glycols with allyl bromide followed by epoxidizing the diallyl ethers with peracetic acid yields diglycidyl ethers (B), which contain acetyl groups Crosslinking mixtures from diglycidyl ether of bisphenol‐A and polyoxypropylene. glycol diglycidyl ethers A or B with diethylene triamine yields flexible epoxy resins. Properties of epoxy resin systems containing diglycidyl ethers A or B differ only slightly. By applying the theory of rubberlike elasticity the crosslinking density and thes hear modulus G of the flexible epoxy resins systems are calculated. The calculated shear moduli and those measured above the glass transition temperature are in relatively good agreement. Epoxy resin systems with none or a high content of flexibilizer show differences, which are caused by two effects.
Infrarot‐ und kernresonanzspektroskopische untersuchungen der umwandlungen des polytetrafluoräthylens bei 20 und 30°C
Authors: Kriegsmann H. , Seifert G. , Frigge K. , Dube G.
Published: June 2010

The well‐known transitions that occur in polytetrafluoraethylene at about 20 and 30°C. also appear in infrared and nuclear magnetic resonance spectra. In the infrared spectrum the band at 625 cm.−1 increases and the band at 638 cm.−1 decreases with an increasing temperature. At 20 and 30°C. two abrupt changes in intensity of these bands occur. In the nuclear magnetic resonance spectrum the linewidth and the second moment are reduced at the same temperatures. An attempt is made to explain these results on the basis of the known conception of the inversion of the helix. The motion producing this inversion is hindered very strongly by the existing crystal lattice below 20°C. At about 20°C. the thermal energy is high enough for motion to set in in spite of this hindering, accompanied by the transition into a new crystal lattice. The transition at about 30°C. is an analogous process.
Homo‐ and copolymerization of vinyl phosphates and phosphonates
Authors: Muray B. J.
Published: June 2010

Phosphorus–containing monomers of general formulae

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homopolymerized, copolymerized with methyl methacrylate, vinyl acetate, and styrene under a variety of conditions, and the products were characterized. The results of homopolymerization show that yields and the degree of polymerization depend on the purity of the monomers, method of polymerization, and the initiator used. With the exception of monomers containing β‐chloroethoxy group attached to the phosphorus atom, polymers obtained from the dialkyl vinyl phosphates had higher molecular weights than the corresponding dialkyl vinyl phosphonates. Dialkyl isopropenyl phosphates polymerized less readily than the dialkyl vinyl phosphates and diethyl styryl phosphate did not polymerize at all. An attempt is made to explain these results in terms of steric hindrance, charge distribution, and chain transfer. Examination of the copolymerization products, with a number of techniques used, indicates that these consist of polymers with a wide range of compositions and molecular weights. The copolymers with methyl methacrylate appear to consist of a large block of poly(methyl methacrylate) at one end and a smaller block of polymer formed from the vinyl phosphate or phosphonate at the other. Similar conclusions are drawn about copolymers involving styrene. It is likely that the monomer units in copolymers with vinyl acetate are randomly distributed.
Dynamic birefringence of poly(methyl methacrylate)
Authors: Read B. E.
Published: June 2010

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).
Die Kinetik der Biosynthese der Cellulose in den Höheren Pflanzen
Authors: Marx‐Figini M.
Published: June 2010

Kinetic investigations on the cellulose of cotton bolls with increasing maturity have shown that the degree of polymerization remains constant by P̄w = 13,000 during the entire course of secondary wall synthesis, from which arise more than 90% of the material. Therefore the conclusion had been drawn that the biosynthesis of the plant cellulose proceeds by a template mechanism. To confirm this result molecular weight distributions at conversions of 18 and 100% had been investigated. They show that the cellulose of the secondary wall has a nearly complete uniform degree of polymerization about Pw = 14,000 independent of the conversion. Both molecular weight distributions differ only in the percentage content of primary wall cellulose, which nearly disappears in the sample of 100% conversion, as was expected. The molecular weight distribution curve of a cellulose, which was harvested a short time before the beginning of the secondary wall synthesis, shows that the degrees of polymerization smaller than Pw = 6,000 belong to the primary wall cellulose. The template mechanism for the biosynthesis of the cellulose was confirmed further by the independence of the degree of polymerization from the rate of the synthesis and the variety of the cotton plants.
Zur Theorie der Glastemperatur von Vernetzten Polymeren
Authors: Kanig Gerhard
Published: June 2010

Iu a previous work the corresponding state at the glass temperature has been described: (1) by means of a material‐independent constant ratio between the holes volume and the vibrational expansion volume, and (2) by means of material‐dependent work parameters which are characteristic for the production of a hole and, at the same time, constitute a measure for the affinities between the local regions of the molecules. If a crosslinked polymer is considered as a copolymer of monomeric units and crosslinking units, a thermodynamic relationship corresponding to that for copolymers may be derived in the same way as before. By neglecting a square term, very simple relationships can be derived from this for more weakly crosslinked polymers. The relationships agree closely with experimental results.
Elastic and viscoelastic behavior of glass‐reinforced plastics
Authors: Zvonač Vladimír , Tamchyna Jiří
Published: June 2010

The measurements of short‐term creep in dry and wet states are interpreted in terms of relationships among the composition, adhesion, and properties of glass‐reinforced plastics. Elementary constants of a rheological model were determined and the factors controlling the behavior of glass‐reinforced plastics are discussed. The role of adhesion is emphasized and the influence of water is interpreted.