bluuebunny/crossref_metadata_2025 huggingface dataset:
Fries Rearrangement of Polyphenyl Esters to Polyhydroxyphenones
Authors: Belluš D. , Maňásek Z. , Hrdlovič P. , Sláma P.
Published: June 2010

Six different polyphenyl esters were rearranged in a nitrobenzene solution under the action of AlCl3, in melt under the action of AlCl3, TiCl4, and SnCl4 and under the action of UV light. In the rearranged polymers a characteristic absorption band at v = 1636–1656 cm.−1 attributed to vibrations of o‐hydroxycarbonyl groups in IR spectra and a new one with λmax = 322–337 mμ in UV spectra were found. For model compounds, p‐cresyl benzoate and resorcinol monobenzoate, quantum yields of the formation of the corresponding o‐hydroxyphenones Φphi = 0.55 and 0.36 mole‐einstein−1 at λirr = 254 mμ were found. In a rearrangement initiated by UV light, as well as in that catalyzed by Lewis' acids, a decrease in molecular weight occurs and in the latter occurs crosslinking also. A reaction mechanism is suggested. The AlCl3‐catalyzed rearrangement in nitrobenzene solution is governed in the initial phases by the first‐order reaction with an activation energy for the disappearance of ester groups E = 20 kcalμ.‐mole−1 for poly‐2,2‐bis(4‐hydroxyphenyl)propane isophthalate and E = 19 kcalμ‐mole−1 for p‐cresyl benzoate.
Effect of Diluent Content during Polymerization on Equilibrium Deformational Behavior and Structural Parameters of Polymer Network
Authors: Hasa J. , Janáček J.
Published: June 2010

The deformational behavior of poly(ethylene glycol monomethacrylate) which was crosslinked by ethylene glycol dimethacrylate in a concentration range c = 0.05–1.0 × 10−4 mole/cm.3 and polymerized in the presence of 0.05–0.75 volume parts of water was studied. The deformational behavior of these systems may be described by a two‐parameter equation. We found that the value of the constant C2 and the content of permanent entanglements increased linearly with increasing content of polymer in the polymerizing mixture v0. The efficiency of crosslinking also increased and approached the theoretical value at v0 = 1. The measured data can be expressed by the relation v = Kv + Q, where v is the number of effective network chains, and K and Q are the constants depending on the crosslinking agent content, the crosslinking efficiency, and the entanglement content. On the basis of experimental data obtained it is assumed that the entanglements show partly a permanent effect and partly a labile one, the latter influencing the value of the constant C2.
Alkaline Polymerization of Caprolactam. XX. Changes in Catalytic Activity in Activated Alkaline Polymerization of Caprolactam
Authors: Šebenda J. , Masař B. , Bukač Z.
Published: June 2010

The degradation of imide groups (I) in the presence of strongly basic sodium salts (Na) of alkylamides or caprolactam was followed at temperatures of 80‐210°C. in order to elucidate the decay of the catalytic activity during anionic polymerization of caprolactam. It was found that the degradation of I is accompanied by the formation of substances with a strong absorption at 280 mμ, the absorption being proportional to the decrease of the imide group concentration. At temperatures up to 100°C. the rapid degradation of I stops after one I per molecule of Na has disappeared. This may be explained by the formation of acidic derivatives of β‐keto acids through condensations of I. These acidic groups decrease the basieity to such an extent that the further condensation of I is markedly slowed down. At higher temperatures, e.g. 210°C., the equilibrium between the mesomeric enolate anions of the β‐keto acid derivatives and amide groups favors the formation of strongly basic amide anions (—CON—)° which in turn give rise to further condensations of I. At temperatures around 200°C. as much as 3I disappear per Na within a few minutes. The degradation of I is accompanied by a corresponding decrease of the concentration of amide or lactam anions and therefore polymers prepared at 200°C. with I/Na = 3 reveal practically no catalytical effect. On the other hand, polymers prepared with I/Na > 3 or <3 contain either I or strong bases. This could be proved by the use of such polymers as components of the catalytical system instead of I or sodium caprolactam. If more than 3I per molecule of sodium caprolactam are used as catalyst at 200°C. then the decay of the catalytic activity is so rapid that the polymerization stops before the monomer–polymer equilibrium has been attained. Although there is a simple ratio at which I and Na are destroyed, the scheme of the decay of the catalytic effect is not so simple because the extent of the individual side reactions will depend on the temperature and on the initial I/Na ratio.
A Comparison of the Viscoelastic and Dielectric Properties of Natural Rubber—Sulfur Systems
Authors: Havranek A. , Bakule R.
Published: June 2010

This paper presents a comparison of viscoelastic and dielectric retardation time spectra of a rubber‐sulfur system with a sulfur concentration ranging from 1.75 to 16.4%. The viscoelastic spectra were obtained from creep measurements which were carried out in the time interval 3 × 10−2 to 5 × 10+1 sec. and a temperature range from −40°C. to + 70°C. The dielectric spectra were derived from measurements of the frequency dependence of the real and imaginary part of the complex dielectric constant in the frequency range 3 × 101 to 3 × 104 cps or temperatures between −50° and +35°C. The temperature‐time superposition principle was used in the derivation of the spectra. The following conclusions may be deduced from the comparison: (1) The retardation times corresponding to the spectral maximas for mechanical measurements are displaced by several orders toward longer times with respect to those for dielectric measurements. (2) The reference temperatures T determined from the WLF equation are higher for viscoelastic measurements than for dielectric measurements, especially for samples with a higher sulfur content. (3) The viscoelastic spectra become narrower, while the dielectric spectra broaden with increasing sulfur content. Further, it was ascertained that the results of dielectric measurements correspond to the presumption that the logarithmie retardation time spectrum has the Gaussian form in logarithmic time scale.
Preparation of Alternating Copolymers of the N‐Substituted Maleimides
Authors: Cubbon R. C. P.
Published: June 2010

Alternating copolymers of the N‐substituted maleimides with styrene, propylene, and ethylene have been prepared by reacting the appropriate maleic anhydride copolymer with primary amines in glacial acetic acid. The x‐ray spectra of these alternating copolymers indicate that the N‐substituted maleimide units form the same 31 helix found in the N‐substituted polymaleimides.
Copolymers of Butene with α‐Olefins. Cocrystallizing Behavior and Polybutene Type II Type I Crystal Phase Transition
Authors: Jones A. Turner
Published: June 2010

The cocrystallizing behavior shown by copolymers of butene with a number of linear and branched α‐olefins has been investigated by x‐rays over a range of copolymer compositions; degrees of crystallinity, crystal phase changes from those of the relevant homo‐polymers including lattice expansion and contraction and helix modification, and melting points have been observed. Lack of randomness in the copolymers is discussed. Pentene forms a highly cocrystallizing system based on type I polybutene (PB‐I); propylene shows limited, and ethylene no isomerism of monomer units. These three comonomers markedly accelerate the well‐known spontaneous transition from PB‐II to PB‐I, and in sufficient amount cause direct crystallization from the melt to PB‐I. Hexene and octene units can enter the PB‐II lattice, but α‐olefins with C > 8 do not. Butene‐3‐methylbutene is a highly cocrystallizing system; 4‐methylpentene and 4,4‐dimethyl‐pentene copolymers show limited cocrystallization and no cocrystallization, respectively. Linear α‐olefins with C > 5 and the branched comonomers retard the PB‐II PB‐I transition and in sufficient amount stabilize the PB‐II form completely. For comonomers which enter the PB‐II lattice, stabilization is attributed to steric inhibition of the change from an 113 (PB‐II) to a more tightly coiled 31 (PB‐I) helix, but for those that do not, it is believed that the large units act as “stops” at the fold boundaries, which prevent the helical chains being drawn through the crystallites and thus inhibit the transition.
Cyclo‐ and Cyclized Diene Polymers. X. Formation of Cyclopolyisoprenes on Ziegler‐type Catalysts
Authors: Krauserová H. , Mach K. , Matyska B. , Kössler I.
Published: June 2010

Polymerizations of isoprene in n‐heptane medium catalyzed by the systems Et2AlX + TiCl4 (X = F, Cl, Br) are characterized by a strong dependence of the reaction rate on the Al/Ti ratio. Changes in the polymerization rate are accompanied by the changes of the microstructure of polymers. Polymers obtained at Al/Ti ratios lower than 1.5 contain very low amounts of common linear forms and can be thus considered as practically cyclic. The highest polymerization rate in formation of cyclic polymers lies for all three diethylaluminum halide catalysts at the ratio Al/Ti = 0.75. The systems EtAlX2 + TiCl4 are considered as actual catalysts. When diethylaluminum iodide is used as the organoaluminum compound formation of cyclopolymers takes place at all Al/Ti ratios.
ESR Study on the Mechanism of UV‐Initiated Polymerization of Methyl Methacrylate
Authors: Komatsu T. , Seguchi T. , Kashiwabara H. , Sohma J.
Published: June 2010

The ESR spectrum of methyl methacrylate, which had been mixed with 0.1 wt.‐% benzoyl peroxide as the initiator and irradiated by UV at 77°K., was observed. The observed spectrum was found to be the superposition of the singlet, triplet, quintet, and septet spectra. In addition to this superposed spectrum, the spectrum due to hydrogen atom was also observed. The four kinds of radical which give these four components of the superposed spectrum could be identified. On warming up the sample to 115°K., 195°K., both the pattern and the intensities of ESR spectra were found to be changed. Based on this change of spectra induced by the heat treatment and on the identification of the radical species, the initiation mechanism of this UV‐induced polymerization is discussed.
Preparation and Polymerization of Tetrolonitrile
Authors: Beneš M. J. , Peška J. , Wichterle O.
Published: June 2010

A polyconjugated polymer obtained by polymerization of tetrolonitrile with anionic catalysts is described. The monomer was synthetized from methyltetrolate via tetrol‐amide with better yields and purity than obtained with other methods. Polymerization was initiated by butyllithium and lithium naphthalene in tetrahydrofuran at 0° and −80°C., yielding a dark‐brown product, soluble in polar solvents. Molecular weight, electrical conductivity in solid state and in solution, as well as infrared and ESR spectra were determined. The properties of the substance are discussed in connection with the proposed polyenic structure.
On the mechanism of the radical polymerization of vinyl chloride
Authors: Ryska M. , Kolínský M. , Lím D.
Published: June 2010

The mechanism of precipitation polymerization of vinyl chloride was studied by gradual transition from homogeneous to heterogeneous polymerization. Diethyl oxalate and 2,4‐dichloropentane were used as solvents. In diethyl oxalate the initial course of polymerization is homogeneous up to 7.5 moles/l. The order with respect to monomer is 1.2. At higher concentration of monomers, the order decreases due to aggregation. From about 10 moles/l, the polymerization is heterogeneous. A break is observed in the kinetic curves with a distinct acceleration accompanied by a decrease of the order with respect to monomer and of the degree of polymerization. In the presence of CBr4 the polymerization is heterogeneous in the whole range of monomer concentration studied. In 2,4‐dichloropentane the initial rate is lower than in diethyl oxalate and the order with respect to monomer is 1.6. It was shown that in the initial course of precipitation polymerization the propagation rate decreases to such an extent that a termination reaction besides the transfer to monomer bimolecular termination must be taken into consideration.
Synthesis of poly(arylene sulfones) and poly(arylene ketones) by reactions involving substitution at aromatic nuclei
Authors: Jennings B. E. , Jones M. E. B. , Rose J. B.
Published: June 2010

The preparation of aromatic macromolecular structures by nucleophilic substitution reactions (A), in which polymerization proceeds via the formation of ether linkages, and by the electrophilic substitutions, (B) and (C), where sulfone or ketone linkages are formed is described.
Photoisomerization of polybutadiene
Authors: Golub M. A. , Stephens C. L.
Published: June 2010

Polybutadiene, in the solid state, and in the absence of added sensitizer, undergoes photochemical cis‐trans isomerization and loss of unsaturation when irradiated in vacua with krypton 1236 A. or mercury 2537 A. radiation. The estimated quantum yields for these two reactions are 0.25 and 1.53, respectively, for the krypton irradiations, and 0.09 and 0.07 for the mercury irradiations. The G‐values (or 100‐e.v. yields) for the vacuum photochemical isomerization and consumption of double bonds indicated by the krypton data (2.5 and 15.3) are comparable to the G‐values obtained previously for the corresponding radiation‐induced reactions in polybutadiene (7.2 and 13.6–7.9, respectively). This suggests that the mechanisms in these two systems are similar, involving both ionized and excited species; the high yield for loss of double bonds with krypton is attributed to a chain cyclization analogous to that postulated in the radiation chemistry of diene polymers. The photoisomerization with mercury is assumed to be sensitized by adventitious impurities present in the polymer which absorb in the ordinary ultraviolet (where the polymer is transparent) and which transfer energy to the double bonds, causing their excitation and eventual isomerization.
Dynamical equilibria of swollen gels
Authors: Kuhn H. J.
Published: June 2010

Swollen macromolecular networks, e.g., vulcanized rubbers swollen in benzene, have different static elastic moduli for open and closed systems. Such gels may, in contact with pure solvent, relax under stress without chemical damages to the network. It is possible on thermodynamic foundations to correlate the relaxation times of a simple stretch experiment to the permeability coefficient of such a gel, to the Young's modulus of the closed system, to the Poisson number of the open system, and to the shape (thickness) of the gel sheet. The relative elongation of a swollen network which is in contact with pure solvent is calculated as a function of time. The calculated and experimentally determined values of the relaxation time are in excellent agreement.
Novel initiating systems of the type AIR3‐acylic peroxide
Authors: Milovskaya E. B. , Zhuravleva T. G. , Zamoyskaya L. V.
Published: June 2010

Systems capable of releasing the polymerization of polar monomers (VA, AN, etc.) at low temperature are formed with the use of aluminum alkyls and acylic peroxides. It was shown for VA that the process obeyed the free‐radical laws; the most active of the systems studied until now AlEt3‐PC, permits the process even at −60°C. In this article the kinetics of polymerization of AN in DMF initiated by the system AlEt3‐BP is given. The reaction order with respect to the product of the concentrations of the system components is found to be 0.45. The results obtained using the derivatives of BP together with AlEt3 in VA polymerization show that the activity of the systems corresponds to the thermal stability of the peroxide used. The interaction of BP with AlEt3 proceeds as that of the donor‐acceptor type; 2 molecules of AlEt3 react with one molecule of peroxide. The reaction occurs practically instantaneously even at −40°C. and is followed by the evolution of C2H6, C2H4 and C4H10. The main product of the transformation of the peroxide is diethylaluminum benzoate. The character of the interaction between AlEt3 and peroxide changes in the presence of the complexing agent (polar monomer). Data obtained during the study of the kinetics of VA and AN polymerization and the results of the experiments with AlEt3 and BP under model conditions lead to the following mechanism of the initiating step: AlEt3 + M → (AlEt3.M); (AlEt3.M) + BP 44 (AlEt3.M.BP) → Et. + AlEt2OCOC6 H5 + C6H5COO. + M. The influence of the nature of the polar monomer and the peroxide upon the energy of the activation of the initiation step has been shown. The corresponding values for the systems VA‐AlEt3‐BP, AN‐AlEt3‐BP, and VA‐AlEt3‐PC are 16, 19, and 13 kcal./mole.
Umwandlung von cis‐ und trans‐1,4‐polybutadien in polymere mit konjugierten doppelbindungssystemen
Authors: Drefahl G. , Hörhold H.‐H. , Hesse E.
Published: June 2010

1,4‐Polybutadienes (cis and trans) are transformed into conjugated polymers by bromination and dehydrobromination. trans‐1,4‐Polybutadiene of both a high and lower molecular weight as well as cis‐1,4‐polybutadiene are completely brominated by means of pyridinium perbromide in pyridine‐carbon disulfide solution. The bromination products obtained from the polymers with a trans structure are much less soluble than the corresponding addition products from the cis‐structured polymeride. The addition products are dehydrobrominated to a large extent with KOH/Py, and with KNH2 in liquid NH3 and NaH in DMF the elimination is even complete. The brownish black insoluble products obtained have long sequences of conjugated double bonds and exhibit a single narrow ESR signal; the conductivity obeys an exponential dependence on temperature.
Supermolecular particles in acetylcellulose solutions
Authors: Klenin V. J. , Klenina O. V.
Published: June 2010

The curves of the size distribution, average radii (r), and concentration (N number of particles in 1 cc.) of finely dispersed supermolecular particles (SMP) in solutions of several batches of acetylcellulose (AC) have been determined by the method of turbidity spectra based upon the combination of two theories of Heller and co‐workers. It was observed that for some batches of AC the SMP in acetone solutions at 2% concentration are aggregates which are destroyed, forming smaller fragments when the solution is diluted. For an AC sample with high Ca++ content a twofold increase in SMP dimensions is observed. Nevertheless, the volume fraction of the population of small SMP (θ) remains constant. Temperature dependence of the dimensions of SMP r(T) in dioxane solutions has been studied. It has a smooth character with a considerable (for certain AC batches) decrease in SMP dimensions (and a corresponding increase in N) in the temperature range from 14 to 40°C. This dependence of r(T) gave rise to a suggestion about a marked influence of hydrogen bonds upon the aggregation process of the SMP fragment at room temperature (and at lower temperatures). The SMP radius corresponding to the flat part of r(T) (high temperatures‐interfragment hydrogen bonds are broken) varies with the content of bi‐ and trivalent metal cations in the AC preparation. This provides evidence of the participation of bridge bonds in the aggregation of SMP fragments: metal ions carboxyl or sulfoester groups on the surface of the SMP fragments. Comparison of r(T) and N(T) shows that on heating (as well as on dilution of the solution) SMP are destroyed without a change in θ, and in the spherical shape of SMP, i.e., N1∼D13 = N2∼D23. If the SMP population at maximum destruction (high temperature) is defined as a system of structural elements of SMP characterized by the parameters De (diameter) and Ne (reduced to the 2% polymer concentration), the above condition is given by N.r3 = Ne.re3 or N.D3 = Ne.De3. The linear dependence of the number and dimensions of SMP in a logarithmic scale resulting from the scheme log N = (log Ne + 3.log De) ‐ 3.log D, describes well the experimental results of the determination of the SMP parameters both in the AC solutions (different samples, solvents, concentrations, and temperatures) and in the viscose solutions (published data) over a wide range of the SMP dimensions. The parameters of the smallest SMP fragments which we have determined experimentally (De ∼ 500 A., Ne ∼ 1011) closely agree with the extrapolated value B = log Ne + 3.log De.
Optic, thermodynamic, and rheologic properties of concentrated solutions of polystyrene and polyisobutylene
Authors: Tager A. A. , Andreeva V. M.
Published: June 2010

The light scattering by moderately concentrated solutions of polystyrene and poly‐isobutylene has been studied. The dependence of excess light scattering on the concentration of the solution has been expressed by a curve with a maximum, the height and sharpness of which depend on the temperature, the molecular weight of the polymer, and on its interaction with the solvent. With an increase in the molecular weight of the polymer the position of the maximum is displaced toward lower volume fraction φ2, which with impairment of the thermodynamic interaction the maximum is found at higher φ2. The position of the maximum does not depend on the temperature. Light scattering increases with a drop in temperature if the system has an upper critical solution temperature (UCST) and with a rise in temperature if phase separation takes place when the solution is heated (LCST). These results are in accord with the signs of the excess thermodynamic functions in these systems. Comparing the results with the Newtonian viscosity data on the same systems and with the literature on the aggregation of macromolecules, we conclude that polymer solutions exhibit two regions at concentration below φ2 = 0.5 characterized by differences in: (1) the region of interaction of uncoiling macromolecules, which is characterized by a considerable increase in light scattering and a relatively slight increase in viscosity; and (2) the region where the aggregates form a continuous random network, the order of which increases with the increase of concentration. This is followed by a decrease in fluctuations of concentration and hence of light scattering and a sharp increase in viscosity.
Electron spin resonance studies of propagating type radicals of vinyl esters and butadiene
Authors: Yoshida Hiroshi , Rånby Bengt
Published: June 2010

Electron spin resonance spectra of short‐lived free radicals formed by addition of HO. to vinyl acetate, vinyl propionate, and 1,3‐butadiene in aqueous solution were studied by means of a rapid flow technique. The observed spectra were assigned to be due to free radicals, CH2CHOCOCH3, CH2CHOCOC2H5, and CH2CH(CHCHS2), respectively. The observed hyperfine coupling constants give the spin density of 0.855, 0.848, and 0.629. Taking previously reported spin densities of propagating type free radicals of acrylic acid, methyl acrylate, and ethylene, as well as the present results into consideration, the order of the spin density is ethylene > methyl acrylate ≈ acrylic acid ≈ vinyl acetate > butadiene, which is in agreement with the order of the reactivity of the propagating radicals in addition polymerization. This is interpreted as an effect of resonance stabilization due to the side‐chain substituent of the vinyl monomers. In addition, there are differences between vinyl ester and acrylic ester radicals which tentatively are interpreted as related to the hindered rotation of the endgroups of the growing chain radicals.
The mechanism of polymerization of tetrahydrofuran
Authors: Rosenberg B. A. , Ludvig E. B. , Gantmakher A. R. , Medvedev S. S.
Published: June 2010

The cyclic monomer‐polymer equilibrium in cationic THF polymerization is a true thermodynamic one. Kinetic parameters of reactions of THF polymerization and depolymeriization are presented. The active center is an oxonium ion. The structure of this ion is much more stable than that of the corresponding carbcation, which enables polymerization to proceed without chain termination and yield “living” polymers. The mechanism of THF polymerization by trialkyloxonium salts (C2H5)3OSbCl6 and (C2H5)3OBF4, acetylhexachlorantimonate, antimony pentachloride, and catalytic system BF3‐etherate‐epichlorhydrin was investigated by means of the kinetic method along with a detailed analysis of the molecular weights and molecular weight distribution of the resultant polymer. The catalysts investigated differ markedly in their initiating power, which is displayed both in the completeness of the reaction and in the initiation rate. The polymerization is a stationary or a nonstationary process (depending on the initiation type) and belongs to the “living polymer” type. Water additives are effective chain transfer agents. The phenomenon of chain transfer to polymer, which leads to a marked increase of the reaction mixture viscosity toward the end of the polymerization process, has been discovered. The reactivity of cyclic ethers has been discussed and the following relationship established: the mure active the monomer, the less active the corresponding oxonium ion, basicity being a factor and thus determining their reactivity in copolymerization.
Stereoregularily and reaction of polyacrylates and polyacrylonitriles
Authors: Matsuzaki Kei , Uryu Toshiyuki , Ishida Akira , Takeuchi Makoto
Published: June 2010

Reactions of polyacrylates of different stereoregularities were briefly outlined. Then, NMR spectra of poly( methyl acrylates) polymerized with various initiators and also those of model compounds were analyzed and compared. Theoretical spectra agreed well with the observed ones. In order to examine the stability of tertiary CH in poly‐acrylonitrile and polyacrylonitrile‐a‐d were hydrolyzed with sodium hydroxide solution, sulfuric acid, or deuterated sulfuric acid, and racemization of the tertiary carbons was found.
Degradation of polyphosphates in solution. II. Hydrolysis of sodium hexaphosphate
Authors: Strauss Ulrich P. , Day Jean W.
Published: June 2010

The individual rate constants for each of the reactions occurring during the degradation of sodium hexaphosphate, derived from trömelite, were determined at 65.5°C. and pH 5. Since pentaphosphate was produced in significant amounts it was possible to calculate the rate constants for each of the reactions occurring during its degradation also. These constants demonstrate that these phosphates degrade mainly by two routes, the first and faster producing orthophosphate with a chain shorter by one phosphate unit and the second producing trimetaphosphate with a chain shorter by three phosphate units. The rate constants for the hydrolysis of polyphosphates with DP < 5 were redetermined. The constant for the degradation of tetraphosphate presented here differs from that published previously, while the constants for tri‐ and pyrophosphate check with those obtained by other workers.
Kinetics of alcohol and polyether polyol‐isocyanate reactions using metal catalysts
Authors: Frisch K. C. , Reegen S. L. , Thir B.
Published: June 2010

A study has been conducted of the kinetics of the reaction of ether alcohols, primary and secondary methoxypropanols, with phenyl isocyanate in the presence of metal catalysts. The proximity of the methoxy and methyl groups to the hydroxyls had a significant effect on the reaction rates as did the type and concentration of metal catalysts (lead naphthenate or dibutyltin dilaurate). The reaction rates in toluene solution were found to be faster than in Cellosolve acetate solution. The study of the reaction of poly(oxy‐propylene)glycols with isocyanate showed the existence of two rate constants due to the reactions of the primary and secondary alcohol groups present in the glycols. The mechanism of the metal‐catalyzed reaction between alcohols and isocyanates was investigated by means of IR and NMR spectra. No direct evidence of alcohol‐catalyst complex formation could be obtained by IR spectroscopy. NMR spectra indicated the existence of a 1:1 complex in the system dibutyltin dilaurate‐1‐methoxy‐2‐propanol.
Some comments on carrier generation and transport in short‐range order systems
Authors: Gutmann F.
Published: June 2010

A criterion for long‐range order is derived as the distance covered by a disturbance of the ordered crystal within a quarter lattice wavelength: for typical organic solids, order extending to several 1000 A. would be required for appreciable band broadening. Let a periodic one‐dimensional array of point molecules be disturbed by deviations δ = 1.575 e−ε, where ε is a small positive random number <1, obeying Poisson's distribution, 1.575 being a normalizing factor. A disordered spacing s results, s = a[1 + 1.575ε exp {−ε}]. The deviations accumulate, so that after n terms the original lattice reappears. A computer solution was obtained to find the number(s) n so that \documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_0^n {\varepsilon _n e^{- \varepsilon _n} = I} $\end{document}, a positive integer subject to a Heisenberg positional uncertainty approximated by cutoff functions e−2, e−3, e−5, or e−7: regions of residual long‐range order reappear extending up to at least 135a. The extent of residual long‐range order increases for high molecular weight M but the probability of its occurrence is reduced, producing ordered “island domains” in a “disordered sea.” For higher M, the concentration of such islands drops but their size increases. This residual, temporary long‐range order should give rise to temporary relatively wide energy bands. Electrical conductivity may then be determined by the probability that two such domains meet in a sterically favorable configuration.
Spin resonance, hall effect, and transport properties of poly(N‐vinyl carbazole)—iodine complex
Authors: Hermann A. M. , Rembaum A.
Published: June 2010

The results and interpretations of Hall effect, resistivity, electron spin resonance, Dember effect, and thermoelectric measurements on the poly(N‐vinyl carbazole)—iodine complex are presented. The existence of a charge‐transfer state in this system is demonstrated by three independent techniques: (1) the variation of resistivity with iodine content; (2) study of unpaired spin concentration; (3) optical absorption measurements. Many complexes have high impedances that have prohibited heretofore measurement of fundamental characteristics such as Hall mobility. The development of an AC technique9 for the measurement of the Hall effect in materials of high resistivity and low mobility has permitted the measurement of the Hall mobility in compressed pellets of poly(N‐vinyl carbazole) complexed with iodine (impedance ∼1 megohm). It is believed that the Hall mobilities are the first to be reported for a charge‐transfer complex. A discrepancy in the sign of the majority carriers is observed: the Hall coefficient is negative, the Seebeck coefficient is positive. The Dember voltage supports n‐type conduction as found in the Hall effect. It is suggested that this sign discrepancy can be resolved by consideration of surface states. The concentration of carriers deduced from Hall measurements is four orders of magnitude smaller than the unpaired spin concentration. The mechanism of conduction proposed invokes a hopping process in which a localized electron in an unpaired spin state makes phonon‐assisted jumps from site to site.
Magnetic and electrical properties of coordination polymers formed with copper and rubeanic acid
Authors: Kanda Seiichi , Ito Kazuo , Nogaito Takeshi
Published: June 2010

A crystalline form of a rubeanato‐copper coordination polymer has been synthesized by a solid‐solid reaction. The electrical and magnetic properties of the crystalline form have been studied and compared with the properties of the normally synthesized amorphous form. Molecular structures are proposed for both forms, which are consistent with the resistivity of the samples. Infrared spectra support the proposed structures. In particular, the static magnetic susceptibility was measured in a temperature range from 100–380°K. Typical values at room temperature are: 271 × 10−6 c.g.s.‐e.m.u. for the crystalline form and 236 × 10−6 c.g.s.‐e.m.u. for the amorphous form. The d.c. resistivities at room temperature are 1010 and 4 × 104 Ω‐cm. for the crystalline and amorphous forms, respectively. Also the temperature variation of the ESR absorption was studied. The anomalous behavior of the magnetic susceptibility, i.e. (1) it exhibits very low value, and (2) it exhibits essentially no temperature dependence, requires a new magnetic model to be set forth. Three models are considered: (1) Copper aceta e model, (2) One‐dimensional Heisenberg model, (3) “Equiinteraction” model. Either the second and third model may be employed to explain the behavior as seen. By these models, the effective number of the magnetic copper chain is estimated as nine.
Molecular mechanism of plastic deformation of polyethylene
Authors: Peterlin A.
Published: June 2010

Studies of single‐crystal deformation explain the small‐ and wide‐angle x‐ray observations of the cold drawing of PE, particularly the effects in the necking zone where the original spherulitic structure is transformed into a highly aligned fiber structure. Whole blocks of folded chains are broken out of the original crystals, which have already undergone a substantial deformation by chain tilting and slip, and incorporated in the new fiber structure. In variance with drawing of single crystals, the plastic deformation of bulk samples adjusts the long period of folded chain blocks to the temperature of drawing so that the obtained value is a function of the latter, but very nearly independent of the long period of the sample before drawing. The amorphous regions of the drawn polyethylene contain a great many highly strained tie molecules with a lower entropy and heat content than in a completely relaxed supercooled liquid. Melting experiments yield the heat content reduction which is a consequence of more extended chain conformation(intramolecular energy)and of closer chain packing(intermolecular energy). The entropy and enthalpy reduction explains the drastic decrease of sorption and diffusion of solvents first observed in wide‐line NMR experiment. Annealing lets the sample relax and return to thermodynamic equilibrium nearly instantaneously. The heat content, the diffusion, and sorption resume the values of the undrawn bulk material. The long period grows to the value which one would obtain if the original drawing were performed at the temperature of annealing.
Glass fibers in industrial applications
Authors: Marzocchi A. , Rooney M. J.
Published: June 2010

In the past thirty years, glass fibers have progressed from the realm of decorative curiosities to a basic commercial product with many decorative and industrial applications. Their thermal endurance, dimensional stability, resistance to environmental effects, high strength, and low cost have resulted in a variety of uses such as reinforced plastics, high temperature filter media, thermal insulation, distillation media, paper reinforcement, etc. Recent developments in fiber surface treatments, glass composition, fiber diameters, and product forms have contributed greatly to an ever‐increasing pace of new product developments. This paper will consider the properties of some of our newer glasses, fiber sizes, and chemical treatments. Physical properties and application of the concepts involved in glass and organic fiber combinations will be discussed, as will the recent work which has led to the use of glass fibers in rubber reinforcements, the first application of glass fibers to a dynamic use.
Optical diffraction techniques for interpreting X‐ray diffraction photographs of fiber structures
Authors: Taylor C. A.
Published: June 2010

The classical interpretation of x‐ray diffraction patterns of single crystals is through Bragg's law and it leads to the notion that each “reflection” is a separate entity in a list of data. The adoption of the optical diffraction, or transform, approach leads to a much more physical view of the diffraction process in which the pattern is assessed as a whole. Studies of the Fraunhofer diffraction pattern in visible light of masks representing the unit crystal cell provide a means of testing the validity of trial structures. The particular value of this approach in fiber studies is that masks can be made to represent extremely complicated atomic arrangements and their patterns can be observed instantaneously. The key problem, is, of course, the preparation of the masks. The most versatile procedure would be to build a semi‐automated machine controlled by punched tape prepared on a computer. Design studies are in progress. Several interim methods, including photographic etching, are in use at the moment and various aspects of the interpretation of fiber photographs will be illustrated with diffraction patterns prepared from masks made in this way. Interpreting fiber photographs from the standpoint of their diffraction aspects rather than from a structural model may provide valuable complementary evidence to that produced in the more conventional way.
Application of histochemical techniques in electron microscopy as applied to high polymers
Authors: Kassenbeck P.
Published: June 2010

Staining reactions are necessary to reveal the fine structure of fibrous polymers in electron microscopical investigations. Reactions of heavy metal salts with organic compounds yield different results depending on pretreatment of the fibers, the nature of the heavy metal employed, and the conditions of treatment. In the case of keratin fibers, the structure as revealed by the electron microscope depends mainly on the conditions of treatment. For example, wool, after carboxymethylation, shows a complete reversion in contrast compared with untreated material. It is thus possible to reveal the sulfur‐rich fraction of keratin with a staining reactive which normally reveals the low‐sulfur fraction. The quantitative analysis is, in both cases, in good agreement with the electron‐microscopical results. Further examples of staining reactions are discussed, especially the reactions of keratin and cellulose fibers with silver salts.
Fiber length changes and their relation to fiber structure
Authors: Bosley D. E.
Published: June 2010

Deformation processes in polymers are reviewed within the framework of rubber elasticity theory. The effect of hindered rotation on imposed and spontaneous length changes of polymeric fibers is discussed, leading to a new definition of crystallinity as a localized region of hindered rotation. This concept, together with a fringed‐micelle model, is used to relate length changes to molecular fine structure of polymers. The details of this model are described and compared with lamellar and paracrystalline models.
Gel permeation chromatography. II. Molecular size separability and the determination of polymer polydispersity
Authors: Osterhoudt H. W. , Ray L. N.
Published: June 2010

An equation describing the relationship between the GPC determined breadth of the molecular weight distribution, (σn/Mn)G, the true breadth of the distribution, σn/Mn, zone spreading or tailing ΔVe, and the separability employed, K(M), has been derived:

magnified image.

Here K(M) is the absolute value of the derivative dVe/dM, in which Ve is elution volume and M is molecular weight. The validity of this equation was established through GPC fractionations of blends of narrow molecular weight distribution polystyrenes. Application of the equation to experimental data shows that ΔVe increases with increasing M. The equation indicates that GPC molecular weight data are less in error with polymers of broader molecular weight distributions and with larger values of K(M). The importance of the experimental variable K(M) is that it defines the degree of fractionation, higher values of K(M) denoting more complete fractionation.
A method of solving Tung's axial‐diffusion equation for gel permeation chromatography
Authors: Pierce P. E. , Armonas J. E.
Published: June 2010

A new method of solving Tung's diffusion equation for gel permeation chromatography is presented. The method is based on the Fourier transform method for solving integral equations. Three examples (narrow, bimodal, and broad distributions) are used for illustrating the method of solution. A simple means of estimating the resolution factor h for a multicolumn system, based on a knowledge of the resolution factors h, for the individual columns and the gel permeation chromatograph piping system, is described and tested.
Polymer reactors and molecular weight distribution. Part III. Gel permeation chromatography, methods of correcting for imperfect resolution
Authors: Duerksen J. H. , Hamielec A. E.
Published: June 2010

This paper reports a preliminary evaluation of four methods of correcting for imperfect resolution in gel permeation chromatography. These are methods of Tung, Smith, Hess and Kratz, and Pickett. To evaluate the methods over a range of resolutions, many broad‐ and narrow‐distribution polystyrene samples covering the molecular weight range 1000–500,000 were analyzed with three different column combinations having residence times from 20 to 150 min. The results show the increasing importance of the resolution correction with increasing molecular weight and decreasing residence times. For Tung's method the correction to molecular weight averages ranged from about 4% for 150 min. of residence time to about 12% for 20 min. Residence times as short as 10 or 15 min. should be possible without serious loss of accuracy. Inconsistencies in the high molecular weight results for the methods of Tung and Smith indicate inadequacies in the assumed chromatogram shapes for single molecular species, due to effects of column overloading and species interaction. These effects can be reduced by decreasing the sample concentration. When these effects are not prominent, the methods of Tung and Smith appear to be adequate. Smith's modified method permits the use of various chromatogram shapes for single species to account for overloading and interaction. Computational difficulties at present limit the use of the method of Hess and Kratz. Pickett's method looks promising, especially if concentration dependence can be included in the chromatograms representing the single species. Further evaluation needs to be done to determine which method best handles the region where overloading and species interaction occur.
The molecular weight distribution of polypropylene
Authors: Ouano Augustus C. , Mercier Philip L.
Published: June 2010

The Gel Permeation Chromatograph has been used for obtaining values of weight‐average and number‐average molecular sizes Aw and An and the heterogeneity indices Aw/An for a series of polypropylenes. Absolute values of Mw and Mn, the weight‐average and number‐average molecular weights, have also been obtained from the same samples with light‐scattering and osmotic pressure methods. Comparisons of the data from the gel permeation chromatograph with the data from the absolute measurements have been used for calculating Q, the constant used for converting Aw and An to the corresponding Mw and Mn values. Other correlations of interest, such as intrinsic viscosity versus weight‐average molecular weight and melt flow, and Newtonian viscosity versus weight‐average molecular weight, are also given.
The electrochemical polymerization of 4‐vinylpyridine in liquid ammonia
Authors: Laurin D. , Parravano G.
Published: June 2010

The polymerization of 4‐vinylpyridine (4VP) in an electrochemical cell in liquid NH3 solutions was studied. With monomer concentrations of 5 to 25 vol.‐% in the temperature range −33 to −78°C. rapid polymerization takes place when current is passed through the cell. Polymer yields of 80 to 90% are easily obtained in a few hours with NaN3 or NaCl as electrolyte and smooth Pt electrodes in a stirred three‐compartment cell. Current densities of 1 × 10−2 to 10 ma./cm.2 and applied voltages of 2.5 to 50 v. were employed. Different anodic materials were used, including Pt and pyrolitic graphite. The electrochemical yield is about 1 mole of polymer per faraday for current densities of ⩽ 1 × 10−2 ma./cm.2, and it becomes 0.5 and lower at higher current densities. The rate of polymerization was found to increase, and the molecular weight of the polymer to decrease, with increasing current density. It is concluded that the initiation step consists of electron transfer between the cathode and the monomer. Depending on the amount of polymer deposited on the cathode and on the current density, initiation may occur on the cathode surface or within the polymer deposit on the cathode or in the free liquid solvent. The consequence of the electron transfer to monomer is the formation of radical anions. Electrochemical yields of about 1.0 mole of polymer per faraday suggest that radical anion dimerization does not take place extensively, while dimerization may predominate when electrochemical yields are about 0.5. Subsequent chain growth occurs through an anionic mechanism, as evidenced by the nonterminating nature of the polymerization, the presistent red color of the polymer formed, and the sensitivity of the polymerization to the addition of protic substances. Polymer molecular weights were in the range of 10,000 to 360,000. Molecular weight distributions with Mw/Mn ratios of 1.21 or larger were found. Softening points, solubility characteristics, and infrared spectra of the electrochemical polymer are presented and discussed in comparison with those of poly(4‐vinylpyridine) prepared with chemical initiators.
Polymerization of isobutylene catalyzed by the Binary system TiCl4‐AlBr3
Authors: Chmelir̃ M. , Marek M.
Published: June 2010

In the course of a study of the influence of some Friedel‐Crafts halides on isobutylene polymerization catalyzed by aluminum bromide it was found that the most active catalytic complex is formed in the reaction of titanium chloride with aluminum bromide. The conversion and the molecular weight of the polymer depend on the aluminum bromide concentration but are practically independent of the TiCl4 concentration. The polymerization mechanism has been solved by means of the nonstationary‐state theory, by means of which values have been obtained for the rate constants of the individual partial elementary reactions (growth, monomer transfer, spontaneous transfer, and termination).
Correlations between the structure of some soluble catalytic complexes and their activity in the polymerization of acetylene. III
Authors: Angelescu Emilian , Nicolescu I. V.
Published: June 2010

In this work are described studies of the correlations between the catalytic activities and some physical‐structural properties of soluble complex catalysts of the type Al(C2H5)3‐Me(C5H7O2)n, where Me is V, Cr, or Co. These catalysts were used as active phases in the process of stereoregular polymerization of the acetylene. It was established that the catalytic activity varies as a function of the molar ratio of Al(C2H5)3 to Me(C5H7O2)n. On the basis of EPR determinations of the values of the electrical conductivity of the catalyst solutions and of the gas‐volumetric data there were established correlations between the optimal catalytic activity and the physical‐structural characteristics of the catalysts. These correlations throw light on the chemical nature of the catalytic complexes and on the interaction between catalyst and solvent.
Specific preparation of diolefin homopolymers with equimolecular binary microstructures
Authors: Teyssie Ph. , Dawans F. , Durand J. P.
Published: June 2010

During an investigation of some structural features in the stereospecific polymerization of conjugated diolefins evidence was obtained that some catalytic species are able to yield high molecular weight polymers containing selectively two of the several possible geometric isomers; moreover, the two isomers involved are present in equimolecular amounts, in a nonsequential arrangement. Up to now equimolecular (cis‐1,4‐3,4)‐polyisoprene, (1,2‐3,4)‐polyisoprene, and (cis‐1,4‐trans‐1,4)‐polybutadiene were obtained with different catalytic systems (among which, monometallic complexes). The preliminary results suggest an alternating propagation mechanism, similar to the one already proposed by several authors for Ziegler‐type catalysts. Further work is in progress to prepare new binary polymers of this type, with different microstructures.