bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the mechanism of the radical polymerization of vinyl chloride
Authors: Ryska M. , Kolínský M. , Lím D. 
Published: June 2010

AbstractThe 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

AbstractThe 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

AbstractPolybutadiene, 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

AbstractSwollen 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

AbstractSystems 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

Abstract1,4‐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

AbstractThe 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

AbstractThe 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

AbstractElectron 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

AbstractThe 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

AbstractReactions 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractStudies 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.