bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization kinetics in highly viscous media
Authors: De Schrijver F. , Smets G. 
Published: April 2003

AbstractThe influence of the viscosity of the reaction medium on the rate of polymerization of styrene has been examined by adding different amounts of inert polystyrene to pure monomer and its solutions in benzene. Azobisisobutyronitrile was decomposed photochemically (λ = 365 mμ) at 25°C. or thermally at 70°C.; its rate of decomposition was followed by ultraviolet spectrometry. The rate of formation of dimethyl‐N‐cyanoisopropylketenimine (DKI) was followed by infrared spectrometry (2020 cm.−1). The initiation efficiency was determined by the scintillation method with the use of a 14Clabeled initiator. The rate of polymerization was followed dilatometrically. An increase of viscosity does not affect the rate of decomposition of the initiator; on the contrary, during the photochemical decomposition, it causes an increase of DKI concentration and an appreciable decrease of efficiency (from 0.51 to 0.30). From the point of view of the rate of photopolymerization, an increase of viscosity causes a decrease in the order of the reaction with respect to the initiator (from 0.5 to 0.3) and an increase with respect to monomer from 1.5 to 2. These results are interpreted on the basis of a decrease of termination rate constant between two growing chains in favor of a termination reaction between a growing chain and a primary radical. These effects, due to an increase of the viscosity of the solution, on the initiation and termination reactions influence the rate of polymerization in opposite direction and compensate each other to approximatively 25%.
Studies on polymers containing functional groups. III. Charge‐transfer interaction between quinone and aza polymers
Authors: Sugiyama Hiroko , Kamogawa Hiroyoshi 
Published: April 2003

AbstractAbsorption maxima and equilibrium constants for charge‐transfer complexes between quinone and aza polymers, such as poly‐2‐vinylpyridine, poly‐4‐vinylpyridine, poly‐2‐methyl‐5‐vinylpyridine, and poly‐N‐dimethylaminomethylacrylamide, were determined spectrophotometrically. For comparison, those for charge‐transfer complexes between quinone and aza compounds, such as pyridine, methyl‐substituted pyridines, quinoline, triethylamine, and dimethylaniline were also presented. It was found that the equilibrium constants for polymer complexes are always larger than those for the corresponding monomer complexes, while the time required for attaining the equilibrium was longer for polymer complexes than for monomer complexes. In the interaction between quinone and poly‐N‐dimethylaminomethylacrylamide, two absorption maxima which gradually shifted towards each other were observed. The same phenomenon was found in the interaction between quinone and the corresponding monomer, triethylamine.
Fluorodienes. V. Copolymerization of 1,1,4,4‐tetrafluoro‐1,3‐butadiene with oxygen and nitric oxide
Authors: Putnam R. E. , Sharkey W. H. 
Published: April 2003

Abstract1,1,4,4‐Tetrafluoro‐1,3‐butadiene reacts with oxygen to form a polyperoxide containing 1.0–1.1 peroxide groups for each diene unit. This polymer behaves like a typical peroxide. It explodes violently when heated to 120°C. or when subjected to shock, and it initiates polymerization of vinyl monomers at temperatures of 90°C. or higher. The tetrafluorobutadiene also copolymerizes with nitric oxide to give a highly crosslinked polymer containing three molecules of diene for each two molecules of nitric oxide.
γ‐radiation‐induced ionic polymerization of pure liquid styrene. II
Authors: Potter R. C. , Bretton R. H. , Metz D. J. 
Published: April 2003

AbstractIn this second paper of the series we present additional evidence that the γ‐radiation‐induced polymerization of very pure, ultradry styrene exhibits kinetics that can best be explained as due to one or more ionic processes, depending on the dryness of the sample. We have shown the effect of the various steps in the drying procedure on the observed kinetics, and we have described a preparative procedure which yields good reproducibility among independently prepared samples. Under these conditions, the rate of polymerization is proportional to the 0.70 power of the dose rate at 0°C.; there appears to be no wall effect; and the temperature coefficient for the process appears to be a complicated function, most probably a small negative value over the range of temperature (0–50°C.) and dose rates (∼103–105 rad/hr.) covered in this study. The maximum G value for disappearance of monomer which we have observed is of the order of 6 × 105 molecules of monomer/100 e.v. at 0°C. and a dose rate of 2 × 103 rad/hr.
Preparation and thermal stability of organometallosiloxanes and organometallic compounds
Authors: Delman A. D. , Stein A. A. , Simms B. B. , Katzenstein R. J. 
Published: April 2003

AbstractThis study covers the results of synthesis and investigation of thermal stabilities of several organometallosiloxanes and organometal compounds containing Group IV elements. Investigations indicate, in general, that heat resistance is related to the dissociation energies of the MO bonds, the number of organic groups connected to the metal atom, and the structure of the molecule as a whole. More specifically, the substitution of GeO and SnO bonds for some SiO linkages in organosiloxanes produces a reduction in heat stability. The influence of the GeO bond to decrease the resistance of siloxanes is less than that of the SnO linkage; an increase in the number of SnO linkages producing a corresponding decrease in heat stability of the organosiloxane. The resistances of the germoxysiloxanes to heat degradation are less than that which would be expected from indications given by the relative stabilities of more simple organometallic compounds.
Photolysis of poly(tert‐butyl acrylate) in the region of the glass transition temperature
Authors: Monahan Alan R. 
Published: April 2003

AbstractThe thin film (1 × 10−5 cm.) photolysis (2537 A.) of poly(tert‐butyl acrylate) under 1 atm. helium pressure has been investigated in detail. Isobutene was the only significant volatile product in the temperature range 20–110°C. The reaction was demonstrated to be initially a first‐order decomposition with an energy of activation of 3.3 kcal./mole in the glassy state. Above the glass transition temperature a value of 1.8 kcal./mole was found. The rate of isobutene formation is autoaccelerated when a minimum of one acrylic acid unit is generated per chain. The initial quantum yield for the formation of isobutene varies from 0.083 to 0.17 over the temperature range studied. There was no dependence of quantum yield on the exciting wavelength using sources of 1849, 2537, and 3660 A. The intensity exponent was found to be unity, consistent with first‐order decomposition kinetics.
Thermal degradation of polyacrylonitrile in the temperature range 280–450°c.
Authors: Monahan Alan R. 
Published: April 2003

AbstractThis paper presents a study of the thermal degradation of polyacrylonitrile of 13,000 to 43,000 number‐average molecular weight in vacuum over the temperature range 280–450°C. Sixteen products of the decomposition were identified by chromatographic and infrared analytical techniques. The five major products, i.e., cyanogen, hydrogen cyanide, acrylonitrile, acetonitrile, and vinylacetonitrile, were monitored at intervals during the decomposition using gas chromatography. Activation energies of 15 and 23 kcal./mole were calculated from initial rates of formation of HCN and cyanogen, respectively. The overall activation energy of the polymer degradation was found to be 3.6 kcal./mole. The residue of the decomposition in the temperature region 280–450°C. was suggested by infrared absorption measurements and elemental analysis to be a polymer of the structure
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The rate of production of vinylacetonitrile was found to be proportional to the production of the residual black poly‐1,4,4‐trihydronaphthyridine. A new photothermal degradation cell is also presented.
Kinetic studies of polymerization of propylene with active TiCl3–Zn(C2H5)2
Authors: Soga Kazuo , Keii Tominaga 
Published: April 2003

AbstractIn order to elucidate the structure of the Ziegler‐Natta polymerization center, we have carried out some kinetic studies on the polymerization of propylene with active TiCl3—Zn(C2H5)2 in the temperature range of 25–56°C. and the Zn(C2H5)2 concentration range of 4 × 10−3–8 × 10−2 mole/1., and compared the results with those obtained with active TiCl3—Al(C2H5)3. The following differences were found: (1) the activation energy of the stationary rate of polymerization is 6.5 kcal/mole with Zn(C2H5)2 and 13.8 kcal./mole with Al(C2H5)3; (2) the growth rate of the polymer chains with Zn(C2H5)2 is about times slower at 43.5°C.; and (3) the polymerization centers formed with Zn(C2H5)2 are more unstable. It can be concluded that the structure of the polymerization center with Zn(C2H5)2 is different from that with Al(C2H5)3.
Graft copolymers of phenolic novolacs on polyamide backbones
Authors: Ravve A. , Fitko C. W. 
Published: April 2003

AbstractThe formation of graft copolymers of novolacs on polyamide backbones was carried out under conditions which permitted product isolation and investigation. Grafting was performed on nylons 11, 610, 66, and 6 with the use of the condensates of formaldehyde with either phenol, p‐cresol, or p‐nonyl phenol. Physical properties of the reaction products were studied, and the proof of grafting was established by means of chemical, infrared, and NMR investigations.
Kinetics of urethane cleavage in crosslinked polyurethanes
Authors: Singh Ajaib , Weissbein Leonard 
Published: April 2003

AbstractA series of clean, well‐defined polyurethane networks was synthesized from polyester glycols, 2,4‐tolylene diisocyanate, and 1,1′,1″‐trimethylolpropane by means that afforded precise control over the content of urethane groups per network chain. The thermal cleavage of these networks was studied using the technique of stress relaxation. Analysis of the stress‐relaxation data on each network structure revealed two exponential decay processes differing in rate by about an order of magnitude. The rate of the slower process, which dominates the overall stress decay, was shown to be directly dependent on the content of urethane groups per network chain. Positive identification of this process with urethane cleavage was thereby established. The kinetic and thermodynamic constants associated with urethane cleavage were then calculated from data on this process at different temperatures. The more transient stress‐decay process was not uniquely definable, but probably originated from the cleavage of one or more types of weak linkages found in small but variable proportions in the different polyurethane networks. The nature and origin of these weak linkages was discussed.
Costereosymmetric α‐olefin copolymers
Authors: Coover H. W. , McConnell Richard L. , Joyner F. B. , Slonaker D. F. , Combs R. L. 
Published: April 2003

AbstractCopolymerization of propylene and 1‐butene with highly stereospecific three‐component coordination catalysts produced multiblock crystalline copolymers having stereo‐regular sequences of both propylene and 1‐butene. Copolymers containing from 3 to about 80% 1‐butene had two DTA melting points which were attributable to polypropylene and poly‐1‐butene crystallinity. Those containing from 18 to about 70% 1‐butene had x‐ray diffraction patterns showing peaks characteristic of polypropylene and form I poly‐1‐butene, but form II poly‐1‐butene crystallinity was never observed. The multiblock copolymer structure observed is also supported by the fact that the product of the reactivity ratios is greater than unity. The composition distributions of low‐conversion and continuously prepared copolymers were similar and relatively broad. For example, copolymers containing an average of 12% 1‐butene had species containing from 5–30% 1‐butene. High‐conversion copolymers had an even broader composition distribution due to the gradual increase of the 1‐butene concentration in the comonomer mixture as the copolymerization proceeded. The absence of homopolymers was demonstrated by fractionation. The ability to detect homopolymers was proved by the fact that a mixture of stereoregular polypropylene and poly‐1‐butene were readily separated. Increasing the amount of 1‐butene tended to decrease those properties dependent upon crystallinity such as hardness, tensile strength, stiffness, density, and melting point, but tended to improve significantly the impact strength, low temperature properties, and clarity of molded objects. These duocrystalline copolymers retained a much higher level of properties than that observed for random copolymers prepared with less stereospecific coordination catalysts.
Active site measurements in the coordinated anionic polymerization of propylene
Authors: Coover H. W. , Guillet J. E. , Combs R. L. , Joyner F. B. 
Published: April 2003

AbstractThe active‐site concentration was determined by using tritium labeling on three coordinate anionic catalysts containing violet titanium(III) chloride [hereafter referred to as titanium(III) chloride or TiCl3]. These catalysts were used in the polymerization of propylene. Three‐component catalysts, as well as two‐component catalysts, were investigated. Previous estimates of active‐site concentrations for (C2H5)2AlCl—TiCl3 catalysts appear to be too high by at least a factor of 10. The reason for the previous high estimates can be attributed to the marked reduction in chain‐transfer rate which occurs when the amount of polymer formed exceeds about 2 g./g. TiCl3. The chain‐transfer process appears to involve both alkylaluminum and monomer, but the effective monomer concentration is apparently not reduced until a later stage in the polymerization. The propagation rate is, therefore, unaffected; but the transfer rate is reduced, leading to the formation of polymer with much higher molecular weight. Extension of this process could lead to the observed broad distribution of molecular weights in polypropylene. As a result of the low value of active‐site concentrations [about 10−3 mole/mole titanium(III) chloride], the absolute value calculated for the propagation rate constant for propylene polymerization is in the range of 50 l./mole sec., and the average lifetime of a growing polymer molecule during the early stages of the polymerization is about 1 min.
Poly(vinyl fluoride) solution characteristics
Authors: Wallach M. L. , Kabayama M. A. 
Published: April 2003

AbstractNine unfractionated poly(vinyl fluoride) samples were characterized for molecular weight and polydispersity by means of sedimentation velocity, osmometry, and viscosity measurements. Molecular weights were in the range of 143,000–654,000 and Mw/Mn = 2.5–5.6. The Mark‐Houwink (M‐H) relation was established as [η] = 6.52 × 10−5 M0.80. The M‐H exponent is at the Flory‐Fox upper limit (0.80), as is characteristic of extended, polar polymers, in good solvents. The unperturbed chain dimensions, characteristic ratio and steric factor were derived by the methods of Stockmayer and Fixman and Kurata and Stockmayer. The steric factor is 1.7, which agrees with data reported for other poly(vinyl halides).
Copolymerization of trialkylvinyltin compounds
Authors: Minoura Yuji , Suzuki Yasuyuki , Sakanaka Yasuhiro , Doi Hiroyuki 
Published: April 2003

AbstractThe polymerizations of trimethylvinyltin (TMSnV) and tributylvinyltin (TBSnV) were carried out with the use of γ‐ray, radical, or ionic initiators. These monomers did not undergo the polymerization by themselves, but they did copolymerize with styrene (St) or methyl methacrylate (MMA) when a radical initiator was used. From the results obtained by the copolymerization, monomer reactivity ratios and Q–e values were obtained as follows: for the system St(M1)TMSnV, r1 = 44.8, r2 = 0.001, Q2 = 0.005, e2 = 0.962; for the system MMA (M1)TMSnV, r1 = 25.1, r2 = 0.03, Q2 = 0.036, e2 = 0.933; for the system St(M1)TBSnV, r1 = 16.0, r2 = 0.005, Q2 = 0.017, e2 = 0.822; for the system MMA(M1)TBSnV, r1 = 27.9, r2 = 0.03, Q2 = 0.031, e2 = 0.822. The abilities of TMSnV and TBSnV to polymerize are discussed on the basis of the Q and e values obtained.
Influence of catalyst depletion or deactivation on polymerization kinetics. III. Solution polymerization of acrylonitrile in N,N‐dimethylformamide at −30°C.
Authors: Chiang R. , Friedlander H. N. 
Published: April 2003

AbstractThe experimental results on homogeneous polymerization of acrylonitrile initiated with the sodium triethylthioisopropoxyaluminate, NaAlEt3S(i‐Pr), catalyst in DMF at −30°C. are compared with the prediction of equations based on a postulated mechanism. The agreement between the calculated and observed number‐average molecular weight combined with the kinetic data and the relationship between the conversion and the initial catalyst concentration provides a rigorous test concerning the validity of the equations and the mechanism of the polymerization. A plausible mechanism is postulated as follows: The initiation must be relatively fast in accordance with the rate equations and the growing polymer undergoes propagation, transfer (to monomer), and deactivation simultaneously. The infrared spectrum of the low molecular weight polymer prepared at a high catalyst concentration showed strong absorption at 2337, 2205, and 1620 cm.−1 but no absorption at 900 cm.−1, indicating that there are two nitriles in the polymer, one of which is conjugated. The possibility of having CHCH2 groups in the polymer is ruled out by the absence of the band at 900 cm.−1. In view of these facts, it is concluded that the polymer has a CHCHCN endgroup resulting from the transfer reaction.
Electrolytic formation and destruction of living anions
Authors: Funt B. L. , Bhadani S. N. , Richardson D. 
Published: April 2003

AbstractElectrolysis of solutions of α‐methylstyrene in THF resulted in the formation of the characteristic spectra of the living anions in the cathode compartment. The increase in absorbance of the solution was strictly proportional to the charge transferred at the electrode, and was independent of the electrolyte for NaAl(C2H5)4, NaB(C6H5)4, and KB(C6H5)4. For solutions of LiB(C6H5)4 the color decreased spontaneously on standing, and a linear relationship between absorbance and charge transferred was not obtained. Mixing of the anode and cathode solutions resulted in a destruction of the living ends and a disappearance of the color, which could be regenerated by further electrolysis. Reversal of the polarity of the electrodes produced a stoichiometric destruction of the living ends and a decrease in absorbance directly dependent on the charge transferred. The exact stoichiometric dependence furnished means of estimating impurity levels, living anion concentrations, and optical extinction coefficients based on the number of faradays passed through the solution. The control of molecular weight distribution and rate of reaction by these methods is indicated.
Study of Hydrocarbon‐Soluble Organometallic Catalysts. III. Investigations on the Activity and Electric Conductivity of Al(C2H5)3—M(C5H7O2)n Catalysts Employed in the Synthesis of Stereoregular Polyacetylene
Authors: Nicolescu I. V. , Angelescu Em. 
Published: April 2003

AbstractThe aim of the present work is to establish some correlations between the catalytic activity of several organometallic hydrocarbon‐soluble complex systems and the electric conductivity, as a method which expresses the ionization degree of these catalyst types. The following systems were studied: Al(C2H5)3—VO(C5H7O2)2; Al(C2H5)3—Cr(C5H7O2)3, Al(C2H5)3—Co(C5H7O2)3. The catalytic activity was determined at various molar ratios of AlEt3/M(C5H7O2)n in the stereoregular polymerization reaction of acetylene, where M is a metal. The visible and ultraviolet absorption spectra of the catalysts, as well as the variation of extinctions at various AlEt3/M(C5H7O2)n molar ratios were also determined. The systems with an optimal catalytic activity also show maximum values of electric conductivity and extinctions. The composition, degree of ionization of the catalyst, and the way in which this influences the catalytic activity are also discussed.
Aminobutadienes. VI. Polymerization and Copolymerization of 2‐Phthalimido‐1,3‐butadiene
Authors: Murata Kenichi , Terada Akira 
Published: April 2003

Abstract2‐Phthalimido‐1,3‐butadiene (2‐PB) was polymerized either radically or thermally in bulk and in solution. While the polymer obtained by solution polymerization was soluble in some solvents such as halogenated hydrocarbons, dioxane, and dimethylformamide and had a softening point in the range of 160–170°C., that obtained by polymerization in bulk was insoluble in any solvent and only swollen on being immersed in such solvents as above. The reduced viscosity of the soluble polymer obtained by solution polymerization was approximately 1.0, and this value remained almost unchanged with varying polymerization time. Likewise the cationic polymerization in acetylene tetrachloride or in chloroform at 20°C. with the use of cationic catalysts such as boron trifluoride and stannic chloride was attempted, but no formation of polymer was observed. This monomer preferentially reacted with acrylonitrile, methyl methacrylate, styrene, and N‐vinylphthalimide to form the respective copolymers; it reacted somewhat less readily with vinyl acetate. The monomer reactivity ratios in the copolymerization with styrene were calculated by the Fineman and Ross method and found to be r1 (2‐PB) = 5.2 and r2 (styrene) = 0.11, respectively, from which the Q, e parameters were successively evaluated to be Q = 5.0 and e = −0.05. The fact that e value is close to zero, easily explains why this monomer can copolymerize well both with acrylonitrile, which has a highly positive value of e (1.2) and with styrene, for which e is considerably negative (‐0.8).
Monomer‐Polymer Equilibria of Deuterated α‐Methylstyrenes
Authors: Fetters Lewis J. , Pummer Walter J. , Wall Leo A. 
Published: April 2003

AbstractThe equilibria between α‐trideuteromethyl‐β,β‐dideuterostyrene, α‐methyl‐2,3,4,5,6‐pentadeuterostyrene, and perdeutero‐α‐methylstyrene and their respective polymeric anions in tetrahydrofuran have been investigated between 253 and 308°K. The heat and entropy changes were both increased by deuteration of the alkyl group. Qualitatively the effect observed appears best explained by the premise that a lowering of steric repulsions occurs with deuterium and hence the effective volume for deuterium is less than that for hydrogen.
Aromatic Polyamides of 2,6‐Naphthalenedicarboxylic Acid
Authors: Starr L. 
Published: April 2003

AbstractWholly aromatic polyamides have been prepared by the interfacial polycondensation of 2,6‐naphthalenedicarboxylic acid chloride with m‐phenylenediamine. Also, copolyamides with isophthaloyl or terephthaloyl chlorides and the naphthalene diacid chloride were synthesized. The resultant polyamides were amorphous or slightly crystalline as determined by x‐ray diffraction, had tensile properties characteristic of hard, strong materials, and were more thermally stable than aromatic polyamides prepared solely from benzene diacid chlorides.