bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymerization of trioxane by γ‐radiation
Authors: Rösinger S. , Hermann H. , Weissermel K. 
Published: April 2003

AbstractHigh molecular copolymers of trioxane with different cyclic ethers and formals were produced by γ‐radiation from a 60Co source. It was polymerized in the solid state at 53°C. Polymerization does not occur in the melt. Irradiation was carried out with exclusion of air at a dose rate of 7 × 103 rad/hr. The polymerization rate was increased very considerably in the presence of 1,3‐dioxolane and epichlorhydrin; the addition of other comonomers may reduce the yield. The concentration of the comonomer is generally higher in the polymer than in the initial mix. These comonomers which increase the polymerization rate are introduced preferentially into the polymer chain; this is proved by the unstable polymer part and the thermal stability. Experiments with the trioxane–1,3‐dioxolane system revealed that the unstable polymer part is markedly reduced and the heat stability considerably inproved with rising concentrations of this monomer. The thermal stability and the reduced viscosity of these copolymers are within the range of technical processability.
Polymerization with heterogeneous metalorganic catalysts. VI. Differences in polymerization activity of α‐olefins and some kinetic results on butene‐1 polymerization
Authors: Schnecko H. , Lintz W. , Kern W. 
Published: April 2003

AbstractRelative changes in polymerization activity of ethylene, propylene, and butene‐1 in Ziegler‐Natta polymerization were compared by use of TiCl3 samples contaminated with O2 and H2O to various extents. Catalyst depletion varied for the three monomers which supported the existence of different active centers. In butene‐1 polymerizations with the system Al(C2H5)2Cl–TiCl3, the formation of active centers involves an irreversible and a reversible (adsorption) reaction, the former pertaining to the formation of Al(C2H5)Cl2 and dependent upon the purity of the TiCl3. The kinetic treatment of the rate curves suggests a mixed order of catalyst deactivation and again points to the importance of Al(C2H5)Cl2.
Course of the terpolymerization of ethylene, propylene, and dicyclopentadiene. I. Single initial addition of dicyclopentadiene
Authors: Cunningham Robert E. 
Published: April 2003

AbstractDetailed studies were made of the course of the terpolymerization of ethylene, propylene, and dicyclopentadiene to form unsaturated elastomers. All the dicyclopentadiene was added at the start of a polymerization, but the monoolefins were added continuously throughout the run. Under these conditions, unsaturation of the initial polymer is fairly high but decreases steadily as the reaction progresses. From analyses of the initial samples from each run, the catalyst of VCl4 (with Al2Et3Cl3 cocatalyst), with heptane as the polymerization solvent, was most efficient for introducing unsaturation into terpolymer. This system also produces gel in the terpolymer in the latter stages of reaction, however. Catalysts of VCl4, VOCl3, or V(C5H7O2)3, with Al2Et3Cl3 cocatalyst, in benzene solvent gave terpolymers of quite similar unsaturations. With all systems, terpolymer yield increases very rapidly in the first few minutes of reaction, then very slowly for the remainder of the 30‐min. reaction time, reflecting the rapid loss of activity of the vanadium catalysts. Molecular weight growth of the terpolymer prepared in heptane was extremely rapid, reaching a high value in a few minutes. When prepared in benzene, the terpolymers showed a steady increase in molecular weight throughout the reaction but reached only a moderate final value (as expressed by inherent viscosity).
Preparation and polymerization of some vinyl monomers containing the 2‐oxo‐1,3‐dioxolane group
Authors: D'Alelio G. F. , Huemmer T. 
Published: April 2003

AbstractThe syntheses and polymerizations of (2‐oxo‐1,3‐dioxolan‐4‐yl)methyl acrylate, 4‐(2‐oxo‐1,3‐dioxolan‐4‐yl)methyl itaconate, and (2‐oxo‐1,3‐dioxolan‐4‐yl)methyl maleate are described. Reactivity ratios in the copolymerization of these monomers with other comonomers are reported and the Alfrey‐PriceQandevalues calculated. The post‐polymerization effects of ultraviolet light and heat on these polymers and copolymers are presented and compared to those for similar polymers containing the 2,2‐dimethyl‐1,3‐dixolane groups, which performs as an internal ultraviolet sensitizer. The 2‐oxo derivatives are crosslinked thermally but not by ultraviolet light. The crosslinking reaction can be catalyzed by acids, bases, and salts.
Structural effects in heteroatom systems. II. The calculated influence of steric effects on polymerization–depolymerization equilibria in the siloxane and oxymethylene series. Comparisons with the phosphazene system.
Authors: Allcock H. R. 
Published: April 2003

AbstractThe relative stabilities of symmetrically substituted polysiloxanes and polyoxymethylenes are compared in terms of the side‐group steric overlap parameters, by means of a semiempirical method described previously. The results provide a qualitative estimate of the relative thermodynamic ease of polymerization of cyclic siloxanes or monomeric methylene oxides or, conversely, of the relative resistance to depolymerization of the polymers. These calculated values are compared with those reported previously for phosphazenes. In general, for polymers of the type, [R2SiO]n, [R2CO]n, and [R2PN]n, if the side group, R, is small (H, halogen or methyl) the inherent steric and bonding characteristics of the chain should cause the polymer stabilities to decrease in the order phosphazenes ≈ siloxanes ≫ oxymethylenes. If, however, bulkier side groups are present, the order of decreasing stability to depolymerization should be siloxanes > phosphazenes ≫ oxymethylenes. In all cases, the depolymerization tendency should increase markedly as the side group overlap parameters increase, and polyoxymethylenes should be the most sensitive to such changes. The calculated results are compared with the limited experimental evidence at present available.
Head‐to‐head units in poly(propylene oxide) by ozonation
Authors: Price Charles C. , Spector Robert , Tumolo Anthony L. 
Published: April 2003

AbstractBy extensive ozonation and lithium aluminum hydride reduction, poly(propylene oxide) can be converted to material containing dipropylene glycol. Since the diprimary, disecondary, and primary‐secondary isomers are readily separable by vapor‐phase chromatography, it has been possible to show that some (but not all) noncrystalline PPO samples contain many head‐to‐head, tail‐to‐tail monomer units. Correlation of the fraction of head‐to‐head units with the optical rotation of noncrystalline fractions from optically active monomer, indicates that there is one asymmetric center inverted for every unit inserted head‐to‐head. The earlier suggestion that the noncrystalline fraction was due to atactic stereochemistry is thus shown to be generally incorrect in favor of an explanation due to positional isomerization.
Ionic polymerization of p‐vinylbenzyl methyl ether
Authors: Symcox Robert O. , Cotman John D. 
Published: April 2003

AbstractIonic polymerizations of vinylbenzyl methyl ether initiated by either carbanions or Lewis acids has been found to lead to crosslinked polymers. By comparative studies of strong carbanionic bases and Lewis acids with benzyl ethers, it has been possible to define details of mechanisms which in conjunction with cationic or anionic propagation lead to crosslinks. The α‐hydrogens of benzyl ethers have been found to be sufficiently acidic to terminate anionic polymerization of styrene and displacement of alkoxide anion from the benzyl ether linkage by nucelophilic polymer anions is proposed as a mechanism leading to branching and eventual crosslinking in anionic polymerization of vinylbenzyl methyl ether. Cationic polymerization of vinylbenzyl methyl ether is quite complex. In addition to propagation, chain transfer, and spontaneous termination of cation chain carriers, there is evidence for complex formation between Lewis acid initiator and the benzyl ether substituent. A slow decomposition of ether–Lewis acid complexes produces benzylcarbonium ions which alkylate aromatic rings of polymer and thereby crosslink the polymer. Benzyl ether has been found to be an effective chain terminator for cationic styrene polymerization.
Graft copolymerizations of gaseous vinyl chloride and vinylidene chloride on preirradiated polypropylene
Authors: Hayakawa Kiyoshi , Kawase Kaoru 
Published: April 2003

AbstractThe graft copolymerizations onto the preirradiated polypropylene fibers of gaseous vinyl chloride and also of gaseous vinylidene chloride were carried out. The fibers were preirradiated with γ‐rays from a 60Co source at −78°C. in air to a total dose of 8 X 105 rad, and were thus presumed to contain peroxide radicals which were active in grafting at ordinary temperature. The volume decrease of monomers at constant pressures due to the sorption and the grafting reaction was followed automatically at temperatures ranging from −10 to 80°C. The net monomer consumption through the grafting process was estimated by subtracting the volume change due to the sorption from the total volume change of monomers. In general, the extent of grafting was lower at the higher grafting temperature and the decrease of the grafting activity of fibers was also accelerated. The grafting was found to increase almost linearly with the logarithm of the reaction time and the logarithm of the radiation of the radiation dose to the fibers. The extent of grafting was also proportional to the vapor pressure of monomer at a given reaction temperature and was supposed to be controlled by the amount of the monomer adsorbed. Raising the irradiation temperature higher than 0°C. brought about a marked decrease in the activity of preirradiated polypropylene. The grafting activity was successfully retained by the polymer for at least a fortnight at −78°C.
Emulsion polymerization of acrylonitrile. Part I. Role and effect of emulsifiers in the emulsion polymerization of acrylonitrile
Authors: Izumi Zenzi , Kiuchi Hiroshi , Watanabe Masamoto 
Published: April 2003

AbstractThe role in and effects on the emulsion polymerization of acrylonitrile (AN) of three different groups of emulsifiers, i.e., low molecular emulsfiers, well‐known water‐soluble polymers, and new water‐soluble polymers containing a sulfonate group have been investigated by a dilatometry and electron microscopy. The major part of this paper concentrates on the study of the relation between the properties of the third group of emulsifiers and emulsion polymerization characteristics of AN such as rate, degree of polymerization, diameter and number of particles, and the degree of dispersion, by adding copolymers of AN and sodium p‐styrenesulfonate (SSS) having various compositions. In the emulsion polymerization of AN, the hydrophobic portion of the emulsifier seems to act as a kind of nucleus around which polymer molecules precipitate and particle formation may occur, and the hydrophilic portion stabilizes the polymer particles thus formed. As the number of particles and the degree of dispersion increases, the total surface of the particles increases, which may raise the overall rate of polymerization due mainly to an increased polymerization on the surface of the polymer particles. The well‐known emulsifiers may be classified by the properties and ratio of the nucleus portion and the stabilizing portion. The unusual effect of emulsifiers on the degree of polymerization may be explained by a chain‐transfer mechanism.
Mechanism of stereoregular polymerization of butadiene by homogeneous Ziegler‐Natta catalysts. I. Effects of the species of transition metals
Authors: Matsuzaki Kei , Yasukawa Tamio 
Published: April 2003

AbstractButadiene was polymerized by catalysts of the type: metal acetylacetonate (metal: Ti to Ni in the periodic table)–triethylaluminum–aluminum halide, with various ratios of triethylaluminum to aluminum halide. The minimum cis content was observed with vanadium catalyst in all cases, while the minimum polymer yields were observed with the iron and the manganese catalysts. These transition metal effects are discussed in terms of the crystal field theory, and it is suggested that the electrostatic interaction between the nearly nonbonding electrons of transition metal atom and a butadiene molecule or a growing end of the polymeric chain plays an important role in the stereoregular polymerization of butadiene by homogeneous Ziegler‐Natta catalysts.
Mechanism of stereoregular polymerization of butadiene by homogeneous Ziegler‐Natta catalysts. II. Effects of the nature of bases and halogens
Authors: Matsuzaki Kei , Yasukawa Tamio 
Published: April 2003

AbstractThe effects of the addition of various bases to metal acetylacetonate–diethylaluminum chloride catalyst systems were investigated. Generally speaking, the cis content of polybutadiene decreases as the basicity of bases in a homologous series increases. The effects were more prominent for the cobalt and the titanium catalysts than for the nickel and the vanadium catalysts. The effects of the species of halogens on the microstructure of polybutadiene were also discussed. In conclusion, the decrease of the cis content was ascribed to the decrease of the electron density of dπ orbitals of the transition metal atoms.
Polymers with quinoxaline units. II
Authors: De Schryver Frans , Marvel C. S. 
Published: April 2003

AbstractA double chain or ladder polymer was obtained by the condensation of 1,2,4,5‐tetraaminobenzene with 2,3,7,8‐tetrasubstituted‐1,4,6,9‐tetraazaanthracene and self‐condensation of 2,3‐dihydroxy‐6,7‐diaminoquinoxaline and of 2,3‐diphenoxy‐6,7‐diaminoquinoxaline. The polycondensations were carried out in solution or in melt. The polymers thus obtained were highly colored products which had inherent viscosities up to 2.5. The structures of the polymers were established by comparison with model compounds.
Polymerization of gaseous diazomethane on silicone grease
Authors: Kubota H. , Morawetz H. 
Published: April 2003

AbstractDow Corning high vacuum silicone grease is a powerful catalyst for the polymerization of gaseous diazomethane. The catalytic activity is due to boric ester groups incorporated in the polysiloxane contained in the grease. The polymerization rate is proportional to the area of the interface but independent of the thickness of the grease layer, indicating that only a surface layer is involved in the catalytic action. The chain length of the polymethylene formed does not depend on the area of the interface or the pressure of the gaseous monomer. The dependence of the polymerization rate and polymer chain length on temperature is analogous to that for similar processes in homogeneous solution.
Molecular parameters of sodium cellulose xanthate in dilute solution
Authors: Das Bibekananda , Choudhury P. K. 
Published: April 2003

AbstractMolecular parameters of sodium cellulose xanthate in NaOH solution have been determined by means of light scattering and viscometry. The effect of the degree of substitution on the molecular configuration of sodium cellulose xanthate has been studied for three series of samples of varying degree of substitution. The expansion factor has been determined from the expression due to Orofino and Flory. The effective bond length b and the ratio of the unperturbed dimension to the dimension assuming free rotation of the chain units (R̄o2/R̄f2)1/2, have also been determined. It is concluded that sodium cellulose xanthate in dilute solution is a loosely coiled molecule, comparable to other cellulose derivatives in chain stiffness.
Kinetics of the γ‐radiation‐induced polymerization of methyl methacrylate in the solid state
Authors: Lipscomb N. Thornton , Weber Edwin C. 
Published: April 2003

AbstractStudies have been made of the γ‐radiation‐induced polymerization of methyl methacrylate in bulk, in the solid state at a temperature of −65°C. and a radiation intensity of 346,000 rad/hr. The reaction was found to have an extremely long induction period (∼50 hr.) when pure monomer was used, and to be first‐order with respect to polymer concentration. This first‐order dependency was confirmed by a series of irradiations in which 0.6% poly(methyl methacrylate) was dissolved in the monomer before irradiation. These irradiations showed no induction period. Nuclear magnetic resonance spectroscopy indicated a much more heterotactic polymer than that obtained in the liquid state at −49°C.
Linear polymers of acrylic monomers containing an acetylenic moiety
Authors: D'Alelio G. F. , Evers R. C. 
Published: April 2003

Abstract1‐Acryloxy‐2‐butyne and 1‐methacryloxy‐2‐butyne were synthesized and polymerized by means of anionic initiators to soluble linear polymers containing acetylenic bonds in the pendant side chains. In contrast, insoluble, crosslinked polymers were formed when cationic and radical initiators were used. The unpolymerized acetylenic bonds in the resulting linear polymers were shown to be present by infrared spectroscopic methods and by the following post‐reactions of these bonds: (1) the thermal‐ and radical‐initiated crosslinking of the linear polymers through the acetylenic bonds; (2) the post‐bromination of the acetylenic bonds; and (3) the reaction of decaborane with the acetylenic bonds. The anionic copolymerization of both monomers with a number of selected monomers was performed and the copolymer reactivity ratios for several of the comonomer pairs were determined. Dibromination of the linear polymers affords self‐extinguishing polymers with apparently good hydrolytic stability. Decarbonation of the linear polymers yields soluble polymers which do not soften up to 300°C. The linear polymers and copolymers, as well as their partially brominated and partially decaboronated products, may be classified as “self‐reactive” polymers which yield thermosetting polymers.
Studies on anionic polymerization of lactams. Part III. Copolymerization of pyrrolidone and caprolactam
Authors: Bar‐Zakay S. , Levy M. , Vofsi D. 
Published: April 2003

AbstractOn reacting acetylcaprolactam (AcCL) and pyrrolidonate MgBr (Py−) in tetrahydrofuran solution, transacetylation takes place, giving acetylpyrrolidone (AcPy) and caprolactamate MgBr (CL−). The rate constants for the transacetylation reactions were measured at 25°C. Their values in units of liters/mole‐second were:

The rate constants for the addition reactions measured were:

As the transacetylation is much faster than the addition reaction the copolymer composition should be given by the equation:

where Ktrans, the transacetylation equilibrium constant, equals 0.3 while Kacidity reflects the relative acidities of the monomers and its value (from the literature) is about 0.4. Pyrrolidone is, therefore, more reactive than caprolactam in anionic copolymerization by a factor of about 8.
Poly(chloroaldehydes). IV. Copolymerization of chloral and dichloroacetaldehyde catalyzed by organometallic compounds
Authors: McCain G. H. , Hudgin D. E. , Rosen Irving 
Published: April 2003

AbstractThe copolymerization of chloral and dichloroacetaldehyde (DCA) has been studied with the use of organometallic compounds as initiators. The alkylzincs were the most effective catalysts, giving good conversions to copolymers of apparently high molecular weight. The polymerizations were best carried out at temperatures below −40°C. at an initiator concentration of at least 0.4 mmole/mole of monomers. The copolymerization proceeds to high conversions in toluene as the solvent, but the presence of small amounts of either n‐heptane or tetrahydrofuran greatly decreases the yield. This, coupled with the fact that little polymerization occurs at DCA concentrations above 70 mole‐%, leads to the proposal of a propagation reaction mechanism involving the coordination of the monomeric aldehydes with a cyclic zinc alkoxide dimer. Monomer reactivity ratios with chloral as M1 and DCA as M2 were r1 = 1.50 and r2 = 0.65. The copolymer is stiff and inelastic with a tensile strength of ca. 6000 psi.
Linear polymers of some vinyl monomers containing a terminal acetylenic group
Authors: D'Alelio G. F. , Evers R. C. 
Published: April 2003

AbstractThe synthesis and polymerization of representative acrylic‐type esters containing a terminal acetylene group, CH2C(R)COO(CHR′)mCCH, where R and R′ are H and CH3 and m = 1 or 2, by anionic initiation to linear polymers are described. In contrast, crosslinked polymers were formed when radical and cationic initiators were used. Crosslinked polymers were also obtained with organolithium compounds but not with sodium naphthalene and sodium benzalaniline; this observation is discussed and compared to the behavior of the acetylenic acrylic esters which do not contain a terminal acetylenic hydrogen. The unpolymerized acetylenic bonds in the resulting linear polymers were shown to be present by infrared spectroscopic methods and by the following post‐reactions of these bonds: (1) the heat‐ and radical‐initiated crosslinking of the polymers through the acetylenic bonds; (2) the post‐bromination of the acetylenic bonds; and (3) the reaction of decaborane with the acetylenic bonds. The anionic copolymerization of acrylonitrile and styrene with these acetylenic monomers were performed and compared to the copolymerizations with 1‐acryloxy‐2‐butyne and 1‐methacryloxy‐2‐butyne. Dibromination of the linear polymers affords self‐extinguishing polymers, while decaboronation yields soluble polymers which do not soften up to 300°C. The linear polymers may be classified as “self‐reactive” polymers which yield thermosetting polymers.
Solid‐state polymerization of 1,2,3,4‐diepoxybutane initiated by cobalt‐60 γ‐radiation
Authors: Parrish C. F. , Harmer D. E. 
Published: April 2003

AbstractThe solid‐state polymerization of 1,2,3,4‐diepoxybutane appears to proceed “insource” by an ionic mechanism and has an overall activation energy of 0.4 kcal./mole with an intensity dependency of 0.99. There is a rapid increase in the rate of polymerization just prior to the melting point and a very low rate for the liquid‐phase reaction. Limiting conversions of 5% polymer are observed at −196°C. for irradiation in vacuo. No limiting conversion was observed when the monomer was polymerized in the presence of air or in vacuo at −78°C. Under all polymerization conditions the reactions were characterized by the absence of an induction period.
Copolymerization of styrene. II. Emulsion copolymerization with styrene derivatives containing nitrile groups in the side chain
Authors: Narkis Moshe , Kohn David H. 
Published: April 2003

AbstractCopolymers of styrene with cinnamonitrile, ethyl benzylidenecyanoacetate, and benzylidenemalononitrile were prepared in emulsion with the use of the redox system potassium persulfate–sodium bisulfite. The kinetics of copolymerization as a function of the composition of monomers, of the concentration of emulsifier and initiators, and of temperature was studied. Copolymers of high molecular weight were obtained in good yields.
Copolymerization of styrene. III. Physical and mechanical properties of copolymers with styrene derivatives containing nitrile groups in the side chain
Authors: Narkis Moshe , Kohn David H. 
Published: April 2003

AbstractCopolymers of styrene with cinnamonitrile (I), ethyl benzylidenecyanoacetate (II), and benzylidenemalononitrile (III) were prepared in bulk, in suspension, and in emulsion up to high conversion. Their softening points, flexural properties, impact resistance, hardness, and volumetric shrinkage due to polymerization were studied. All three copolymers show improved thermal resistance in comparison to polystyrene, but whereas copolymers styrene–I and styrene–III are inferior to polystyrene in flexural strength and the impact resistance, the copolymer styrene–II is about equal to polystyrene in its flexural properties and impact resistance.