bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vinyl polymerization. 179. Effects of substituents on chain transfer reaction of substituted cumenes toward poly(methyl methacrylate) radical
Authors: Yamamoto Tadahiro , Otsu Takayuki 
Published: April 2003

AbstractIn order to study the effects of substituents on the chain transfer reaction to cumenes, the polymerization of methyl methacrylate in a series of nuclear‐substituted cumenes with α,α′‐azobisisobutyronitrile as initiator was carried out at 60°C. and the chain transfer constants C were determined. The C values obtained for all substituted cumenes were greater than that (C0) for unsubstituted cumene, regardless of the electronattracting or ‐repelling nature of the substituents. Hence the plot of log (C/C0) against the Hammett σ constants gave no linear relationship. When the plots were made by the modified Hammett equation including resonance effect of the substituents: log (C/C) = ρσ + γER, however, a straight line with ρ = 0.03 and γ = 0.9 was obtained. From these results, it may be concluded that the effect of the substitutents on the chain transfer reactivities of cumenes toward attack of a poly(methyl methacrylate) radical is attributable mainly to the resonance contribution in the transition state. These results are also compared with those for polystyryl radical reported previously and discussed.
Polymerization of cyclic iminoethers. IV. Oxazoline polymerization in solvents containing different functional groups
Authors: Levy A. , Litt M. 
Published: April 2003

AbstractThe polymerization of 2‐n‐pentyloxazoline in solvents containing various functional groups showed that many solvents demonstrated no interaction or moderate interaction, whereas others interfered extensively, in some cases preventing polymerization entirely.
Dynamic mechanical properties of plasticized poly(vinyl chloride). Linear free energy relationship in the poly(vinyl chloride)–ester system
Authors: Hammond R. J. , Work J. L. 
Published: April 2003

AbstractA considerable number of quantitative attempts have been made to predict the properties of solutions containing polar polymers and polar solvents. Thermodynamic approaches have generally failed to accurately describe these systems. This can be be ascribed to the difficulty in determining structural characteristics arising from the variety of secondary interactions present in these highly complex solutions. A linear free energy relationship has been used here to explore changes encountered in solutions of monofunctional esters in poly(vinyl chloride) undergoing mechanical deformation. This treatment appears valid only for the rubbery region of the viscoelastic spectrum of this polymer. The data indicate that the observed changes are a function of corresponding changes in polymer intramolecular interactions.
Cyclopolymerization of diallylcyanamide
Authors: Uno K. , Tsuruoka K. , Iwakura Y. 
Published: April 2003

AbstractA soluble polymer of cyclic structure has been obtained by radical polymerization of diallyleyanamide. A kinetic analysis of the polymerization indicated that the overall rate of the system is first‐order with respect to concentration of initiator and either first‐ or second‐order with respect to monomer concentration, depending on the solvent used. The molecular weight of the polymer is independent of the concentration of the initiator and the monomer. The intramolecular abstraction of hydrogen is proposed as a termination reaction.
Cyclo‐ and cyclized diene polymers. XVI. Nature of the active species and a proposed mechanism of cyclopolymerization of isoprene with catalysts containing ethylaluminum halides
Authors: Gaylord N. G. , Kössler I. , Matyska B. , Mach K. 
Published: April 2003

AbstractThe polymerization of isoprene with C2H5AlCl2 to yield solid cyclopolyisoprene is markedly accelerated by the addition of TiCl4. The polymer yield passes through a maximum on increasing the catalyst reaction time with or without monomer present. The active species are probably cations formed by dissociation of the reaction product of C2H5AlCl2 and TiCl4. The polymerization of isoprene with (C2H5)2AlX–TiCl4 (X = F, Br, Cl) has maximum activity at an Al/Ti mole ratio of 0.75 corresponding to conversion of R2AlX to RAIX2 which then reacts with remaining TiCl4. A proposed mechanism of cyclopolymerization of conjugated dienes involves monomer activation, i.e., conversion to cation radical by one‐electron transfer to catalyst cation which is itself neutralized, addition of cation end of monomer cation radical to terminal or internal unsaturation of fused cyclohexane polymer chain, one‐electron transfer from “neutral” catalyst to cation on polymer chain which is then transformed to a diradical which undergoes coupling to form a cyclohexene ring. The mechanism of the “living” polymerization involves addition of catalyst‐activated monomer to a “dead” polymer with a terminal cyclohexene ring and regeneration of the active catalyst.
Cationic polymerization of 4‐methyl‐1,3‐dioxene‐4 and copolymerization with tetrahydrofuran
Authors: Kawai Wasaburo 
Published: April 2003

AbstractA new monomer, 4‐methyl‐1,3‐dioxene‐4 was synthesized from allyl chloride and paraformaldehyde. The monomer was polymerized at room temperature or −78°C. by boron trifluoride etherate catalyst, and the structure of the obtained polymer was determined by infrared, nuclear magnetic resonance spectra, and chemical analysis. It was ascertained that the polymerization process proceeded through a ring‐opening mechanism at the dioxane ring. In the presence of tetrahydrofuran, the polymerization of 4‐methyl‐1–1,3‐dioxene‐4 led to copolymer. The mechanism of the copolymerization is described in detail.
Polyelectrolytes prepared from perfluoroalkylaryl macromolecules
Authors: Hodgdon Russell B. 
Published: April 2003

AbstractThe synthesis of a new generation of high‐capacity oxidation‐resistant ion‐exchange resins and membranes is described which are sulfonic acid polyelectrolytes prepared from high molecular weight poly‐α,β,β‐trifluorostyrene. The difficult sulfonation of poly‐α,β,β‐trifluorostyrene is discussed in terms of the finding that this sulfonation must be effected upon an aromatic ring possessing a meta‐directing substituent group. The oxidative stability of these new types of perfluoroalkyl aromatic sulfonic acid polyelectrolytes is both demonstrated and described with comparisons to their polystyrenesulfonic acid homologs. The difference in their oxidation–depolymerization stabilities is described in terms of benzylic carbon substituents.
Studies of chlorinated polyisobutenes. Part I. Investigations of structure by proton magnetic resonance and of thermal stability by thermal volatilization analysis
Authors: McGuchan R. , McNeill I. C. 
Published: April 2003

AbstractPolyisobutene was chlorinated in carbon tetrachloride solution at 60°C. with radiochlorine, and the degree of chlorination was determined radiochemically. The extent of chlorination was varied by using a wide range of chlorine/polyisobutene ratios in the reaction mixture. The products were examined by PMR spectroscopy, which showed that both methyl and methylene groups were chlorinated but that the methylene hydrogens were more readily substituted and some disubstitution of the methylene groups occurred. The effect of chlorination on the thermal stability compared to the original polymer was studied by the new technique of thermal volatilization analysis. All the chlorinated derivatives were found to degrade at lower temperatures than polyisobutene. The stability dropped progressively as the chlorine content was increased to one chlorine atom per isobutene unit and then showed less change with further increase in chlorine content.
Polymerization and copolymerization of methacrylic esters derived from glycidyl methacrylate
Authors: Uno K. , Makita M. , Ooi S. , Iwakura Y. 
Published: April 2003

AbstractCopolymerization of methacrylic esters derived from glycidyl methacrylate and nucleophiles with styrene was carried out. The monomer reactivity ratios of these methacrylic esters were varied with the alkoxy groups of the esters and the solvent used.
Polymerization and copolymerization studies on vinyl fluoride
Authors: Sianesi Dario , Caporiccio Gerardo 
Published: April 2003

AbstractThe polymerization of vinyl fluoride has been studied in the temperature range of 0–50°C. with the aid of different types of initiators. Ziegler‐Natta systems based on vanadyl acetylacetonate and AIR(OR)Cl compounds showed good activity. Enhanced reaction rates and higher polymerization degrees were achieved with boron alkyls (and, to a lesser degree, Cd, Zn, and Be alkyls) activated by oxygen. With either types of initiator, the main features and the kinetic parameters of the polymerization were determined. In all cases, the polymerization is considered to be of the free‐radical type, though some properties (crystallinity, melting temperature) of the polymer are shown to be markedly improved over the previously described high‐pressure polymer. This is chiefly ascribed to an improved degree of chemical regularity of the chains. The copolymerization of vinyl fluoride in the presence of the cited initiators was studied with a number of monomers. The values of the copolymerization parameters allow us to obtain Q (0.010 ± 0.005) and e (−0.8±0.2) values and to discuss the reactivity of vinyl fluoride in radical chain propagation.
PVC–rubber blends. VI. The structure
Authors: Zítek P. , Zelinger J. 
Published: April 2003

AbstractThe dependence of the dynamic shear modulus of blends of polyvinyl chloride and rubber on the temperature and concentration of the rubber was investigated. For a calculation of a theoretical value of the modulus a formula recently derived by Uemura and Takayanagi was adopted. This formula is based on the assumption of a two‐phase system, in which one phase is a continual matrix and the other is discrete spherical particles, and of perfect adhesion between the phases. Most of the theories that clarify the part played by rubber in rubber‐modified vitreous materials are based on these assumptions. In most cases we have found a good conformity between the theoretical and experimental values of the modulus. In a certain system with an outstanding impact strength, however, a severe discrepancy has been found. This implies that the present structural explanation of the high impact strengths of two‐phase systems is not quite generally applicable.
Electron spin resonance study of polyglycols
Authors: Thryion F. C. , Baijal M. D. 
Published: April 2003

AbstractPolyethylene glycols and polypropylene glycols were irradiated with gamma‐rays from a 60Co source at 77°K. Electron spin resonance spectra of the free radicals produced were recorded. It was found that the rupture in the polymer chain takes place at *CC and CO bonds. The radicals identified were OCH2 in polyethylene glycols and mainly
magnified image
in polypropylene glycols. Thermal decay of these radicals followed a second‐order law, and the decay constant calculated was k = 2.32 × 105 cm.3 mole−1 sec.−1 A complete discussion of the results is presented.
Effect of the initiator solvation on the change in polymerization rates of dioxolane and tetrahydrofuran
Authors: Kučera M. , Majerová K. 
Published: April 2003

AbstractThe cocatalytical effects of water and ethanol on the cationic polymerization of dioxolane and tetrahydrofuran were studied. The ion pair or were used for initiating the polymerization. The dependence of the polymerization rate on the concentration of cocatalyst was examined with various temperatures, concentrations of monomer, solvents (heptane, tetrachloroethane, tetrachloroethane‐heptane mixtures, and 1,4‐dioxane), and concentrations of initiator. The abscissa of the maximum of the reaction rate in the dependence mentioned above was the criterion for evaluation of the effect of the reaction variables. The changes observed are small; nevertheless, they prove the share of all components of the polymerizing system in establishing solvation equilibria, which determine the number and the reactivity of active centers and, in fact, the reaction rate.
Linear molecules based on dimethylgermanium and dimethylsilicon groups bridged with oxygen atoms and terminated with chlorine atoms
Authors: Moedritzer Kurt , Van Wazer John R. 
Published: April 2003

AbstractThis article deals with the equilibrated system (CH3)2SiCl2–(CH3)2GeCl2–[(CH3)2SiO]–[(CH3)2GeO], which consists of a range of various chain, and some ring, molecules resulting from scrambling of the bridging oxygen with the monofunctional chlorine atoms between the dimethylgermanium and dimethylsilicon moieties. The proton nuclear magnetic resonance of the methyl groups (which do not exchange appreciably under the conditions employed) bonded to the germanium and silicon atoms shows that there is a strong preference of the chlorine atoms for being on the dimethylgermanium and the bridging group for being on the dimethlysilicon moiety at equilibrium. This means that thermodynamic factors alone cause the germanium atoms to be found as “unreacted” dimethyldichlorogermane with siloxane polymers or to be preferentially arranged at the ends of the chain molecules in the case of the mixed germoxane–siloxanes. The NMR fine structure is interpreted in these terms, and it is shown that the experimental data may be fitted by appropriate calculations based on only four equilibrium constants, which define the arrangement of neighboring atoms about any given atom in a molecule and the size distribution of the linear molecules.
Emulsion polymerization. I. Recalculation and extension of the Smith‐Ewart theory
Authors: Gardon J. L. 
Published: April 2003

AbstractThe most important assumptions underlying the Smith‐Ewart theory are that the locus of chain propagation is the monomer‐swollen latex particle, polymeric chains are initiated by radicals entering from the water phase into the particles, chain termination is an instantaneous reaction between two radicals within one particle, and particles are nucleated by radicals absorbed into monomer‐swollen soap micelles. Right or wrong, these and other assumptions used by Smith and Ewart are retained in this paper. The newly derived and experimentally verifiable equations contain only such parameters which can be determined by experiments not involving emulsion polymerization. The proportionality constant between the particle number and the appropriate powers of soap and initiator concentrations is defined in terms of these independent parameters. Absolute rate equations are presented for the intervals before and after the completion of particle nucleation. To calculate these rates it is not necessary to have prior knowledge of the experimental particle number. The conversion at which particle nucleation is complete is calculated. The molecular weight is defined in terms of independent parameters. Predictions are made for the particle size distribution. It is shown that the validity of the theory is confined to specifiable intervals of conversion, to a certain range of monomer/water ratio, and to soap concentrations whose upper and lower limits are given.
Crystalline titanium dichloride—an active catalyst in ethylene polymerization. I. Catalyst activation
Authors: Werber F. X. , Benning C. J. , Wszolek W. R. , Ashby G. E. 
Published: April 2003

AbstractCrystalline titanium dichloride, in the absence of organometallic cocatalyst, is a very poor catalyst for the polymerization of ethylene. It is transformed into a very active catalyst through mechanical activation (ball‐milling). This catalyst is active in the absence not only of organometallic cocatalysts, but also metals and compounds (such as aluminium and AlCl3) capable of forming organometallic compoundsin situ(i.e., with ethylene, before polymerization starts). Ball‐milling causes not only the expected increase in surface area but also disproportionation of Ti++to Ti+++and metallic titanium, as well as a crystal phase change to a structure not previously identified with those of TiCl2or TiCl3. Catalyst activity (polymerization rate) is shown to be proportional to surface area and a direct function of Ti++content of the catalyst; an empirical equation relates catalyst activity to surface area and to Ti++lost through disproportionation. Titanium trichloride was found to be inactive in the absence of organometallic cocatalyst, even after ball‐milling. The difference in structure of the catalytically active species in the conventional Ziegler (organometallic cocatalyst) and in the titanium dichloride catalyst are discussed. The mechanism of polymerization is compared with that of the supported (CrO3on SiO2/Al2O3and MoO3on Al2O3) catalyst systems.
Photoinduced microstructural changes in 1,4‐polyisoprene
Authors: Golub Morton A. , Stephens C. L. 
Published: April 2003

AbstractAn infrared and NMR study was made of the microstructural changes produced in thin films of purified cis‐ and trans‐1,4‐polyisoprene when irradiated with ultraviolet light in vacuo at room temperature. The major photochemical processes observed were cis–trans isomerization and loss of 1,4 double bonds, the latter process being accompanied by the formation of vinylidene and vinyl double bonds as well as some endlinking. Very surprisingly, the loss of original double bonds contributed also to a novel photocyclization which gave rise to cyclopropyl groups in the polyisoprene chain. The isomerization and the formation of cycloprophyl groups are presumed to proceed through triplet and biradical states of the 1,4 double bonds, while the vinylidene and vinyl double bonds must result from chain repture at the carbon–carbon bond joining successive isoprene units. Hydrogen abstraction and double‐bond migration are of neglible importance in the overall photochemistry of polyisoprene.
Synthesis of polyamideamines from 5‐oxazolones
Authors: Iwakura Yoshio , Toda Fujio , Torii Yoshinori , Murata Katsuaki 
Published: April 2003

AbstractPolyamideamines with a sequence of two amide and one amine linkage in a main chain were synthesized from the polyaddition of 2‐isopropylidene‐4‐alkyl‐3‐oxazolin‐5‐ones and primary diamines. The polyaddition reaction proceeded through 1,4‐conjugate addition of an amine group to 3‐oxazolin‐5‐one and subsequent ring opening of the intermediate addition product with another amine. Although aliphatic diamines gave oily polymers, xylylenediamines afforded amorphous solid polymers. The reduced viscosities and polymer melt temperature of the polymers were 0.05–0.12 and 90–130°C., respectively.
Preparation of highly branched graft copolymers by the ceric ion method
Authors: Iwakura Yoshio , Imai Yohji , Yagi Kohji 
Published: April 2003

AbstractGrafting of methyl methacrylate onto poly(6‐methacryloyl‐D‐galactose) was very rapid, and the increase in weight reached about 1500% after 2–3 min. The maximum number of branches of the graft copolymers obtained was about 50. In the closest position two adjacent grafted branches were separated from each other by about 45–50 units of 6‐methacryloyl‐D‐galactose on the average. Susceptibility of the various polymers containing sugar residues to grafting was compared, and the importance of the hemiacetal group in the grafting was revealed. Solubility of the backbone polymer in water was also important for rapid grafting by the ceric ion method.
Thermosetting polyimides
Authors: Bower G. M. , Freeman J. H. , Traynor E. J. , Frost L. W. , Burgman H. A. , Ruffing C. R. 
Published: April 2003

AbstractLinear polyimides prepared from m‐phenylene diamine (MPD) and 3,4,3′,4′‐benzophenonetetracarboxylic dianhydride (BTDA) were modified so as to be thermosetting. This was done by replacing a portion of the MPD with either 2,4‐diaminoacetanilide or p‐(2,4‐diaminophenoxy) acetanilide and 3,5‐diaminobenzoic acid; it is thought that during final processing of the laminates the carboxyl group and the acetamido group react, forming amide crosslinks. Alternatively, excess anhydride was incorporated into the polymer to react with some of the attached acetamido groups; these would give imide crosslinks. A series of resins and glass‐reinforced laminates incorporating these resins was prepared. The laminates were aged and tested at 315°C. Flexural strength at 315°C. versus hours aged at 315°C. is presented. Flexural strength after 100 hr. at 315°C. for two of the better laminates from modified polymers was about 48,000 psi, compared to 24,000 psi for the straight linear polymer. The flexural strength of the modified polymers decreased more rapidly, however, and after 1000 hr. of aging at 315°C. the flexural strength of the best laminates, including the linear polymer, was 12,000 psi.
Part I. On the synthesis and pyrolysis of a tetrafluoroethylene–acrylonitrile graft copolymer
Authors: Fock J. 
Published: April 2003

AbstractRadiation‐induced grafting of acrylonitrile onto films of polytetrafluoroethylene has been studied. Irradiation has been carried out in a 60Co gamma source at −78°C., and the graft polymerization was facilitated by being held at 100°C. for 150 hr. The amount of acrylonitrile grafted per unit surface area apparently increases with the thickness of the film. Grafting is also accompanied by slight swelling. This indicates that the reaction occurs in depth. The relative decrease of the amount of grafted acrylonitrile with thickness of the film, referred to the weight of the film, shows that grafting is controlled by the diffusion of the monomer. The rate of grafting was found to be lower in a material with a higher degree of crystallinity; i.e., grafting occurs faster in the amorphous areas of the polymer. The final yield of graft decreases with the temperature at which the reaction is carried out. This may be explained on the basis of kinetics or by assuming a simultaneous disappearance of free polymer radicals.
Structure and reactivity α,β‐unsaturated ethers. II. Cationic copolymerizations of propenyl isobutyl ether
Authors: Okuyama T. , Fueno T. , Furukawa J. 
Published: April 2003

Abstractcis‐ and trans‐Propenyl isobutyl ethers were copolymerized with each other and each with vinyl isobutyl ether separately under various conditions. In homogeneous polymerizations a cis‐β‐methyl substitution on vinyl isobutyl ether apparently enhanced the reactivity, whereas the trans substitution tended to reduce it slightly. In heterogeneous catalysis, on the other hand, a β‐methyl group on the vinyl ether, whether cis or trans, greatly reduced the reactivity, probably because of the steric hindrance toward the adsorption of monomers on the catalyst surface. The relative reactivities of cis‐ and trans‐propenyl isobutyl ethers ranged from 2 to 20, depending on the polymerization conditions. The polymer end formed from the cis monomer exhibited special steric effects. It was concluded that even in homogeneous media the rotation of the polymer end around the terminal carbon–carbon bond is restricted.