bluuebunny/crossref_metadata_2025_split huggingface dataset:
Icosahedral carboranes. XVI. Preparation of linear poly‐m‐carboranylenesiloxanes
Authors: Knollmueller Karl O. , Scott Robert N. , Kwasnik Herbert , Sieckhaus John F. 
Published: April 2003

AbstractThe first members of the series of poly‐m‐carboranylenesiloxanes were synthesized by the ferric chloride‐catalyzed condensation of methoxy‐ and chloro‐terminated monomers and generally obtained as insoluble crosslinked gums It has now been discovered that long‐chain, linear polymers can be prepared by simple hydrolytic condensation of m‐B10H10C2(SiMe2OSiMe2Cl)2 and m‐B10H10C2(SiMe2OSiMe2OSiMe2Cl)2 at ice bath temperature, as well as by acid‐catalyzed condensation of the corresponding silanols. In addition, phenyl‐substituted copolymers have been obtained which show outstanding thermo‐oxidative stability at elevated temperature. These linear polymers are soluble waxes and liquids with molecular weights between 16,000 and 30,000; they are potentially useful as high‐temperature liquids and coatings and can be cured at room temperature to form elastomers.
Methyl methacrylate in sulfur dioxide: Solvated radical polymerization
Authors: Kearney J. J. , Clark H. G. , Stannett V. , Campbell D. 
Published: April 2003

AbstractMethyl methacrylate may be polymerized by free‐radical initiators in liquid sulfur dioxide without incorporating sulfur dioxide in the polymer chain, even though methacrylate radicals and sulfur dioxide readily as indicated by electron spin resonance studies. An explanation for this anomalous result is advanced, and evidence for the participation of sulfur dioxide in the transition state of the addition reaction is presented.
Poly(ethylene sulfide). III. Oxidative degradation
Authors: Gillis Marina N. , Catsiff E. H. , Gobran Riad H. 
Published: April 2003

AbstractInjection‐molded poly(ethylene sulfide) containing polyamines and zinc salts as thermal stabilizers has excellent physical properties at room temperature, but discolors rapidly on air aging at 150°C, with embrittlement and general deterioration of properties. Degradative breakdown under these conditions is preponderantly thermo‐oxidative in nature. The site of the polymer's thermo‐oxidative instability was sought in oxidation experiments involving the resin as well as model compounds for the polymer's organic structure. Identification studies were carried out on the oxidation products of 3,6‐dithiaoctane (a model compound). Rate of oxygen consumption by the model compound was measured by a pressure‐bomb technique and by a volumetric method. Oxidation of the model compound was found to proceed indefinitely as long as the supply of oxygen was replenished. Rate of oxidation was nonaccelerating and independent of oxygen pressure within the range 1.7–3 atm O2. The gaseous products of the oxidation of unstabilized (no polyamine) resin were found to be identical to the products from the oxidation of the model compound. A mechanism has been proposed taking into account the products isolated and identified, and the nonaccelerating nature of the oxidation. The poly(ethylene sulfide) structure is able to decompose hydroperoxides via formation of sulfoxides, preventing the acceleration of the oxidation reaction. While effecting this radical deactivation, the polymer chains are cleaved, with a resultant loss in molecular weight and physical properties. Some success has been met in the use of inorganic or metallo‐organic additives as antioxidants. Among these are dithiocarbamate salts and selenocyanates. The effectiveness of these compounds has been demonstrated in the polymer, and a suggested rationale for stabilization is given.
Polymerization of aminoalkyl methacrylates in a thin layer in the presence of atmospheric oxygen
Authors: Jelisejeva V. I. , Morozova E. M. 
Published: April 2003

AbstractChemically initiated monomer polymerization in a thin layer in air has been studied. Under these conditions the process is intensively inhibited by oxygen. Aminoalkyl methacrylates characterized by low volatility and high reactivity were used as monomers. Conditions ensuring a high degree of conversion, control of the process have been found determined. Monomer structurization by an active filler such as carbon black and redox initiation with peroxides and copper salts were found to be the main factors diminishing the induction period and increasing rate of polymerization of the aminoalkyl methacrylates.
Pyrolysis–gas chromatographic analysis of poly(vinyl chloride). II. In situ absorption of HCl during pyrolysis and combustion of PVC
Authors: O'mara Michael M. 
Published: April 2003

AbstractA pyrolysis–gas chromatographic technique for measuring the amount of hydrogen chloride released during the high temperature pyrolysis of poly(vinyl chloride) resins, plastisols, copolymers and compounds containing inert fillers has been developed. The technique, which is also applicable to the analysis of chlorinated polyethylene and chlorinated poly(vinyl chloride), is based on the use of a standard precursor of HCl, poly(vinyl chloride) homopolymer. The analysis has been successfully used to measure the degree of in situ absorption of HCl during pyrolysis by certain basic fillers [K2CO3, CaCO3, CaO, MgO, Al(OH)3, Na2CO3, Al2O3 and LiOH] dispersed in a poly(vinyl chloride)–o‐dioctyl phthalate matrix. Combustion of a number of combustion residues (chloride determination) revealed that the amount of HCl absorbed by the basic filler was independent of the method of degradation (pyrolysis or combustion). Flammability measurements of those matrices having the same composition indicate that in situ absorption of HCl during combustion has little effect on the overall flammability of these materials.
Availability and state of order of hydroxyl groups on the surfaces of microstructural units of crystalline cotton cellulose
Authors: Rowland S. P. , Roberts E. J. , Bose J. L. 
Published: April 2003

AbstractThe relative accessibilities of the hydroxyl groups of the D‐glucopyranosyl units of hydrocellulose have been studied by means of the reaction of N,N‐diethylaziridinium chloride, which produces 2‐(diethylamino)ethyl cellulose. The deviation in the distribution of substituents among the 2‐O‐, 3‐O‐, and 6‐O‐positions of the D‐glucopyranosyl residues in a hydrocellulose from that in a disordered cellulose in which the three types of hydroxyl groups are equally accessible is the basis for estimating the selective accessibilities of the hydroxyl groups in the crystalline cellulose. A particular hydrocellulose, lying within the range of leveling‐off degree of polymerization, was studied in detail; this hydrocellulose, designated EHC (“Exemplar Hydrocellulose”), was formed from fibrous cotton by hydrolysis for 0.67 hr in 2.5N hydrochloric acid at reflux. EHC exhibited higher selective accessibility (larger deviation from equal accessibility) of the hydroxyl groups at C‐2, C‐3, and C‐6, than samples of hydrocellulose formed in shorter or longer periods of hydrolysis. This selective accessibility is discussed in terms of intra‐ and intermolecular hydrogen bonding on the surfaces of crystalline microstructural units in EHC.
Fundamental studies on cationic polymerizations: Molecular weights and molecular weight distributions of polyisobutylenes produced by γ‐irradiation (free ions) and chemical catalysis (ion pairs)
Authors: Kennedy Joseph P. , Shinkawa Akihiro , Williams Ffrancon 
Published: April 2003

AbstractThe molecular weights (M̄n, M̄v, and M̄w) and molecular weight distributions of polyisobutylenes synthesized by γ‐irradiation in the range 29 to −78°C have been determined. The plots of log M̄n, log M̄v, and log M̄w versus 1/T are linear and parallel (EM̄ = −6.36 ± 0.5), and M̄w/M̄n ≈ 3.0 ± 0.5 over this temperature range. The viscosity‐average molecular weights of polyisobutylenes obtained by γ‐irradiation were compared with those of polymers prepared by BF3, EtAlCl2, and AlCl3. It is found that, at the same polymerization temperature, the M̄v of radiation‐induced polyisobutylenes, which propagate by free carbonium ions, is significantly higher than those synthesized by the Lewis acids, which probably propagate via ion pairs. The implications of these findings are discussed, and it is concluded that the counterion in the proximity of the growing cation impedes propagation to a greater extent than it does the competing process of chain transfer to monomer.
Cationic polymerization of vinyl compounds in the presence of tetra‐n‐butylammonium salts
Authors: Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractThe effects of salts were examined in cationic polymerization of vinyl compounds. Cationic polymerization of styrene was carried out at 0°C, with acetyl perchlorate, stannic chloride, stannic chloride–trichloroacetic acid and boron trifluoride etherate as catalysts. Tetra‐n‐butylammonium perchlorate, fluoroborate and iodide were used as salts. The presence of small amounts of the salts changed both the polymerization rate and the molecular weight of polymer considerably. The consideration of various effects led to the conclusion that the results are explicable principally on the basis of counterion exchange. To confirm this, the copolymerization of 2‐chloroethyl vinyl ether with γ‐methylstyrene was investigated at −78°C. The copolymer composition curve when stannic chloride was used as catalyst was changed and coincided with that of polymer obtained with acetyl perchlorate catalysis when the perchlorate salt was added. This supports the concept of counterion exchange.
Criticisms of claims in the field of isomerization polymerization. I. Polymerization of p‐methylstyrene
Authors: Kennedy Joseph P. , Magagnini P. L. , Plesch Peter H. 
Published: April 2003

AbstractThe polymerization of p‐methylstyrene with cationic initiators at low temperatures has been reinvestigated. It was found that, contrary to claims by Krentsel et al., this polymerization produces a conventional 1,2 structure and consequently proceeds by a conventional mechanism.
Structures of reagent residues resulting from reactions of divinyl sulfone with cotton cellulose
Authors: Rowland S. P. , Cirino V. O. , Bullock A. L. 
Published: April 2003

AbstractCotton cellulose in fabric form was crosslinked with divinyl sulfone by catalysis with solutions of sodium hydroxide of normalities ranging from 0.1 to 4.0. The molecular chains of cellulose were hydrolyzed with sulfuric acid to yield hydrolyzates from which simple substituted glucoses (i.e., those bonded to a single unit of DVS), the simple crosslinked glucoses (i.e., those joined together by a single unit of DVS), and complex structures (i.e., those substituted or crosslinked with more than one unit of DVS in the chain) were isolated and measured. The fractions of the reagent residues in the forms of the structures noted above were found to change substantially with the concentration of base employed to catalyze the reaction. The constitution of the reagent residues resulting from reaction in 0.1N base was remarkably simple: 82% of the DVS residues in the form of simple crosslinks and 18% in the form of simple substituents. Complex structures accounted for as much as 70% of the DVS residues under other conditions of reaction.
Side‐chain crystallinity. I. Heats of fusion and melting transitions on selected homopolymers having long side chains
Authors: Jordan Edmund F. , Feldeisen Donald W. , Wrigley A. N. 
Published: April 2003

AbstractHeats of fusion, melting transitions, and the derived entropies of fusion were obtained by differential scanning calorimetry for examples from three homologous series of homopolymers having long side chains. Homopolymers having side‐chain lengths between 12 and 22 carbon atoms were chosen from the poly(n‐alkyl acrylates), the poly(N‐n‐alkyl‐acrylamides) and the poly(vinyl esters). The data demonstrated that only the outer paraffinic methylene groups were present in the crystal lattice. This was concluded because phase diagrams obtained for mixtures of structurally different monomers and homopolymers, as well as for selected copolymers, showed only isomorphism in the polymeric examples. In addition, scanning curves, reflecting the distribution of crystallite sizes, became narrower as the side chains became longer. The critical chain length required to maintain a stable nucleus in the bulk homopolymers was a constant value for each homologous series. It varied between 9 to 12 carbon atoms. When heats of fusion were determined in the presence of methanol, main‐chain restraints were freed, thus permitting more methylene groups to enter the crystal lattice. Hence, the heats of fusion, the crystallinity, and melting points increased above that of the bulk state. The magnitude of the contribution to the heats of fusion by each methylene group indicated that the hexagonal paraffin crystal modification prevailed in these homopolymers, in agreement with x‐ray data from the literature.
Thermal bulk polymerization of cholesteryl acrylate
Authors: De Visser A. C. , De Groot K. , Feyen J. , Bantjes A. 
Published: April 2003

AbstractThe thermal bulk polymerization of cholesteryl acrylate was carried out in the solid phase, the mesomorphic phase, and the liquid phase to study the effect of monomer ordering on polymerization rate and polymer properties. The rate increased with decreasing ordering (or enhanced mobility) of the monomer. Formation of inhibitive by‐products during the polymerization limited conversions to 35%. The sedimentation constant S0 = 6.2 S was the same for the polymers obtained in the three phases. The weight‐average molecular weight (M̄w) was 480,000 as determined by ultracentrifugation. Poly‐(cholesteryl acrylate) formed in bulk is randomly coiled when dissolved in tetrahydrofuran. The thermal properties of the monomer are given.
Polyesters. I. Rate of polyesterification of γ‐arylitaconic acids with ethylene glycol
Authors: Baddar F. G. , Nosseir M. H. , Gabra G. G. , Ikladious N. E. 
Published: April 2003

AbstractA kinetic study of the polyesterification reaction of γ‐phenyl‐ γ‐p‐methoxyphenyl‐, and γ‐p‐chlorophenylitaconic acids (1 mole) with ethylene glycol in the presence or in absence of p‐toluenesulfonic acid as a catalyst has been carried out in order to show the effect of substituents on the rate and degree of polymerization. The reaction of 1 mole of the acid and an excess of ethylene glycol has also been studied. In all cases the reaction is found to follow the second‐order rate equation. The mechanism of polyesterification has been discussed. In catalyzed polyesterification electron‐withdrawing groups (CI) decrease the velocity of the reaction. The low values of ρ in both the auto‐catalyzed and catalyzed reaction indicate that this polyesterification is slightly sensitive to the polar nature of the substituent.
Constitutive equations for elastomers
Authors: Tschoegl Nicholas W. 
Published: April 2003

AbstractGeneral relations were derived by expanding the strain‐energy density function in terms of the invariants of the deformation tensor. Some constitutive equations obtained by keeping a third term in the expansion in addition to the two terms retained in the Mooney‐Rivlin equation were tested in the light of currently available experimental data. It is shown that by the retention of the third term the upswing in the Mooney stress at low values of λ−1 is successfully predicted, and the stress–strain behavior can be described with excellent accuracy up to break, even in carbon black‐filled rubber which is notoriously difficult to describe by the Mooney‐Rivlin equation.
π‐Allyl nickel halide–oxygen system as a catalyst for polymerization of butadiene
Authors: Matsumoto Tsuyoshi , Furukawa Junji , Morimura Hirohisa 
Published: April 2003

AbstractThe π‐allyl nickel halide‐oxygen system was found to be active as catalyst for stereospecific polymerization of butadiene. The catalyst from π‐allyl nickel chloride or π‐allyl nickel bromide yields the polymer of 90% cis‐1,4 content with high activity, whereas the catalyst from π‐allyl nickel iodide affords a polymer of 70% or less cis‐1,4 content. The catalyst systems can be fractionated into two parts on the basis of solubility in benzene. It is concluded that the catalyst activity originates essentially from the benzene‐insoluble nickel complex which is composed of oxygen, halogen, σ‐allyl group, and nickel. The structure of growing polymer terminal is discussed in relation to the mechanism of the stereospecific polymerization.
Radiation‐induced polymerization at high pressure of 2,3,3,3‐tetrafluoropropene in bulk and with tetrafluoroethylene
Authors: Brown Daniel W. , Lowry Robert E. , Wall Leo A. 
Published: April 2003

AbstractThe radiation‐induced polymerization of 2,3,3,3‐tetrafluoropropene was studied as a function of temperature (22–100°C) and pressure (autogenous to 104 atm). Rates have varied 100‐fold for the same reaction conditions probably because of trace impurities. The most rapidly polymerizing material has a rate of 4.5%/hr at 6000 atm, 22°C, and 1500 rad/hr. The activation enthalpy and volume are 4 kcal/mole and −13 cc/mole, respectively. Rates are proportional to the square root of the radiation intensity. Degrees of polymerization varied between 2 × 103 and 2 × 106. In copolymerization with tetrafluoroethylene the reactivity ratios at 22°C and 5000 atm are 0.37 (the ratio for addition to the tetrafluoroethylene‐ended radical) and 5.4 (the ratio for addition to the tetrafluoropropene‐ended radical). Comparison of ratios for the copolymerization of other fluorinej‐containing monomers with tetrafluoroethylene shows that they generally disfavor incorporation of the latter.
Electrochemical preparation of polymers with multinodal molecular weight distributions
Authors: Funt B. L. , Hornof V. 
Published: April 2003

AbstractA direct electrochemical preparation of polybutadiene to a predetermined molecular weight distribution has been achieved. Butadiene is a good model compound, inasmuch as the rate of electrochemical initiation is high relative to the rate of propagation. Rate constants for the temperature interval of interest and for systems of comparable composition were reported and permitted a priori prediction of the weight fractions and the number average molecular weight of each fraction. Polymer was formed by a series of pulses which successively initiated polymerization, permitted growth in the absence of current, and electrochemically terminated polymerization. The polymers produced showed excellent agreement with calculated composition and distribution in the range of molecular weights 10,000 to 50,000.
Copolymerization of ethylene and vinyl acetate at low pressure: Determination of the kinetics by sequential sampling
Authors: German A. L. , Heikens D. 
Published: April 2003

AbstractIn behalf of a detailed study on the course of copolymerization reactions, this paper describes an improved and generally applicable experimental method and an efficient computational procedure to match. The experimental method is based on quantitative gas chromatography, and permits frequent measurement of the monomer feed composition throughout (co)polymerization processes at pressures up to 40 kgf/cm2 ( = 38.7 atm). The given method is applied to the study of the radical copolymerization of ethylene with vinyl acetate in a series of kinetic experiments, at 62°C and 35 kgf/cm2 ( = 33.9 atm) in tert‐butyl alcohol, in which 20–40% conversion is reached. Monomer feed composition and degree of conversion are entered into a computational procedure based on nonlinear least‐squares methods applied to the integrated version of the copolymer equation. The experimental data, covering a region of ethylene molar feed fractions between 0.24 and 0.74 and copolymer concentrations up to 8 wt‐%, are precisely consistent with the usual model. The respective reactivity ratios are r̂e = 0.743 ± 0.005 and r̂v = 1.515 ± 0.007.
Problems in low‐temperature polymerization of lactams with MAlEt4–n (Lac)n as catalyst
Authors: Konomi Tuyoshi , Tani Hisaya 
Published: April 2003

AbstractThe NaAl(Lac)4‐catalyzed polymerization of ε‐caprolactam at the medium temperature range (70–150°C) was investigated. The initiation temperature was observed to decrease to about 100°C in the case of a high concentration (such as 2.0 mole‐%) of catalyst. Moreover, in the prolonged polymerization of lactams with KAl(Lac)2Et2 catalyst, in the absence of initiator, the low activity of aluminum lactamate as initiator was observed. In connection with the polymerization of lactams with MAl(Lac)nEt4–n catalyst, the reactivity of MAlEt4 (where M is Na or K) with N‐acetyllactams was investigated. The results imply that no consumption of N‐acyllactams by the reaction with MAl(Lac)nEt4–n occurs in the course of the low‐temperature polymerization of lactams.
Curing mechanism for phenol—formaldehyde resins
Authors: Kurachenkov Vladimir Ivanovich , Igonin Leonid Andreevich 
Published: April 2003

AbstractA pressure DTA method was used to study the curing of resins. The hardening of novolacs by hexamine was studied at pressures up to 5000 kg/cm2. The application of the pressure DTA method to the thermal curing of some dioxymethylated para‐substituted phenols indicates that the endothermic peak observed at about 75°C at ambient pressure is due to the superposition of two peaks due to melting of the substance and formation of ester bonds.
Polyquinazolotriazoles
Authors: Hergenrother P. M. 
Published: April 2003

AbstractA novel high molecular weight (ηinh = 1.4 dl/g) polyquinazolotriazole (PQT) was prepared from the reaction of 3,3′‐(2″,6″‐pyridinediyl)bis[5‐(o‐aminophenyl)‐1,2,4‐triazole] with isophthalic acid by solution cyclopolycondensation in polyphosphoric acid, with diphenyl isophthalate by melt polycondensation, and with isophthaloyl chloride to form a precursor polyamide which subsequently underway cyclodehydration. Thermal characterization of the PQT by thermogravimetric analysis showed initial weight loss in air commencing at ∼490°C. The PQT exhibited a weight loss of only 4% after aging in static air for 200 hr at 316°C and a Tg of 342°C as measured by differential scanning calorimetry. Prior to polymer synthesis, a series of model compounds was prepared as a guide to polymer synthesis and identification.
Polymerization of propadiene. II. Catalyst systems based on 3d transition metals and various stabilizing ligands
Authors: Van Den Enk J. E. , Van Der Ploeg H. J. 
Published: April 2003

AbstractA variety of catalyst systems based on 3d transition metals, i.e., V(III), Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and various stabilizing ligands, i.e., propadiene, methylacetylene, phenylacetylene, and 1,4‐butadiene, were prepared. The activity of these catalytic systems towards the polymerization of a series of monomers (propadiene, methylacetylene, phenylacetylene, 1,4‐butadiene, ethene, and propene) is investigated. Optimum conditions for the preparation of 1,2‐polyallene, polymethylacetylene and polyphenylacetylene are given.
Determination of kinetic rate constants in electrochemically initiated anionic polymerization of 1,3‐butadiene
Authors: Funt B. L. , Hornof V. 
Published: April 2003

AbstractThe rate constants for electrochemically initiated polymerization were determined by employing a pulsing technique. An electrochemical titration was conducted in which polymer chains were initiated electrochemically, propagated in the absence of current, and terminated electrochemically. The concentrations of supporting electrolyte and monomer were chosen to correspond to those employed in electropolymerization syntheses. The temperature range −10°C to −72°C gave kp = 1.45 × 102 exp {2600/RT}. The Arrhenius parameters are compared to those from previous studies and are interpreted in terms of ion‐pair propagation. Precise control of molecular weight distributions is implicit from an accurate knowledge of the kinetic parameters and is reported separately.