bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physicochemical study of crystals of ethylene–butadiene copolymers
Authors: Cernia E. , Conte G. , D'Ilario L. , Pavel N. V. , Giglio E. , Petri S. 
Published: April 2003

AbstractEthylene–butadiene (PEBU) copolymer with low percentage of butadiene was previously investigated by van der Waals potential energy calculations. The trans HCCH group (TDB) was found to show fold‐supporting behavior, so that it was supposed that many TDB's were located on the surface of PEBU single crystals under favorable conditions of TDB concentration and of thickness of crystal platelets. In order to verify this hypothesis, three PEBU samples with a butadiene/(ethylene + butadiene) molar ratio of 2.3% (B), 3.6% (C), and 4.6% (D), by assuming that the HCCH groups are all trans, were studied and compared with a polyethylene (PE) sample (A). Samples A, B, C, and D were grown isothermally at temperatures of 50, 55, 60, 61, 70, 71, 75, and 80°C from dilute xylene solutions. Infrared, differential scanning calorimetry (DSC), small‐angle x‐ray scattering (SAXS), bromination kinetics, and density measurements were performed. B, C, and D lamellar crystals show a long spacing L nearly equal to that of A at crystallization temperatures Tc of 50 and 60°C. For Tc ≥ 70°C, the fold period of samples B, C, and D increases more rapidly than that of A in the order D > C > B. The melting temperature Tm and the enthalpy of fusion ΣHf decrease with increasing content of butadiene, except for B and C, which show nearly equal Tm and ΔHf values. Two peaks appear in the fusion curves at temperatures T1 and T2, T1 > T2. The area of the peak at T2 increases with the butadiene content, and, in the same sample, with Tc. Results of bromination in suspension of B, C, and D single crystals, crystallized in the range 50–71°C, indicate that a high percentage of TDB's react on the fold surfaces. The chemical attack is more successful with crystals grown in the range 60–66°C, and, in the case of sample C, as much as 81% of the TDB's are consumed. The density of the samples increases with both Tc and TDB percentage. On the basis of these observed results a simple model for PEBU is proposed. It is supposed that the copolymerization reaction leads to the formation of defects, consisting of one (b), two (bb), three (bbb), or more sequential molecules of butadiene, almost homogeneously distributed along a macromolecular chain. At very small percentage of butadiene, b defects prevail. The addition of further butadiene gives rise mainly to bb defects, and so on. Thus each kind of defect characterizes PEBU copolymers with a certain butadiene/ethylene molar ratio. The experimental data, valid for low butadiene/ethylene molar ratios, agree with this reasonable model and with the potential energy calculations.
Synthesis of N‐substituted bisitaconimide monomers for use as thermosetting polyimide resins
Authors: Hartford S. L. , Subramanian S. , Parker J. A. 
Published: April 2003

AbstractTwo monomeric N‐substituted bisitaconimides, N,N′‐bisitaconimido‐p,p′‐diphenylmethane and N,N′‐bis(itaconimido‐p,p′‐diphenyl ether), were synthesized from the corresponding diamines. The synthesis was accomplished by reaction of the diamine with itaconic anhydride and cyclocondensation of the resultant bisitaconamic acid. Attempts to use p,p′‐diaminodiphenylsulfone as the diamine gave N,N′‐biscitraconimido‐p,p′‐diphenylsulfone and N‐citraconimido‐N′‐itaconimido‐p,p′‐diphenylsulfone instead of the bisitaconimide. The two bisitaconimides polymerize thermally at 180°C and 225°C, respectively, and yield tough polymers with very high thermal stability.
Synthesis of polydihydropyridazinones from bis(3‐benzoylpropionic acids) and aromatic dihydrazines
Authors: Imai Yoshio , Ueda Mitsuru , Aizawa Tatsuo 
Published: April 2003

AbstractA new class of polydihydropyridazinones has been synthesized by the solution cyclopolycondensation in m‐cresol of 4,4′‐oxy‐ and 4,4′‐ethylenebis(3‐benzoylpropionic acids) with aromatic dihydrazines such as bis(4‐hydrazinophenyl) sulfone and bis(4‐hydrazinophenyl)methane. The polymers having inherent viscosities of 0.2–0.4 were highly soluble in a wide range of solvents including m‐cresol, N,N‐dimethylacetamide, and pyridine. Thermogravimetric analysis of the polydihydropyridazinones showed initial weight losses commencing at 290–350°C in both air and nitrogen.
Effect of polyion conformation on dye binding. II. Fluorescence of 2‐p‐toluidinylnaphthalene‐6‐sulfonic acid (TNS) in the presence of synthetic polyacid and polybase
Authors: Muller G. , Fenyo J. C. 
Published: April 2003

AbstractThe interaction between 2‐p‐toluidinylnaphthalene‐6‐sulfonic acid (TNS), a hydrophobic fluorescent probe, and poly(2‐vinylpyridinium) polyions (PVP) has been investigated by fluorescence spectroscopy. Both the effect of the charge and the concentration of PVP on the fluorescence behavior of TNS indicate that interaction between TNS and hydrophobic sites present in the PVP chain is responsible for the observed phenomena. It is shown that PVP which exists with predominant hydrophobic regions leads to TNS fluorescence, but some residual charge must be present to facilitate the penetration of the dye into the hydrophobic regions. Various situations existing in some polyelectrolyte systems are discussed.
Phase formation and phase inversion during the bulk precopolymerization of solutions of rubber in styrene–methyl methacrylate
Authors: Karaenev S. S. , Chilingirjan M. K. 
Published: April 2003

AbstractThis paper is a report on the investigation of the phase formation and phase inversion during the bulk‐agitated polymerization of styrene and methyl methacrylate containing dissolved SBR. Microphase separation in the rubber solution began at about the 2% conversion level. That process coincided with a constant level of dynamic viscosity and a sharp decrease in the intrinsic viscosity. Before the phase‐inversion point the system became a multiple “oil‐in‐oil” emulsion. The rubber particles began to form before the phase‐inversion point. In the region of phase inversion, the dynamic viscosity decreased and the intrinsic viscosity showed irregularities. After 20% conversion level, the average parameters of the particles did not change.
Structure and properties of poly(2,5‐dimethylterephthalamides)
Authors: Takatsuka Ryozo , Uno Keikichi , Toda Fujio , Iwakura Yoshio 
Published: April 2003

AbstractSix methyl‐substituted wholly aromatic polyamides were synthesized from the reaction of 2,5‐dimethylterephthaloyl chloride with p‐phenylenediamine, its 2,5‐dimethyl and 2‐methyl derivatives, m‐phenylenediamine, or its 2‐methyl and 4‐methyl derivatives by solution polycondensation at low temperature. The x‐ray diffraction diagrams of the polyamides obtained exhibit crystal patterns. Density values range from 1.26 to 1.37 g/cm3. NMR spectra determined in concentrated H2SO4 solution are reported. Poly(2,5‐dimethylterephthalamides) have lower thermal stability than the corresponding polyterephthalamides. The increase in solubility of polyamide by the introduction of the 2,5‐dimethylterephthaloyl linkage is accompanied by a decrease in thermal stability. The effect of methyl substituents on thermal properties and solubility is discussed in terms of the packing of polymeric molecules and the extent of hydrogen bonding of the amide groups.
Vinyl polymerization: Kinetics of Ce(IV)–acetophenone‐initiated polymerization of acrylonitrile in acetic–sulfuric acid mixtures
Authors: Rout Anuradha , Rout Swoyam P. , Mallick Nigamananda , Singh Baishnab C. , Santappa M. 
Published: April 2003

AbstractThe polymerization of acrylonitrile (M) initiated by the Ce(IV)–acetophenone (AP) redox pair has been studied in acetic–sulfuric acid mixtures in a nitrogen atmosphere. The rate of polymerization is proportional to [M]3/2, [AP]1/2 and [Ce(IV)]1/2. The rate of disappearance of ceric ion,–RCe, is proportional to [AP], [M], and [Ce(IV)]. The effect of certain salts, solvent, acid and temperature on both the rates have been investigated. A suitable kinetic scheme has been proposed, and the composite rate constants kp 2(k/k/t) and k0/ki are reported.
Free‐radical polymerization of phenylacetylene
Authors: Amdur S. , Cheng A. T. Y. , Wong C. J. , Ehrlich P. , Allendoerfer R. D. 
Published: April 2003

AbstractThe free‐radical polymerization of phenylacetylene initiated by azobisisobutyronitrile at 50°C was studied in bulk and in the presence of benzene and toluene. The polymerization rate is approximately first‐order with respect to the initiator concentration. The number‐average molecular weight of the polymer is independent of the initiator concentration in bulk and is approximately proportional to the monomer concentration in the presence of the two diluents, but independent of their nature. The data are consistent with a mechanism based on first‐order decay of active to inactive radicals. This step appears to exert the major control over kinetic and molecular chain lengths. Chain transfer to the monomer is concluded to be absent or to make only a small contribution to molecular termination.
Radical polymerization of methyl methacrylate in the presence of isotactic poly(methyl methacrylate). VIII. Influence of template concentration
Authors: Gons J. , Straatman L. J. P. , Challa G. 
Published: April 2003

AbstractThe influence of template concentration on the radical polymerization of methyl methacrylate along isotactic poly(methyl methacrylate) template was studied. The polymerizations were carried out on three template polymers with different molar masses in dimethylformamide at −5°C. The initial polymerization rate increased linearly with template concentration until the distribution of template chain segments became homogeneous. At that critical concentration a strong increase in the polymerization rate was observed, whereas still higher template concentrations had only a slight effect on the polymerization rate. The polymerizations were stopped when the weight ratio of formed polymer and template was equal to one. The viscometrically determined molar mass of the formed polymers showed a remarkable behavior in the low template concentration region. It was obviously related to the molar mass of the template polymer and was lower than the molar mass found for blank polymerization. This decrease in molar mass was most pronounced in the case of the lowest template molar mass. It is suggested that nondegradative chain transfer occurring near a template chain end is responsible for this decrease. An increase in the molar mass occurred at the critical concentration, similarly to the change of polymerization rate. However, at still higher template concentrations, where template coils started to overlap each other, the molar mass of the formed polymers increased further. The growing chains could leap from one template chain to another and attain a greater chain length than the blank polymerizate.
Equilibrium anionic polymerization of 4,7‐dioxaoctanal and n‐octanal
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Ohsawa Shinji 
Published: April 2003

AbstractEquilibrium anionic polymerization of 4,7‐dioxaoctanal (DOA) and n‐octanal (OA) was carried out in tetrahydrofuran in the temperature range of −90 to −68°C, and thermodynamic parameters were evaluated as follows: ΔHss = −4.0 ± 0.1 kcal/mole, ΔSss = −18.4 ± 0.5 cal/mole‐deg, and Tc,ss = −56°C for the DOA system; ΔHsc = −3.4 ± 0.1 kcal/mole, ΔSsc = −15.7 ± 0.4 cal/mole‐deg, and Tc,sc = −59°C for the OA system. Comparison of these values with those in the cases of β‐methoxypropionaldehyde and n‐valeraldehyde made it clear that the aliphatic aldehyde having a longer alkyl group polymerizes with smaller changes of enthalpy and entropy and that the polar‐substituted aldehydes have higher polymerizability than the corresponding unsubstituted aliphatic aldehydes in the temperature range studied. These effects of substituents are interpreted from the viewpoint of the intermolecular interactions of polar groups in monomers and their polymers.
Some reaction variables in the solution synthesis of lead (IV) polyesters
Authors: Carraher Jr. Charles E. , Reese Charlene Deremo 
Published: April 2003

AbstractA number of reaction variables in the solution synthesis of lead (IV) polyesters were examined. Both electronic nature of the diacid and lead‐containing material is important, with an increase in yield resulting as the nucleophilicity of the salt increases. Diffusion is also an important factor. Reaction is favored by an increase in the concentration of reactants.
Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. IV. Common‐ion salt effect on the polymerization rate and the steric structure of the polymer obtained by acetyl perchlorate
Authors: Higashimura Toshinobu , Takeda Takashi , Sawamoto Mitsuo , Matsuzaki Kei , Uryu Toshiyuki 
Published: April 2003

AbstractEffects of a common‐ion salt, n‐Bu4NClO4, on the cationic polymerization of styrene and p‐chlorostyrene by acetyl perchlorate were studied in a variety of solvents at 0°C. In polymerization (in CH2Cl2) which yielded polymers with a bimodal molecular weight distribution (MWD), addition of the salt suppressed the formation of higher polymers, but affected neither the molecular weight nor the steric structure of the lower polymers. The polymerization rate decreased with increasing salt concentration and became constant at or above a certain concentration. In nitrobenzene, on the other hand, the MWD of the polymers was unimodal and steric structure was unchanged even in the presence of salt at a concentration 50 times that of the catalyst. However, the polymerization rate and the polymer molecular weight decreased monotonically as salt concentration increased. On the basis of these results, it was concluded that the ion pair in methylene chloride differs from that in nitrobenzene, and that the species in the latter solvent is similar in nature to free ions. The fractional contribution of the dissociated and nondissociated propagating species to polymer formation was determined from the rate depression caused by addition of the salt.
Limiting conversions in two‐phase polymer reactions
Authors: Sundberg D. C. , James D. R. 
Published: April 2003

AbstractThe concepts of limiting conversion in one‐phase polymer reactions have been extended to two‐phase reaction systems. The analysis of the two‐phase reaction requires the consideration of the glass transition temperature of each phase and the distribution of the reacting monomer between the phases. Predicted limiting conversions are compared with experimental data for simple polystyrene and polystyrene–polybutadiene reactions in latex form. Strong agreement is found for these comparisons.
Polymerization of alkoxyallenes by transition‐metal catalysts
Authors: Ghalamkar‐Moazzam Mohsen , Jacobs Thomas L. 
Published: April 2003

AbstractThe structure of polymers obtained by polymerization of methoxyallene and ethoxyallene with transition‐metal catalysts depends on the catalyst employed. Rapid polymerization at 0°C through the unsubstituted double bond occurred with π‐allylnickel halides, NiCl2/AlEt3 and CoCl2/AlEt3, yielding polymers with the structure magnified image Typical Ziegler–Natta catalysts (TiCl4, VOCl3 or FeCl3 with AIEt3) gave polymers mainly with the structure magnified image although some of the structural units were probably present as well. Polymers having conjugated double bonds magnified image were prepared with PdCl2, [(π‐allyl)PdCl]2, and PdCl2(C6H5CN)2 as catalysts. Palladium iodide produced polymers with all three of the above structural units present. Polymerization occurred more slowly with these palladium catalysts. A preliminary examination of the effect of variation of solvent, ligand, co‐catalyst, and temperature on the rate and structure of the polymers obtained with the palladium catalysts is reported.
Chain‐configurational properties of novolac phenol–formaldehyde resins
Authors: Tobiason Fred L. , Cain Greg H. , Gregory Steve M. 
Published: April 2003

AbstractRotational isomeric‐state chain‐configurational calculations have been applied to the novolac phenol–formaldehyde structure. Steric interference allows the chain to be considered with a twofold potential energy barrier model. Computations that fit the observed dipole‐moment data over a range of molecular weights indicate that the conformational angle is near ±80°, with the g±g= states on the average being 155 cal/mole below the g±g± states. The limiting dipole‐moment ratio is computed to be 1.47, compared to the experimental value of 1.48. A negative temperature coefficient agrees in sign with the experimental value, and the characteristic ratio of the end‐to‐end molecular dimensions is calculated to be 3.27, as compared to the experimental value of 4.76.
Critical evaluation of conditions of plasma polymerization
Authors: Yasuda H. , Hirotsu Toshihiro 
Published: April 2003

AbstractUnder conditions of plasma polymerization, we are dealing with the “reactive” or “self‐exhausting” rather than the “nonreactive” or “non‐self‐exhausting” gas phase (plasma). Therefore, many parameters that define the gas phase, such as system pressure and monomer flow rate, which are measured in the nonplasma state (before glow discharge is initiated), do not apply to a steady state of plasma, the conditions under which most of the studies on plasma polymerization are carried out. Consequently, information based on: (1) the polymer deposition rate measured at a fixed flow rate and discharge power, (2) the dependence of deposition rate on flow rate at fixed discharge power, or (3) the dependence of deposition rate on discharge power at fixed flow rate, does not provide meaningful data that can be used to compare the characteristic nature of various organic compounds in plasma polymerization. The significance and true meaning of experimental parameters applicable to conditions of plasma polymerization are discussed. The most important feature is that plasma polymerizations of various organic compounds should be compared at comparable levels of composite discharge power parameter W/FM, where W is discharge power, F is the monomer flow rate (given in moles), and M is the molecular weight of a monomer.
Cationic polymerization of N‐ethyl‐3‐vinylcarbazole
Authors: De Mola A. H. , Ledwith A. , Yanus J. F. , Limburg W. W. , Pearson J. M. 
Published: April 2003

AbstractHighly purified samples of N‐ethyl‐3‐vinylcarbazole are readily polymerized in CH2Cl2 by conventional initiators of cationic polymerization, including boron trifluoride etherate and tropylium hexachloroantimonate. Reaction rates measured calorimetrically yield an estimate for the free‐cation propagation rate coefficient (kp+ = 2 x 10+4 liter/mole‐sec) at 0°C, which is some 20 times smaller than that for the closely related monomer N‐vinylcarbazole. Distinguishing aspects of the cationic polymerization of N‐ethyl‐3‐vinylcarbazole are the very high molecular weights obtained and the linear dependence of M̄n of the monomer/catalyst mole ratio, indicating that transfer and termination are comparatively unimportant. Polymerizations initiated by tropylium hexachloroantimonate exhibit a characteristic absorption band at 468 nm, tentatively assigned to the propagating cation, which undergoes rapid changes after all monomer has been consumed. The stability of the species responsible for the absorption band at 468 nm appears to be least in conditions where ion pairs are important.
Applications of ESCA to polymer chemistry. XVII. Systematic investigation of the core levels of simple homopolymers
Authors: Clark D. T. , Thomas H. R. 
Published: April 2003

AbstractThe core levels of a series of 83 homopolymers have been studied by electron spectroscopy for chemical analysis (ESCA). Comparisons of the experimentally determined core‐level binding energies with theoretical calculations using the ground‐state potential model in the complete neglect of differential overlap (CNDO/2) self‐consistent field molecular orbital (SCF MO) formalism have been made on the C1s and O1s core levels for the oxygen‐containing polymers in the series. A comparison of the ground‐state potential model (GPM) and relaxation potential model (RPM) on a series of six model compounds representative on the series of polymers is given. Compilations are given of binding energies of C1s, O1s, N1s, Cl2p, S2p, Si2p, and Br3d levels for typical structural features of common occurrence in polymer systems. These data, taken in conjunction with that previously published on fluoropolymers, provide a sound basis for the development of ESCA as a fingerprint tool in the elaboration of features of structure and bonding in polymers in general.
Vinylation and polymerization with trivinylaluminum. II. Synthesis of α,ω‐diene‐polyisobutylene
Authors: Mandal Broja M. , Kennedy Joseph P. 
Published: April 2003

AbstractThe polymerization of isobutylene by 3‐chloro‐1‐butene/trivinylaluminum (V3Al) and t‐butyl chloride/V3Al initiator systems with methyl chloride and methylene chloride as solvents has been investigated in the range from −30 to −72−C. The rate of polymerization increases with decreasing temperatures from −30 to −50°C and then decreases when the temperature is further lowered, for example, to −72°C. Mayo plots and a determination of the number of polymer molecules n̄ formed per molecule of initiator employed suggests a transfer‐less, i.e., termination‐dominated system. A critical analysis shows that for systems containing both free ions and ion pairs, the Mayo equation is meaningful only when the degree of dissociation α remains constant over the whole [M] range investigated. This condition is achieved in RCl/V3Al‐initiated systems by using an initiator (t‐BuCl) for which the rate of catalyst destruction is insignificant compared to rate of initiation, Ri, i.e., initiation efficiency, f ≈ 1 and Ri independent of [M]. Polyisobutylene, containing, 1.8 ± 0.1 terminal unsaturation, has been synthesized by the use of 3‐chloro‐1‐butene initiator in conjunction with V3Al coinitiator, and avenues for further efficient synthesis of α,ω‐diene‐polyisobutylenes have been outlined.
Polymerization of vinylene carbonate in dimethyl sulfoxide
Authors: Reimschuessel H. K. , Creasy W. S. 
Published: April 2003

AbstractPure vinylene carbonate polymerizes readily in dimethyl sulfoxide solutions upon initiation by azobisisobutyronitrile (AIBN). The monomer conversion is characterized by a limiting value which appears to be a function of the temperature and the initial concentrations of both the initiator and the monomer. Increasing both initiator concentration and temperature results in higher final conversions, whereas a maximum conversion is indicated for initial monomer concentrations in the range of 80% to 90%. Principal kinetic quantities were found to be adequately represented by the equations kd = 24.3 × 105 exp {−11300/RT} and kp(f/kt)1/2 = 46.3 × 105 exp {−8900/RT} for the temperature range of 50–80°C. The average degree of polymerization was found to be affected by chain transfer to the solvent. A value of 5.8 × 10−4 was determined for the corresponding chain transfer constant.
Some aspects of the polymerization of N‐vinylcarbazole by grignard reagents
Authors: Biswas Mukul , John K. J. 
Published: April 2003

AbstractThe polymerization of N‐vinylcarbazole (NVC) initiated by PhMgBr in benzene was studied at 32°C. Rp is second order with respect to PhMgBr concentration but increases with NVC concentration (up to 0.06 M) and falls thereafter. Rp and Pn are depressed by the addition of thiophene and water. Modifiers such as benzaldehyde, butanone, and ethylene glycol practically inhibit the polymerization. Carbon tetrachloride and carbon dioxide, when passed through the NVC solution first, enhance the Rp and Pn increases with increasing PhMgBr and NVC concentrations, respectively. Rp increases with temperature, but Pn shows a maxium at a certain temperature. A cationic mechanism has been proposed where the polymerization is initiated by RMg+ cations produced from the ionization of PhMgBr by the Ashby and Smith mechanism.