bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemistry of alkenyl azlactones. IV. Preparation and properties of telechelic acrylamides derived from amine‐terminated oligomers
Authors: Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R. , Smith Howell K. 
Published: April 2003

AbstractThe ring‐opening, nucleophilic addition of amine‐terminated oligomers to alkenyl azlactones was exploited to prepare reactive, that is, in free radical polymerizations, oligomers that could be used in 100% solids resin systems. Acrylamide‐functional oligomers resulted from the reaction that used 2‐vinyl‐4,4‐dimethylazlactone, whereas methacrylamide‐functional oligomers were produced with 2‐isopropenyl‐4,4‐dimethylazlactone. The overall reaction took place under mild conditions, for example, a few hours at room temperature, and was particularly free of side reactions. Examination of reaction rates with the two alkenyl azlactones revealed that the 2‐vinyl derivative reacted ca. four times faster. The (meth)acrylamide‐terminated resins were characterized by IR, NMR, and molecular weight analyses.
Kinetics of emulsion polymerization of methyl methacrylate
Authors: Ballard Mathew J. , Napper Donald H. , Gilbert Robert G. 
Published: April 2003

AbstractThe kinetics of the emulsion polymerization of methyl methacrylate at 50°C have been studied in seeded systems using both chemical initiation and γ‐radiolysis initiation. Both steady‐state rates and (for γ‐radiolysis) the relaxation from the steady state were observed. The average number of free radicals per particle was quite high (e.g., ∼0.7 for 10−3 mol dm−3 S2O28 initiator). The data are quantitatively interpreted using a generalized Smith–Ewart–Harkins model, allowing for free radical entry, exit, biomolecular termination within the latex particles, and aqueous phase hetero‐termination and re‐entry. From this treatment, there results (i) the dependence of the termination rate coefficient (kt) on the weight fraction of polymer (wp), (ii) lower bounds for the dependence of the entry rate coefficient on initiator concentration, and (iii) the conclusion that most exited free radicals undergo subsequent re‐entry into particles rather than hetero‐termination. The results for kt(wp) are consistent with diffusion control at temperatures below the glass transition point. Comparisons are presented of the behavior of methyl methacrylate, butyl methacrylate, and styrene in emulsion polymerization systems.
Radiation‐induced copolymerisation of trioxane with penta‐acetyl‐glucose
Authors: Sagu M. L. , Bhattacharyya K. K. 
Published: April 2003

AbstractCopolymerisation of trioxane (TOX) with penta‐acetyl‐glucose (PAG) in the solid state was investigated by gamma radiation. Effects of radiation doses, PAG concentration, and related parameters were studied and compared with that of the homopolymerisation of TOX. The yield of copolymer was lower than homopolymer and only a fraction of the PAG taken entered into the polymer. Chemical properties of the copolymer were determined; after amine treatment the copolymer showed good thermal stability. The kinetics of homopolymerisation were similar to those of TOX‐homopolymerisation.
Styrylpyridine‐based epoxy resins: Synthesis and characterization
Authors: Yan Hoh‐Jiear , Pearce Eli M. 
Published: April 2003

AbstractPolymers containing rigid aromatic structures in the chain backbone usually gave high thermal stability and good flammability resistance. Three glycidyl ethers of epoxy resins were prepared from 2,4‐di(p‐hydroxystyryl)pyridine (2,4‐DGESP), 2,6‐di‐(p‐hydroxystyryl)pyridine (2,6‐DGESP), and 2,4,6‐tri‐(p‐hydroxystyryl)pryidine (2,4,6‐TGESP) to study the relationships of structure to polymer degradation. To prepare a highly crosslinked material, trimethoxyboroxine (TMB) was used as the curing agent. The relative char yields of the three different resins, as measured by TGA, were 2,4‐DGESP ≈ 2,6‐DGESP > 2,4,6‐TGESP. The char yield of the cured 2,6‐DGESP varied with different amounts of the TMB curing agent, and was higher than the uncured 2,6‐DGESP. The oxygen index increased as a function of thermal curing time for the 2,6‐DGESP epoxy resin. An intermolecular Diels–Alder reaction with 2,6‐DGESP is proposed as a primary reaction during thermal curing.
n‐Butyllithium/α‐methylstyrene/benzene/diethyl ether: A suitable initiation system for anionic syntheses of model co‐ and homopolymers of styrene and isoprene
Authors: Podešva J. , Špaček P. , Sikora A. , Podol'Skii A. F. 
Published: April 2003

AbstractAn initiation system of the anionic polymerization, intended for the syntheses of homopolymers and block copolymers with narrow molar mass distribution, was tested with styrene and isoprene. The actual initiating species, viz., the oligomeric α‐methylstyryl anion, originates by the reaction of n‐butyllithium with α‐methylstyrene in a benzene/diethyl ether 1:1 (v:v) solvent mixture at room temperature. The homopolymers and two‐block copolymers of styrene and isoprene, prepared by using this system, were characterized by light scattering, membrance osmometry, GPC, and 1H NMR spectroscopy. By using the suggested initiation system, it is possible to synthesize well‐defined homopolymers and block copolymers with low polydispersity (as judged by the shape of the GPC peaks and by the values of the polydispersity index), especially in a molar mass region between 4 × 104 and 1.5 × 105 g/mol. Above the upper limit of this interval, an appropriate decrease of the diethyl ether/benzene volume ratio is recommended, though the polymerization time must then be prolonged.
Studies on plasma‐initiated polymerization of acrylamide in solid state and in solution
Authors: Akovali Güneri , Orhan Bilge 
Published: April 2003

AbstractPlasma‐initiated polymerization is applied to acrylamide both in solid state and in solution. The effect of the amount of water, in addition to certain operational parameters such as applied vacuum, post polymerization period, and temperature, are well verified. Characteristics of polymers are determined by IR spectroscopy and X‐ray diffraction studies as well as by intrinsic viscosity determinations.
Correlation between macromolecular parameters and the average breaking strength of agave fibers
Authors: Patel A. , Prasad J. R. , Nayak S. K. 
Published: April 2003

AbstractThe small‐angle X‐ray scattering method was applied to evaluate macromolecular parameters of Agave fibers (Agave sisalana, A. cantala, A. hybrid, A. elongata, and A. ameniensis). The macromolecular parameters such as specific inner surface, percentage of void, length of coherence, range of inhomogeneity, and transversal lengths were evaluated. The correlation of macromolecular parameters with the average breaking strength of Agave fibers did not lead to a linear relation, however, the specific macromolecular organization in A. sisalana manifested higher breaking strength.
Synthesis and thermal characteristics of phosphorus‐containing polyureas and copolyureas based on 1‐[(dialkoxyphosphinyl)methyl]‐2,4‐ and ‐2,6‐diaminobenzenes
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractThe reactions of 1‐[(dialkoxyphosphinyl)methyl]‐2,4‐ and ‐2,6‐diaminobenzenes (1) with various diisocyanates such as tolylene diisocyanate, methylenebis(4‐phenylisocyanate), and hexamethylene‐1,6‐diisocyanate were studied for the synthesis of phosphorus‐containing polyureas. Furthermore, diamines 1 were used as comonomers for preparing fire‐resistant copolyureas. In addition, the corresponding common polyureas were synthesized for comparative purposes. All polymers were characterized by elemental analysis, inherent viscosity measurements, infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The relatively low chemical reactivity of 1 toward diisocyanates was interpreted on the basis of their structural features. The phosphorus‐containing polyureas showed a lower molecular weight, a lower polymer decomposition temperature, and a higher char yield than the corresponding common polyureas. Their fire‐resistance was evaluated by determining the limiting oxygen index value.
Water‐soluble copolymers. X. Copolymers of acrylamide with N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide and N,N‐dimethylacrylamide: Solution properties
Authors: McCormick C. L. , Chen G. S. 
Published: April 2003

AbstractDilute solution properties of copolymers of acrylamide (AM) with N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide (DAAM) and with N,N‐dimethylacrylamide (DMAM) have been studied as a function of composition, temperature, time, and added electrolytes sodium chloride and calcium chloride. Unlike the AM‐DMAM copolymers, the AM‐DAAM copolymers show solution viscosity increases in the presence of added NaCl and CaCl2 and decreases with increasing temperature which are related to copolymer composition. The unusual viscosity behavior of the DAAM‐AM copolymers is suspected to be due to chain extension resulting from intramolecular hydrogen bonding and other cooperative associations along the macromolecular backbone.
Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether)
Authors: Hegazy El‐Sayed A. , Dessouki Ahmed M. , Rabie A. M. , Ishigaki I. 
Published: April 2003

AbstractSome properties of the membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene‐perfluorovinyl ether) copolymer (PFA) films have been investigated. The dimensional change caused by grafting and swelling behavior, water uptake, electrical conductivity, and mechanical properties of the grafted films were found to increase as the grafting proceeds. The influence of the preparation conditions (such as preirradiation dose, monomer concentration, grafting temperature, and film thickness) on those properties was studied. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions, except at higher monomer concentration (>40 wt %). The electric conductivity and mechanical properties for the membranes obtained at higher AAc concentrations were lower than those obtained at lower ones. Analysis by x‐ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the central part with progressive diffusion of monomer to give finally homogeneous distribution of the electrolytes in the whole bulk of the polymer. The membranes show good electrochemical and mechanical properties which make them acceptable for practical use as cation‐exchange membranes.
Synthesis and characterization of some aromatic polyamides containing double bonds
Authors: Sachindrapal P. , Nanjan M. J. 
Published: April 2003

AbstractTen polyfumaramides based on fumaric acid and aromatic diamines and six polystilbenediamides based on 4,4′‐stilbenedicarboxylic acid and aromatic diamines were synthesized and characterized by solubility, viscosity, density, infrared and UV‐visible spectroscopy, and thermal analyses. Variation in properties with structure is discussed here.
Copolymers containing alternating sequences of nucleic acid base pairs. III. Spectroscopic studies
Authors: Aponte Maria A. , Butler George B. 
Published: April 2003

AbstractA study was conducted of the complementary base pair interactions between various pairs of electron‐donor monomers, electron‐acceptor monomers, homopolymers and alternating copolymers selected from the following group: (1) 9‐(2‐vinyloxyethyl)adenine; (2) 1‐(2‐vinyloxyethyl)thymine; (3) 1‐(2‐vinyloxyethyl)cytosine; (4) 9‐(2‐maleimidoethyl)adenine; (5) 6‐chloro‐9‐(2‐maleimidoethyl)purine; (6) 1‐(2‐maleimidoethyl)thymine; (7) 1‐(2‐maleimidoethyl)cytosine; (8) homopolymer of (4); (9) homopolymer of (6); (10) alternating copolymer of (2) and maleic anhydride; (11) alternating copolymer of (2) and (5); and (12) alternating copolymer of (2) and (4). By 1H‐NMR, in CDCL3, the base pair interactions between (1) and (2) were shown to be hydrogen bonding, the extent of which was shown by a calculated binding constant, K = 61.81 L/mol. The nature of this interaction was conformed by IR. Neither monomer pairs (1)/(2) nor (4)/(6) exhibited hydrogen bonding in DMSO‐d6. However, hydrogen bonding interaction was observed for DMSO‐d6 solutions of homopolymers (8) and (9) and for alternating copolymer (12). On the basis of an upfield chemical shift of the 2‐ and 8‐aromatic protons of ademine of (1) in D2O, a partial overlap stacking interaction is proposed. No charge‐transfer interactions could be observed by UV between donor‐acceptor monomer pairs.
Modification of catalysts for propylene polymerization: Alcohols and lewis bases
Authors: Sivak A. J. , Kissin Y. V. 
Published: April 2003

AbstractA series of compounds were examined as modifiers for the high activity supported catalyst TiCl4/MgCl2–AlEt3 for isospecific propylene polymerization. The list included two aromatic acid esters, 21 various Lewis bases, and 12 alcohols. A convenient graphic method is described for comparing the performance of different modifiers by plotting experimental results in coordinates “relative activity‐isotactic index” and a kinetic rationale for this evaluation is presented. Aromatic acid esters exhibit much better performance than the bulk of Lewis bases but some sterically demanding aromatic alcohols show behavior show similar to that of the esters.
Thermal analysis of the pyrolytic behaviors of a highly crosslinked polymer
Authors: Tou James C. 
Published: April 2003

AbstractThermogravimetric‐mass spectrometric (TG/MS) and differential scanning calorimetric (DSC) techniques were used in the characterization of oxidative and nonoxidative degradation reactions of a highly crosslinked divinylbenzene/styrene copolymer. When the copolymer was subjected to a temperature‐programmed air environment, four exothermic reactions were detected. The initial small exothermic reaction, starting at ca. 125°C and reaching its maximum at ca. 180°C, was presumed to result from the decomposition of peroxides. The second exothermic reaction, which overlapped with the initial one and peaked at ca. 270°C, was attributed to oxidation with a significant amount of oxygen uptake and liberation of some gaseous products such as CO2, styrene, benzaldehyde, ethylstyrene, and ethylbenzaldehyde. The strongest exothermic reaction took place at ca. 290–380°C and had its peak at ca. 360°C. Associated with this reaction was the generation of many gaseous pyrolysates, as given above. The exothermic reaction continued at a relatively constant rate from ca. 380°C to the maximum temperature of the experiment (500°C) with the release of only one gaseous product (CO2). The initial exothermic reaction can be eliminated by controlled thermal decomposition of peroxides; therefore, a more thermally stable polymer can be obtained. Exothermic reactions, starting at ca. 170°C, were observed. Pyrolytic reactions in an inert gas were also studied.
Intrinsic reactivity of active species in Ziegler–Natta polymerization of ethylene initiated with Li/Ti‐based macromolecular complexes
Authors: Siove Alain , Fontanille Michel 
Published: April 2003

AbstractPolymerization of ethylene was initiated with soluble polystyrene100‐butadiene3‐Li/TiCI4 complexes in toluene leading to block copolymers. The activity of the system was measured at a constant ratio r = [Li]/[Ti] and for different concentrations in active centers and in monomer. Measurement of the amount of the block copolymers formed led to the direct determination of the efficiency of the catalytic system. This efficiency is defined with respect to the number of potentially active centers and is close to 90%. From both measured values of activity of the catalytic system and of its efficiency, the rate constants of propagation were deduced. The kinetic behavior of the system is fully consistent with that of a living system. The rate is first order towards both ethylene and active centers concentrations. So, the rate constant of propagation is an absolute rate constant, measuring the intrinsic reactivity of active sites. Determination of the absolute rate constant at different temperatures, led to thermodynamic parameters of the propagation reaction. The chemical composition of the complex and the absence of polymeric aggregation, leads to propose a structure of the active species: a bioctahedral binuclear structure is consistent with kinetic, thermodynamic results, and structural determinations.
Modelization of photocatalyzed oxidation of polyolefins. II. ZnO and TiO2 photocatalyzed decomposition of tert‐butyl hydroperoxide and atactic polypropylene hydroperoxides
Authors: Lacoste Jacques , Arnaud Rene , Lemaire Jacques 
Published: April 2003

AbstractDirect evidence of the TiO2 and ZnO photocatalytic decomposition of tert‐butyl hydroperoxide and atactic polypropylene hydroperoxides in solution is reported. Molecular and macromolecular hydroperoxides behaved similarly. Untreated TiO2 in the rutile form was a far more efficient photocatalyst than ZnO in solution; the photoactivities of both pigments were limited on preferential absorption sites. In the solid state no preferential reaction sites were observed. When added to preoxidized atactic polypropylene both pigments were photocatalysts of the formation of macromolecular hydroperoxides and of their decomposition. The photoreactivities of untreated TiO2 and ZnO varied less than in solution.
Partitioning of polystyrene between incompatible phases and distributional effects in the system polystyrene–polybutadiene–toluene
Authors: Narasimhan Venkataraman , Huang Robert Y. M. , Burns Charles M. 
Published: April 2003

AbstractThe average molecular weights and the molecular weight distributions of polystyrene (PS) in the conjugate incompatible phases of the ternary system of PS and polybutadiene with toluene as solvent were studied at 23°C. Gelpermeation chromatography, with ultraviolet and differential refractive index detectors, was used for analyzing the compositions of the conjugate phases and for obtaining the molecular weight averages of PS in the phases. Both narrow and broad molecular weight distribution (MWD) polymer samples were used. The effect of broad MWD polymers is seen as one of narrowing the shape of the binodal, thus effectively increasing the compatible region. The molecular weight averages of PS in the two conjugate phases do not vary significantly in the case of the narrow MWD PS sample while for broad MWD samples the average molecular weight of PS is found to be higher in the PS‐rich phase than in the polybutadiene‐rich phase for tie lines closer to the plait point indicating a partitioning or redistribution of the molecular weight species of PS between the incompatible phases.
Sulfonation chemistry of some small molecule models of EPDM rubbers. II. The structure of intermediate adducts
Authors: Thaler Warren A. , Dubreuil Catherine 
Published: April 2003

AbstractAs previously reported, our initial investigation was concerned with the bicyclic olefins, ethylidene norbornane, and dihydrodicyclopentadiene. The former produced a skeletally rearranged γ‐sultone and the latter an allylic sulfonic acid. In an attempt to further clarify the mechanisms of the sulfonation of these two models and to extend the study to models of other types of EPDM, we have now examined the sulfonation of several other model olefins. In addition to the bicyclic olefins reported previously, we have studied the sulfonation of monocyclic type II and III olefins and cyclic type I and type II olefins. The results showed that the bicyclic olefins behaved differently from their monocyclic analogs reinforcing earlier speculation as to a synchronous reaction mechanism. Exocyclics gave allylic sulfonic acids while endocyclics produced β‐sultones, which is the exact reverse of what was observed for the bicyclic counterparts. Acyclic type II olefins produced “stable” β‐sultones, and the influence of the sulfonating reagent on the subsequent chemistry is discussed. Type I olefins, curiously, gave a complex mixture of initial products which tended to rearrange to essentially a single thermodynamic product. The results of the investigation suggest that based on these models, each of the three major types of EPDM should have a different sulfonation mechanism.
Synthesis of high‐molecular‐weight poly(amide‐ester)s by direct polycondensation with diphenyl chlorophosphate
Authors: Higashi Fukuji , Hoshio Atsushi , Ohtani Hiroshi 
Published: April 2003

AbstractHigh molecular weight aromatic poly(amide‐ester)s were prepared by the direct polycondensation reactions between aromatic dicarboxylic acids and aminophenols under mild conditions in pyridine. The condensing agents examined in this study were diphenyl chlorophosphate (DPCP), DPCP/LiCl, and DPCP/DMF. Addition time of the aminophenols, depending on their nucleophilicities, affected the ηinh values and monomer sequence of the resulting polymer. Their thermal properties were studied in terms of the sequences in the polymer backbones.
Preparation and hydrogenation studies of rhodium(I) catalyst supported on polymer crystal surfaces
Authors: Iii Bernard Gordon , Butler Jacqueline S. , Harrison Ian R. 
Published: April 2003

AbstractIn recent years polymers have been utilized as binding sites for transition metal catalysts (e.g. crosslinked polystyrene beads). However, general problems exist with the above system. The rate of reaction depends on the presence of solvents that adequately swell the polystyrene bead in order to allow access to the catalytic sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed whereby tris(triphenyl phosphine) chlororhodium (Wilkinson's catalyst) is bound to the surface of polyethylene single crystals. Polyethylene single crystals have a very high surface to volume ratios allowing for greater ease of reaction compared to the polystyrene system. Diffusion control of the reactant poses no problem as the catalyst is bound to the surface of the crystal rather than the interior (as in the case of polystyrene beads). In addition, many solvents can be used due to the difficulty of dissolving crystalline polyethylene (except at high temperatures). The polyethylene crystals were tested for their catalyst content using neutron activation analysis. Test results showed 3.11 wt% catalyst present on the surface of the PE single crystals. Hydrogenation studies have been conducted using the PE supported catalyst system to show the potential effectiveness of the new system.
Plasma polymerization investigated by the substrate temperature dependence
Authors: Yasuda H. , Wang C. R. 
Published: April 2003

AbstractPlasma polymerization of tetra fluoroethylene (TFE), perfluoro‐2‐butyl‐tetrahydrofuran (PFBTHF), ethylene, and styrene were investigated in various combinations of monomer flow rates and discharge wattages for the substrate temperature range of −50 to 80°C. The polymer deposition rates can be generally expressed by k0 = Ae−bt, where k0 is the specific deposition rate given by k0 = (deposition rate)/(mass flow rate of monomer), A is the preexponential factor representing the extrapolated value of k0 at zero absolute temperature, and b is the temperature‐dependence coefficient. It was found that the value of b is not dependent on the condensibility of monomer but depends largely on the group of monomer; that is, perfluorocarbons versus hydrocarbons. The values of A are dependent on domains of plasma polymerization. In the energy deficient region A is given by A = α(W/FM)n, where α is the proportionality constant, W is discharge wattage, FM is the mass flow rate, and n is close to unity. In the monomer deficient region A becomes a constant. The kinetic equation is discussed in view of the bicyclic rapid step‐growth polymerization mechanisms.