bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemistry of ketone polymers. XIV. Studies of ethylene copolymers
Authors: Li S. K. L. , Guillet J. E. 
Published: April 2003

AbstractStudies have been made of the photochemistry of ethylene copolymers with carbon monoxide (CO), methyl vinyl ketone (MVK), and methyl isopropenyl ketone (MIPK) in solid films. Infrared (IR) evidence is presented to show that a variety of unexpected ketone structures is present in these polymers as a result of 1,5‐hydrogen transfer or “back‐biting” during the high‐pressure polymerization reaction. These additional structures complicate the analysis of the quantum yield data. The overall quantum yield for carbonyl disappearance (ϕ‐co) which increases from 0.074 to 0.24 to 0.26 in the series PE‐1% CO, PE‐2% MVK, and PE‐20% MIPK reflects the increasing stability of the alkyl radicals produced from the type I process in the respective ketone structures. It is also shown that ketone groups located in the backbone of the polymer, as in the 1% CO copolymer, have lower quantum yields for photochemical reactions, particularly those that produce free radical intermediates. Studies of the gaseous products from extensive photodegradation under nitrogen show that in all three cases carbon monoxide is the major product (46‐65% of the total). Acetaldehyde and methane, expected from the type I reaction, are major products only for the MVK and MIPK copolymers. Reaction schemes are presented to explain the major products observed.
Quaternary ammonium polyelectrolytes. IV. Addition reaction between poly(4‐vinylpyridinium chloride) and electrophilic vinyl compounds
Authors: Luca Cornelia , Bǎrboiu V. , Petrariu I. , Dima M. 
Published: April 2003

AbstractIt was found that the addition reaction between poly(4‐vinylpyridinium chloride) and electrophilic vinyl compounds, such as acrylic acid, acrylamide, methylacrylate, and acrylonitrile. leads to ammonium quaternary polymers with a transformation degree that depends oil the reactivity of vinyl compounds. The structure of addition compounds was established by using 1H‐NMR IR, and UV spectral methods. NMR‐determined values of transformation degree indicate that the reactivity of vinyl compounds decreases as follows:
Silylation of water glass. I. Solvent extraction and trimethylsilylation of silicic acid
Authors: Kohama Shigemi , Inoue Hiroshi , Yasuda Takahisa 
Published: April 2003

AbstractHomogeneous trimethylsilylation of silicic acid in nonaqueous media was studied. The silylation process consisted of three steps: acidification of sodium silicate, solvent extraction. and trimethylation of silicic acid. Sodium silicate was first acidified with dilute sulfuric acid to form silicic acid: extraction followed with hydrophilic organic solvents. The Silicic acid obtained was finally allowed to react with trimethylchlorosilane to give trimethylsilylates with molecular weights of 1000–12,000. Optimum conditions for each step have been intensively sought to achieve trimethylsilylates in high yield. The trimethylsilylates exhibited excellent thermal stability and surface properties, such as water repellency and antifoaming properties, comparable to those of conventional polydimethylsiloxanes.
Polymerization of aromatic nuclei. XXIV. Investigation of oligomer and polymer from furan and trichloroacetic acid
Authors: Lamb Bruce S. , Kovacic Peter 
Published: April 2003

AbstractA reinvestigation of the oligomeric and polymeric products obtained from furan and trichloroacetic acid was carried out to establish their structures. Comparison of spectral data with those of authentic materials indicated that the major oligomeric products are IV and V. The ratio of the products IV:V was 1:52. Comparison of the polymeric material with IV and V suggests that V is the primary component of the larger chains. In addition, microanalytical and molecular weight data were obtained. These findings are in disagreement with the structural designation of Wassermann et al., who proposed the presence of units that possessed aliphatic unsaturation (I), and of Kresta and Livingston, who put forth structure III for the same product. Mechanistic aspects are discussed. A limited study was carried out on insoluble polyfuran which was isolated from the reaction of furan with hydrochloric acid.
Studies on suspension and emulsion. XXXV. Effect of epoxy groups at the surface layer of ethyl acrylate–glycidyl methacrylate copolymer emulsion particles on its crosslinking reactivity
Authors: Okubo Masayoshi , Nakamura Yoshinobu , Matsumoto Tsunetaka 
Published: April 2003

AbstractThe effect of epoxy groups at the surface layer of ethyl acrylate–glycidyl methacrylate copolymer (1) emulsion particles on its crosslinking reactivity has been investigated. For this purpose two series of I emulsions were prepared. In the Y series, of which emulsion particles have epoxy groups at the surface layer, the epoxy content in the polymerization recipe was varied. For preparing the X series, of which emulsion particles have few epoxy groups at the surface layer, the high epoxy content of a given emulsion was reduced by various degrees of cleavage reaction with HCl–CaCl2. In emulsion blend films with amine‐group‐containing copolymer (II) emulsion, where the crosslinking reaction was expected to proceed only at the interfacial layer of I and II emulsion particles, the Y series, compared to the X series at the equal overall epoxy content in particles, showed less swelling and higher gel fraction in dioxane, less swelling in water, and higher tensile strength and modulus. On the other hand, this difference was not observed in the next two crosslinked films in which crosslinking was expected to be homogeneous. First, blends of I and II, which were isolated from the corresponding emulsions discussed above, were cast from dioxane solutions. Second, I emulsions were cast with BF3 ether complex which was expected to penetrate into the particles. It is concluded that the response of I emulsion cleaving the epoxy groups at the surface layer of particles to subsequent interfacial crosslinking is obviously reduced. However, even such an emulsion can be crosslinked to an extent similar to that of an uncleaved emulsion with similar overall epoxy content, if the crosslinking reaction is conducted so as to give an homogeneous effect.
Synthesis and free radical polymerization of N‐substituted citraconimides
Authors: Pyriadi Thanun M. , Mutar Eisa H. 
Published: April 2003

AbstractN‐phenyl and N‐cyclopropylcitraconimides did not polymerize as free radicals with azobisisobutyronitrile (AIBN) as initiator. N‐allylcitraconimide, however, depending on the temperature and concentrations of the reactions, readily polymerized to produce polymers of different molecular weights. These polymers contained as much as 85% cyclic repeating units when the polymer exhibited an average molecular weight of ca. 4000. The softening point of the polymer was higher than 350°C and the compound was highly soluble in many organic solvents. The allylic CH3group in N‐substituted citraconimides and in their corresonding citraconamic acids could not be brominated with N‐bromosuccinimide.
13C‐NMR spectroscopy of polyamic acids and polyimides
Authors: Seshadri K. S. , Antonoplos P. A. , Heilman W. J. 
Published: April 2003

Abstract13Carbon chemical shifts are reported for polyimide and polyamic acid prepared from 3‐aminophenylacetylene, 1,3‐bis(3‐aminophenoxy) benzene, and 3,3′,4,4′‐benzophenoetetracarboxylic dicanhydride. The shielding parameters are correlated with the structure. A spectral analysis of model compounds, monomers, and other oligomers is also included. This analysis resulted in an analytical method by 13C‐NMR spectroscopy of determining the amic acid‐imide ratio in the partly cured polyamic acid. The development of the method is discussed.
Transfer reaction and molecular weight distribution in the anionic polymerization of formaldehyde
Authors: Bianchi Gaudenzio , Colombo Paolo , Custro Sergio , Radici Pierino 
Published: April 2003

AbstractThe anhydrous formaldehyde polymerization is examined. The influence of initiator and monomer concentration on the molecular weight and molecular weight distribution are emphasized. A mechanism for the transfer to the monomer is introduced. This mechanism is confirmed by experimental results and leads to the formation of formyl end groups. The influence of various initiators on the transfer reaction also is evaluated.
Coordination polymers. VIII. IR spectroscopic studies on the mechanism of the reaction between polyesters and zinc oxide
Authors: Szilágyi A. , Izvekov V. , Vancsó‐Szmercsányi I. 
Published: April 2003

AbstractThis article was written for the purpose of investigating the mechanisms of reactions between unsaturated polyester resins and base anhydridelike metal oxides (CaO, MgO, ZnO) which cause an increase in viscosity. As a model system ethyl‐hydrogen‐succinate (ESH) and ZnO were reacted in CCl4 and complexes that contained Zn‐hydroxocarboxylate units took an essential part in this reaction. Solubility measurements of the model compounds and infrared (IR) spectra of the reaction products led to the conclusion that further molecular associates were formed from the mixed metal‐hydroxocarboxylate complex by the carbonyl oxygens of ester groups, which resulted in end products of polymeric structure. It is suggested by IR spectroscopical analogies between the model compounds and reaction products of an adipic acid/butanediol‐1,4 polyester with ZnO that similar reactions can account for the polyesters as well.
Polymerization and polymers of silicic acid
Authors: Bechtold Max F. , Mahler Walter , Schunn Robert A. 
Published: April 2003

AbstractLinear relationships among molecular weight, polymerization time, and gelation for the condensation of any monomer, including those of unknown size and functionality, are developed and applied to data on soluble silicic acids generated from tetraethyl silicate and from sodium silicate. The results suggest the formation of monomers containing ca. 12–15 OSi units with functionality of ca. 2.05 that condense with a rate constant of ca. 10−4 liter/mole sec and an activation energy of 40–70 kJ/mole. One model compatible with these characteristics and the stoichiometry involved is a ladder polymer ca. 3 SiO units wide. Polymer isolation was achieved by replacing residual OH with (CH3)3Sio, as well as by freezing of of aqueous solutions, which yielded fibers under special conditions. Solutions of the uncapped and capped polymers and melts of the latter had low viscosity even for fractions with M̄n ∼100,000. This implies a coiled or globular nature for the polymers, which is supported by their limited propensity for film and fiber formation. Attemps to improve this situation by copolymerization, the use of other capping agents, and by the polymerization of precapped monomers were unsuccessful.
A chemical study of thermally activated chromic titanate on silica ethylene polymerization catalysts
Authors: Pullukat T. J. , Hoff R. E. , Shida M. 
Published: April 2003

AbstractThermally activated ethylene polymerization catalysts which contain chromium and titanium on silica differ from those catalysts which contain only chromium on silica. The characteristics of chromium‐titanium catalysts vary with the method of incorporating the titanium and the thermal activation procedure. Titanated catalysts of the kind examined in this article have faster initiation and a higher polymerization rate per unit catalyst weight than corresponding catalysts without titanium. High‐density polyethylene produced by this type of titanium‐chromium catalyst tends to have a higher melt index and a broader molecular weight distribution than polyethylene made with chromium on silica catalysts. Iodometric titration showed that reduction from the initial hexavalent chromium to trivalent occurs when the dry, catalyst starting material is treated with titanium tetraisopropoxide. A study of the reaction between chromium trioxide and titanium tetraisopropoxide in carbon tetrachloride revealed that (1) it is not necessary to have a reaction between surface silanols and titanium tetraisopropoxide for the reduction to occur, and (2) the reaction product has an absorption near 660 nm in the visible range. Comparison of spectra showed that chromium trioxide on silica reduced by isopropyl alcohol has a shifted absorption, i.e., 600 nm. These findings are interpreted to mean that titanium atoms come sufficiently close to chromium atoms to change their electron density in the starting material and remain close neighbors in the activated catalysts. The interpretation is further supported by ESCA data and leads to the proposal that in this case the activated catalysts contain titanium chromate structures.
Alternating copolymerization of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone with styrene and polymerization behavior with vinyloxy compounds
Authors: Iwatsuki Shouji , Itoh Takahito 
Published: April 2003

Abstract2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) was found to copolymerize alternatingly with styrene (St). DDQ–isobutyl vinyl ether and DDQ–2‐chloroethyl vinyl ether systems gave homopolymers of vinyl ethers, while DDQ–phenyl vinyl ether and DDQ–vinyl acetate systems gave oligomers containing both monomer units. In the terpolymerization of DDQ, p‐chloranil (pCA), and St, terpolymers obtained were found to have about 50 mole % of St units regardless of monomer feed ratio and DDQ was incorporated much more rapidly into the terpolymer than pCA. The difference in the reactivity of the acceptor monomers could be attributed to that in their electron‐accepting character.
Free radical grafting of monomers to polydienes. IV. Kinetics and mechanism of methyl methacrylate grafting to polybutadiene
Authors: Cameron G. Gordon , Qureshi M. Younus 
Published: April 2003

AbstractThe radical grafting of methyl methacrylate (MMA) onto polybutadiene (PBD) in benzene solution at 60°C is more efficiently induced by benzoyl peroxide (BP) than by azoisobutyronitrile (AIBN). PBD exerts a pronounced retardation on the polymerization of MMA and the grafting efficiency is governed by the ratio of rubber to monomer in the system. With BP as initiator, a fairly simple kinetic expression, relating grafting efficiency with reactant concentrations, can be derived by making certain approximations, including the neglect of termination grafting. The experimental data are reasonably consistent with this equation and yield acceptable values of several kinetic parameters. With AIBN, termination grafting is more significant. In consequence the relevant kinetic equation can be only qualitatively validated.
The formation of radical cations of styrene and α‐methylstyrene in the irradiation of mixtures of these monomers with TiCl4 and SnCl4 in a semicrystalline heptane matrix
Authors: Pilař Jan , Marek Miroslav , Toman Luděk 
Published: April 2003

AbstractThe formation of paramagnetic intermediates following the irradiation of styrene, α‐methylstyrene, and their mixtures at −90°C in the presence of TiCl4 and SnCl4 in the polycrystalline heptane matrix was investigated. The effect of light on vinyl aromatic monomers leads to the formation of radical cations of styrene and α‐methylstyrene, which subsequently initiate the polymerization. The polymerization of styrene and α‐methylstyrene supposedly proceeds via the cationic mechanism.
High‐conversion polymerization. VII. A definition of the explosive region and the influence of free volume on it
Authors: Dionisio J. M. , O'Driscoll K. F. 
Published: April 2003

AbstractThe easily observed autoacceleration of free radical Polymerization is defined as the explosive region and an arbitrary but quantitative definition of it is made. Using this definition it is shown that the explosive regions of solution polymerizations of methyl methacrylate occur at constant values of the product of polymer concentration times (molecular weight)1/2. This upholds the concept that polymer entanglements control the termination reaction in this region. It is also shown that this region does not, as previously suggested, occur at a constant value of free volume, but that free volume does play a role in determining the rate of termination at a given level of chain entanglements.
Synthesis and metal binding properties of novel sulfur‐containing functional oligomer
Authors: Tsukube Hiroshi , Araki Takeo , Nakamura Akira , Maruyama Kazuhiro 
Published: April 2003

AbstractThe synthesis and metal ion binding properties of a new class of functional oligomers are described. Oligo[1‐(N‐phenylthiocarbamoyl)aziridine] (DP ca. 8) and its analogs are prepared by ring‐opening oligomerization of the corresponding aziridine monomers in good yields. These oligomers contain sulfur groups capable of binding “soft” metal ions, and the selective binding properties of the novel oligomer for Cu(II) and Hg(II) ions are investigated by liquid‐solid adsorption and liquid‐liquid extraction experiments.
Synthesis and radiation degradation of vinyl polymers with fluorine: Search for improved lithographic resists
Authors: Pittman Charles U. , Chen Chi‐Yu , Ueda Mitsuru , Helbert J. N. , Kwiatkowski J. H. 
Published: April 2003

AbstractHomopolymers of methyl α‐fluoroacrylate (MFA), trifluoroethyl methacrylate (TFEM), and hexafluoroisopropyl methacrylate (HFIM) were prepared, as were their methyl methacrylate (MMA) copolymers. Copolymers of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) with MMA were also prepared. The radiation susceptibilities of these polymers were measured by the60Co γ‐irradiation method, in which molecular weights were measured by membrane osmometry and gel permeation chromatography (GPC). All the copolymers degraded by predominant chain scission except poly(methyl α‐fluoroacrylate), (PMFA), which crosslinks even at low doses (ca. 1 Mrad). TheGs‐GxandGsvalues of the chain scissioning polymers and copolymers are higher than those of poly(methyl methacrylate) PMMA reference. The high susceptibility of PMFA homopolymer to crosslinking is in contrast to that of poly(methyl α‐chloroacrylate), as we reported earlier. This effect is interpreted as resulting from extensive hydrogen fluoride and polyenlyl radical formation, which leads to facile crosslinking. However, incorporation of the MFA monomer unit causes the (22/78) MFA/MMA copolymer to degrade with a larger value ofGsthat PMMA. Apparently a second‐order process leads to crosslinking in PMFA and this is retarded in the copolymer. In the hehomopolymers of HFIM and TFEM and in the HFIM‐MMA and TFEM‐MMA copolymers the HFIM and TFEM components facilitate degradation with negligible crosslinking. The increased degradation susceptibility of VDF and CTFE copolymers with MMA over that of PMMA is attributed to processes at the VDF or CTFE components present in smaller concentrations (3‐5 mole %) than the threshold levels (25‐50% necessary for significant crosslinking).
The synthesis of sulfonated polymers by free radical copolymerization. Poly(butadiene‐co‐sodium styrene sulfonate)
Authors: Weiss R. A. , Lundberg R. D. , Werner A. 
Published: April 2003

AbstractThe copolymerization of butadiene with sodium styrene sulfonate was studied and the copolymer products characterized. In general these copolymers contain 0.5–4 mole% of sulfonated monomer. The effects of the following reaction variables are described: emulsifier type and concentration, monomers feed ratio, chain transfer agent concentration, and reaction conversion. The products were heterogeneous with regard to composition, molecular weight, and solubility behavior. Copolymers prepared under certain conditions exhibited strong intermolecular interactions derived from associations of the ionic species as observed in other ionomers.
Spectrophotometric studies of some CT complexes of 2,4,7‐trinitrofluorenone with poly(vinyl halogenocarbazole)
Authors: Pielichowski Jan , Obrzut Jan 
Published: April 2003

AbstractThe modified UV‐Vis spectrophotometry has been applied to study of spectral and thermodynamic properties of charge‐transfer complexes of poly‐N ‐vinylhalogenocarbazole with 2,4,7‐trinitrofluorenone. The application of numerical calculation allows for the separation of the absorption bands which result only from donor‐acceptor interaction. The equilibrium constants, entropies, and enthalpies of complexing reaction studied in a wide range point out the beneficial influence of introduced chlorine, bromine, and iodine substituents in position 3 and 6 of carbazole ring over the complexing properties of poly‐N‐vinylhalogenocarbazole and properties of its complexes with 2,4,7‐trinitrofluorenone.
Hydrolysis of Egyptian medicated cotton by HCL–FeCl3 reagent
Authors: Shinouda H. G. , Moteleb M. M. Abdel 
Published: April 2003

AbstractThe initial rate of hydrolysis of Egyptian medicated cotton with HCl or HCL‐FeCl3 as reagent, as well as the total carbonyl content of the hydrolysis products, were determined. The results obtained showed that although cellulose fibers are hydrolyzed more rapidly in an acid‐FeCl3 medium than in acid alone, the fibers resisted oxidation in a Fe3+ solution. Therefore the observed rate increase in Fe3+ solution cannot be explained on the basis of increased oxidation of hydroxyl groups. Consequently it has been suggested that the increase in the rate of hydrolysis is due to complexing between Fe3+ and the carbonium/oxonium ion or the leaving group. A comparison between the fine structure of the hydrolysis products of cotton cellulose by the use of HCl and HCl‐FeCl3 reagent is also given.
Kinetics of hydrolysis of side groups in polyphenylmethacrylate
Authors: Połowiński S. , Bortnowska‐Bareła B. 
Published: April 2003

AbstractUltraviolet (UV) spectrophotometry was used to study the kinetics of basic hydrolysis of side groups in polyphenylmethacrylate in DMSO/H2O at various temperatures. Keller's mathematical analysis was applied to the description of the kinetics. Three rate constants which describe the reaction of ester groups with 0, 1, and 2 reacted neighboring groups, respectively, were determined. Activation energies for the hydrolysis reaction of the respective triads were calculated. The data confirmed the applicability of Keller's model to the computation of rate constants for the reaction of the respective triads in the polymer chain.
Organosilane polymers. III. Block copolymers
Authors: Wesson J. P. , Williams T. C. 
Published: April 2003

AbstractChloro‐ and lithio‐terminated diorganosilylene oligomers were coupled to form block copolymers that were soluble in common solvents and deposited coherent films from solution. Copolymer UV (ultraviolet) spectra showed a red shift in absorption maxima attributed to increased silicon chain length and phenyl‐silicon spine interactions.
The adsorption of fluoride containing polyelectrolytes on hydroxyapatite
Authors: Bartels T. , Arends J. 
Published: April 2003

AbstractIn this study the preparation of three polyvinylpyridinium fluorides with different hexadecyl group contents is described. Their adsorption on hydroxyapatite (the main constituent of dental enamel) was studied as a function of time and concentration. It was found that increasing hexadecyl group content resulted in lower amounts of adsorbed polymer. The adsorption of the polyelectrolytes is accompanied with the uptake of fluoride by hydroxyapatite at a higher rate and with greater amounts. Phosphate ions present in aqueous suspensions of hydroxyapatite were responsible for this phenomenon. Desorption experiments showed that the adsorption of these macromolecules was irreversible in water. Excess calcium resulted to some extent in desorption.