bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of coordinated monomers VII. A kinetic study on the alternating copolymerization of methyl methacrylate with styrene using stannic chloride
Authors: Hirai Hidefumi , Komiyama Makoto 
Published: April 2003

AbstractThe alternating copolymerization of methyl methacrylate with styrene in the presence of stannic chloride at −50°C in toluene was kinetically investigated both under photoirradiation and with the tri‐n‐butylboron‐benzoyl peroxide initiator. The concentrations of the binary and ternary molecular complexes in the copolymerization solution were estimated by use of the equilibrium constants. The rates are found to be proportional to the 1.5th and 1.0th orders of the concentration of the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene, under photoirradiation and with initiator, respectively. The conversion increases proportionally with the polymerization time, while the degree of polymerization is constant irrespective of the time. The rates depend linearly upon the square root of the intensity of the incident light and upon the concentration of tri‐n‐butylboron, respectively. The alternating copolymerization is confirmed experimentally to precede the homopolymerization of the monomer charged in large excess both under photoirradiation and with initiator. The kinetic results indicate consistently that the alternating copolymerization proceeds through the homopolymerization of the ternary molecular complex in the steady state with a bimolecular termination. Both the conventional radical mechanism and the double complex mechanism are unsuitable for the present alternating copolymerization.
Coupling reaction of poly(α‐methylstyryl) anion with (MMA–α‐methylstyrene) block copolymer
Authors: Ishizu Koji , Fukutomi Takashi , Kakurai Toshio 
Published: April 2003

Abstract(MMA–α‐methylstyrene)block copolymer was reacted with poly(α‐methylstyryl)anion at −78°C in a mixture of good tetrahydrofuran (THF) and poor methylcyclohexane solvents. The reaction conditions were chosen so as to produce graft copolymers made up of a backbone (AB‐type block copolymer) and a single branched chain (1:2 graft copolymer). Gel permeation chromatograph (GPC), osmotic pressure measurement, and elemental analysis were used for the characterization of 1:2 graft copolymer. It appeared that poly(α‐methylstyryl)anion reacted with the end pendant groups located farthest away from the branched point of AB‐type block copolymer, when the dimensions of AB‐type block copolymer molecule are small.
Emulsion polymerization of tetrafluoroethylene and isobutylene
Authors: Coker James N. 
Published: April 2003

AbstractInterpolymers of tetrafluoroethylene and isobutylene containing approximately equimolar amounts of each monomer have been prepared by emulsion polymerization. Also prepared were compositions containing small amounts of other monomers such as acrylic acid. The characterization of these products is discussed, as is the preparation of both “ionomer” and iminated derivatives of the carboxylated terpolymers.
Molecular weight distribution and stereoregularity of polypropylenes produced with VCl4–AlEt2Cl catalyst
Authors: Doi Yoshiharu , Kinoshita Jiro , Morinaga Akio , Keii Tominaga 
Published: April 2003

AbstractDependences of the molecular weight distribution and stereochemical regulation of the polypropylenes produced with VCl4–AlEt2Cl catalyst on the polymerization temperature were examined. The molecular weight distributions of the polymers obtained at temperatures below −40°C were unimodal and narrow (Mw/Mn ≤ 2). The molecular weight distributions obtained at higher temperatures (above −21°C) were bimodal with one narrow distribution and one wide one (Mw/Mn > 2), and the polymer fraction of the wide distribution increased with the polymerization temperature. The fractional amount of (CH2)2 groups in the polymers, which corresponds to tail‐to‐tail linkage of two propylene units, increased to a maximum at −21°C followed by a gradual decrease with the polymerization temperature. The production of isotactic polymers was confirmed at temperatures above −21°C. From these data, it is concluded that only the homogeneous form of the catalyst system is responsible for the polymerization at temperatures below about −21°C while the heterogeneous form appears and catalyzes the polymerization together with the homogeneous one at temperatures above −21°C.
Equilibrium anionic polymerization of β‐methoxypropionaldehyde
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Ohsawa Shinji 
Published: April 2003

AbstractAnionic polymerization of β‐methoxypropionaldehyde (MPA) was carried out in tetrahydrofuran (THF) by using benzophenone–monolithium complex as an initiator. An equilibrium between polymerization and depolymerization was observed at a temperature range of −90 to −70°C. From the temperature dependence of the equilibrium monomer concentration, thermodynamic parameters for the polymerization of MPA in THF were evaluated as follows: ΔHss = −4.8 ± 0.2 kcal/mole, ΔHSS = −22.4 ± 1.3 cal/mole‐deg, and (Tc)ss = −59°C. The thermodynamic change upon the conversion of liquid monomer to condensed polymer was computed from both the partial mixing energy of MPA with THF and the linear relationship between the equilibrium volume fraction of MPA monomer and that of the resulting polymer: ΔH1c = −4.7 ± 0.2 kcal/mole, ΔS1c = −19.5 ± 1.3 cal/mole‐deg, and (Tc)1c = −35°C.
Alternating copolymerization of styrene and methyl α‐chloroacrylate with diethylaluminum chloride
Authors: Hirabayashi Tadamichi , Yokota Kenji 
Published: April 2003

AbstractThe alternating copolymerization of styrene and methyl α‐chloroacrylate (MCA) with diethylaluminum chloride (Et2AlCl) in benzene at 0°C has been investigated. The copolymer has an equimolar composition irrespective of the feed monomer composition, the copolymer yield and the amount of Et2AlCl used. The copolymerization proceeds first very rapidly and then rather slowly after attaining a certain yield which varies proportionally to the amount of Et2AlCl used. A maximum copolymer yield is observed at about 60% MCA feed composition. The 1H‐NMR analyses of dyad, triad, and pentad of the alternating deuterated α‐d‐St‐MCA copolymer indicate that the configuration of this copolymer can be explained by a single parameter, coisotacticity σ(σ = 0.69). A favorable mechanism of the alternating propagation as well as of the stereoregularity control is discussed.
Sequence distribution of 1,4 and 3,4 units in polyisoprenes
Authors: Tanaka Yasuyuki , Sato Hisaya , Ogura Atsuko , Nagoya Ichiro 
Published: April 2003

AbstractThe 13C‐NMR spectra of hydrogenated polyisoprenes were investigated. Polyisoprenes containing various ratios of 1,4 and 3,4 units were prepared with n‐BuLi/Et2O and were hydrogenated by using p‐toluenesulfonylhydrazide. 13C‐NMR signals of the hydrogenated polymers were assigned for the triad sequences
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arising respectively from the 1, 4 and 3, 4 units of polyisoprenes. On the basis of these assignments it was confirmed that 1,4 and 3,4 units were randomly distributed in the polyisoprenes prepared with n‐BuLi and that these polymers did not contain appreciable amounts of head‐to‐head or tail‐to‐tail 1,4 linkages.
Monomer sequence distribution in α‐methylstyrene–methacrylonitrile copolymer
Authors: Kenney James F. 
Published: April 2003

AbstractThe sequence distributions of α‐methylstyrene‐methacrylonitrile copolymers have been determined quantitatively as a function of monomer feed composition and conversion at 60°C by use of the run‐number concept. The azeotropic copolymer was found to be highly alternating. For this copolymer the data showed that 83% of the diad placements took the form of an AMS unit followed by a MAN unit, or vice versa. The triad sequence in which an AMS unit is centered between two MAN units was 92%. It was found that the AMS‐AMS diad sequence is only 2%, and there were no AMS‐AMS‐AMS triad sequences in the copolymer. The sequence distributions were correlated with Izod impact strength and heat‐deflection temperature properties.
Homogeneous polyblend of poly(vinyl chloride) with α‐methylstyrene–methacrylonitrile–ethyl acrylate terpolymer
Authors: Kenney James F. 
Published: April 2003

AbstractBlends of poly(vinyl chloride) (PVC) and α‐methylstyrene–methacrylonitrile–ethyl acrylate (AMS‐MAN‐EA) terpolymer have been prepared and properties studied. The polyblends are unusual inasmuch as they are transparent and possess a single glass transition; therefore, they are homogeneous. The single Tg suggests a single‐phase system. The polyblends exhibit rarely observed polymer–polymer compatibility.
Chemorheology of linear polymers
Authors: Murakami Kenkichi , Nakanishi Hiromasa 
Published: April 2003

AbstractThe structural changes brought about by chemical reactions are reflected in the viscoelastic behavior of polymers. Viscoelastic behavior induced by such chemical reactions is called chemorheology. This phenomenon is not readily observed in linear polymers, because molecular flow by diffusion is generally much more rapid than relaxation or flow caused by chemical reaction. It has become possible, however, to treat chemorheology of linear polymers theoretically by taking such physical flow into consideration. The experimental results for linear polystyrene compared with the theoretical ones are described in this paper. Good agreement between theoretical results and experimental ones is obtained for monodisperse polystyrene with low concentration of accelerators.
Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation
Authors: Daňhelka J. , Kössler I. , Boháčková V. 
Published: April 2003

AbstractTwo samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone‐water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran. Tetrahydrofuran appeared to be a more suitable solvent. The molecular weights of fractions obtained by the elution fractionation were determined by the light‐scattering method in tetrahydrofuran. The width of fractions was determined by the GPC method (average Mw/Mn = 1.37); the [η] values and the Mark‐Houwink constants (K = 5.3 × 10‐3, a = 0.84) for tetrahydrofuran at 25°C were determined. The calibration curve for the GP method was constructed by means of the fractions thus obtained; it was demonstrated that the universal calibration curve according to Benoit can also be used. It was demonstrated that the molecular weight distribution of cellulose can be conveniently determined by conversion into CTC followed either by the elution fractionation (for preparative purposes) or by fractionation by the GPC method (for analytical purposes).
Photopolymerization via the Paterno‐Büchi reaction. II. Reaction of aromatic diketones with furans
Authors: Andrews D. J. , Feast W. J. 
Published: April 2003

AbstractAttempts to photopolymerize 1:1 mixtures of furan and aromatic diketones of the benzophenone type by irradiation of benzene solutions at 350 nm were unsuccessful. An alternative route via furan‐diketone 2:1 adducts was more successful but was complicated by the intervention of hydrogen abstraction reactions in competition with oxetane formation, leading to crosslinking and insolubilization in some cases.
Polyfluoreoethers from 1,1,5,5‐tetrahydryl‐F‐1,5‐pentanediol and polyfluoroaromatic and polyfluoroheteroaromatic compounds
Authors: Johncock Peter , Hewins Maurice A. H. , Cunliffe Anthony V. 
Published: April 2003

AbstractThe use of the Williamson reaction to prepare polyfluoroethers, [OArOCH2(CF2)3CH2]n from 1,1,5,5‐tetrahydryl‐F‐1,5‐pentanediol and polyfluoroaromatic and polyfluoroheteroaromatic compounds was investigated. Fluorine NMR spectroscopy was used to determine the structures of the resultant polymers. F‐Biphenyl and 1,5‐bis(F‐2‐pyridyloxy)‐1,1,5,5‐tetrahydryl‐F‐pentane (BPFP) afforded the polymers where Ar is 4,4′‐C6F4C6F4 and
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respectively. The polymer prepared from F‐pyridine differed from that obtained from BPFP in that it had an irregular structure and contained 2,4′‐ as well as 2,2′ ‐ and 4,4′‐linked rings. F‐Benzene, 4‐(1,1‐dihydryl‐F‐butoxy)‐F‐pyridine, and F‐pyrimidine each gave materials having copolymer structures. The inherent viscosities of the polymers depended on the polyfluorocyclic compound used and ranged from 0.05 to 0.2 dl/g. The heterocyclic polymers were elastomeric. The polymers from F‐pyridine and BPFP had the lowest glass transition temperatures (∼−10°C), and started to lose weight (by thermogravimetry) at ∼300°C in oxygen and at ∼350°C in nitrogen.
Effects of diethylzinc in alkyllithium‐initiated polymerizations
Authors: Hsieh H. L. 
Published: April 2003

AbstractIn an alkyllithium‐initiated polymerization of butadiene or styrene, dialkylzinc complexed with the initiator and effectively increased the initiation rate. This is particularly true with initiator of low solubility due to its very high state of aggregation. Dialkylzinc also complexes with the aggregated polymer‐lithium molecules to give a lower apparent solution viscosity. In the presence of a base such as tetrahydrofuran, diethylzinc served as chain‐transfer agent.
Reactivity changes during polyimide formation
Authors: Hodgkin J. H. 
Published: April 2003

AbstractThe raactivity changes which occur in diamine monomers during polymide formation were investigated. A series of aromatic diamines were reacted with three aromatic anhydrides (including 1,4,5,8‐naphthalene tetracarboxylic dianhydride) under different conditions and the products isolated and identified. There was a great range of reactivity changes depending on the conjugation between the two amino groups of the diamine monomer. For highly conjugated groups, imide formation at one group can prevent any reaction at the other, and hence polymer formation is curtailed.
Ferric oxide‐catalyzed polymerization of methyl methacrylate
Authors: Moustafa A. B. , Abd‐El‐Hakim A. A. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10−5 mole/l.‐sec to 11.8 × 10−5 mole/l.‐sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 106 in the absence of ferric oxide to 2.8 × 105 when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 105 at 30°C to 2.2 × 105 at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 104 to 5.3 × 105 and from 3.4 × 105 to 8.9 × 105 as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferric oxide, respectively.
Poly(vinyl alcohol) hydrogels: Reinforcement of radiation‐crosslinked networks by crystallization
Authors: Peppas Nikolaos A. , Merrill Edward W. 
Published: April 2003

AbstractAqueous poly(vinyl alcohol) solutions were crosslinked via electron‐beam irradiation to form transparent hydrogels of varying crosslinking densities. Typical crosslinked hydrogels with Mc between 3500 and 8000 were weak, easily shattered, nonextensible materials with very low tensile moduli (up to 70 psi) and tensile strengths at break (less than 10 psi). Reinforcement by induction of partial crystallization was accomplished by a two‐stage drying process, consisting of a slow dehydration stage at room temperature and an annealing stage at elevated temperatures, which was mainly responsible for the introduction of the crystallites. The swollen hydrogels after the annealing process had crystallinities widely varying between 30 and 65% and polymer volume fractions between 30 and 60%, depending on the temperature‐time history of the specimen. These materials showed greatly improved mechanical properties (modulus, ultimate tensile strength, tear strength), as compared to the uncrystallized hydrogels.
Metalation of unsaturated polymers by using activated organolithium compounds and the formation of graft copolymers. II
Authors: Halasa A. F. , Mitchell G. B. , Stayer M. , Tate D. P. , Oberster A. E. , Koch R. W. 
Published: April 2003

AbstractPolybutadiene was successfully metalated by use of tert‐butyllithium activated with alkoxides of Group I metals without chain degradation. The metalated polymer was grafted with styrene and 1,3‐butadiene to give novel graft copolymers of varying microstructure. This metalating system was found to be highly efficient; however, its catalyst effectiveness is less than that of organolithium‐TMEDA metalation agent.
Effect of evolved hydrogen fluoride on radiation‐induced crosslinking and dehydrofluorination of poly(vinylidene fluoride)
Authors: Makuuchi Keizo , Asano Masaharu , Abe Toshihiko 
Published: April 2003

AbstractPoly(vinylidene fluoride) (PVdF) was irradiated by 60Co γ‐rays with and without potassium hydroxide (KOH) under vacum. KOH tablets were added to absorb completely hydrogen fluoride (HF) which is the main volatile product of radiolysis of PVdF in the irradiation cell. In the presence of HF, the rates of radiation‐induced crosslinking and dehydrofluorination of PVdF were lower than those in the absence of HF. The experimental results are discussed from the standpoint of stabilization of alkyl free radicals in PVdF by reaction with hydrogen fluoride.
Copolymerization of ethylene sulfide and carbon disulfide
Authors: Soga Kazuo , Imamura Hayao , Sato Masaru , Ikeda Sakuji 
Published: April 2003

AbstractEthylene sulfide was found to copolymerize with carbon disulfide to give poly(ethylene trithiocarbonate) in the presence of Hg(SC4H9)2, Zn(C2H5)2, or Cd(C2H5)2, which are well known as the effective catalysts for the coordinated anionic copolymerization of episulfides. The structure and the composition of the copolymer was determined by the infrared and NMR spectra. To establishe the mechanism of the copolymerization, the reaction of carbon disulfide and Hg(SC4H9)2, and also the ring‐opening polymerization of ethylene trithiocarbonate were examined. Carbon disulfide was found to insert easily into the metal‐sulfur bond of Hg(SC4H9)2 under the experimental conditions of the copolymerization. On the other hand, the ring‐opening polymerization of ethylene trithiocarbonate did not take place with these catalysts, occurring only with the use of sulfuric acid. From these results, the mechanism of the copolymerization was discussed.
Radical polymerization of butadiene‐1‐carboxylic acid
Authors: Bando Yoshihumi , Minoura Yuji 
Published: April 2003

AbstractThe homopolymerization and copolymerization of butadiene‐1‐carboxylic acid (Bu‐1‐Acid) (M1) were studied in tetrahydrofuran at 50°C with azobisisobutyronitrile as an initiator. The initial rate of polymerization was proportional to [AIBN]1/2 and [Bu‐1‐Acid]1. The overall activation energy for the polymerization was 22.87 kcal/mole. For copolymerization with styrene (M2) and acrylonitrile (M2), the monomer reactivity ratios r1, r2 were determined by the Fineman‐Ross method, as follows; r1 = 5.55, r2 = 0.08 (M2 = styrene); r1 = 11.0, r2 = 0.03 (M2 = acrylonitrile). Alfrey‐Price Q‐e values calculated from these values were 6.0 and +0.11, respectively. The Bu‐1‐Acid unit in the copolymer as well as the homopolymer was found from infrared and NMR spectral analyses to be composed of a trans‐1,4 bond. The hydrogen‐transfer polymerization of Bu‐1‐Acid leading to polyester was attempted with triphenylphosphine as initiator, but did not occur.
Effects of molecular weight distribution in drag reduction and shear degradation
Authors: Hunston Donald L. 
Published: April 2003

AbstractA reduction of frictional drag in turbulent flow was obtained in benzene by using three monodisperse polystyrene samples having weight‐average molecular weights of 1.8, 4.1 and 7.1 × 106. By testing these polymers individually and in mixtures, data were obtained for samples with known molecular weight distributions. The drag reduction of these samples was studied as a function of polymer concentration and flow rate so that a generalized picture of the effects of polydispersity could be obtained. These results are used to help explain much of the behavior that was observed for polystyrene and other polymers. This includes the fact that the polystyrene samples exhibit a remarkably high resistance to the loss of drag reduction via degradation in turbulent flow. Such experiments indicate that drag reduction and degradation depend strongly on molecular weight distribution. Thus a molecular level interpretation of experimental results cannot be made unless the effects of the distribution are considered.
Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. II. Kinetics of polymerization
Authors: Lee C. L. , Marko O. W. , Johannson O. K. 
Published: April 2003

AbstractThe kinetics of polymerization were investigated for the polymerization of hexamethylcyclotrisiloxane (D3) in toluene with methanol or water as an initiator, benzyltrimethylammonium bis(o‐phenylenedioxy)phenylsiliconate as a catalyst, and dimethyl sulfoxide (DMSO) as a promoter. The rate of initiation was found to be comparable with both water and methanol. Addition of catechol drastically reduces the rate of initiation. The rate of propagation was found to be dependent upon the catalyst, DMSO, catechol and the aging of the catalyst solution. Two types of functional groups were postulated to be present during the propagation reaction, i.e., SiOH (dormant form) and SiONR4 (living form). The former can be converted to the latter by R4NOH derived from hydrolysis of catalyst. A postulated mechanism of polymerization with biscatecholsiliconate is presented.
Short branching in poly(vinyl alcohol). II. NMR spectroscopy of model polymers of short‐branched poly(vinyl alcohol)
Authors: Nozakura Shun‐Ichi , Morishima Yotaro , Iimuro Hiroyuki , Irie Yoshio 
Published: April 2003

AbstractIn order to develop a method of measuring the amounts of short branches in PVA, an NMR study was made of a model poly(vinyl alcohol) having short branches, one or two monomer units in length. Detection and estimation of the short branches were shown to be possible by using the 13C‐NMR spectra of PVA and the 1H‐NMR of acetylated PVA. In the 19F‐NMR spectra of trifluoroacetylated model PVA, the resonance peaks of primary and tertiary alcohols in the branching structure were not well resolved from that of secondary alcohol of the main chain.
Active polycondensation of diethyl 2,3,4,5‐tetrahydroxyadipate with diamines
Authors: Ogata Naoya , Sanui Kohei , Hosoda Yoshikazu , Nakamura Hiroyuki 
Published: April 2003

AbstractPolycondensation of diethyl 2,3,4,5‐tetrahydroxyadipate with various diamines was carried out in solutions under mild conditions. The polycondensation reaction occurred rapidly even at room temperature in polar solvents such as alcohols, and in aqueous solution a cyclic product was obtained instead of linear polymers although the reaction with diamines was completed within several minutes. Polymers obtained from diethyl 2,3,4,5‐tetrahydroxyadipate were a linear polyamide having pendant hydroxyl groups, which decomposed on heating at around 200°C. A solid‐phase polycondensation of the precursor polyamide yielded a high molecular weight polyamide.