bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnesium chloride supported catalysts for olefin polymerization. XIX. Titanium oxidation states, catalyst deactivation, and active site structure
Authors: Chien James C. W. , Weber Siegfried , Hu Youliang 
Published: April 2003

AbstractA precise method for the determinations of Ti+2, Ti+3 and Ti+4 was developed. The CW‐procatalyst before activation contains mostly Ti+4 ions with 6% Ti+3 and 4% Ti+2 ions. Activation with AlEt3 alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti+3 and 29% Ti+2. Reduction is incomplete when methyl‐p‐toluate was present as external Lewis base during activation: at 25°C the distribution of Ti+4 : Ti+3 : Ti+2 is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti+n]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti+n] was determined for the CW‐catalyst during the course of a decene polymerization; they were found to be Ti+4 : Ti+3 : Ti+2 = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti+4 species by AlEt3 or 3AlEt3/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.
Laser‐initiated polymerization of lauryl methacrylate: Laser repetition rate effect
Authors: Hoyle Charles E. , Trapp M. A. , Chang C. H. 
Published: April 2003

AbstractThe photoinitiated polymerization of lauryl methacrylate with a pulsed excimer laser source is highly dependent on the laser repetition rate and the absorbance (optical density) of the photoinitiator. The GPC chromatograms of poly(lauryl methacrylate) generated by the laser‐initiated polymerization of lauryl methacrylate decrease in size and shift to lower molecular weight species with increasing repetition rate. In addition, the polymers produced at high laser repetition rates are characterized by a number of distinct narrow molecular weight GPC peaks. The decrease in polymerization efficiency is especially pronounced at laser pulsing frequencies greater than 3 Hz.
Structure of macronet styrene polymer as studied by inverse steric exclusion chromatography and by selective sulfonation
Authors: Jeřábek K. , Setínek K. 
Published: April 2003

AbstractThe structure of macronet styrene polymer in original, partially sulfonated and fully sulfonated form was studied using inverse steric exclusion chromatography. By alternative measurements of the partially sulfonated sample in water and in tetrahydrofuran, it was possible to characterize separately sulfonated and unsulfonated domains. It was found that the polymer contains 10–15% of highly expandable polymer mass and the rest is formed by much more dense polymer skeleton.
Effect of γ‐ray and photoirradiation on very low density polyethylene
Authors: Geetha R. , Torikai A. , Yashida S. , Nagaya S. , Fueki K. 
Published: April 2003

AbstractThe fourth type of polyethylene—very low density polyethylene (VLDPE)—has been developed very recently. VLDPE is a copolymer of ethylene and 1‐butene. The radiation and photo degradation of VLDPE was studied using gel, FT‐IR, and UV spectral measurements. Mechanical tests were also done; the rate of gel and carbonyl formation was high. End methyl CH3 group was found to increase in the case of radiation degradation. The initial modulus was very low indicating the rubbery nature in the copolymer. VLDPE was found to be highly resistant to radiation‐induced degradation than linear low density polyethylene. VLDPE is highly susceptible to thermal effects.
Grafting onto carbon black by the reaction of reactive carbon black having epoxide groups with several polymers
Authors: Tsubokawa Norio , Kuroda Akio , Sone Yasuo 
Published: April 2003

AbstractThe grafting of functional polymers onto carbon black surface by the reaction of epoxide groups introduced onto the surface was investigated. The introduction of epoxide groups was achieved by the reaction of the phenolic hydroxyl and carboxyl groups on carbon black with chloromethyloxirane in the presence of sodium hydroxide. The amount of epoxide groups introduced onto the channel black Neospectra II was equal to 0.40 meq/g. The epoxide groups were reacted with polypropylene glycol, silicone diol (SDO), silicone diamine (SDA), and polyethyleneimine to give polymer‐grafted carbon blacks. For example, the percentage of grafting of SDO (Mn = 1.0 × 103) and SDA (Mn = 3.9 × 103) reached to 23.6 and 67.2%, respectively. The percentage of grafting increased with the molecular weight (Mn) of the polymers, while the number of grafted chain (Gn) decreased. In the case of SDO, the relationship between Mn and Gn was found to be Gn = 4.68 × 10−2 M. The carbon black obtained from the reaction gave stable colloidal dispersions in tetrahydrofuran and the stability of dispersion increased with an increase in the percentage of grafting.
Temperature dependence of unperturbed dimensions for isotactic poly(2‐hydroxyethyl methacrylate)
Authors: Oh Seok Heon , Jhon Mu Shik 
Published: April 2003

AbstractThe unperturbed dimensions of isotactic poly(2‐hydroxyethyl methacrylate) (PHEMA) were evaluated from intrinsic viscosity measurements in water, ethanol, 1‐propanol, 2‐propanol, and 2‐butanol under θ conditions over the temperature range of 3.7–32.1°C. The smallest value of unperturbed dimensions (Kθ) and the largest negative temperature dependence of unperturbed dimensions and the polymer–solvent interaction parameter (B) were obtained in aqueous θ solvent relative to the corresponding organic θ solvents. These results were interpreted by the hydrophobic interaction between the hydrophobic groups of isotactic PHEMA and water solvent. The temperature coefficient of the unperturbed dimensions, d ln〈r〉/dT, obtained in this study has a negative value of −1.44 × 10−3 deg−1 under chemically similar θ solvents such as ethanol, 1‐propanol, 2‐propanol, and 2‐butanol where specific solvent effects are eliminated or minimized. In order to obtain the thermodynamic parameters for mixing between isotactic PHEMA and solvents, the plots of the polymer–solvent interaction parameter versus reciprocal absolute temperature (1/T) were carried out. Both the entropy of dilution and enthalpy of dilution show the negative values for water, methanol, and t‐butanol, whereas the positive ones for ethanol, 1‐propanol, 2‐propanol, and 2‐butanol. This result indicates that the solution of isotactic PHEMA behave as exothermal systems in the former class of solvents and endothermal ones in the latter class of solvents.
Polymerization reactivity of unsaturated end group generated during the disproportionation in termination reaction of methyl methacrylate polymerization: A study using model compounds
Authors: Tanaka Hitoshi , Kawai Hirofumi , Sato Tsuneyuki , Ota Tadatoshi 
Published: April 2003

AbstractPolymerizations of some vinyl monomers were carried out with 2,2′‐azobisisobutyronitrile at 60°C in the presence of a methyl methacrylate (MMA) dimer (I) or a MMA polymer (II) with a double bond at their ends to confirm the polymerization reactivity of unsaturated end group generated during the disproportionation in termination reaction of MMA polymerization. It was found that the polymerizations of α‐monosubstituted monomers have been much retarded than those of α,α‐disubstituted monomers by the addition of I. Kinetic study on MMA and methyl acrylate polymerizations showed that the rate constant for the reaction of a propagating radical with I was 5.4 and 29.2 L/mol s in their polymerizations, respectively. ESR study using I and II suggested that an addition reaction was a predominant mechanism for the reaction of an unsaturated end group with a radical rather than a hydrogen abstraction.
Stereoregularity of fractionally crystallized poly(propylene oxide) samples by 13C‐NMR spectroscopy
Authors: Uğur N. , Alyürük K. 
Published: April 2003

AbstractSeveral stereoregular poly(propylene oxide) (PPO) samples were synthesized employing either trimethyl aluminum hydrolyzates or Pruitt–Baggett type catalysts. Dilute isooctane solutions of these samples were fractionally crystallized by stepwise cooling from 333 K down to 273 K. The fractions which dissolve at 273 K were noncrystallizable and were further fractionated by GFC. The isolated fractions were characterized by 13C‐NMR, DSC, and viscometry techniques. Both structural (head‐to‐head and tail‐to‐tail linkages) and steric (syndiotactic dyads) irregularities were found in otherwise isotactic chains and their abundance apparently increased as the melting point and the chain length of the fractions decreased.
Thermal behavior of amide substituted diacetylenes
Authors: Kato Jinichiro , Nakamura Katsuyuki , Yamazaki Satoru , Tokushige Kensaku , Amano Toshihiko 
Published: April 2003

AbstractDiacetylenes substituted with various amide groups were prepared and their solid‐state polymerization behavior was studied. A calorimetric study of the isothermal polymerization of 1,6‐diacetylamino‐2,4‐hexadiyne was performed in detail. This compound has an extremely high reactivity. The reaction proceeded very quickly and the ultimate conversion reached over 40% slightly above room temperature. The feature of the reaction resembles those observed in the solid‐state polymerization of other diacetylene compounds, i.e., the reaction proceeds slowly in the initial stage, but the rate of reaction increases drastically at about 5% conversion to polymer. Quantitative conversion, however, was not attained at any temperature, and the reaction leveled off within 1.5 h. It is assumed that the reaction cannot continue owing to the distortions generated in the crystals during the polymerization process. The crystalline state of the polymer obtained was highly disordered.
Synthesis, surface accumulation, and micellar properties of amphiphilic block copolymers
Authors: Chujo Yoshiki , Kohno Kenji , Usami Noriyuki , Yamashita Yuya 
Published: April 2003

AbstractAmphiphilic block copolymers, i.e., poly(methyl methacrylate)‐b‐poly(2‐dimethylethylammoniumethyl methacrylate), were synthesized by the reaction between two prepolymers. Carboxyl‐terminated poly(methyl methacrylate) and hydroxyl‐terminated poly(2‐dimethylaminoethyl methacrylate) were prepared by radical polymerization of the corresponding monomers in the presence of thioglycolic acid and 2‐mercaptoethanol as a chain transfer agent, respectively. Two condensation methods, i.e., DCC and the acid chloride method, were used for the reactions of these prepolymers. The subsequent quarternization produced the amphiphilic block copolymers. Surface property of poly(methyl methacrylate) films containing this amphiphilic block copolymer was examined by measuring contact angles for water. The addition of only 0.5 wt% of the block copolymer was sufficient to make poly(methyl methacrylate) surfaces hydrophilic. The block copolymer formed a polymeric micelle in acetone–water mixed solvent.
Molecular orbital calculations of poly(vinylidene fluoride) and its model compounds
Authors: Takakubo M. , Teramura K. 
Published: April 2003

AbstractCalculations of dipole moments of poly(vinylidene fluoride)(PVDF) and its model compounds were performed by the MNDO method. 2,2‐difluoropropane as a model compound was found to have a dipole moment of 8.97 × 10−30C m (2.69 D). It was in satisfactory agreement with a previously obtained experimental value, 8.01 × 10−30C m. Dipole moments of two other model compounds, tetrafluoropentane and octafluorononane, were calculated to be 1.70 and 3.24 × 10−29C m, respectively. Ratios of repeat unit moments of the second and third compounds to the first compound moment were equal to 0.95 and 0.90, respectively. These were nearly identical with a theoretical ratio, 0.96, derived from the free rotation model of a polymer chain. The calculated dipole moments were considered to reflect the molecular structures in which free rotations of nearly tetrahedral bond angles might be allowed around C—C links. Dipole moments of each monomer unit for three polymorphs of PVDF, Form I, II, and III were calculated to be 7.64, 5.40, and 5.07 × 10−30C m, respectively. Ratios of the three moments to the first model compound moment were found to be 0.85, 0.60, and 0.57. The decreasing order of the three factors suggests that orientations of monomer unit dipoles are more and more interdependent, and free internal rotations around skeletal bonds are more and more hindered, when the conformation varies from Form I to III. Also it was confirmed that the atomic charge distributions of the three polymorphs were very similar, and that the difference in dipole moments were primarily caused by conformation changes of the polymer chain.
Synthesis of polyester by novel addition reaction of active di‐ester with di‐epoxy compound
Authors: Nishikubo Tadatomi , Iizawa Takashi , Matsumura Takahisa 
Published: April 2003

AbstractSome polyesters having pendant ether groups were synthesized with high yield by polyaddition of active di‐esters such as di(S‐phenyl)thioisophthalate (PTIP) and di(S‐phenyl)thiosebacate with di‐epoxy compounds such as diglycidyl ether of bisphenol A (BPGE) and diglycidyl ether of ethylene glycol using some quaternary ammonium salts as a catalyst. The degree of polymerization in the reaction of PTIP with BPGE was strongly affected by the kind of reaction solvent, monomer concentration, the reaction temperature, and the kind of catalyst. As a result, it is found that tetrabutylammonium chloride has the highest catalytic activity for the polyaddition of PTIP with BPGE, and dimethylsulfoxide is a suitable solvent for the reaction system.
Synthesis of aliphatic–aromatic polyamides by palladium‐catalyzed polycondensation of aliphatic diamines, aromatic dibromides, and carbon monoxide
Authors: Yoneyama Masaru , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractAliphatic–aromatic polyamides were synthesized by the palladium‐catalyzed polycondensation of aliphatic diamines, aromatic dibromides, and carbon monoxide. The effects of variables, such as the kind and amount of base, reaction temperature, and the kind of palladium catalyst were investigated in detail on the reaction of hexamethylenediamine and bis(4‐bromophenyl) ether with carbon monoxide. Inherent viscosities of the polyamides were between 0.13 and 1.21 dL/g and varied markedly with the structure of the diamine component. Solubility of the polyamides decreased with increase of chain length of aliphatic diamines, and the polyamides derived from p‐dibromobenzene was insoluble in organic solvents except for m‐cresol. Polyamides obtained from primary aliphatic diamines began to decompose at 210–250°C in air due to decomposition of the aliphatic chain.
Polymer drying. II. Replicated time‐studies of molecular desorption from liquid swollen poly(styrene‐co‐divinylbenzene) before and after transition from the gel‐state to the glass‐state
Authors: Errede L. A. , Van Bogart J. W. C. 
Published: April 2003

AbstractA total of 90 time‐studies were monitored gravimetrically in order to establish the parameters that affect the reproducibility of the kinetic changes that occur sequentially when liquid‐saturated poly(styrene‐co‐divinylbenzene) [poly(Sty‐co‐DVB)] particles, enmeshed in a matrix of polytetrafluroethylene (PTFE) microfibers, are allowed to evaporate to apparent dryness at constant temperature. The test liquids were toluene, chloroform, and acetone. The absorbent samples were made from six different compositions of polymer particles, the DVB mode fractions, x, of which increased from 0.01 to 0.11. The weight, Wg, of residual sorbed molecules per gram of polymer at the glass‐transition composition was constant despite the large differences in x. Thereafter the weight of residual sorbed molecules was given by a linear combination of up to six exponential decay functions, which indicated that these molecules were “locked” into six different types of molecular environments (i.e., populations) created by the change from the gel‐state to the glass‐state. The fractions of Wg in the populations with the fastest (k1) and the slowest (kn) decay rates were usually less than those with intermediate decay rates. The logarithm of ki in a given time study was a linear function of i, the numerical sequence of decreasing k.
Depolymerization of poly(ethylene terephthalate) recycled from post‐consumer soft‐drink bottles
Authors: Baliga Satish , Wong Wing T. 
Published: April 2003

AbstractPoly(ethylene terephthalate), recycled from post‐consumer soft‐drink bottles, is depolymerized by glycolysis in excess ethylene glycol at 190°C in the presence of a metal acetate catalyst. The glycolyzed products consist mostly of the PET monomer, bis(hydroxyethyl) terephthalate, and the dimer, and after long reaction time (up to and longer than 8 h), an equilibrium is attained between these two species. No other higher PET oligomers were detected in the study. Of the four metal acetates (lead, zinc, cobalt, and manganese) tested, zinc acetate is the best in terms of the extent of depolymerization, that is, the relative amount of monomer formed. The presence of green pigment in one type of recycled PET apparently has no effects on the glycolysis reaction.
MS and GC–MS studies on phthalocyanine monomers
Authors: Achar B. N. , Fohlen G. M. , Keshavayya J. 
Published: April 2003

AbstractPhthalocyanines are a class of macrocyclic organic compounds known for their high tinctorial properties, thermal stability, chemical inertness, catalytic activity, and photoconductivity. A mass spectral study on metal phthalocyanines presented many difficulties because of their excellent thermal stability. The present work deals with MS and GC–MS studies of phthalocyanine, copper, and nickel phthalocyanine monomers at various temperatures. Tentative mechanism for the modes of fragmentation is proposed.
Graft copolymerization of acrylamide onto casein: A kinetic study
Authors: Mohan D. , Radhakrishnan Ganga , Rajadurai S. , Rao K. Venkata , Cameron Gordon G. 
Published: April 2003

AbstractPolyacrylamide has been grafted onto casein in phosphate buffer medium using potassium peroxodisulfate as initiator. The influence of synthetic variables on percent grafting, grafting efficiency, rates of conversion of monomer, and the rates of graft copolymerization have been discussed. A possible kinetic scheme based on experimental results has been derived.
Solvent effect on the radical polymerization of di‐n‐butyl itaconate
Authors: Sato Tsuneyuki , Morita Naoki , Tanaka Hitoshi , Ota Tadatoshi 
Published: April 2003

AbstractSolvent effect on the polymerization of di‐n‐butyl itaconate (DBI) with dimethyl azobisisobutyrate (MAIB) was investigated at 50 and 61°C. The solvents used were found to affect significantly the polymerization. The polymerization rate (Rp) and the molecular weight of the resulting polymer are lower in more polar solvents. The initiation rate (Ri) by MAIB, however, shows a trend of being rather higher in polar solvents. The stationary state concentration of propagating poly(DBI) radical was determined by ESR in seven solvents. The rate constants of propagation (kp) and termination (kt) were evaluated by using Rp, Ri, and the polymer radical concentration observed. The kp value decreases fairly with increasing polarity of the solvent used, whereas kt is not so influenced by the solvents. The solvent effect on kp is explained in terms of a difference in the environment around the terminal radical center of the growing chain. Copolymerization of DBI with styrene (St) was also examined in three solvents with different physical properties. The poly(DBI) radical shows a lower reactivity toward St in a more polar solvent.
Synthesis, characterization, and thermal stability of bismaleimides derived from maleimido benzoic acid
Authors: Rao B. S. 
Published: April 2003

AbstractBismaleimides containing ester, amide, urethane, and imide groups in the backbone were synthesized from maleimido benzoic acid via its acid chloride or isocyanate with 4,4′‐dihydroxy‐diphenyl‐2,2‐propane, 3,3′‐diamino diphenyl sulfone, and 3,3′,4,4′‐benzophenone tetracarboxylic acid anhydride by simple condensation or addition reaction. The new bismaleimides are characterized by IR, 1H‐NMR, and elemental analysis. DSC studies of these bismaleimides indicated a curing exotherm in the temperature range 150–270°C with heat of polymerization 30–50 J/g. Thermogravimetric analysis of the uncured resins showed high thermal stability and char yield for imide containing bismaleimide. The observed char yields of the bismaleimide resins are in accordance with the calculated C/H ratios.
Poly 4‐(3‐chloropropyl)styrene: Syntheses of monomer, polymerization, characterizations, and thermal degradation of polymer
Authors: Montheard J. P. , Boinon B. , Benayad B. 
Published: April 2003

Abstract4‐(3‐Chloropropyl)styrene, a new functionalized styrene, has been synthesized in three steps from 3‐chloropropylbenzene or in two steps from 4‐chlorostyrene, and the polymerization has been carried out in bulk, with azobisisobutyronitrile as an initiator. The polymer has been characterized by its molecular weights, glass transition temperature, and NMR spectra. Thermal degradation has also been studied and volatile fractions characterized by GC‐MS. A mechanism of depolymerization, very similar to those of various polystyrenes, can be proposed.
Synthesis of nearly monodisperse poly(α‐methylstyrene)s containing two Si atoms and an allyl group and the application to resist
Authors: Saigo Kazuhide , Watanabe Fumitake 
Published: April 2003

AbstractThe anionic polymerizations of 4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene (1), 4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene (2), and 4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene (3) have been conducted. Nearly monodisperse poly(4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene) (4), poly(4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene) (5), and poly(4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene) (6) were obtained. The Tgs of 4, 5, and 6 are 100.5, 39.0, and 30.5°C, respectively. Among these, 4 has attracted most interest because of a high Tg (100.5°C) and a high Si content (20.5%, w/w). Therefore, a near‐UV resist (DMAS‐A) composed of 4 and a bisazide has been developed as a top resist layer for a bilayer system.
Ethylene polymerization catalysts from supported organotransition metal complexes: I. Pentadienyl derivatives of Ti, V, and Cr
Authors: Smith P. D. , McDaniel M. P. 
Published: April 2003

AbstractA new class of ethylene polymerization catalysts, namely the bis‐(2,4‐dimethyl pentadienyl) derivatives of titanium, vanadium, and chromium, have been synthesized and tested. When supported on a variety of inorganic carriers, these compounds yielded 0.2–1.0 million g polymer/g metal/h under typical slurry conditions. Sensitivity to H2 as a molecular weight regulator varied among the three metals, but in the absence of H2 all produced ultrahigh‐molecular‐weight polyethylene. The molecular weight distribution varied from moderately narrow to very broad (bimodal) depending on the metal and the carrier. Catalyst synthesis and polymer properties are discussed.