bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of chromium residues on the stability of gas‐phase high‐density polyethylene produced by supported catalysts
Authors: Scheirs J. , Bigger S. W. , Billingham N. C.
Published: April 2003

The thermo‐oxidative stability of high‐density polyethylene (HDPE) prepared by silica supported Ziegler‐Natta, bis(triphenylsilyl)chromate and bis(cyclopentadienyl)‐chromium(II) catalyst systems was examined by chemiluminescence (CL) techniques and thermogravimetric (TG) analysis. In particular, the technique of dynamic CL in nitrogen allows the concentration of polymer hydroperoxides and the relative stability of these to be simultaneously determined. Polymer hydroperoxides in Ziegler‐Natta catalyzed HDPE are relatively stable because titanium and aluminum residues are poor pro‐oxidants compared with chromium residues. HDPE produced by bis(cyclopentadienyl)chromium(II) has a low intrinsic thermo‐oxidative stability due to the chromium‐catalyzed conversion of polymer hydroperoxides into degradation products during thermal aging. Concentrations of residual chromium as low as 1 ppm can profoundly affect the oxidative stability of the polymer and exert a much greater influence than either the extent of branching or the degree of unsaturation. The appearance of the silica catalyst support before and after gas‐phase polymerization was studied by scanning electron microscopy. During polymerization the silica support shatters and the resulting submicron fragments are dispersed throughout the polymer particles. On exposure of the nascent polymer to the atmosphere, bis(cyclopentadienyl)chromium(II) is converted to a trivalent chromium species which remains associated with the silica substrate. The presence of trivalent chromium in the poisoned chromium catalyst was confirmed by UV/visible spectrophotometry and the nature of the Cr(III) species was investigated by diffuse reflectance Fourier transform infrared (FTIR) spectroscopy. The high surface area of the catalyst residue renders it a powerful pro‐oxidant despite its low concentration. © 1992 John Wiley & Sons, Inc.
Polymeric isocyanates by nontoxic routes. II. Nucleophilic displacement reaction on chloromethyl pendant groups by alkali cyanates
Authors: Gaonkar S. R. , Srinivasan K. , Kumar G. Sudesh
Published: April 2003

The environmental regulations regarding the solvent emissions have given impetus to the formulation of powder coatings and high solids coatings which require oligomeric or polymeric crosslinkers of desired functionality. We are exploring nontoxic routes for the preparation of polymeric isocyanates and isocyanate precursors. In this article, we report nucleophilic displacement of polymer‐bound alkyl halides by cyanate ion as a novel route to polymeric isocyanate crosslinkers with no intermediacy of either phosgene or low molecular weight isocyanates. The effects of solvent and phase‐transfer catalyst on the selectivity of the reaction are discussed. © 1992 John Wiley & Sons, Inc.
Synthesis of polystyrene‐block‐polyoxyethylene for use as a stabilizer in the emulsion polymerization of styrene
Authors: Jialanella Gary L. , Firer Edward M. , Piirma Irja
Published: April 2003

Five well‐defined polystyrene‐block‐polyoxyethylene copolymers were synthesized by anionic polymerization for use as stabilizers in the emulsion polymerization of styrene. The size of the blocks and their relative weight ratios to each other were the main variables. The molecular weights of the blocks varied from M̄n = 1000–7000 for polystyrene, and M̄w = 3000–9000 for polyoxyethylene. The results of the styrene emulsion polymerization with these block copolymers as stabilizers indicate that for efficient anchoring the block length need not be more than 10 monomer units, possibly even less, and that the polyoxyethylene block M̄w = 3000 is just as capable of stabilizing the polystyrene particle as the higher molecular weight blocks. A very important factor was found to be the weight ratio of the two blocks: block copolymers with a polyoxyethylene content between 75 and 90 wt % were effective stabilizers for the emulsion polymerization of styrene © 1992 John Wiley & Sons, Inc.
Charge transfer complexes of polyimines containing trans‐1,2‐bis‐9‐carbazolylcyclobutane
Authors: Yang H. , Jin A. , Natansohn A.
Published: April 2003

Polyimines containing trans‐1,2‐bis‐9‐carbazolylcyclobutane (CzD) and a spacer of a variable number of methylene groups (3–10 and 12) were synthesized from the diformylated CzD and the corresponding aliphatic diamine. The charge transfer complexes (CTCs) of these polyimines with electron‐acceptors such as tetracyanoethylene (TCNE) and 2,4,7‐trinitro‐9‐fluorenone (TNF) were analyzed in solution and in the solid state using electronic and CP‐MAS 13C‐NMR spectra. Model studies indicate that TCNE does not form a stable complex in the solid state with CzD, while TNF forms a complex in the molar ratio of 1 : 1. Solid‐state CTCs of the polyimines with either acceptor retain some solvent which helps in formation of some supramolecular organization. After the solvent is eliminated the CTCs are amorphous and do not show decomplexation. Cross‐polarization experiments and T1ρH measurements in the solid‐state NMR spectra demonstrate that the polymer CTCs are very mobile, with a solution‐like behavior. © 1992 John Wiley & Sons, Inc.
Homogeneous catalytic hydrogenation of liquid carboxylated nitrile rubber
Authors: Bhattacharjee Susmita , Bhowmick Anil K. , Avasthi B. N.
Published: April 2003

Homogeneous catalytic hydrogenation of olefinic bonds in liquid carboxylated nitrile rubber (L‐XNBR) has been carried out selectively in the presence of nitrile and carboxyl functionality using a six‐membered cyclopalladate complex of 2‐benzoyl pyridine as catalyst. The degree of hydrogenation has been calculated from IR and NMR spectroscopic studies. For example, 68% hydrogenation has been obtained for a sample (containing 0.057 carboxyl equivalent/100 g and 26.1% acrylonitrile) under 2.7 MPa hydrogenation pressure, 0.18 mmol/L catalyst, at 333 K for 1 h in acetone solution. The overall extent of hydrogenation depends on the catalyst‐to‐double‐bond ratio. The kinetics of hydrogenation of L‐XNBR has been investigated. The reaction exhibits a pseudo‐first order dependence on the concentration of the substrate. The rate constant of the reaction is reduced by the increase in carboxyl and nitrile content of the polymer. The effect of temperature on reaction kinetics has also been studied and the activation energy of hydrogenation of L‐XNBR is 20.2 kJ/mol. Intrinsic viscosity of the polymer remains unchanged during the reaction. A significant lowering of the glass transition temperature and improvement of thermal stability have been observed on hydrogenation. © 1992 John Wiley & Sons, Inc.
Radiation‐induced graft polymerization of acrylic acid onto fluorinated polymers. I. Kinetic study on the grafting onto poly(tetrafluoroethylene‐ethylene) copolymer
Authors: Hegazy El‐Sayed A. , Dessouki Ahmed M. , El‐Assy N. B. , El‐Sawy Naeem M. , El‐Ghaffar M. A. Abd
Published: April 2003

Direct radiation‐induced grafting of aqueous acrylic acid (AAc) onto poly(tetrafluoroethylene‐ethylene) (ET) film has been studied. The effect of grafting conditions such as monomer concentration, exposure dose, dose rate, and film thickness on the grafting yield was investigated. The dependence of the grafting rate on monomer concentration was found to be 1.2 order. The dependence of the grafting rate on dose rate was found to be 0.6 order regardless of the film thickness. The relationship between the grafting rate and film thickness gave a negative first‐order dependence. The results suggest that the grafting process is mainly controlled by monomer diffusion, and it was concluded that this grafting system proceeded by the front mechanism. The swelling behavior increases linearly with degree of grafting. The electrical conductivity and mechanical properties for the trunk and grafted polymer were investigated at different irradiation doses in air and under vacuum irradiations. © 1992 John Wiley & Sons, Inc.
Preparation of dibenzofuran‐type amorphous polyetherketone by novel etherification reaction
Authors: Fukawa Isaburo , Tanabe Tsuneaki
Published: April 2003

4‐Fluorobenzophenone reacted with potassium carbonate in the presence of silica catalyst in diphenyl sulfone solvent to yield 4,4′‐dibenzoyldiphenyl ether. This new etherification reaction was extended to three difluoro aromatic ketones. 4,4′‐Bis(4‐fluorobenzoyl)diphenyl ether (I) reacted with potassium carbonate to yield a crystalline poly(oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene) (PEK) and 4,4′‐bis{4‐[4‐(4‐fluorobenzoyl)phenoxy]benzoyl}benzene (II) gave a crystalline poly(oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene‐oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene‐oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene‐carbonyl‐1,4‐phenylene)(PEKEKEKK). 2,8‐Bis(4‐fluorobenzoyl)dibenzofuran (III) or 2,8‐bis(4‐chlorobenzoyl)dibenzofuran (IV) reacted with potassium carbonate to yield a poly(oxy‐1,4‐phenylene‐carbonyl‐2,8‐dibenzofuran‐carbonyl‐1,4‐phenylene) (PEKBK). The PEKBK was a noval amorphous polymer with the glass transition temperature of 222°C and it showed excellent thermal stability [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 64–74223 (1989)]. Several amorphous dibenzofuran type polyetherketone copolymers were prepared by coplycondensation of III with 4,4′‐difluorobenzophenone (V) or 1,4‐bis(4‐fluorobenzoyl)benzene (VI) [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 1153722 (1989)]. © 1992 John Wiley & Sons, Inc.
Polymerization of coordinated monomers. XXI. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trifluoride
Authors: Sato Kota , Sakuma Yoshiro , Iwabuchi Susumu , Hirai Hidefumi
Published: April 2003

The stereo‐ and electronic structures of the binary molecular complex composed of methyl methacrylate and boron trifluoride are obtained by using an ab initio molecular orbital method with an STO‐3G basis set. The total energy change on the binary molecular complex formation is −1.3 X 10−2 Hartree (−8.2 kcal/mol). The electron transfer from methyl methacrylate to boron trifluoride and the change in the energy level of the lowest unoccupied molecular orbital of methyl methacrylate on the complex formation with boron trifluoride are much smaller than those on the complex formation with boron trichloride. A twisted form in which the dihedral angle between the vinyl plane and the ester plane is 16.9° is the most stable structure of the binary molecular complex composed of methyl methacrylate and boron trifluoride. A strong bonding overlap population between a β‐hydrogen of methyl methacrylate and a fluorine of boron trifluoride is found in this conformation. © 1992 John Wiley & Sons, Inc.
Furyl‐maleimidein situ generated ab‐monomers: Synthesis, characterization, and Diels‐Alder polymerization
Authors: Mikroyannidis John A.
Published: April 2003

2‐Furoyl chloride reacted with the monomaleamic acids 1a‐1d derived from a aromatic diamine to yield a new series of maleamic acids 2a–2d. The latter were cyclodehydrated to afford maleimides 3a‐3d which behaved as AB‐monomers for a Diels‐Alder polymerization. In addition, the monomaleamic acid 4 derived from 4‐aminophenol reacted with 2‐furoyl chloride to yield maleamic acid 5. It was cyclodehydrated to maleimide 6 which is a novel polymer precursor. The monomers were characterized by IR and 1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. Maleamic acids 2a–2d and 5 were cured at 280°C for 22 h to yield polymers which were characterized by TGA and isothermal gravimetric analysis (IGA). They were stable up to 340–376°C and afforded anaerobic char yield of 55–64% at 800°C. © 1992 John Wiley & Sons, Inc.
Ionic conductivity and compatibility studies of blends of poly(methyl methacrylate) and poly(propylene glycol) complexed with LICF3SO3
Authors: Mani R. , Mani T. , Stevens J. R.
Published: April 2003

Stable to atmospheric moisture, adhesive and transparent polymer electrolytes have been prepared by blending poly(methyl methacrylate) (PMMA) with poly(propylene glycol)‐425/LiCF3SO3 complexes. The blending of the polymers has been achieved by a method developed in our laboratory: free radical polymerization of methylmethacrylate in the polyether/salt matrix. A series of polymer blend complexes varying in PMMA content (up to 20% by weight) and oxygen/metal ratios (25, 16, and 8) have been synthesized and their properties studied. All the samples prepared in this study were found to be optically clear unlike the higher molecular weight poly(propylene glycol)‐2000 (PPG‐2000) system which required a minimum salt concentration to compatibilize a specific amount of PMMA with PPG. The mechanisms by which the salt holds the otherwise incompatible polymers together in a single phase have been investigated by FT‐IR. Our studies show a weak coupling of the ether oxygens in the PPG with the ester groups of the PMMA through the lithium cations. Discrete changes has been observed in the FT‐IR spectrum of PMMA when doped with the lithium salt hitherto unnoticed with other dopants. Gel permeation chromatography results of the PMMA samples isolated from the solid electrolytes indicate the molecular weight to vary between 43000 and 121000 with relatively narrow distributions, 1.6−2.0. The ionic conductivities of the polymer blend electrolytes were fairly high (10−5 S/cm) at room temperature. The PMMA neither significantly influenced the Tg of the blend complexes nor effected the ionic conductivities drastically. The ionic conductivity as a function of temperature followed the empirical Vogel‐Tammann‐Fulcher equation. The blending of PMMA with PPG/LiCF3SO3 complexes was found to impart good adhesiveness to the solid electrolytes while making them stable to atmospheric moisture. © 1992 John Wiley & Sons, Inc.
Characterization of propylene‐ethylene block copolymers using solid state 13C‐NMR spectroscopy
Authors: Prasad J. V.
Published: April 2003

Commercial block copolymers of propylene with ethylene (PEBC) are multiphase systems comprising block and random copolymers as well as small amounts of homopolymers. At present, no satisfactory method exists for characterizing the “blocky” structure of these copolymers. This article aims to fulfill this need. Accordingly, the block and random copolymers of propylene with ethylene have been investigated using 13C CP/MAS NMR with high‐power dipolar decoupling. Comparisons have been made between the spectra of block and random copolymers and it is shown possible to distinguish between them by means of an additional signal, appearing at 32.5δ, in block copolymers (attributable to block junctions). © 1992 John Wiley & Sons, Inc.
Polymers containing polynuclear aromatics linked by one‐carbon bridges
Authors: Jones Martin B. , Larson Julie E.
Published: April 2003

The conversion of naphthalene, anthracene, and phenanthrene to polymeric material via Friedel‐Crafts chemistry was investigated. Synthesis of the polymers was accomplished by: (1) self‐condensation of the chloromethylated aromatic substrate in the presence of AlCl3 or SnCl4 or (2) treatment with chloromethyl ethyl ether (CMEE) and SnCl4, producing the chloromethylated substrate in situ, followed by self‐condensation polymerization. Soluble or insoluble polymers were preferentially produced by varying the stoichiometry, time, or temperature of the reaction. The resulting polymers consisted of the polycyclic aromatic nuclei bridged by methylene groups. The regiochemistry of the polymer linkages was determined through the use of IR, 1H‐ and 13C‐NMR. The polymers showed relatively high thermal and thermo‐oxidative stabilities (380–495°C). © 1992 John Wiley & Sons, Inc.
Imide‐aryl ether ketone block copolymers
Authors: Hedrick James L. , Volksen W. , Mohanty Dillip K.
Published: April 2003

Imide‐aryl ether ketone block copolymers were prepared and their morphology and thermal and mechanical properties investigated. Two aryl ether ketone blocks were incorporated; the first was an amorphous block derived from bisphenol–A and the second block was a semi‐crystalline poly(aryl ether ether ketone) prepared from a soluble and amorphous ketimine precursor. Bis(amino) aryl ether ketone and aryl ether ketimine oligomers were prepared via a nucleophilic aromaic substitution reaction with molecular weights ranging from 6,000 to 12,000 g/mol. The oligomers were co‐reacted with 4,4′‐oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in N‐methyl–2‐pyrrolidone (NMP) in the presence of N‐methylmorpholine. The copolymer compositions, determined by H‐NMR, of the resulting amic ester based copolymers ranged from 8 to 50 wt % aryl ether ketone or ketimine content. Prior to imide formation, the ketimine moiety of the aryl ether ketimine block was hydrolyzed (p‐toluene sulfonic acid) to the ketone form producing the aryl ether ether ketone block. Compositions of this block were maintained low to retain solubility. Solutions of the copolymers were cast and cured to effect imidization, producing clear films with high moduli (ca. 2200 MPa) and elongations (33–100%). The copolymers displayed good thermal stability with decomposition temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of the co‐block type, block length or composition. © 1992 John Wiley & Sons, Inc.
Synthesis, characterization, and modification of poly(tert‐butyl methacrylate‐b‐alkyl methacrylate‐b‐tert‐butyl methacrylate) by group transfer polymerization
Authors: Choi Weon‐Jung , Kim Yang‐Bae , Kwon Soon‐Ki , Lim Kwon‐Taek , Choi Sam‐Kwon
Published: April 2003

Different poly(tert‐butyl methacrylate) (PTBMA)‐poly(alkyl methacrylate) (PAMA, alkyl=CH3, n‐C4H9) triblock copolymers were synthesized by group transfer polymerization. They were obtained by first preparing “living” PAMA using a difunctional initiator, followed by polymerization of TBMA in THF at room temperature, in the presence of a nucleophilic catalyst. The segment molecular weights and compositions of TBMA segment could be controlled by regulating the feed ratio of two monomers and the ratio of monomer to initiator. As supported by 1H‐NMR, IR analysis, and titration, the PTBMA blocks could be quantitatively hydrolyzed into poly(methacrylic acid) (PMAA) blocks whereas the PAMA blocks were not hydrolyzed. The water‐soluble amphiphiles prepared by neutralization of the PMAA block displayed surface‐active behavior in water, which was characterized by a critical micelle concentration. The thermogravimetric analysis demonstrated the loss of tert‐butyl groups. © 1992 John Wiley & Sons, Inc.
Studies on diacetylenic vinyl compounds. VI. ESR studies on the polymerization of diacetylene containing acrylate and methacrylates
Authors: Burillo Guillermina , Ogawa Takeshi , Hwang Jimmy S.
Published: April 2003

A number of diacetylene containing acrylate and methacrylates have been synthesized and the interaction between their propagating radicals and the diacetylene groups was studied by ESR spectroscopy. In the case of polymerization at 70°C using AIBN as an initiator, the propagating radicals of methacrylates are temporarily trapped with the diacetylenes with rapid exchange of the electron, thus showing strong signals of the propagating radicals. Gamma irradiation of the frozen state produces a blue color in samples, and the ESR signals were found to be those of uninteracted acrylate and methacrylates. From a comparison of spectral widths, there seems to exist an intramolecular interaction between the radicals and the diacetylene group at the frozen state. © 1992 John Wiley & Sons, Inc.
2,4,6‐Tribromophenyl acrylate‐co‐glycidyl methacrylate polymers: Synthesis, characterization, and reactivity ratios
Authors: Narasimhaswamy T. , Sumathi S. C. , Reddy B. S. R.
Published: April 2003

Copolymers of 2,4,6‐tribromophenyl acrylate (TBPA) (1) and glycidyl methacrylate (GMA) (2) with different feed ratios are synthesized in toluene using benzoyl peroxide as a freeradical initiator at 70 ± 1°C. The copolymer composition is calculated using 1H‐NMR spectroscopy by comparing the intensity of aromatic and aliphatic protons. The copolymers are characterized with FT‐IR and proton decoupled 13C‐NMR spectroscopic techniques. The reactivity ratios are calculated by Kelen‐Tüdos method and are r1 = 1.08 ± 0.53, r2 = 0.52 ± 0.26. Gel permeation chromatography is used for determining the M̄n, M̄w molecular weights and dispersity index. Thermogravimetric analysis is employed for the determination of thermal stability of homo‐ and copolymers. The glass transition temperatures of the poly(TBPA), poly(GMA), and copoly(TBPA‐GMA) are determined by differential scanning calorimetry. © 1992 John Wiley & Sons, Inc.
The crosslinking of chitosan fibers
Authors: Wei Y. C. , Hudson S. M. , Mayer J. M. , Kaplan D. L.
Published: April 2003

A need exists for the development of totally biodegradable packaging materials. Chitosan is an under‐utilized polymer which possesses many of the desired characteristics for this application. This article describes the crosslinking of chitosan fibers. Epichlorohydrin (ECH) was selected as a convenient base catalyzed crosslinking agent. The strength of chitosan fibers, especially wet tenacity, is improved by crosslinking. © 1992 John Wiley & Sons, Inc.
Preparation and properties of polyarylates both from 2,2′‐bibenzoyl chloride and bisphenols and from biphenyl‐2,2′‐diol and aromatic dicarboxylic acid chlorides
Authors: Liou Guey‐Sheng , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

Polyarylates having inherent viscosities up to 1.02 dL/g were synthesized both by the phase‐transfer catalyzed two‐phase polycondensation of 2,2′‐bibenzoyl chloride with various bisphenols and by the high‐temperature solution polycondensation of biphenyl‐2,2′‐diol with aromatic dicarboxylic acid chlorides. All the polyarylates were amorphous and soluble in a variety of organic solvents including N,N‐dimethylformamide, N‐methyl–2‐pyrrolidone, chloroform, m‐cresol, and pyridine. Transparent and flexible films of these polymers could be cast from the chloroform solutions. These polyarylates had glass transition temperatures in the range of 120–250°C and began to lose weight at around 380°C in air. © 1992 John Wiley & Sons, Inc.
Synthesis, characterization, and curing of well‐defined allyl ether‐maleate functional ester oligomers: Linear versus nonlinear structures
Authors: Johansson Mats , Trollsås Mikael , Hult Anders
Published: April 2003

A series of allyl ether‐maleate functional star‐shaped esters with from one to four arms has been synthesized. The structures that have been made are an analogous series with increasing molecular weight and functionality where the increase in molecular weight has been made nonlinear, i.e., star‐shaped. The resins are monodisperse in the sense that each arm has a well‐defined structure and that, within a certain sample, only one type of molecule exists. The viscosity and rheological behavior of the resins have been studied. The curing kinetics of the star‐shaped (branched) resins and the properties of the films formed have also been studied. These properties have been related to differences in functionality and to differences in the molecular architecture of the resins. © 1992 John Wiley & Sons, Inc.
Synthesis of core‐shell latexes by redox initiation at ambient temperatures
Authors: Lee Sharon , Rudin Alfred
Published: April 2003

Core‐shell polymer composites made by two‐stage emulsion polymerizations are useful in many applications. In systems involving a hydrophilic/hydrophobic polymer pair, a core‐shell arrangement is thermodynamically unfavorable and may be difficult to achieve. To counteract the thermodynamic forces in such a system, the mobility of the phases can be reduced to such an extent that a core‐shell morphology is achieved. This was accomplished in a PMMA/PS two‐stage system by lowering the second‐stage polymerization temperature to room temperature using a redox initiator. At this relatively low temperature, a core‐shell morphology was obtained even when the second‐stage was carried out as a batch polymerization. © 1992 John Wiley & Sons, Inc.
Synthesis and properties of segmented aromatic poly(ether sulfone)‐amide and poly(ether sulfone)‐imide copolymers
Authors: Oishi Yoshiyuki , Nakata Shoichi , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

New segmented aromatic poly(ether sulfone)‐amide and poly(ether sulfone)‐imide copolymers were synthesized by the chain extension of α,w‐diamine‐terminated poly(ether sulfone) oligomer with both aromatic dicarboxylic acid chlorides and tetracarboxylic dianhydrides, respectively. Crystallization of the poly(ether sulfone)unit was suppressed by the introduction of amide or imide linkage along the polymer backbone, giving amorphous copolymers that were +eadily soluble in various organic solvents. The copolymers had somewhat higher glass transition temperatures than the parent poly(ether sulfone). They afforded transparent and tough films by solution casting. © 1992 John Wiley & Sons, Inc.
The effect of radical trapping reagents upon formation of poly(α‐tetrahydrothiophenio para‐xylylene) polyelectrolytes by the wessling soluble precursor method
Authors: Denton Frank R. , Lahti Paul M. , Karasz Frank E.
Published: April 2003

Molecular weights were studied by gel permeation chromatography of derivatized poly(α‐tetrahydrothiophenio para‐xylylene) chloride produced by aqueous or methanolic base‐induced polymerization of 1,4‐bis(tetrahydrothiopheniomethyl) benzene dichloride, both with and without a variety of added polymerization inhibiting agents. Efficient radical scavenging agents such as 2,2,6,6‐tetramethylpiperidinoxyl and hydrogen atom donor 2,4,6‐tri‐tert‐butylaniline reduced the degree of polymerization of the reactive α‐(tetrahydrothiophenium chloride)‐para‐xylylene intermediate produced in this chemistry, and in some cases completely suppressed formation of high polymer. These two traps did not affect the equilibrium production of the para‐xylylene by UV‐Vis spectral analysis; hence they must affect the subsequent polymerization chain propagation steps in the mechanism. Electron spin resonance studies of polymerization in the presence of 0.00025 equiv of TEMPO showed disappearance of the spin label, a result consistent with a radical scavenging process. The results suggest that production of high molecular weight poly(α‐tetrahydrothiophenio para‐xylylene) chloride proceeds through a radical chain propagation sequence. © 1992 John Wiley & Sons, Inc.
Graft polymerization of methyl methacrylate from silica initiated by peroxide groups introduced onto the surface
Authors: Tsubokawa Norio , Ishida Hisanori
Published: April 2003

The surface grafting onto ultrafine silica by the radical polymerization of methyl methacrylate (MMA) initiated by peroxide groups introduced onto the surface was investigated. The introduction of peroxide groups onto the silica surface was achieved by the reaction of hydrogen peroxide with chlorosilyl groups, which were introduced by the treatment of silica with thionyl chloride. The content of diisopropylbenzene peroxide and tert‐butyl peroxide groups introduced onto the silica according to the above method was determined to be 0.11 and 0.08 mmol/g, respectively. It was found that the polymerization of MMA is initiated by silica having these peroxide groups. In the polymerization, polyMMA was grafted onto silica surface: the percentage of grafting reached about 70%. Therefore, it was concluded that the polymerization of MMA is initiated by surface radicals formed by the decomposition of peroxide groups on silica and polyMMA is grafted through the propagation from the surface. During the polymerization, ungrafted polyMMA was also formed because of the formation of initiator fragments by the decomposition of peroxide groups: the grafting efficiency of the graft polymerization was 30–40%. PolyMMA‐grafted silica produced a stable colloidal dispersion in organic solvents for polyMMA. © 1992 John Wiley & Sons, Inc.
Formose reaction by polymer‐supported thiazolium salts
Authors: Yamashita K. , Wakao N. , Nango M. , Tsuda K.
Published: April 2003

Thiazolium salt polymers synthesized by quaternization of 4‐(4′‐vinylphenyl)thiazole (VPT) polymers with methyl iodide had a highly catalytic activity for “the formose reaction.” Their catalytic activities were comparable to that of a low molecular weight analog, 3‐methyl‐4‐phenylthiazolium iodide (MPTI). In the reaction catalyzed by the polymer catalyst, a main product, dihydroxyacetone (DHA), was detected by gas‐liquid chromatography. The polymer catalysts were easily recovered from the reaction mixture and reused with a sustained catalytic activity. © 1992 John Wiley & Sons, Inc.
15N‐, 1H‐, and 13C‐NMR chemical shifts and electronic properties of aromatic diamines and dianhydrides
Authors: Ando Shinji , Matsuura Tohru , Sasaki Shigekuni
Published: April 2003

We measured the 15N‐, 1H‐, and 13C‐NMR chemical shifts for a series of aromatic diamines and aromatic tetracarboxylic dianhydrides dissolved in DMSO‐d6, and discuss the relationships between these chemical shifts and the rate constants of acylation (k) as well as such electronic‐property‐related parameters such as ionization potential (IP), electronic affinity (EA), and the energy ε of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The 15N chemical shifts of the amino group of diamines (δN) depend monotonically on the logarithm of k (log k) and on IP. We inferred the reactivities of diamines whose acylation rates have not been measured from their δN, and we propose an arrangement of diamines in the order of their reactivity. The 1H chemical shift of amino hydrogens (δH) and the 13C chemical shift of carbons bonded to nitrogen (δC) are roughly proportional to δN, but these shifts are not as closely correlated with log k and IP. Although the 13C chemical shifts of the carbonyl carbon of dianhydrides (δC,) varies much less than the δC and δN of diamines, δC, can be an index of acylation reactivity for dianhydrides because it is closely correlated with εLUMO. These facts indicate that the chemical shifts of diamines and dianhydrides are displaced according to their electron‐donor and electron‐acceptor properties, and that these chemical shifts can be used as indices of the electronic properties of monomers. Changes in reactivity caused by the introduction of trifluoromethyl groups into diamines and dianhydrides are inferred from the displacements of δN and δC © 1992 John Wiley & Sons, Inc.
Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. VII. Preparation and properties of polyzirconoxanes as a precursor for zirconia fibers by the hydrolysis of bis (ethyl acetoacetato) zirconium dialkoxide
Authors: Gunji Takahiro , Goto Hitoshi , Kimata Yoshinori , Nagao Yukinori , Misono Takahisa , Abe Yoshimoto
Published: April 2003

Acid‐catalyzed hydolysis of bis(ethyl acetoacetato) zirconium dialkoxide in methanol or THF was investigated. The hydrolysis of the chelates in the molar ratios of H2O/ chelate = 1.0–2.0 and HCl/chelate = 0.1–0.2 provided concentrated solutions (ca. 83 wt %) of polyzirconoxanes (PZO) which showed excellent spinnability and stability to self‐condensation. Continuous gel fibers were prepared by dry spinning the solutions. Polyzirconoxanes were isolated as powders when the concentrated solution was precipitated with hexane. Silylation allowed the investigation of the structure of PZO. It was confirmed to be the polymers of a low degree of polymerization with the ligand and hydroxy group as pendants. © 1992 John Wiley & Sons, Inc.
Syntheses and characterizations of allyl cellulose and glycidyl cellulose
Authors: Lin Mu‐Shih , Huang Chung‐Song
Published: April 2003

Allyl cellulose was synthesized by reacting cellulose with allyl bromide in homogeneous LiCl/DMAc solution containing NaOH powder. The degree of substitution (DS) per anhydroglucose (AHG) unit was determined by titrating the allyl cellulose with bromine in chloroform solution, and an allyl DS of 2.80 was found. Glycidyl cellulose was then prepared by reacting this allyl cellulose with peracetic acid in methylene chloride at ambient temperature for 6 days. The measured reaction rate constant was 1.33 × 10−3 min−1. The glycidyl cellulose thus obtained with a glycidyl DS of 2.58 was determined by titrating the product with perchloric acid in conjunction with tetrabutylammonium iodide. The 2.58 of glycidyl DS was also confirmed by 1H‐NMR integration. Both allyl cellulose and glycidyl cellulose were analyzed and characterized with FTIR, 1H‐NMR, 13C‐NMR, TGA, and GPC. During epoxidation of allyl cellulose, possible side reaction leading to ester formation was evidenced from the continuous increase of vCO at 1735 cm−1 in FTIR analyses. In addition, a bimodal distribution and a decreased molecular weight for glycidyl cellulose were found from GPC data, which might suggest a possible chain scission at the cellulosic ether linkage. © 1992 John Wiley & Sons, Inc.
Free‐radical homopolymerization and copolymerization of ethyl α‐hydroxymethylacrylate in tetrahydrofuran
Authors: Fernández‐Monreal M. C. , Cuervo R. , Madruga E. L.
Published: April 2003

Ethyl α‐hydroxymethylacrylate (EHMA) was polymerized in a 3 mol/L tetrahydrofuran solution at 50°C, using 2–2' azobisisobutyronitrile as initiator. The kinetic behavior indicates a higher polymerization rate for EHMA than for methyl methacrylate (MMA). Copolymerization reaction between MMA and EHMA, under the same experimental conditions, was carried out and values of rMMA = 1.264 and rEHMA = 1.285 were found for the reactivity ratios. The comparison of triad sequences as determined from Bernouillian statistic to those calculated from the experimental spliting of O‐methyl and α‐methyl 1H‐NMR signals of the copolymers confirm the obtained results. © 1992 John Wiley & Sons, Inc.
Thermolysis of polyarylate model compounds
Authors: Leblanc Jean‐Pierre , Huang Jianing , Padias Anne Buyle , Hall H. K.
Published: April 2003

Thermal decompositions and pyrolyses of p‐tert‐butylphenol, 4,4'‐isopropylidenediphenol (BPA), and their acetate and pivalate esters as model compounds for the polyarylate synthesis have been performed. Acetate esters decompose chiefly into phenols and ketene. Pivalate esters, unable to form ketene, are more stable. Acetates and pivalates undergo homolytic cleavage both at ester and alkyl groups. Styrene derivatives stabilize acetate esters, considerably reducing the amount of phenol formed during the decomposition. No intensely colored aromatic compounds were found, although this result is probably an artifact of the methods used. From this study we conclude that ketene is one source of colored materials during polyarylate synthesis. © 1992 John Wiley & Sons, Inc.
Photocrosslinking of copolymers of vinyloxyethyl methacrylate–styrene initiated by sulfonium salts. I. Transient species formed on photolysis of sulfonium salt
Authors: Lin Mao‐Peng , Kim Haeng‐Boo , Ikeda Tomiki , Endo Takeshi
Published: April 2003

Benzyl cation was detected by transient absorption spectroscopy with a spectroscopic multichannel analyzer on pulse excitation (fourth harmonic of Nd:YAG laser, 266 nm; 10 ns fwhm) of benzyl(4‐hydroxyphenyl) methylsulfonium hexafluoroantimonate(BSS) in 1,2‐dichloroethane (EDC). The benzyl cation was long‐lived (lifetime, 59 ms) at room temperature and quenched by a vinyl ether compound. The formation of the benzyl cation as active species on photolysis of BSS is in contrast to the formation of Brønsted acids in other sulfonium salts so far reported. © 1992 John Wiley & Sons, Inc.
Aromatic polyisophthalamides with N‐benzylidene pendant groups
Authors: Mikroyannidis John A.
Published: April 2003

A new series of modified polyisophthalamides bearing N‐benzylidene pendant groups was prepared by reacting various aromatic diamines with 5‐(N‐benzylidene) isophthalic acid. The latter was synthesized from the reaction of 5‐aminoisophthalic acid with benzaldehyde and characterized by IR and 1H‐NMR spectroscopy. Triphenyl phosphite and pyridine was used as condensing agents for preparing polyamides. In addition, the corresponding unsubstituted polyisophthalamides were prepared under identical experimental conditions for comparative purposes. Characterization of modified polyamides was accomplished by IR as well as inherent viscosity measurements. They showed a slightly lower solubility in various media than the corresponding unsubstituted polyamides. The cured modified polyamides displayed significantly higher thermal stability than the cured unsubstituted polyamides. They were stable up to 355–308°C in N2 or air and afforded anaerobic char yield of 66–61% at 800°C. © 1992 John Wiley & Sons, Inc.
Photoinitiation of acrylamide polymerization using the dianions of rhodizonic and croconic acids
Authors: Zhao B. , Back M. H.
Published: April 2003

Polymerization of acrylamide has been initiated by the photochemical reactions of the dianions of croconic acid (1,2‐dihydroxycyclopentenetrione) and rhodizonic acid (1,2‐dihydroxycyclohexenetetrone) in the presence of various acceptor molecules. Photoinitiation was most efficient with croconic acid where a maximum quantum yield for polymerization of 2 x 103 was observed in neutral solution. Kinetic studies using this initiator showed that the rate of polymerization was a linear function of the concentration of monomer and proportional to the square root of the light absorbed by the croconate dianion. The rate of initiation of radicals calculated from the rate of polymerization was compared with the rate of production of radicals calculated from previous studies of the photochemistry of the croconate dianion and the mechanism of photoinitiation is discussed. © 1992 John Wiley & Sons, Inc.
Substrate temperature effects on film chemistry in plasma deposition of organics. III. Analysis by static secondary ion mass spectrometry
Authors: López Gabriel P. , Chilkoti Ashutosh , Briggs David , Ratner Buddy D.
Published: April 2003

Static secondary ion mass spectrometry (SIMS) was used to examine the effect of reducing the substrate temperature during the radio frequency plasma deposition of organic films. Studies of two polymerizable plasma precursors (2‐hydroxyethyl methacrylate and acrylic acid) and one nonpolymerizable precursor (acetone) deposited without substrate cooling and with liquid nitrogen cooling are presented. Acetone deposited with methanol/dry ice cooling was also investigated. Spectra of polymerizable precursors were analyzed by comparison to spectra for the corresponding conventionally‐polymerized polymer films [i.e., poly(hydroxyethyl methacrylate) and poly(acrylic acid)]. Acetone spectra were interpreted by reference to SIMS analysis of plasma‐deposited films prepared from isotopically‐labelled acetone and to reference homopolymers. Comparison of the SIMS spectra of films deposited at different substrate temperatures indicates that a reduction in substrate temperature generally results in higher intensity of peaks characteristic of oxygenated ion structures. SIMS also suggests that the reduction of substrate temperature results in less polymer unsaturation and fewer structures which form by hydrogen redistribution during the deposition process. These results support the hypothesis that deposition at low substrate temperatures leads to an increase in the proportion of precursor incorporated into the film without substantial fragmentation. Corroborative results from high resolution x‐ray photoelectron spectroscopy (XPS) and assays for precursor functional groups by chemical derivatization reactions in conjunction with XPS are also presented. © 1992 John Wiley & Sons, Inc.
Model filled polymers. XI. Synthesis of monodisperse crosslinked polymethacrylonitrile beads
Authors: Zou Dezhong , Aklonis J. J. , Salovey R.
Published: April 2003

Monodisperse polymethacrylonitrile beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylonitrile and allylmethacrylate in the absence of emulsifier. The particle size is very sensitive to polymerization temperature and initiator concentration. Because of a nitrile group effect, the maximum conversion varies with reaction conditions. The highest conversion obtained was 82%. © 1992 John Wiley & Sons, Inc.
Photochemistry of macromolecular metal complexes. III. Synthesis, spectral and electrochemical properties of macromolecular bound protoporphyrin in aqueous solution
Authors: Narayanan V. , Natarajan P.
Published: April 2003

The macromolecular bound protoporphyrin IX and its metal complexes, poly‐(protoporphyrin‐co‐acrylamide), cobalt(II) [poly(protoporphyrin‐co‐acrylamide)], zinc‐(II)[poly(protoporphyrin‐co‐acrylamide)], and manganese(III) [poly(protoporphyrin‐co‐acrylamide)] chloride were synthesized. The absorption and emission spectra have been obtained for the macromolecular porphyrins. The lifetime of the excited singlet state of the protoporphyrin IX was found to decrease from 13.7 to 6.2 ns after polymerization. The cyclic voltammograms of polymeric protoporphyrin coated electrodes have been obtained. © 1992 John Wiley & Sons, Inc.
Syntheses and properties of polymers from perchloro‐p‐xylene, perclorobi‐p‐tolyl, and perchloro‐m‐xylene with Fe(CO)5 as dechlorinating agent
Authors: Fors P. , Juliá L. , Riera J. , Tura J. M. , Sauló J.
Published: April 2003

We describe a new method for the polymerization of perchloroaromatic compounds using Fe(CO)5 as a dechlorinating agent which allows the syntheses of perchloropoly‐1,4‐phenylene vinylene (8), perchloropoly‐4,4'‐biphenylene vinylene (9), and perchloropoly‐1,3‐phenylene vinylene (10) from perchloro‐p‐xylene (5), perchlorobi‐p‐tolyl (6), and perchloro‐m‐xylene (7), respectively. Polymer 10, a new macromolecular chlorocarbon, was characterized by elemental analysis and infrared and ultraviolet spectra. The molecular weights (MW's) of the polymers were estimated by osmometry. The XPS spectra of these polymers are discussed. Their thermal properties were studied by thermogravimetry. Electron spin resonance (ESR) studies and some preliminary conductivity measurements, made after doping the polymers with SbF5, are reported. © 1992 John Wiley & Sons, Inc.
Synthesis of poly(arylene ethyne)s via palladium‐catalyzed cross‐coupling reactions with Cu and Sn reagents
Authors: Bochmann M. , Kelly K.
Published: April 2003

Comparative studies have been carried out of the effectiveness of two organometallic coupling reagents for the synthesis of poly(alkynylarene)s via palladium catalyzed cross‐coupling reactions of dialkynes with organic dibromides. In comparison to copper reagents, monomeric difunctional trialkyltin acetylides show increased thermal stability which allows reactions to be performed at higher temperatures; they give oligomeric and polymeric materials of improved molecular weight. By contrast, the inferior solubility of copper acetylides limits chain growth, and above 140°C the Pd/Cul system is prone to homopolymerization of the dialkyne. The coupling reactions are solvent‐dependent but not strongly influenced by the nature of the palladium precursor complex or the phosphine ligand. © 1992 John Wiley & Sons, Inc.
Kinetic studies on the n‐alkyl acrylate polymerization
Authors: Subrahmanyam B. , Baruah S. D. , Rahman M. , Baruah J. N. , Dass N. N.
Published: April 2003

Kinetic studies on the polymerization of n‐butyl acrylate and n‐octadecyl acrylate in toluene at 70°C with benzoyl peroxide as initiator are reported. High monomer orders of 1.55 and 1.75 were obtained for n‐butyl and n‐octadecyl acrylates, respectively. Though the initiator order in butyl acrylate polymerization was 0.5, the octadecyl acrylate polymerization showed less than square root initiator order. The activation energy for the polymerization of both the acrylates was determined. Autoacceleration was found even at low conversions. The autoacceleration was influenced by both monomer and initiator concentration. Molecular weight data was presented in support of the gel effect. © 1992 John Wiley & Sons, Inc.
New liquid crystal polyethers and polyesters based on diphenylbutadiene mesogens
Authors: Mates T. E. , Ober C. K.
Published: April 2003

New liquid‐crystalline (LC) polymers and small molecules have been synthesized based on the 1,4‐diphenylbutadiene mesogen, a chromophore with χ(3) nonlinear optical properties. Polyethers were formed by phase‐transfer reaction, and polyesters were prepared by Schotten‐Bauman polymerization from these 4,4'‐bisphenolic mesogenic structures. Liquid crystallinity was examined using differential scanning calorimetry (DSC) and optical microscopy. Most of the model compounds were found to be nematic. All mesomorphic polymers were nematic and displayed LC ranges of up to 50°C as well as a wide diversity of melting points. The melting points varied with the flexible (methylene) spacer length and were strongly dependent upon the presence of substituents in the mesogenic core. Crosslinking and cis‐trans isomerization were observed under the influence of heat and ultraviolet radiation. © 1992 John Wiley & Sons, Inc.
Polyimides derived from diels‐alder polymerization of furfuryl‐substituted maleamic acids or from the reaction of bismaleamic with bisfurfurylpyromellitamic acids
Authors: Diakoumakos Constantinos D. , Mikroyannidis John A.
Published: April 2003

Certain AB or AA and BB Diels‐Alder polymer precursors bearing maleimide and furan segments were synthesized, characterized, and polymerized. Particularly, the monomaleamic acid derived from 4,4'‐diaminodiphenylmethane, reacted with the monofurfurylpyromellitamic acid to yield a triamic acid which was cyclodehydrated to the corresponding triimide. A polyimide was obtained upon heat‐curing of triimide or the intermediate triamic acid. In addition, equimolar amounts of N,N'‐bismaleimido‐4,4'‐diphenylmethane (BMDM) and bisfurfurylpyromellitimide or their intermediate diamic acids were cured to afford a polyimide. The polymer precursors were characterized by IR and 1H‐NMR spectroscopy and their curing behavior was investigated by DTA. It was shown that the Diels‐Alder polymerization of monomers took place at lower temperature than that required for crosslinking of BMDM. The thermal stabilities of polymers were ascertained by TGA and isothermal gravimetric analysis (IGA). The synthesized Diels‐Alder polymers were remarkably more heat‐resistant than the crosslinked polymer obtained from BMDM or its intermediate bismaleamic acid. They were stable up to about 360°C in N2 or air and afforded anaerobic char yield of 58% at 800°C. © 1992 John Wiley & Sons, Inc.
Mixed ligand five coordinate cobalt(II) complexes of a polymer‐bound schiff base derived from 2‐aminobenzimidazole
Authors: Yusuff K. K. Mohammed , Sreekala R.
Published: April 2003

The complexes resulting from the interaction of a new Schiff base ligand derived from crosslinked polystyrene bound benzaldehyde and 2‐aminobenzimidazole with a square planar complex [Co(TPP)] (where TPP = meso‐tetraphenylporphyrin), and also with tetrahedral complexes [Co(BPBI)2X2] (where BPBI = 1‐benzyl‐2‐phenylbenzimidazole, X = Cl, Br, or NCS) have been isolated and characterized. The percentages of cobalt and nitrogen in the complexes show that only one Schiff base unit is coordinated to cobalt. Infrared spectra suggest that the bonding of the polymer ligand to cobalt is through the N‐3 atom of the benzimidazole moiety. The EPR spectra indicate that all the complexes are in the low‐spin state and have a square pyramidal environment around cobalt(II). © 1992 John Wiley & Sons, Inc.