bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on aqueous polymerizations of vinyl monomers initiated by metal oxidant–chelating agent redox initiators
Authors: Hsu Wen‐Cheng , Kuo Jen‐Feng , Chen Chuh‐Yung 
Published: April 2003

AbstractIn this study, a series of chelating type reductants containing redox pairs were tested as the initiator for aqueous polymerizations. The redox pairs consist of Ce(IV) or several first‐row transition metals coupled with chelating agents of amino acids, dibasic acids, or diamine. The initial rates and limiting conversions of acrylamide polymerization initiated by those redox pairs were determined. The reductive reactivity of the chelating agents with Ce(IV) and the oxidative half‐wave potential of Ce(III)‐chelating agent/Ce(IV)‐chelating agent were measured to evaluate the feasibility of these redox pairs as initiators. After the evaluation, the redox pairs other than Ce(IV)‐amino acid type chelating agent were precluded to be promising initiators for aqueous polymerizations. Those Ce(IV)‐amino acid type chelating agent redox pairs which could form at least two five‐ or six‐membered rings were found to be potential initiators. The Ce(IV)‐NTA pair was the most promising one. The mechanism of initiation of the redox pairs was proposed and further confirmed by the 13C‐ and 1H‐NMR spectra of NTA‐terminated polyacrylamide. The complex formation constants (K) and disproportionation constants (kd) of the Ce(IV)‐amino acid type chelating agent redox initiators for acrylamide polymerization were evaluated. The factors governing the parameters of chelated complexes and the performance of polymerizations were discussed. These redox pairs were also used as the initiators for aqueous polymerizations of acrylic acid and acrylonitrile. © 1993 John Wiley & Sons, Inc.
Influence of molecular weight on some properties of liquid crystalline polyurethanes
Authors: Szczepaniak Barbara , Frisch Kurt C. , Penczek Piotr , Rudnik Ewa , Cholińska Mariola 
Published: April 2003

AbstractThis investigation extends our previous investigations of liquid crystalline polyurethanes prepared from 4,4′‐bis(2‐hydroxyethoxy)biphenyl (BHBP), 2,4‐tolylene diisocyanate, and poly(oxytetramethylene)diols as the flexible spacers. The influence of molecular weight of investigated polyurethanes on their properties is discussed for two series with the same content of BHBP and different lengths of flexible spacers. The polyurethanes were investigated by means of DSC, polarizing microscopy, x‐ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. Morphology was studied by the SALS method. The molecular weight of polyurethanes and the length of flexible spacer influence the phase transition temperature and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.
Polymerization of 7‐phenyl‐2,6‐dimethylquinone methide and its derivatives
Authors: Lin Lon‐Tang W. , Bromps William , Ching Ta Yen 
Published: April 2003

Abstract7‐Phenyl‐, 7‐chlorophenyl‐,7‐methylphenyl‐, and 7‐trifluoromethylphenylquinone methide were synthesized to investigate the anionic polymerization of quinone methide. Novel high molecular weight polymers have been prepared and the substitution effects of the monomers on polymerization kinetics were determined. © 1993 John Wiley & Sons, Inc.
Preparation and properties of aromatic polyamides from 2,2′‐bis(p‐carboxyphenoxy) biphenyl or 2,2′‐bis(p‐carboxyphenoxy)‐1,1′‐binaphthyl and aromatic diamines
Authors: Liou Guey‐Sheng , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractNew aromatic dicarboxylic acids having kink and crank structures, 2,2′‐bis(p‐carboxyphenoxy) biphenyl and 2,2′‐bis(p‐carboxyphenoxy)‐1,1′‐binaphthyl, were synthesized by the reaction of p‐fluorobenzonitrile with biphenyl‐2,2′‐diol and 2,2′‐dihydroxy‐1,1′‐binaphthyl, respectively, followed by hydrolysis. Biphenyl‐2,2′‐diyl‐and 1,1′‐binaphthyl‐2,2′‐diyl‐containing aromatic polyamides having inherent viscosities of 0.58–1.46 dL/g and 0.63–1.30 dL/g, respectively, were obtained by the low‐temperature solution polycondensation of the corresponding diacid chlorides with aromatic diamines. These polymers were readily soluble in a variety of organic solvents including N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide, m‐cresol, and pyridine. Transparent, pale yellow, and flexible films of these polymers could be cast from the DMAc or NMP solutions. These aromatic polyamides containing biphenyl and binaphthyl units had glass transition temperatures in the range of 210–272 and 260–315°C, respectively. They began to lose weight around 380°C, with 10% weight loss being recorded at about 450°C in air. © 1993 John Wiley & Sons, Inc.
Preparation and properties of aromatic polyimides from 2,2′‐bis(p‐aminophenoxy)biphenyl or 2,2′‐bis)p‐aminophenoxy)‐1,1′‐binaphthyl and aromatic tetracarboxylic dianhydrides
Authors: Liou Guey‐Sheng , Maruyama Masaki , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractNew aromatic polyimides containing a biphenyl‐2,2′‐diyl or 1,1′‐binaphthyl‐2,2′‐diyl unit were prepared by a conventional two‐step method starting from 2,2′‐bis(p‐aminophenoxy) biphenyl or 2,2′‐bis(p‐aminophenoxy)‐1,1′‐binaphthyl and aromatic tetracarboxylic dianhydrides. The polyimides having inherent viscosities of 0.69–0.99 and 0.51–0.59 dL/g, respectively, were obtained. Some of these polymers were readily soluble in a variety of organic solvents including N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide, and pyridine. Transparent, flexible, and pale yellow to brown films of these polymers could be cast from the DMAc or NMP polyamic acid solutions. These aromatic polyimides containing biphenyl and binaphthyl units had glass transition temperatures in the range of 200–235 and 286–358°C, respectively. They began to lose weight around 380°C, with 10% weight loss being recorded at about 470°C in air. © 1993 John Wiley & Sons, Inc.
Polymeric organosilicon systems. XVII. Synthesis and photochemical and conducting properties of poly[o‐and m‐(disilanylene)phenylene]s
Authors: Ishikawa Mitsuo , Sakamoto Hiromu , Ishii Michie , Ohshita Joji 
Published: April 2003

AbstractPoly[o‐(tetramethyldisilanylene)phenylene] (2a), poly[o‐(1,2‐dimethyldiphenyldisilanylene)‐phenylene] (2b), poly[m‐(tetramethyldisilanylene)phenylene] (2c), and poly[m‐(1,2‐dimethyldiphenyldisilanylene)phenylene] (2d) were prepared by the sodium condensation reaction of the corresponding 1,2‐and 1,3‐bis (chlorosilyl)benzenes in toluene. Irradiation of thin films of 2a‐2d in air resulted in a rapid decrease of absorption maxima in the ultraviolet region. The photolysis of 2b and 2d in benzene afforded photodegradation products with low molecular weights. When thin films of 2b and 2d were doped with antimony pentafluoride vapor, films which have conductivities of semi‐conductor level were obtained. © 1993 John Wiley & Sons, Inc.
Surface fixation of poly(ethylene glycol)via photodimerization of cinnamate group
Authors: Nakayama Yasuhide , Matsuda Takehisa 
Published: April 2003

AbstractThis article reports a new fixation method for hydrophilic layers on substrates. The method is based on the photochemistry of the cinnamate group, which is capable of intermolecular dimerization upon ultraviolet (UV) light irradiation. The method used was as follows. First, two photoreactive polymers were sequentially coated on a polymeric surface: a polycinnamate as an adhesive layer and a cinnamated poly(ethylene glycol) (PEG) as a hydrophilic layer. Subsequently the surface was exposed to UV light. No delamination occurred upon washing with water and methanol; the photoreactive PEG was chemically bonded onto the surface via the polycinnamate. The higher the molecular weight of PEG, the higher the wettability of the surface was formed. Minimal cell adhesion was observed on such a surface. The biomedical applications of the method are discussed. © 1993 John Wiley & Sons, Inc.
Electrical dc conductivity in iodine‐doped pseudo‐IPNs of conjugated polymer network (C‐PDMS/L‐P4BCMU)
Authors: Frisch Harry L. , Chen Xiaomeng 
Published: April 2003

AbstractWe have prepared pseudo‐IPNs (PIPN) of crosslinked PDMS and linear P4BCMU and characterized them by DSC and SEM. The proposed theory about electrical hopping conduction along the linear chain is supported by the observed electrical conductivity properties of these IPNs of conjugated linear polymers. We also studied the low‐temperature (T) DC conductivity of the single‐phase PIPN and these showed a change from minus to plus in dσ/dt below 120 K. At 4 K, σ was about seven times larger than at 120 K. This reversal is not shown by the bulk polymers composing these PIPNs and polymer blends of linear conjugated polymer in linear insulating host polymer. We speculate that this may indicate some degree of quantum coherence in σ of the one‐dimensional pseudo‐ PIPNs. © 1993 John Wiley & Sons, Inc.
Model studies on the structure of poly(amide oxime)s and their cyclodehydration reactions leading to poly(1,2,4‐oxadiazole)s
Authors: Jung Jin Chul , Park Sang‐Bong 
Published: April 2003

AbstractTo obtain an understanding of the low molecular weight character of wholly aromatic poly(1,4‐arylene acyldiamide oxime)s (PAAs) having n‐alkyloxymethyl side braches and the additional decrease in molecular weight during their cyclodehydration reaction leading to the corresponding poly(1,4‐arylene‐1,2,4‐oxadiazole)s (PAOs), tautomeric structures of poly[1,4‐phenylene‐2,5‐bis(n‐octyloxymethyl)terephthaldiamide oxime] (C8‐PAA) were 1H‐NMR‐spectroscopically investigated by using two model compounds: O,O'‐dibenzoyl terephthaldiamide oxime (H‐PAA‐M, 4) and O,O'‐dibenzoyl‐2,5‐bis(n‐octyloxymethyl) terephthaldiamide oxime (C8‐PAA‐M, 5). In solution H‐PAA‐M existed exclusively as oximino isomer, while C8‐PAA‐M consisted only of imino tautomer and C8‐PAA contained both the oximino and imino form, the former being dominant in composition. It was found that the presence of imino tautomer caused serious effects both on the low molecular weight character of C8‐PAA and on the additional decrease in molecular weight during thermal cyclodehydration to C8‐PAO, whereas the presence of oximino tautomer showed practically little effect. A discussion on the results is provided from mechanistic viewpoint. © 1993 John Wiley & Sons, Inc.
The conformational effect of form I helical poly(L‐proline) and form II helical poly(L‐proline) to the complex formation with helical poly(L‐glutamic acid) through hydrogen bonding
Authors: Jung Jaechang , Kim Hyun Don , Ree Taikyue , Jhon Mu Shik 
Published: April 2003

AbstractThe complex formation between helical poly‐L‐glutamic acid (PLGA) and helical poly‐L‐proline (PLP) was studied in a methanol‐water (2 : 1) cosolvent and a propanol‐water cosolvent (9 : 1). Reduced viscosity, circular dichroism, pH, and molar absorptivity were measured. The experimental results exhibit that the interpolymer complex was formed between helical PLGA and helical PLP through hydrogen bonding. When the complex was formed the unit mole ratio of PLGA : PLP(II) is 2 : 1 and PLGA : PLP(I) is 1.5 : 1, the ability of complex formation of PLP (II) with PLGA is better than that of PLP(I). On complexation the conformations of PLGA and PLP change and this change is more enhanced in the PLGA‐PLP(II) than the PLGA‐PLP(I) complex; its cause is studied. © 1993 John Wiley & Sons, Inc.
Polymerization of 2‐(substituted methyl)acrylate bearing ω‐methoxyoligoethyleneoxy groups as side chains to new low Tg polymer
Authors: Yamada Bunichiro , Kobatake Seiya , Aoki Shuzo 
Published: April 2003

AbstractThe polymerization of methyl 2‐(ω‐methoxyoligoethleneoxymethyl)acrylates, which were synthesized from reactions of methyl 2‐bromomethylacrylate with ω‐methoxyoligoethylene glycol, was investigated. All these monomers polymerized readily to high molecular weight despite expectation of the considerable steric hindrance against propagation. No influence of ceiling temperature was observed. The 2‐(2‐methoxyethyleneoxymethyl)acrylate exhibited similar reactivities to methyl 2‐alkoxymethylacrylate reported previously in copolymerization with styrene and methyl methacrylate. The homopolymers synthesized, except for those from methyl 2‐methoxymethyl‐ and 2‐(2‐methoxyethyleneoxymethyl)acrylates, were soluble in water, and all were soluble in benzene. These polymers were thermally less stable than poly(methyl methacrylate) as confirmed by thermogravimetric analysis, and all showed glass transition temperatures below 0°C. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of new crystalline poly(arylene ether nitriles)
Authors: Matsuo Shigeru , Murakami Tomoyoshi , Takasawa Ryuichi 
Published: April 2003

AbstractCrystalline poly(arylene ether nitrile) could be prepared by the polycondensation of 2,6‐dihalobenzonitrile with resorcinol at 200°C in N‐methylpyrrolidone in the presence of sodium carbonate. A reaction temperature of at least 200°C was necessary to attain high molecular weight polymer. Spectral data indicated that the polymer had the structure of a poly(meta‐phenylene ether) with pendent nitrile groups on every other phenylene unit. Despite this structure, the crystallinity and the crystallization rate of the polymer were greater than those of the corresponding polymer with a para‐linked structure. The glass transition temperature and the melting temperature of the polymer were almost the same as those of poly(etheretherketone) (PEEKTM). A series of other new poly(arylene ether nitriles) were also examined. The polymers derived from 4,4′‐biphenol, dihydroxytetra‐phenylmethane, dihydroxydiphenylsulfone, and 1,5‐isoquinolinediol had high glass transition temperatures. The poly(arylene ether nitriles) exhibited excellent tensile strength compared with the corresponding ketone‐ or sulfone‐containing polymers. Comparing the three different kinds of polymers containing the same bisphenol units, the order of glass transition temperature was found to be sulfone‐ > nitrile‐ > ketone‐containing polymers, while the order of tensile strength was nitrile‐ > ketone‐ > sulfone‐containing polymers. The excellent mechanical properties are attributable to dipole‐dipole interactions of nitrile groups. © 1993 John Wiley & Sons, Inc.
Co‐ and terpolymerization of ethylene with 1‐butene and 1‐decene by using Cp2ZrCl2‐methylaluminoxane catalyst
Authors: Seppälä J. V. , Koivumäki J. , Liu X. 
Published: April 2003

AbstractCopolymerizations of ethylene/1‐butene, and ethylene/1‐decene and terpolymerization of ethylene/1‐butene/1‐decene were carried out in n‐heptane with various concentrations of comonomer in the feed. Cp2ZrCl2‐methylaluminoxane (MAO) was used as catalyst. When comonomers were added into the ethylene polymerization, the activity of the catalyst increased significantly and continued to do so as the concentration of the comonomer was increased. At the same time as the comonomer concentration and catalyst activity increased, the molecular weight and crystallinity of the polymers decreased. An important reason for the activity enhancement may, therefore, be that the comonomer takes part in the activation of catalytic centers, decreasing the activation energy required for monomer to insert into the active centers. Use of Cp2ZrCl2‐MAO catalyst allowed the preparation of ethylene/1‐decene copolymers containing 20 wt % of 1‐decene. © 1993 John Wiley & Sons, Inc.
A kinetic model for steric hindrance effects on quaternization of poly(vinylpyridines)
Authors: Hu Guo‐Hua , Wang Wei 
Published: April 2003

AbstractQuaternization reactions of poly(vinylpyridines) with alkyl halides show retardation in excess of that predicted by the classical second‐order kinetics. Based on the classical collision and transition state theories, a kinetic model has been developed to quantify such retardation, in which the overall reaction rate is characterized by a rate constant k0 of the intrinsic reactivity between a pyridyl group and an alkyl halide group, and by a steric hindrance effect parameter α. The latter accounts for the degree to which the rate of collisions of reactants is reduced, or to which the freedom of movement of the reactants in the transition state is restricted as the reaction proceeds. The resulting kinetic expression has been validated using experimental results reported in the literature and those of our own. The functional dependence of k0 and α values on the nature of poly(vinylpyridines) and that of alkyl halides is explained. Other factors affecting k0 and α, including changes in macromolecular dimensions and/or in the distribution of residue environment, quality of solvent, and reaction temperature, are discussed. © 1993 John Wiley & Sons, Inc.
The effect of adsorbed water on the dielectric properties of CaCO3 filled polyethylene composites
Authors: Banhegyi G. , Karasz F. E. 
Published: April 2003

AbstractThe dielectric dispersion and loss of a polyethylene–CaCO3 composite have been investigated in the 50 Hz–100 kHz frequency and 20–140°C temperature ranges, and compared with those for a normal mechanical mixture. The different theoretical interpretations are reviewed and compared with the data. The observed dispersion and loss are probably due to adsorbed water at the PE‐CaCO3 interface; both disappear on heating. The high‐frequency permitivities can be well approximated by theoretical models, but the frequency‐dependent phenomena cannot be interpreted in terms of a simple interfacial polarization mechanism. The universal response theory provides a useful tool for interpreting the measurements.
Mechanical relaxation mechanism of epoxide resins cured with acid anhydrides. II. Effect of the chemical structure of the anhydrides on the β relaxation mechanism
Authors: Ochi Mitsukazu , Iesako Hiroshi , Nakajima Shin , Shimbo Masaki 
Published: April 2003

AbstractThe mechanism of low‐temperature mechanical relaxation of acid‐anhydride‐cured epoxide resins has been investigated in detail. One mechanical relaxation, denoted as the β relaxation, is observed from −80 to −50°C for all epoxide resin systems cured with aromatic, alicyclic, and aliphatic anhydrides. The β relaxation increases in peak height and shifts to higher temperature with increasing molecular volume of the diester segments formed by the reaction of acid anhydrides. From these results, it is concluded that the β relaxation for anhydridecured systems is due to the motion of the diester segment, and that the intensity and peak position of the β relaxation depend on the molecular volume of this segment. Moreover, it was shown that the tensile impact strength of the anhydride‐cured systems is governed by the intensity of the β relaxation of these systems when the parameters Tg and v of these systems are nearly constant.
Phase separation temperatures in the ternary system polystyrene/poly(α‐methyl styrene)/cyclopentane
Authors: Saeki S. , Tsubotani S. , Kominami H. , Tsubokawa M. , Yamaguchi T. 
Published: April 2003

AbstractPhase separation temperatures of the ternary system polystyrene (PS) (Mw = 1.67 × 104)/poly(α‐methyl styrene) (PαMS) (Mw = 9.0 × 104)/cyclopentane with a blend ratio PS/PαMS = 55/45 have been determined over the polymer concentration range 0.02 ≤ ψPS + PαMS ≤ 0.52, where ψ PS + PαMS is the segment fraction of polymer in ternary system. Phase separation temperatures for the upper critical separation in the ternary system decrease with increasing ψ PS + PαMS over the range 0.1 ≤ ψ PS + PαMS ≤ 0.52. The vapor—liquid equilibrium in this system with a blend ratio PS/PαMS=50/50 has been determined over the concentration range 0.925 ≤ ψPS + PαMS < 0.995 and the temperature range 60–100°C by the piezoelectric vapor sorption method. The polymer—polymer interaction parameters χ′12 determined are positive except at 100°C and increase with increasing ψ PS + PαMS. Values of χ′12 extrapolated to zero solvent concentration are positive (0.0–1.3) over the temperature range measured. Phase separation behavior is discussed in terms of phase separation temperature in a ternary system and the polymer–polymer interaction parameter.
Experimental criterion for the crystallization regime in polymer crystals grown from dilute solution: Possible limitation due to fractionation
Authors: Point J. J. , Colet M. Ch. , Dosiere M. 
Published: April 2003

AbstractBy integration of equations previously derived by Frank, the growth rate of polymer crystals is shown to be dependent on their size, provided that the persistence length Lp or the kinetic length Lk = (2g/i)1/2 are significantly larger than the primary nucleus. A new method of decorating the fold surface (isochronous decoration) allows the measurement of the quasi‐instantaneous growth rate of very small crystals obtained from dilute xylene solution of a sharp polyethylene fraction of moderate molecular weight (Mw = 17,000, Mw/Mn = 1.11). Although the theory predicts that the growth rate increases with the size of the crystals as long as its dimension is smaller than the persistence length and/or the kinetic length, such an increase is not observed experimentally with the sharp PE fraction presently used. Therefore it appears that both the kinetic length and the (hypothetical) persistence length are beyond the resolution limit of electron microscopy and that crystallization occurs in the polynucleation regime. An upper bound is obtained for the rate g at which a locally new layer spreads in two directions on the substrate. The rate is lower than is estimated by the commonly Accepted theories. These theories lead also to an abnormally high value for the lateral surface free energy. The possibility that the observed initial linearity of the growth‐rate curve may results from a balance of opposite effects (an increase with the size of the crystals on the one hand, a decrease with decreasing concentration and possible fractionation on the other) is thoroughly examined and ruled out. In fact, it must be stressed that at the early beginning of crystallization, negligible parts of the sample are crystallized and it is only at the end of crystallization that these effects appear. The fall in the growth rate as crystallization ends is due neither to progressive exhaustion of the solution alone nor to a depletion of the concentration by diffusion for this sharp fraction of low‐molecular‐weight PE. The major effect comes from fractionation. This segregation of the various molecular weights is predicted on the basis of a simple model and is verified by gel permeation chromatography (GPC). The fact that in such a sharp fraction significant fractionation occurs precludes any accurate determination of the supercooling and of the concentration of the polymer actually crystallizing. Subtle differences in the molecular weight distributions may result in significant variation of the growth rate. In conclusion, as the data used in the first part of this work were obtained with only a small percentage of the dissolved polymer sample crystallized, the observed constancy of the growth rate does not result from mutual compensation of opposite effects, and our conclusions about crystallization regime, order of magnitude of the kinetic and persistence lengths, and value of the rate of lateral spreading of a secondary nucleus are well founded.