bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel polyurethanes with macroheterocyclic (crown‐ether) structures in the polymer backbone
Authors: Herweh J. E. 
Published: April 2003

AbstractThe synthesis of a functionalized crown ether was accomplished in two steps by condensing 3,4‐dihydroxybenzaldehyde with bis(2‐chloroethyl)ether and subsequent reduction of the reaction product, bis(formylbenzo)‐18‐crown‐6 (4) to a diol (5). Polyurethanes that bear the dibenzo‐18‐crown‐6 moiety in the polymer backbone were synthesized from bis(methylolbenzo)‐18‐crown‐6 (5), a polypropylene glycol, and methylene bis(4‐cyclohexyl isocyanate). The resulting polymers were fibrous white solids with glass transitions from ca. 15–120°C, depending on the starting diol composition. The thermomechanical spectra of melt pressed or solvent cast films of several crown‐ether‐bearing polyurethanes showed evidence of multiphase character. The polymers failed to complex effectively with sodium ions. However, their complexing ability with potassium ion was similar in magnitude to that observed with relatively simple crown ethers.
Phase transfer catalysis in dehydrofluorination of poly(vinylidene fluoride) by aqueous sodium hydroxide solutions
Authors: Kise Hideo , Ogata Hiroshi 
Published: April 2003

AbstractThe reaction of poly(vinylidene fluoride) (PVDF) powder with aqueous sodium hydroxide solutions in the presence of quaternary ammonium or phosphonium halides as phase transfer catalysts afforded dehydrofluorinated polymers. The structure of the products was investigated by infrared spetroscopy, and a fluorine‐substituted conjugated polyene structure was suggested which was found to be stable against air oxidation. Tetrabutylammonium bromide and tetrabutylphosphonium bromide were the most active among the catalysts used. The effects of the reaction conditions on the conversion are described. The treatment of PVDF films under phase transfer conditions increased the wettability of the surface and electric conductivity. The reaction of PVDF with potassium hydroxide in 2‐propanol proceeded not only by elimination but also by substitution of hydroxide ions.
Synthesis, characterization, and diels–alder extension of cyclopentadiene telechelic polyisobutylene. IV. α,ω‐Di(3‐cyclopentadienylpropyldimethylsilyl)polyisobutylene
Authors: Kennedy J. P. , Carlson G. M. 
Published: April 2003

AbstractThe synthesis and chain extension of polyisobutylene having nonfluxional terminal cyclopentadiene groups is described. The fluxional behavior of silylcyclopentadiene end groups was previously found to prevent Diels–Alder dimerization of the end groups. The incorporation of a propyl moiety between the silicon atom and the cyclopentadiene ring was found to prevent this fluxional isomerization. Polyisobutylene was synthesized having 3‐cyclopentadienylpropyldimethylsilyl end groups with a functionality near 2.0. While thermal extension at 80°C resulted in threefold molecular weight increase, coupling with bisdienophiles yielded greater than tenfold molecular weight increases. The retro‐Diels–Alder reaction of coupled end groups prevents the attainment of high‐molecular‐weight polymers at equilibrium.
The synthesis of poly(styrene‐co‐sodium styrene‐p‐carboxylate)
Authors: Brockman N. L. , Eisenberg A. E. 
Published: April 2003

AbstractThis article describes a technique for the homogeneous lithiation and subsequent carboxylation of high‐molecular‐weight polystyrenes containing up to 14 mol %p‐bromostyrene. Thus, poly(styrene‐co‐p‐bromostyrene)s were reacted in dilute tetrahydrofuran solution with large stoichiometric excesses ofn‐butyllithium with no precipitation of ionomer and subsequently carboxylated with anhydrous carbon dioxide or dry ice. By this technique polystyrenes in which up to 100% of the original bromine groups had been replaced by carboxyl functionalities were obtained.
Diffusion of acid dyes in nylon film in the presence of inorganic salts
Authors: Kumazawa Hidehiro , Sada Eizo , Ando Tetsuo 
Published: April 2003

AbstractThe concentration‐dependence measured by steady‐state permeation and unsteady‐state dyeing methods for a system of acid dye C.I.Acid Blue 182–nylon 6 film in the presence of inorganic salts such as NaCl, Na2SO4, and K2SO4, was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption. It would found that the dyeing process with added NaCl was governed by surface diffusion with two kinds of Langmuir adsorption, whereas with added Na2SO4 and K2SO4 it was governed by surface diffusion with three kinds of Langmuir adsorption.
The effect of organic nitriles on the radiation induced polymerization of styrene
Authors: Guthrie J. T. , Squires L. J. 
Published: April 2003

AbstractThe effect of a range of 10 organic nitriles on the radiation‐induced polymerization of styrene was studied. A dose rate of 4.4 rad s−1 was used. A rate of polymerization of styrene (1.744 mol L−1 of toluene solution) of 5.0 × 10−7 mol L−1 s−1 was found. With organic nitriles present (styrene:nitrile ratio of 1:0.28) the rate of polymerization increased. Rates in the range of 5.5 × 10−7 −5.2 × 10−6 mol L−1 s−1, depending on the nitrile present, were obtained. The polymers were partially characterized and evidence of involvement of each of the nitriles in the polymer chains was revealed. The increase in rate of polymerization has been attributed to the part played by nitrile radicals in the initiation of styrene polymerization. Radical yield values [as G(nitrile radical)] were derived from the relevant rate expressions. Values ranged from 2.7 to 49.5, depending on the particular nitrile. Corresponding values of G(nitrile radical) in the range of 5.1–129.4 were obtained by the manipulation of number‐average molar mass data. Values of kpkt of approximately 2 × 10−5 L mol−1 s−1 were found. Trommsdorff types of effect are absent from these systems.
Acrolein polymerization: Monodisperse, homo, and hybrido microspheres, synthesis, mechanism, and reactions
Authors: Margel Shlomo , Wiesel Erika 
Published: April 2003

AbstractMonodisperse polyacrolien (PA) microspheres were obtained by a single step process via two mechanisms: (a) aqueous polymerization of acrolein under alkaline conditions and (b) aqueous radical polymerization of acrolein by irradiation with a cobalt source. The diameter of the former microspheres can be varied from 0.04 up to 8 μm. The monodispersity of the system is also discussed. The diameter of the latter microspheres can be varied up to 0.2 μm. Hybrido PA microspheres were formed by grafting PA microspheres of average diameter of 0.1 μm obtained by irradiation onto the surface of PA microspheres produced by the alkaline mechanism. The aldehyde content of the microspheres prepared by irradiation is much higher than those of the microspheres formed under alkaline conditions. The aldehyde groups were used for the covalent binding of ligands containing primary amino groups, such as proteins and drugs, in a single step under physiological pH.
Radiolysis of resist polymers. III. Copolymers of methyl‐α‐chloroacrylate and trihaloethylmethacrylates
Authors: Babu G. N. , Lu P. H. , Hsu S. L. , Chien James C. W. 
Published: April 2003

AbstractHomopolymers of 2,2,2‐trifluoroethyl(methacrylate) (TFEMA) and 2,2,2‐trichloroethyl‐(methacrylate) (TCEMA) and copolymers with methyl‐α‐chloroacrylate (MCA) in a range of compositions were synthesized. The reactivity ratios were obtained; the two copolymerizations were close to ideal. Poly(MCA) showed Gs = 7.4 and Gs = 0.9 by γ‐radiolysis. On the other hand, poly(TFEMA) and poly(TCEMA) and Gs values of 2.0 and 2.4, respectively, and Gx = 0. Radiolysis of copolymers was initiated to a large degree by dissociative electron capture by the halogen atoms in both comonomers, as revealed by the ESR spectra of radicals derived from them. Germinal recombinations in irradiated poly(TFEMA) suggested the presence of radicals in proximity. This process was absent in the copolymers. GC‐MS analysis of volatile products and other supporting evidence showed that TFEMA monomers tended to depolymerize; the TCEMA monomers did not. The radiolysis yields varied monotonically with the comonomer composition for the MCA–TFEMA system but the yield–composition relationship was irregular in MCA–TCEMA copolymers. Four noncrosslinking systems are potential radiation resists arranged in increasing order of promise: poly(TFEMA) (Gs = 2.0, Tg = 70°); poly(TCEMA) (Gs = 2.7, Tg = 142°); poly(94MCA‐co‐6TCEMA) (Gs = 2.7, Tg = 142°); and poly(68MCA‐co‐32TFEMA) (Gs = 3.0, Tg = 112°). These materials merit further investigation for E‐beam or x‐ray lithographic applications. Mechanisms of radiolysis for these materials, based on ESR, GC‐MS, and radiolysis yield data, were discussed.
Lyotropic mesophases of hydroxypropylcellulose in pure acetic acid, in water, and in mixed solvents
Authors: Fried F. , Sixou P. 
Published: April 2003

AbstractPhotomicrographys of concentrated lyotropic hydroxypropylcellulose solutions confirm the cholesteric nature of the anisotropic phases in acetic acid and water. They reveal the existence of biphasic separation. Typical liquid‐crystal solvent‐dependent textures are observed. The behavior of liquid‐crystalline phases in mixed solvents is also studied, and the cholesteric pitch of the twist structure is measured for various relative concentrations of solvents. Spherical droplets, or “spherulites,” in well‐defined relative concentrations of solvents have been observed.
Multifunctional polycondensation distributions: A kinetic approach to mixed monomer systems
Authors: Stafford J. W. 
Published: April 2003

AbstractThe size distributions of a number of multifunctional polycondensations which contained mixtures of monomers of different functionalities were derived from kinetic reaction schemes. The distributions obtained were in agreement with those derived by other authors on similar systems. The distribution functions differed, however, from those obtained by a kinetic method by using mean functionalities of the monomer mixtures; the reasons for the differences were explored. Size distribution parameters also obtained were used to consider the differences between actually observed gel points and gel points calculated for multifunctional polycondensing systems.
Radical polymerization behavior of N,N‐disubstituted acrylamide: Absolute rate constants for polymerization and copolymerization of N‐acryloylpiperidine
Authors: Yamada Bunichiro , Yoshioka Minoru , Otsu Takayuki 
Published: April 2003

AbstractThe absolute rate constants of propagation (kp) and of termination (kt) of N‐acryloylpiperidine (NAPi) were determined by the rotating sector method in bulk; kp = 273 and kt = 1.79 × 107 L/mol s at 30°C. It was noted that kp for NAPi was 100 times smaller than that for N,N‐dimethylacrylamide (DMAcAm). The absolute rate constants of cross‐propagations for copolymerizations with common monomers were evaluated by combination of the kp value and the monomer reactivity ratios. Quantitative comparison of the rate constants with those of DMAcAm and poly(DMAcAm) radical shows that NAPi is as reactive as DMAcAm and the smaller kp value for NAPi is ascribable to much the lower reactivity of the poly(NAPi) radical. The large difference in reactivity of the polymer radicals is discussed in relation to the steric factor of the piperadino and the dimethylamino groups which seems to affect the capability of the carboxamide group to stabilize the polymer radical.
Functional monomers and polymers. CXIII. Photoinduced conformational change of thymine containing poly‐lysine derivatives
Authors: Suda Yasuo , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractThe photodimerization reaction between thymine bases in thymine‐grafted poly‐D‐ and poly‐L‐lysine derivatives was studied in an alkaline, aqueous, buffered solution. It was found that the helix content of the polymers changes by photodimerization. The result was discussed in terms of conversion, the rate of photodimerization, and the helix content of the polymers.
Tetraalkyl titanium and zirconium metal chloride catalyst systems for ethylene polymerization
Authors: Herskovitz Thomas 
Published: April 2003

AbstractCoordination polymerization of olefins has become an industrially important, yet still poorly understood enterprise. The ethylene polymerization activity of (neophyl)nZrCl4‐n shows a twentyfold increase from n = 4 to n = 3 and a further tenfold increase to n = 2. The heterogeneous MR4/TiCl4 catalysts (M = Ti, R = benzyl; M = Zr, R = benzyl, neophyl) have been developed. To explore the breadth of extendability, other metal chlorides (main group and transition metal) were substituted for TiCl4. Indeed, excess AlCl3 or MgCl2 and the MR4 compounds also produced ethylene polymerization catalysts. The inactivity of corresponding (neophyl)4Ti systems is attributed to sterics. The abovementioned catalysts highlight the necessity of alkyl and chloride ligands at the transition metal catalyst centers.
Preparation of polysiloxanes from silicic acid. V. Condensation of silicic acid butyl esters and formation of silica fiber from the ester solutions
Authors: Abe Yoshimoto , Sekiguchi Tetsushi , Misono Takahisha 
Published: April 2003

AbstractThe condensation of silicic acid butyl esters was investigated by gel permeation chromatographic (GPC) analysis. The results revealed that the condensation was greatly dependent on a degree of esterification of the esters. The ester with the lowest degree of esterification underwent condensation to form a highly polymerized ester. It was found that fibers could be drawn from the ester solution before gelation.
Radical copolymerization of acrylic monomers. VI. Copolymerization of methyl methacrylate with methyl α‐benzylacrylate
Authors: Madruga E. L. , San Román J. , Lavia M. A. 
Published: April 2003

AbstractFree‐radical copolymerization of methyl methacrylate and methyl α‐benzylacrylate has been studied in benzene solutions at 40 and 60°C. A simple copolymerization model fits the composition data at both temperatures. However, considering that the ceiling temperature for the polymerization of methyl α‐benzylacrylate in benzene solution (|M| = 5 mol/L) is 67°C and that the overall rate of copolymerization drastically decreases with respect to that of methyl methacrylate homopolymerization with an increase of the molar fraction of methyl α‐benzylacrylate in the feed, the behavior of this system is analyzed from both simple and reversible copolymerization models.
Solid products from thermal decomposition of polyethylene terephthalate: Investigation by CP/MAS 13C‐NMR and fourier transform‐IR spectroscopy
Authors: Suebsaeng Thitivat , Wilkie Charles A. , Burger Vern T. , Carter Janet , Brown Charles Eric 
Published: April 2003

AbstractThe solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13C‐NMR, FR‐IR, and MAS 31P‐NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO2, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation.
Vinyl polymerization initiated by peroxydiphosphate. XII. Polymerization of acrylamide and acrylic acid by peroxydiphosphate–sodium thiosulfate redox system
Authors: Lenka Subasini , Nayak Padma L. , Ray Suparna 
Published: April 2003

AbstractThe aqueous polymerization of acrylic acid and acrylamide initiated by peroxydiphosphate–sodium thiosulfate redox system was investigated within the temperature range of 25–35°C. The rates of polymerization were measured at different concentrations of oxidant, activator and monomer. The monomer and the initiator exponents were evaluated to be 1.12 and 0.51. The rate of polymerization decreases with increasing thiosulfate concentration. On the basis of the experimental observation of the dependence of the rate of polymerization, Rp, on various variables, a suitable kinetic scheme has been proposed and the rate parameters have been evaluated.
Spectrophotometric studies of some charge‐transfer complexes of tetracyanoethylene with poly(N‐vinyl halogenocarbazoles)
Authors: Pielichowski Jan , Sanetra Jerzy 
Published: April 2003

AbstractThe results and numerical analysis of measurements of absorption spectra of charge‐transfer complexes of poly(N‐vinyl halogenocarbazoles) with tetracyanoethylene are presented. The absorption bands result from donor–acceptor interaction together with values of equilibrium constants, enthalpy, and oscillators strengths of investigated complexes allowed us to conclude that isomerism of complexing took place. The influence of halogen substituents (mono‐ and disubstitution) in positions 3 and 6 of the carbazole ring (polymeric donor) on the spectral properties of its complexes was observed.
Polymerization of terminal alkynes by a new Ziegler–Natta catalyst system: Scandium naphthenate/trialkylaluminum
Authors: Shen Zhiquan , Farona Michael F. 
Published: April 2003

AbstractThe scandium naphthenate/trialkylaluminum system was investigated as a catalyst in the polymerization of substituted alkynes. Phenylacetylene was converted to a moderately crystalline, high cis polymer. The alkyl‐substituted acetylenes produced rubbery or solid materials of relatively high molecular weight. Infrared (IR), ultraviolet (UV), 1H‐NMR, and 13C‐NMR studies of the polyalkylacetylenes revealed high cis conformation, but apparently twisted from planarity to decrease molecular orbital overlap in the polyconjugated chain.
Linear polythioesters. VII. Products of interfacial polycondensation of 1,4‐di(mercaptomethyl)‐2,3,5,6‐tetramethylbenzene with some aliphatic acid dichlorides
Authors: Podkoscielny Wawrzyniec , Kowalewska Wanda 
Published: April 2003

AbstractSeveral polythioesters by interfacial polycondensation of 1,4‐di(mercaptomethyl)‐2,3,5,6‐tetramethylbenzene with oxalyl, succinyl, adipoyl, suberoyl, and sebacoyl chlorides were obtained. To determine the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: type of organic phase, concentration of hydrogen chloride acceptor, the quantitative ratio of aqueous to organic phase, molar ratio of reagents; temperature of reaction, rate of acid chloride addition, and contribution of catalyst. Thorough studies were carried out only for polycondensation of the dithiol with adipoyl and sebacoyl chlorides. The structure of all polythioesters obtained under the model conditions was determined by elementary analysis and infrared spectra. Initial decomposition temperature, mass loss in percentage at the same temperature, maximum rate of decomposition, and mass loss percentage at 100–400°C were defined by thermogravimetric analyses. Chemical resistance of the polythioesters was determined by treatment with some organic solvents, mineral acids (concentrated and 10%), and sodium hydroxide (10 and 50%). Some mechanical and electrical properties of the polythioesters obtained from dithiol and adipoyl and sebacoyl chlorides were determined. The molecular weight was not measured because of the low solubility of the polythioesters.
Synthesis and conformation of asymmetric rigid polyamides
Authors: Overberger C. G. , Wang David Wei 
Published: April 2003

AbstractAsymmetric polyamides from the reaction of either optically active trans‐1,2‐cyclopropanedicarboxylic acid (C3) or trans‐1,2‐cyclohexanedicarboxylic acid (C6) with 2,7‐diazaspiro[4,4]nonane(DSN) were synthesized. The possible conformations of these polymers and their model compounds in 2,2,2‐trifluoroethanol (TFE), water, methanesulfonic acid (MSA), and sulfuric acid were examined by circular dichroism (CD), NMR, viscosity, and dipole moment measurements. The racemic polyamides (±)C3·(±)DSN and (±)C6·(±)DSN exist in extended forms. No intrinsic viscosity changes were observed for these two polymers in TFE and MSA. Certain viscosity and spectral changes have been observed for the optically active polyamides, although no specific ordered conformations can be assigned. The optically active diacid units incorporated into the polymer give a conformation unique from the totally extended chain. CD studies seem to evidence some conformational differences among the polyamide derived from (+)C6 diacid and the optically active DSN. By changing the solvent from TFE to MSA a blue shift of the trough was observed for (+)C6·(±)DSN, a red shift for (+)C6·(−)DSN, and an inversion of the CD spectrum for (+)C6·(+)DSN polyamides. The results of the work with (+)C6·(−)DSN in dilute acid solution suggest that the rotation around the C–N bond is a relatively low‐energy process. The spectral and intrinsic viscosity data are consistent with this suggestion. No drastic spectral changes have been observed for the C3·DSN polyamides by changing the solvent from TFE to MSA. The amide group in the C3·DSN polyamide and the corresponding model compound prefer a similar conformation with the carbonyl group bisecting the cyclopropane ring. The C3·DSN polyamide seems to exist in an extended form.
Interaction of α‐poly‐L‐lysine and ε‐poly‐L‐lysine with methyl orange and its homologs in aqueous solution: Results from dialysis and spectroscopic measurements
Authors: Takagishi Toru , Ueno Toshihiko , Kuroki Nobuhiko , Shima Shoji , Sakai Heiichi 
Published: April 2003

AbstractThe interaction of α‐poly‐L‐lysine and ε‐poly‐L‐lysine with methyl and ethyl orange was studied by equilibrium dialysis and spectroscopic methods. The results of the dialysis measurements indicated that the extent of binding by ε‐polypeptide is substantially higher than that by α‐polypeptide, despite the much greater molecular weight of the latter. This difference in binding affinity was interpreted in terms of the increased conformational adaptability of ε‐polypeptide because of its highly flexible structure. Furthermore, ε‐polypeptide exhibited strong cooperative binding. In addition, the effect of the successive addition of α‐ and ε‐polypeptides on the absorption spectra of methyl and ethyl orange was investigated. The addition of α‐polypeptide with a molecular weight of 400,000 produced a new absorption peak at a shorter wavelength, due to the stacked dye molecules on the polypeptide chain, whereas that of ε‐polypeptide did not. From the results of spectroscopic measurements a possible mode of interaction between these two polypeptides and the small molecule is discussed.